Android(安卓)Development
16lz
2021-12-04
Android
Beginner’s entry level
文章目录
- Android
-
- Beginner's entry level
- Introduce
- Project
- Activity
- LinearLayout
- RelativeLayout
- TextView
- Button
- EditText
- RadioButton
- CheckBox
- ImageView
- ListView
- GridView
- ScrollView&HorizontalScrollView
- WebView
- Toast
- AlertDialog
- ProgressBar&ProgressDialogue
- PopuppWindow
- Activity
- Fragment
- Handler
- Android Storage
- SharedPreferences
- InternalStorage
- ExternalStorage
- BroadCast
- ValueAnimator
Introduce
Android是Google开发的操作系统，是移动应用开发的表现之一
项目流程：Android <–> 接口 <–> 数据库
开发工具Android Studio，利用JAVA语言，因此需要JDK
Project
新建一个项目，依次展开文件夹
JAVA文件AndroidLearn\app\src\main\java\com.example.androidlearn
资源和样式文件AndroidLearn\app\src\main\res\drawable
布局文件AndroidLearn\app\src\main\res\layout
Manifest文件AndroidLearn\app\src\main\AndroidManifest.xml
gradle配置文件AndroidLearn\app\build.gradle
Activity
每一个界面可以看成一个Activity，新建一个Empty Activity作为MainActivity
每一个Activity需要对应的布局文件
public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); }}<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity">LinearLayout>此时可运行该程序，为空白界面
LinearLayout
利用线性布局，可绘制一些图案
对于线性布局，设置方向是必须的
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".LinearLayout"> <LinearLayout android:id="@+id/ll_ll_1" android:layout_width="200dp" android:layout_height="200dp" android:orientation="vertical" android:background="#000000" android:paddingLeft="20dp" android:paddingRight="10dp" android:paddingTop="10dp" android:paddingBottom="10dp"> <View android:layout_width="match_parent" android:layout_height="match_parent" android:background="#FF0033"/> LinearLayout> <LinearLayout android:layout_width="match_parent" android:layout_height="200dp" android:orientation="horizontal" android:background="#0066FF" android:layout_marginTop="10dp" android:layout_marginLeft="15dp" android:layout_marginRight="15dp"> <View android:layout_width="50dp" android:layout_height="match_parent" android:background="#FFFFFF" android:layout_weight="1"/> <View android:layout_width="0dp" android:layout_height="match_parent" android:background="#000000" android:layout_weight="1"/> <View android:layout_width="20dp" android:layout_height="match_parent" android:background="#55AA99" android:layout_weight="1"/> LinearLayout>LinearLayout>RelativeLayout
<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".RelativeLayout"> <View android:layout_width="100dp" android:layout_height="100dp" android:background="#000000" android:layout_alignParentBottom="true" android:layout_alignParentRight="true"/> <View android:id="@+id/rl_view_1" android:layout_width="100dp" android:layout_height="100dp" android:background="#000000"/> <View android:id="@+id/rl_view_2" android:layout_width="100dp" android:layout_height="100dp" android:background="#FF0033" android:layout_toRightOf="@id/rl_view_1" android:layout_below="@id/rl_view_1"/> <LinearLayout android:layout_width="match_parent" android:layout_height="200dp" android:layout_below="@id/rl_view_2" android:orientation="horizontal" android:background="#0066FF" android:padding="15dp"> <View android:layout_width="100dp" android:layout_height="match_parent" android:background="#FF0033"/> <RelativeLayout android:layout_width="match_parent" android:layout_height="match_parent" android:background="#000000" android:padding="15dp"> <View android:id="@+id/rl_view_3" android:layout_width="100dp" android:layout_height="match_parent" android:background="#FF9900"/> <View android:layout_width="100dp" android:layout_height="match_parent" android:background="#FFFFFF" android:layout_toRightOf="@id/rl_view_3" android:layout_marginLeft="10dp"/> RelativeLayout> LinearLayout>RelativeLayout>TextView
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".TextView"> <TextView android:id="@+id/tv_tv_1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="hello" android:textColor="#000000" android:textSize="34sp"/> <TextView android:id="@+id/tv_tv_2" android:layout_width="100dp" android:layout_height="wrap_content" android:maxLines="1" android:ellipsize="end" android:text="hello world" android:textColor="#000000" android:textSize="34sp" /> <TextView android:id="@+id/tv_tv_3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="choose" android:textColor="#000000" android:textSize="34sp" android:drawableRight="@drawable/choose" android:drawablePadding="5dp" /> <TextView android:id="@+id/tv_tv_4" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="choose" android:textColor="#000000" android:textSize="34sp" android:drawableRight="@drawable/choose" android:drawablePadding="5dp" />LinearLayout>public class TextViewActivity extends AppCompatActivity { private TextView textView1; private TextView textView2; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_text_view); textView1 = (TextView)findViewById(R.id.tv_tv_3);//找到对应的控件，并复制 textView1.getPaint().setFlags(Paint.STRIKE_THRU_TEXT_FLAG);//中划线 textView1.getPaint().setAntiAlias(true); textView2 = (TextView)findViewById(R.id.tv_tv_4); textView2.getPaint().setFlags(Paint.UNDERLINE_TEXT_FLAG);//下划线 }}Button
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:padding="15dp" tools:context=".ButtonActivity"> <Button android:id="@+id/btn_btn_1" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Button" android:textSize="20sp" android:textColor="#FF0000" android:background="@drawable/ripple_button"/> <Button android:id="@+id/btn_btn_2" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Button" android:textSize="20sp" android:layout_marginTop="10dp" android:textColor="#000000" android:background="@drawable/button"/>LinearLayout><?xml version="1.0" encoding="utf-8"?><ripple xmlns:android="http://schemas.android.com/apk/res/android" android:color="#979292"> <item android:drawable="@drawable/shape_button"/>ripple><?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle"> <solid android:color="#FFC107"/> <corners android:radius="25dp"/>shape>设置按钮监听器
public class ButtonActivity extends AppCompatActivity { private Button button; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_button); button = (Button)findViewById(R.id.btn_btn_2); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Toast.makeText(ButtonActivity.this, "button is clicked", Toast.LENGTH_SHORT).show(); //弹出一个Toast } }); }}EditText
绘制一个登录界面
<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" tools:context=".EditViewActivity"> <EditText android:id="@+id/et_et_user" android:layout_width="match_parent" android:layout_height="50dp" android:layout_margin="15dp" android:paddingLeft="10dp" android:paddingRight="10dp" android:textSize="15sp" android:textColor="#000000" android:inputType="number" android:maxLines="1" android:background="@drawable/edit_text" android:hint="User" android:maxLength="8" android:drawableLeft="@drawable/account" android:drawablePadding="5dp"/> <EditText android:id="@+id/et_et_password" android:layout_width="match_parent" android:layout_height="50dp" android:layout_margin="15dp" android:paddingLeft="10dp" android:paddingRight="10dp" android:textSize="15sp" android:textColor="#000000" android:hint="Password" android:maxLength="16" android:inputType="textPassword" android:maxLines="1" android:background="@drawable/edit_text" android:drawableLeft="@drawable/password" android:layout_below="@id/et_et_user" android:drawablePadding="5dp"/> <Button android:id="@+id/et_btn_login" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@id/et_et_password" android:layout_marginTop="30dp" android:text="Login" android:textColor="#000000" android:textSize="20sp" android:background="@drawable/button" android:layout_marginLeft="30dp" android:layout_marginRight="30dp"/>RelativeLayout>为文本框设置圆角样式
<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"> <stroke android:width="2dp" android:color="#7E7575"/> <corners android:radius="10dp"/>shape>Java部分设置好监听器
public class EditTextActivity extends AppCompatActivity { private Button login; private EditText editText_user; private EditText editText_password; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_edit_view); login = (Button)findViewById(R.id.et_btn_login); //设置按钮监听 login.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //利用editText_user.getText()获取输入内容 Toast.makeText(EditTextActivity.this, "success", Toast.LENGTH_SHORT).show(); } }); editText_user = (EditText)findViewById(R.id.et_et_user); //文本框监听器 editText_user.addTextChangedListener(new TextWatcher() { @Override public void beforeTextChanged(CharSequence s, int start, int count, int after) { } @Override public void onTextChanged(CharSequence s, int start, int before, int count) { } @Override public void afterTextChanged(Editable s) { Toast.makeText(EditTextActivity.this, s, Toast.LENGTH_SHORT).show(); } }); editText_password = (EditText)findViewById(R.id.et_et_password);//文本框监听器 editText_password.addTextChangedListener(new TextWatcher() { @Override public void beforeTextChanged(CharSequence s, int start, int count, int after) { } @Override public void onTextChanged(CharSequence s, int start, int before, int count) { } @Override public void afterTextChanged(Editable s) { Toast.makeText(EditTextActivity.this, s, Toast.LENGTH_SHORT).show(); } }); }}RadioButton
将单个单选按钮包装实现RadioGrop
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:padding="15dp" tools:context=".RadioButtonActivity"> <RadioGroup android:id="@+id/rb_rg_switch" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal"> <RadioButton android:id="@+id/rb_rb_on" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="on" android:textSize="20sp" android:textColor="#000000"/> <RadioButton android:id="@+id/rb_rb_off" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="off" android:textSize="20sp" android:textColor="#000000" android:checked="true"/> RadioGroup> <RadioGroup android:id="@+id/rb_rg_choose" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal"> <RadioButton android:id="@+id/rb_rb_yes" android:layout_width="wrap_content" android:layout_height="wrap_content" android:paddingLeft="15dp" android:paddingRight="15dp" android:text="√" android:textSize="20sp" android:button="@null" android:background="@drawable/radio_button" android:textColor="#000000"/> <RadioButton android:id="@+id/rb_rb_no" android:layout_width="wrap_content" android:layout_height="wrap_content" android:paddingLeft="15dp" android:paddingRight="15dp" android:text="×" android:textSize="20sp" android:button="@null" android:background="@drawable/radio_button" android:textColor="#000000" android:checked="true"/> RadioGroup>LinearLayout>自定义效果
<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_checked="false"> <shape> <solid android:width="3dp" android:color="#03A9F4"/> shape> item> <item android:state_checked="true"> <shape> <solid android:color="#FF5722"/> shape> item>selector>public class RadioButtonActivity extends AppCompatActivity { private RadioGroup radioGroup; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_radio_button); radioGroup = (RadioGroup)findViewById(R.id.rb_rg_choose); //设置当选择结果改变时的监听 radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() { @Override public void onCheckedChanged(RadioGroup group, int checkedId) { //在所监听的Group中，找到当前所选的Id的Text RadioButton radioButton = (RadioButton)group.findViewById(checkedId); Toast.makeText(RadioButtonActivity.this, radioButton.getText(), Toast.LENGTH_SHORT).show(); } }); }}CheckBox
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".CheckBoxActivity"> <CheckBox android:id="@+id/cb_cb_android" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Android Development"/> <CheckBox android:id="@+id/cb_cb_IOS" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="IOS"/> <CheckBox android:id="@+id/cb_cb_mac" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="MAC" android:paddingLeft="20dp" android:button="@drawable/check_box"/> <CheckBox android:id="@+id/cb_cb_windows" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="WINDOWS" android:padding="20dp" android:button="@drawable/check_box"/>/>LinearLayout>当然也可以自定义button的样式
<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_checked="true" android:drawable="@drawable/checkedbox"/> <item android:state_checked="false" android:drawable="@drawable/uncheckedbox"/>selector>public class CheckBoxActivity extends AppCompatActivity { private CheckBox ios; private CheckBox android; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_check_box); ios = (CheckBox)findViewById(R.id.cb_cb_android); android = (CheckBox)findViewById(R.id.cb_cb_IOS); //设置监听器，当选择项改变时获取选中状态 ios.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { @Override public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { Toast.makeText(CheckBoxActivity.this, isChecked?"yes":"no", Toast.LENGTH_SHORT).show(); } }); android.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { @Override public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { Toast.makeText(CheckBoxActivity.this, isChecked?"yes":"no", Toast.LENGTH_SHORT).show(); } }); }}ImageView
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".ImageViewActivity"> <ImageView android:layout_width="300dp" android:layout_height="200dp" android:background="#972F2F" android:src="@drawable/image" android:scaleType="center"/> <ImageView android:id="@+id/iv_iv_internet" android:layout_width="300dp" android:layout_height="200dp" android:background="#A39696" android:layout_marginTop="10dp" android:scaleType="fitXY"/>LinearLayout>public class ImageViewActivity extends AppCompatActivity { private ImageView inetPic; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_image_view); inetPic = (ImageView)findViewById(R.id.iv_iv_internet); loadImage(); } //通过开源库实现加载网络图片 public void loadImage() { Glide.with(this).load("").into(inetPic); }}此时需要在Manifest中声明网络请求权限
<uses-permission android:name="android.permission.INTERNET" />并借助gradle下载依赖包
repositories { google() jcenter()}dependencies { implementation 'com.github.bumptech.glide:glide:4.11.0' implementation 'org.jetbrains:annotations-java5:15.0' annotationProcessor 'com.github.bumptech.glide:compiler:4.11.0'}ListView
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".ListViewActivity"> <ListView android:id="@+id/lv_lv_testLv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:listSelector="@drawable/list_view_item"/>LinearLayout>设置对每一项不同触摸操作时的不同效果
<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_selected="true" android:drawable="@color/colorGrey"/> <item android:state_pressed="true" android:drawable="@color/colorGrey"/> <item android:state_focused="true" android:drawable="@color/colorGrey"/> <item android:drawable="@color/colorWhite"/>selector>public class ListViewActivity extends AppCompatActivity { private ListView listView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_list_view); listView = (ListView)findViewById(R.id.lv_lv_testLv); //给ListView设置适配器 listView.setAdapter(new ListAdapter(ListViewActivity.this)); //设置每一个item的监听 listView.setOnItemClickListener(new AdapterView.OnItemClickListener(){ @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Toast.makeText(ListViewActivity.this, "click"+position, Toast.LENGTH_SHORT).show(); } }); listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener(){ @Override public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) { Toast.makeText(ListViewActivity.this, "longClick"+position, Toast.LENGTH_SHORT).show(); return true; } }); }}class ListAdapter extends BaseAdapter{ private Context context; private LayoutInflater layoutInflater; ListAdapter(Context context){ this.context = context; layoutInflater = LayoutInflater.from(context); } @Override public int getCount() { return 10;} @Override public Object getItem(int position) { return null;} @Override public long getItemId(int position) { return 0;} //设置每一个item的样式 static class ViewHolder{ public ImageView imageView1; public ImageView imageView2; public TextView textView; } @Override public View getView(int position, View convertView, ViewGroup parent) { //此时可以为每一个item设置样式，可以把它们放在集合框架中 ViewHolder viewHolder = null; if(convertView == null){ convertView = layoutInflater.inflate(R.layout.listview_item,null); viewHolder = new ViewHolder(); viewHolder.imageView1 = convertView.findViewById(R.id.lvitm_iv_iv1); viewHolder.imageView2 = convertView.findViewById(R.id.lvitm_iv_iv2); viewHolder.textView = convertView.findViewById(R.id.lvitm_tv_test); convertView.setTag(viewHolder); }else{ viewHolder = (ViewHolder)convertView.getTag(); } Glide.with(context).load("").into(viewHolder.imageView2); viewHolder.textView.setText("this is test"+position); return convertView; }}每一个item的样式
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" android:padding="15dp"> <ImageView android:id="@+id/lvitm_iv_iv1" android:layout_width="100dp" android:layout_height="100dp" android:background="#000000"/> <ImageView android:id="@+id/lvitm_iv_iv2" android:layout_marginLeft="20dp" android:layout_marginRight="20dp" android:layout_width="100dp" android:layout_height="100dp" android:background="#9A5050" /> <TextView android:id="@+id/lvitm_tv_test" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="test" android:textSize="50sp" android:textColor="@color/colorRed"/>LinearLayout>GridView
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".GridViewActivity"> <GridView android:id="@+id/gv_gv_gvTest" android:layout_width="wrap_content" android:layout_height="wrap_content" android:numColumns="3" android:horizontalSpacing="10dp"/>LinearLayout>和listView一样，每一个item也通过适配器来实现
public class GridViewActivity extends AppCompatActivity { private GridView gridView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_grid_view); gridView = (GridView)findViewById(R.id.gv_gv_gvTest); //setAdapter gridView.setAdapter(new GridViewAdapter(GridViewActivity.this)); //设置监听 gridView.setOnItemClickListener(new AdapterView.OnItemClickListener(){ @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Toast.makeText(GridViewActivity.this, "click"+position, Toast.LENGTH_SHORT).show(); } }); gridView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener(){ @Override public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) { Toast.makeText(GridViewActivity.this, "longClick"+position, Toast.LENGTH_SHORT).show(); return true; } }); }}class GridViewAdapter extends BaseAdapter{ private Context context; private LayoutInflater layoutInflater; GridViewAdapter(Context context){ this.context = context; layoutInflater = LayoutInflater.from(context); } @Override public int getCount() { return 10;} @Override public Object getItem(int position) { return null;} @Override public long getItemId(int position) { return 0;} static class ViewHolder{ public ImageView imageView; public TextView textView; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder viewHolder; if(convertView == null){ convertView = layoutInflater.inflate(R.layout.gridview_item,null); viewHolder = new ViewHolder(); viewHolder.imageView = (ImageView) convertView.findViewById(R.id.gvitm_iv_test); viewHolder.textView = (TextView) convertView.findViewById(R.id.gvitm_tv_test); convertView.setTag(viewHolder); }else{ viewHolder = (ViewHolder) convertView.getTag(); } viewHolder.textView.setText("hello"); Glide.with(context).load("").into(viewHolder.imageView); return convertView; }}同样的，为每一个item绘制布局
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:padding="15dp"> <ImageView android:id="@+id/gvitm_iv_test" android:layout_width="100dp" android:layout_height="100dp" android:background="@color/colorGrey"/> <TextView android:id="@+id/gvitm_tv_test" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:text="test" android:textSize="50sp" android:textColor="@color/colorRed"/>LinearLayout>ScrollView&HorizontalScrollView
其直接的子控件只能有一个
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <Button android:id="@+id/ma_btn_es" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="ExternalStorage" android:textAllCaps="false"/> <Button android:id="@+id/ma_btn_bc" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="BroadCast" android:textAllCaps="false"/> <Button android:id="@+id/ma_btn_va" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="ValueAnimator" android:textAllCaps="false"/> LinearLayout>ScrollView><?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".ScrollViewActivity"> <HorizontalScrollView android:layout_width="match_parent" android:layout_height="wrap_content"> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal"> <ImageView android:layout_width="300dp" android:layout_height="100dp" android:background="@color/colorGrey"/> <ImageView android:layout_width="300dp" android:layout_height="100dp" android:background="@color/colorRed"/> LinearLayout> HorizontalScrollView>LinearLayout>WebView
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".WebViewActivity"> <WebView android:id="@+id/wv_wv_wv" android:layout_width="match_parent" android:layout_height="match_parent"/>LinearLayout>public class WebViewActivity extends AppCompatActivity { private WebView webView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_web_view); webView = (WebView)findViewById(R.id.wv_wv_wv); //加载本地html文件 //webView.loadUrl("file:///android_asset/test.html"); //加载网页 //启用javaScript webView.getSettings().setJavaScriptEnabled(true); //禁用跳转本地浏览器 webView.setWebViewClient(new WebViewClient(){ @Override public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) { view.loadUrl(request.getUrl().toString()); return true; } @Override public void onPageStarted(WebView view, String url, Bitmap favicon) { super.onPageStarted(view, url, favicon); } @Override public void onPageFinished(WebView view, String url) { super.onPageFinished(view, url); } }); //实现进度条和获得网页title(继承WebChromeClient) webView.setWebChromeClient(new WebChromeClient(){ @Override public void onProgressChanged(WebView view, int newProgress) { //newProgress是0-100之间，可以实现加载百分比 super.onProgressChanged(view, newProgress); } @Override public void onReceivedTitle(WebView view, String title) { //将网页标题设置为activity的标题 setTitle(title); super.onReceivedTitle(view, title); } }); webView.loadUrl("https://m.baidu.com"); } @Override //实现返回键用于返回上一个网页界面，而非返回上一个应用界面 //重写返回方法 public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK && webView.canGoBack()) { webView.goBack(); return true; } return super.onKeyDown(keyCode, event); }}Toast
private Button btn1; private Button btn2; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_toast); btn1 = (Button) findViewById(R.id.tst_btn_test1); btn2 = (Button) findViewById(R.id.tst_btn_test2); clickListener clickListener = new clickListener(); btn1.setOnClickListener(clickListener); btn2.setOnClickListener(clickListener); } class clickListener implements View.OnClickListener{ @Override public void onClick(View v) { switch(v.getId()){ case R.id.tst_btn_test1: //在默认位置弹出Toast Toast.makeText(ToastActivity.this, "toast", Toast.LENGTH_SHORT).show(); break; case R.id.tst_btn_test2: //在自定义位置弹出Toast Toast toast = Toast.makeText(getApplicationContext(),"toastTest",Toast.LENGTH_LONG); toast.setGravity(Gravity.CENTER,0,0); toast.show(); break; } } }AlertDialog
AlertDialog.Builder builder = new AlertDialog.Builder(AlertDialogActivity.this);builder.setTitle("title");builder.setMessage("test");builder.setPositiveButton("pos", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(AlertDialogActivity.this, "ok", Toast.LENGTH_SHORT).show(); }});builder.setNeutralButton("neu", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(AlertDialogActivity.this, "emmm...", Toast.LENGTH_SHORT).show(); }});builder.setNegativeButton("nea", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(AlertDialogActivity.this, "no", Toast.LENGTH_SHORT).show(); }});builder.show();String[] strings = new String[]{ "1","2","3"};AlertDialog.Builder builder = new AlertDialog.Builder(AlertDialogActivity.this);builder.setTitle("title");//内容以字符串数组形式给出builder.setItems(strings, new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(AlertDialogActivity.this, ""+which, Toast.LENGTH_SHORT).show(); }});builder.show();AlertDialog.Builder builder = new AlertDialog.Builder(AlertDialogActivity.this);builder.setTitle("login");//AlertDialog布局由R.layout.alert_dialog_item给出View view = LayoutInflater.from(AlertDialogActivity.this).inflate(R.layout.alert_dialog_item, null);EditText user = (EditText) findViewById(R.id.et_et_user);EditText pw = (EditText)findViewById(R.id.et_et_password);//Todo About EditText ActionListenerbuilder.setView(view);//设置点击监听器builder.setPositiveButton("login", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(AlertDialogActivity.this, "success", Toast.LENGTH_SHORT).show(); dialog.dismiss(); }});//设置不可点击其他区域取消builder.setCancelable(false);builder.show();String[] strings = new String[]{ "1", "2", "3"};boolean[] booleans = new boolean[]{ true, false, true};AlertDialog.Builder builder = new AlertDialog.Builder(AlertDialogActivity.this);builder.setTitle("title");//设置监听事件builder.setMultiChoiceItems(strings, booleans, new DialogInterface.OnMultiChoiceClickListener() { @Override public void onClick(DialogInterface dialog, int which, boolean isChecked) { Toast.makeText(AlertDialogActivity.this, ""+which+isChecked, Toast.LENGTH_SHORT).show(); }});builder.setPositiveButton("yes", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(AlertDialogActivity.this, ""+which, Toast.LENGTH_SHORT).show(); }});builder.show();ProgressBar&ProgressDialogue
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".ProgressBarActivity"> <ProgressBar android:id="@+id/pb_pb_pb1" android:layout_width="match_parent" android:layout_height="wrap_content"/> <ProgressBar android:id="@+id/pb_pb_pb2" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="10dp" style="@style/Widget.AppCompat.ProgressBar.Horizontal" android:max="100"/> LinearLayout>在java中设置进度信息
private ProgressBar progressBar;//-------------------------------------------progressBar = (ProgressBar)findViewById(R.id.pb_pb_pb2);handler.sendEmptyMessage(0);//-------------------------------------------Handler handler = new Handler(){ @Override public void handleMessage(@NonNull Message msg) { super.handleMessage(msg); if(progressBar.getProgress()<100){ handler.postDelayed(runnable,50); }else{ progressBar.setVisibility(View.GONE); Toast.makeText(ProgressBarActivity.this, "finish", Toast.LENGTH_SHORT).show(); } }};Runnable runnable = new Runnable() { @Override public void run() { progressBar.setProgress(progressBar.getProgress()+1); handler.sendEmptyMessage(0); }};private ProgressDialog progressDialog;//-------------------------------------------progressDialog = new ProgressDialog(ProgressBarActivity.this);progressDialog.setTitle("waiting");progressDialog.setMessage("connecting");progressDialog.setOnDismissListener(new DialogInterface.OnDismissListener(){ @Override public void onDismiss(DialogInterface dialog) { Toast.makeText(ProgressBarActivity.this, "cancel", Toast.LENGTH_SHORT).show(); }});progressDialog.setCancelable(false);progressDialog.show();//progressDialog.dismiss()用于结束progressDialoguePopuppWindow
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@color/colorGrey" android:orientation="vertical"> <TextView android:id="@+id/pw_tv_ok" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="ok" android:layout_margin="10dp" android:gravity="center"/> <View android:layout_width="match_parent" android:layout_height="0.5dp"/> <TextView android:id="@+id/pw_tv_no" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="no" android:layout_margin="10dp" android:gravity="center"/> <View android:layout_width="match_parent" android:layout_height="0.5dp"/> <TextView android:id="@+id/pw_tv_emmm" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="emmm" android:layout_margin="10dp" android:gravity="center"/>LinearLayout>public class PopupWindowActivity extends AppCompatActivity { private Button button; private PopupWindow popupWindow; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_popup_window); button = (Button)findViewById(R.id.pw_btn_pw); button.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View v) { //为PopuppWindow中的每一条文本和界面布局做出声明 View view = getLayoutInflater().inflate(R.layout.popupwindow_item,null); TextView textView1 = (TextView)view.findViewById(R.id.pw_tv_ok); TextView textView2 = (TextView)view.findViewById(R.id.pw_tv_emmm); TextView textView3 = (TextView)view.findViewById(R.id.pw_tv_no); //可以依次为每一个文本设置监听 textView1.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { popupWindow.dismiss(); Toast.makeText(PopupWindowActivity.this, "ok is your choice", Toast.LENGTH_SHORT).show(); } }); //创建一个PopuppWindow，传入view popupWindow = new PopupWindow(view,button.getWidth(), ViewGroup.LayoutParams.WRAP_CONTENT); //设置PopuppWindow可以通过触摸空白区域和点击按钮关闭 popupWindow.setOutsideTouchable(true); popupWindow.setFocusable(true); popupWindow.showAsDropDown(button); } }); }}Activity
每一个Activity都有自己的生命周期，在不同生命周期调用不同的方法
每一个Activity都因该在Manifest中做出声明
<application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".ValueAnimatorActivity">activity> <activity android:name=".BroadCastBActivity" /> <activity android:name=".BroadCastActivity" /> <activity android:name=".ExternalStorageActivity" android:requestLegacyExternalStorage="true" /> <activity android:name=".InternalStorageActivity" /> <activity android:name=".SharedPreferencesActivity" /> <activity android:name=".HandlerActivity" /> <activity android:name=".ContainerActivity" /> <activity android:name=".ActivityJumpActivity" android:label="JumpActivity" /> <activity android:name=".ActivityActivity" android:label="activity" android:launchMode="standard" android:screenOrientation="portrait" android:theme="@style/Theme.AppCompat.Light.NoActionBar" /> <activity android:name=".MainActivity" android:label="Activity"/> <activity android:name=".StartActivity" android:theme="@style/Theme.AppCompat.Light.NoActionBar"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> intent-filter> activity> application>可以设置一个启动页
protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN); setContentView(R.layout.activity_start); new Thread(){ //创建子线程，在2秒后实现跳转 @Override public void run() { try{ sleep(2000); Intent it=new Intent(StartActivity.this,MainActivity.class); startActivity(it); finish(); }catch (Exception e){ e.printStackTrace(); } } }.start();}Activity之间的信息传递
//显示跳转Intent intent = new Intent(ActivityActivity.this,ActivityJumpActivity.class);//发送bundleBundle data = new Bundle();data.putString("Username","Username");intent.putExtras(data);startActivity(intent);//在onCreate中获取bundleBundle data = getIntent().getExtras();String s = data.getString("Username");除了重写最常用的onCreate方法，根据需要重写该界面进入不同状态时所调用的方法
@Overrideprotected void onStart() { super.onStart(); //打印日志信息 Log.d("Activity","onStart");}@Override//用于每次进入的刷新protected void onResume() { super.onResume(); Log.d("Activity","onResume");}@Override//退出会暂停，此时调用protected void onPause() { super.onPause(); Log.d("Activity","onPause");}@Overrideprotected void onStop() { super.onStop(); Log.d("Activity","onStop");}@Overrideprotected void onRestart() { super.onRestart(); Log.d("Activity","onRestart");}@Override//摧毁时调用protected void onDestroy() { super.onDestroy(); Log.d("Activity","onDestroy");}Fragment
Fragment有自己的生命周期，Fragment依赖于Activity，Fragment通过getActivity()可以获取所在的Activity；Activity通过FragmentManger的findFragmentById()获取Fragment，Fragment依赖于Activity，它们是多对多的关系
点击按钮触发事件，更换一个Fragment
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".ContainerActivity"> <Button android:id="@+id/ctn_btn_change" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="change"/> <FrameLayout android:id="@+id/ctn_flt_flt" android:layout_width="match_parent" android:layout_height="match_parent"/>LinearLayout>public class ContainerActivity extends AppCompatActivity { private Fragment fragment; private Fragment bFragment; private Button button; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_container); //实例化 fragment = new AFragment(); button = (Button)findViewById(R.id.ctn_btn_change); //点击事件 button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if(bFragment == null){ bFragment = new BFragment(); } getSupportFragmentManager().beginTransaction().replace(R.id.ctn_flt_flt,bFragment).commitAllowingStateLoss(); } }); //添加到指定的fragment，并调用commit方法 getSupportFragmentManager().beginTransaction().add(R.id.ctn_flt_flt,fragment).commitAllowingStateLoss(); } @Override protected void onDestroy() { super.onDestroy(); //取消异步，处理fragment中的还在运行的线程等 }}fragment也需要一个布局文件
public class AFragment extends Fragment { private TextView textView; //给它一个布局文件 @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { View view = inflater.inflate(R.layout.a_fragment_item,container,false); return view; } @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); textView = (TextView)view.findViewById(R.id.aft_tv_test); //操作所在的Activity if(getActivity() != null){ //Todo something about activity } } //当fragment与Activity建立联系的时候，此方法被调用 @Override public void onAttach(@NonNull Context context) { super.onAttach(context); } //当fragment被destroy或与Activity失去联系的时候，此方法被调用 @Override public void onDetach() { super.onDetach(); }}Fragment回退栈
//在替换之前放到回退栈中，这样以便按返回键返回上一个fragment，而不是上一个ActivitygetSupportFragmentManager().beginTransaction().replace(R.id.ctn_flt_flt,bFragment).addToBackStack(null).commitAllowingStateLoss();当然，返回时onCreateView会被调用，即使是同一个实例，那么就会造成对fragment中文字内容的更改后，再返回则回到默认的样式
//这是因为replace可以看成remove和add两个动作的叠加getSupportFragmentManager().beginTransaction().replace(R.id.ctn_flt_flt,bFragment).addToBackStack(null).commitAllowingStateLoss();如果在add一个fragment时候加一个tag
getSupportFragmentManager().beginTransaction().add(R.id.ctn_flt_flt,fragment).commitAllowingStateLoss();然后在更换为BFragment的时候隐藏fragment，再创建新的fragment，并加入回退栈
if(bFragment == null){ bFragment = new BFragment();}//寻找是否有tag的fragmentFragment fragment = getFragmentManager().findFragmentByTag("a");if(fragment != null){ //如果有tag标记的fragment，就隐藏当前fragment，添加bfragment getFragmentManager().beginTransaction().hide(fragment).add(R.id.fl_container,bFragment).addToBackStack(null).commitAllowingStateLoss();} else { //否则就直接replace getFragmentManager().beginTransaction().replace(R.id.fl_container,bFragment).addToBackStack(null).commitAllowingStateLoss();}可以在fragment中getActivity来获取所在的Activity，来实现消息传递
而推荐的fragment与Activity之间的消息传递
//在fragment中声明一个接口public interface Message{ void onClick(String text);}该接口在Activity中被实现
public class ContainerActivity extends AppCompatActivity implements AFragment.Message{ //...... @Override public void onClick(String text) { mTvTitle.setText(text); } //......}在fragment的onAttach方法中赋值，以获取所在的Activity
private Message listener;//.....@Overridepublic void onAttach(Context context) { super.onAttach(context); try { listener = (Message) context; }catch (ClassCastException e){ //没有实现抛出异常 throw new ClassCastException("Activity must implements Message interface"); }}那么现在在fragment中可以调用在Activity中实现接口的方法实现信息传递了
listener.onClick("msg");Handler
private Handler handler;@Overrideprotected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_handler); { //应用1：延时一段时间来处理某事 Handler handler = new Handler(); //延时Millis执行某个线程 handler.postDelayed(new Runnable() { @Override public void run() { //finish(); } }, 1000); } //应用2：线程通信，等待收到消息后，处理某事 handler = new Handler(){ @Override public void handleMessage(Message msg) { super.handleMessage(msg); //等待接收msg，接收后进行处理 if(msg.what == 1){ Toast.makeText(HandlerActivity.this, "got msg", Toast.LENGTH_SHORT).show(); } } }; //创建了一个线程，给主线程发送一个msg new Thread(){ @Override public void run() { super.run(); Message message = new Message(); message.what = 1; handler.sendMessage(message); } }.start();}Android Storage
内部存储（Internal Storage） 外部存储（External Storage）
内部存储会随着应用卸载被删除
/data/data//shared_prefs
/data/data//databases
/data/data//file
上述都是通过类方法来操作
外部存储有公有目录（Download等）和私有目录（Android文件下的文件）
共有目录可以通过类方法来获取
私有目录
/mnt/sdcard/data/data//cache
/mnt/sdcard/data/data//files
会随着应用程序的卸载而删除，当然你可以自行在sdcard下创建目录，该目录不会随着应用的卸载而删除
SharedPreferences
private SharedPreferences sharedPreferences;private SharedPreferences.Editor editor;//MODE_PRIVATE表示该数据为该程序私有sharedPreferences = this.getSharedPreferences("data",MODE_PRIVATE);editor = sharedPreferences.edit();//写使用editor的方法editor.putString("user","Jack");editor.apply();//Apply是异步存储//读取时，数据在磁盘上不一定已经生效，但立即读取不受影响，因为它会从内存中读取sharedPreferences.getString("user","")InternalStorage
final private String file = "test.txt";//以读写字符串为例//save file private void save(String content) { FileOutputStream fileOutputStream = null; try { fileOutputStream = openFileOutput(file,MODE_PRIVATE); fileOutputStream.write(content.getBytes()); } catch (IOException e) { } finally { try { if(fileOutputStream != null){ fileOutputStream.close(); } } catch (IOException e) { } } } //read file private String read(){ FileInputStream fileInputStream = null; try { fileInputStream = openFileInput(file); //每次最多读1024个字节 byte[] buf = new byte[1024]; StringBuilder stringBuilder = new StringBuilder(""); int len = 0; while((len = fileInputStream.read(buf))>0){ stringBuilder.append(new String(buf,0,len)); } return stringBuilder.toString(); } catch (IOException e) { } finally { try { if(fileInputStream != null){ fileInputStream.close(); } } catch (IOException e) { } } return null; }ExternalStorage
外部存储的读写需要访问权限
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /><uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" tools:ignore="ProtectedPermissions" />需要在使用的界面动态申请，如
ActivityCompat.requestPermissions(this,new String[]{ Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.READ_EXTERNAL_STORAGE},2);依然以读写文本文件为例
final private String fileName = "test.txt";//save file private void save(String content) { FileOutputStream fileOutputStream = null; String sdStatus = Environment.getExternalStorageState(); if (!sdStatus.equals(Environment.MEDIA_MOUNTED)) { // 检测sd是否可用 Toast.makeText(this, "sdcard error!", Toast.LENGTH_SHORT).show(); return; } try { //文件夹 File dir = new File(getExternalFilesDir(null),"sky"); if(!dir.exists()){ boolean jg = dir.mkdirs(); Log.d("dir",""+jg); } //文件 File file = new File(dir,fileName); if(!file.exists()){ boolean jg = file.createNewFile(); Log.d("mkFile",""+jg); } //写入 fileOutputStream = new FileOutputStream(file); fileOutputStream.write(content.getBytes()); } catch (IOException e) { e.printStackTrace(); } finally { try { if(fileOutputStream != null){ fileOutputStream.close(); } } catch (IOException e) { e.printStackTrace(); } } } //read file private String read(){ FileInputStream fileInputStream = null; try { //寻找文件 File file = new File(getExternalFilesDir(null).getAbsolutePath()+File.separator+"sky",fileName); fileInputStream = new FileInputStream(file); //读取文件，每次最多读1024个字节 byte[] buf = new byte[1024]; StringBuilder stringBuilder = new StringBuilder(""); int len = 0; while((len = fileInputStream.read(buf))>0){ stringBuilder.append(new String(buf,0,len)); } return stringBuilder.toString(); } catch (IOException e) { e.printStackTrace(); } finally { try { if(fileInputStream != null){ fileInputStream.close(); } } catch (IOException e) { e.printStackTrace(); } } return null; }BroadCast
添加依赖包
dependencies { implementation 'androidx.localbroadcastmanager:localbroadcastmanager:1.0.0'}当一个界面需要发送广播时
private BroadCast broadCast;//说明要发送的intentIntentFilter intentFilter = new IntentFilter();intentFilter.addAction("com.bc.modifyText");//注册广播LocalBroadcastManager.getInstance(this).registerReceiver(broadCast,intentFiler);相应的，因该重写onDestroy方法，来取消注册广播
@Overrideprotected void onDestroy() { super.onDestroy(); //destroy该页面后取消注册的广播 LocalBroadcastManager.getInstance(this).unregisterReceiver(broadCast);}在其他类中可以接受该广播，并处理
@Override//重写接收方法public void onReceive(Context context, Intent intent) { switch (intent.getAction()){ case "com.bc.modifyText": //textView.setText("Text is changed"); break; }}ValueAnimator
private TextView textView;//将textView沿y轴移动500，在2000ms内textView.animate().translationYBy(100).setDuration(2000).start();//渐变到消失textView.animate().alpha(0).setDuration(2000);//ValueAnimatorValueAnimator valueAnimator = ValueAnimator.ofInt(0,100);valueAnimator.setDuration(2000);valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { //实际值，0~100 int s = (int) animation.getAnimatedValue(); textView.setTextSize(s); //动画进度，0~1.0 animation.getAnimatedFraction(); }});valueAnimator.start();//依次沿y轴移动100，0，100，0ObjectAnimator objectAnimator = ObjectAnimator.ofFloat(textView,"translationY",100,0,100,0);objectAnimator.setDuration(2000);objectAnimator.start();更多相关文章
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