android--(布局ListView、优化、刷新分页、ArrayAdapter、SimpleAdapter 、BaseAdapter)

ListView组件：

列表视图是Android 中最为常用的一种视图组件，它以垂直列表的方式列出
需要显示的列表项，例如:显示联系人名单、系统设置项等，都用到了ListView组件

public class MainActivity extends Activity {    private ListView listView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);         listView = (ListView) findViewById(R.id.listView);    //当单击item时的监听事件        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {            @Override            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {                //获取点击的文本组件                TextView tv = (TextView) view;                Toast.makeText(MainActivity.this,"view="+tv.getText().toString(),Toast.LENGTH_SHORT).show();            }        });    }

列表数据资源文件：

arrays.xml:------------------------------------------------------------<?xml version="1.0" encoding="utf-8"?><resources>    <array name="name">        <item>张建斌item>        <item>冰冰item>        <item>小李子item>        <item>非非item>        <item>张建斌item>        <item>冰冰item>        <item>小李子item>        <item>非非item>    array>resources>

//使用代码来实现listViewpublic class list2 extends ListActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);//R.array.name：定义好的资源//利用系统的listView视图        ArrayAdapter arrayAdapter = ArrayAdapter.createFromResource(this,                R.array.name,android.R.layout.simple_list_item_1);        //设置视配器        setListAdapter(arrayAdapter);    }//每一项的单击处理事件：  @Override    protected void onListItemClick(ListView l, View v, int position, long id) {        super.onListItemClick(l, v, position, id);        Toast.makeText(this,((TextView)v).getText().toString(),Toast.LENGTH_SHORT).show();    }}

列表数据的单选和多选模式

public class list3 extends Activity {    private ListView listView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_list3);        listView = (ListView) findViewById(R.id.listView2);//资源xml        String[] arr = getResources().getStringArray(R.array.name);        //是单选模式        ArrayAdapter aa = new ArrayAdapter(this,android.R.layout.simple_list_item_single_choice,arr);        listView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);        //多选模式       // ArrayAdapter aa1 = new ArrayAdapter(this,android.R.layout.simple_list_item_multiple_choice,arr);        //listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);        listView.setAdapter(aa);    }

ListView实现图文列表

1.创建两个activity一个主，另一个为item的布局例：item布局，  "wrap_content"        android:layout_height="wrap_content"        android:id="@+id/imageView_icon"        android:src="@drawable/ic_launcher"     />    "wrap_content"        android:layout_height="wrap_content"        android:text="New Text"        android:id="@+id/textView_text"        android:layout_marginLeft="60dp"     />  主：     "wrap_content"        android:layout_height="wrap_content"        android:id="@+id/listView3"        android:layout_alignParentTop="true"        android:layout_alignParentEnd="true"        android:layout_marginEnd="98dp"        />2.在主activity中代码：public class list4 extends Activity {    private ListView listView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_list4);        listView = (ListView) findViewById(R.id.listView3);        //准备数据,每个hashmap就是一条记录        HashMap title1 = new HashMap<>();        title1.put("title","title-1");        title1.put("icon",android.R.drawable.alert_light_frame);        HashMap title2 = new HashMap<>();        title2.put("title","title-2");        title2.put("icon",android.R.drawable.arrow_up_float);        HashMap title3 = new HashMap<>();        title3.put("title", "title-3");        title3.put("icon",android.R.drawable.btn_plus);        ArrayList> list = new ArrayList<>();        list.add(title1);        list.add(title2);        list.add(title3);//this:上下文//list:数据//R.layout.activity_list4_item:布局文件//开始//结束        SimpleAdapter sa = new SimpleAdapter(this,list,R.layout.activity_list4_item,new String[]{"title","icon"},new int[]{R.id.textView_text,R.id.imageView_icon});        listView.setAdapter(sa);    }

一个activity,还有一个item.xml//自定义的适配器实现public class list5 extends Activity {    private ListView listView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_list5);       listView = (ListView)findViewById(R.id.listView4);       listView.setAdapter(new MyAdapter(this));    }    static class MyAdapter extends BaseAdapter{        private Context context;        public MyAdapter(Context context){            this.context= context;        }        private String[] titles = {"title1","title2","title3","title4"};        private int[] icons = {android.R.drawable.arrow_up_float,                android.R.drawable.btn_default,                android.R.drawable.btn_dialog,                android.R.drawable.btn_radio};        @Override        public int getCount() {            return titles.length;        }        @Override        public Object getItem(int position) {            return titles[position];        }        @Override        public long getItemId(int position) {            return position;        }        @Override        public View getView(int position, View convertView, ViewGroup parent) {            LayoutInflater inflater = LayoutInflater.from(context);        //实例化布局文件            View view = inflater.inflate(R.layout.activity_list4_item, null);            TextView tv_title = (TextView) view.findViewById(R.id.textView_text);            ImageView iv_icon = (ImageView) view.findViewById(R.id.imageView_icon);            tv_title.setText(titles[position]);            iv_icon.setImageResource(icons[position]);            return view;        }    }优化：1.使用ListView的宽高固定，避免内容变化导致ListView重新渲染2.使用ConvertView 减少对象的创建3.使用ViewHolder减少对象的查找核心代码：        @Override        public View getView(int position, View convertView, ViewGroup parent) {            ViewHold vh;            if(convertView == null){                LayoutInflater inflater = LayoutInflater.from(context);                convertView = inflater.inflate(R.layout.activity_list4_item, null);                vh = new ViewHold();                vh.iv_icon = (ImageView)convertView.findViewById(R.id.imageView_icon);                vh.tv_title = (TextView)convertView.findViewById(R.id.textView_text);                //设置标志                convertView.setTag(vh);            }else {                vh = (ViewHold) convertView.getTag();            }            vh.tv_title.setText(titles[position]);            vh.iv_icon.setImageResource(icons[position]);            return convertView;        }        //内部类:用于保存每一次查找的组件，避免下次重复查找        static class ViewHold{            ImageView iv_icon;            TextView tv_title;        }    }

ListView刷新分页：1.当前Activity implements OnScrollLister2.实现接口方法3.listView注册滚动监听4.Adapter中添加数据的函数5.获得2页以后的数据后，，adpter增加数据，并刷新notifyDataSetChanged();public class list6 extends Activity implements AbsListView.OnScrollListener{    private Vector listNews = new Vector<>();    private ListView listView;    private  MyAdatper myAdatper;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_list6);       listView  = (ListView) findViewById(R.id.listView5);        //注册滚动条事件       listView.setOnScrollListener(this);        //实例化数据加载视图        View vi = getLayoutInflater().inflate(R.layout.loding, null);        listView.addFooterView(vi);        //初始化数据        initData();        //适配器        myAdatper = new MyAdatper();        listView.setAdapter(myAdatper);    }    //初始化数据    private  int index = 1;    private void initData(){        for(int i=0;i<24;i++){            News ns = new News();            ns.title = "title===="+index;            ns.content = "content===="+index;            index++;            listNews.add(ns);        }    }    //滚动状态改变    @Override    public void onScrollStateChanged(AbsListView view, int scrollState) {        //1.能显示的个数 等于滚动加载的个数        //2.滚动条停止 滚动        //myAdatper.getCount() 显示了多少条项        if(myAdatper.getCount() == vissibleLastIndex && scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE){            //开启线程            new loadDataThread().start();        }    }    private  int vissibleLastIndex = 0;//用来可显示的最后一条数据索引值    //正在滚动的方法    @Override    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {        //firstVisibleItem :第个显示的项的画索引        //visibleItemCount：可以显示几项个数        // -1 ：因为最后一个是加载项        vissibleLastIndex = firstVisibleItem+visibleItemCount-1;    }    private  static final int DATA_UPDATE = 0X1;//数据更新完成后的标记;    //线程之间通讯的机制    private Handler hander = new Handler(){        @Override        public void handleMessage(Message msg) {            //处理消息用的          switch (msg.what){              case DATA_UPDATE:                  myAdatper.notifyDataSetChanged();//视图更新通知                  break;          }        }    };    //子线程模拟加载效果    class loadDataThread extends Thread{        @Override        public void run() {            try {                initData();                Thread.sleep(2000);            } catch (InterruptedException e) {                e.printStackTrace();            }            //更新完数据，发一个标记            hander.sendEmptyMessage(DATA_UPDATE);        }    }    //自定适配器    class MyAdatper extends BaseAdapter{        @Override        public int getCount() {            return listNews.size();        }        @Override        public Object getItem(int position) {            return listNews.get(position);        }        @Override        public long getItemId(int position) {            return position;        }        @Override        public View getView(int position, View convertView, ViewGroup parent) {            ViewHolder vh;            if(convertView == null){              convertView =  getLayoutInflater().inflate(R.layout.list6_item,null);               vh = new ViewHolder();               vh.tv_title = (TextView) convertView.findViewById(R.id.title6);               vh.tv_content = (TextView) convertView.findViewById(R.id.content6);                convertView.setTag(vh);            }else {                vh = (ViewHolder) convertView.getTag();            }            News ns = listNews.get(position);            vh.tv_title.setText(ns.title);            vh.tv_content.setText(ns.content);            return convertView;        }        class  ViewHolder{            TextView tv_title;            TextView tv_content;        }    }}

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