android listview局部刷新和模拟应用下载
16lz
2021-12-04
在android开发中,listview是比较常用的一个组件,在listview的数据需要更新的时候,一般会用notifyDataSetChanged()这个函数,但是它会更新listview中所有可视范围内的item,这样对性能肯定会有影响。比较常见的情景是android应用商店中的下载列表,当我们下载一款游戏的时候,只需要更新这款游戏对应的进度就可以了。本文就来模拟android应用商店的游戏下载,实现对listview的局部刷新,只实现一个简单的demo,不去真的下载文件。
1. 首先来创建代表应用商店中的app文件的类:AppFile.java,包含了一些基本的属性,源码:
3. 接下来需要一个下载管理类:DownloadManager.java,它管理所有下载任务。当同时下载很多任务的时候,界面会卡,所以指定只能同时下载3个任务,每个任务会启动一个线程,这里使用了ExecutorService线程池。当提交了超过三个下载任务时,只执行前3个任务,第四个任务会等到前面有一个下载完成后再下载,以此类推。这里还用到了android提供的一个工具类SparseArray,它是用来替代HashMap的,性能比HashMap要好。下面看源码:
4. 接下来就需要实现listview的adapter了,这里比较重要的一个函数是updateView,这是实现listview局部刷新的关键,通过索引index得到listview中对应位置的子view,然后再更新该view的数据。源码:
布局文件listitem_app.xml:
listview中item样式文件style_listitem_background.xml:
item中的button样式文件style_btn_download.xml:
字符文件strings.xml:
5. 最后创建MainActivity.java,源码:
布局文件activity_main.xml:
1. 首先来创建代表应用商店中的app文件的类:AppFile.java,包含了一些基本的属性,源码:
package com.alexzhou.downloadfile; /** * author:alexzhou * email :zhoujiangbohai@163.com * date :2013-1-27 * * 游戏列表中的app文件 **/ public class AppFile { public int id; public String name; // app的大小 public int size; // 已下载大小 public int downloadSize; // 下载状态:正常,正在下载,暂停,等待,已下载 public int downloadState;}2. 由于实际开发时,AppFile的属性比较多,这里创建一个辅助类:DownloadFile.java,代表下载中的文件,源码:
package com.alexzhou.downloadfile; /** * author:alexzhou * email :zhoujiangbohai@163.com * date :2013-1-27 * * 下载的文件 **/ public class DownloadFile { public int downloadID; public int downloadSize; public int totalSize; public int downloadState;}
3. 接下来需要一个下载管理类:DownloadManager.java,它管理所有下载任务。当同时下载很多任务的时候,界面会卡,所以指定只能同时下载3个任务,每个任务会启动一个线程,这里使用了ExecutorService线程池。当提交了超过三个下载任务时,只执行前3个任务,第四个任务会等到前面有一个下载完成后再下载,以此类推。这里还用到了android提供的一个工具类SparseArray,它是用来替代HashMap的,性能比HashMap要好。下面看源码:
package com.alexzhou.downloadfile;import java.util.ArrayList;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import android.os.Handler;import android.os.Message;import android.util.Log;import android.util.SparseArray;/**author:alexzhou email :zhoujiangbohai@163.comdate :2013-1-27下载管理 **/public class DownloadManager {// 下载状态:正常,暂停,下载中,已下载,排队中public static final int DOWNLOAD_STATE_NORMAL = 0x00;public static final int DOWNLOAD_STATE_PAUSE = 0x01;public static final int DOWNLOAD_STATE_DOWNLOADING = 0x02;public static final int DOWNLOAD_STATE_FINISH = 0x03;public static final int DOWNLOAD_STATE_WAITING = 0x04;// SparseArray是android中替代Hashmap的类,可以提高效率private SparseArray<DownloadFile> downloadFiles = new SparseArray<DownloadFile>();// 用来管理所有下载任务private ArrayList<DownloadTask> taskList = new ArrayList<DownloadTask>();private Handler mHandler;private final static Object syncObj = new Object();private static DownloadManager instance;private ExecutorService executorService;private DownloadManager(){// 最多只能同时下载3个任务,其余的任务排队等待executorService = Executors.newFixedThreadPool(3);}public static DownloadManager getInstance(){if(null == instance){synchronized(syncObj) {instance = new DownloadManager();}return instance;}return instance;}public void setHandler(Handler handler) {this.mHandler = handler;}// 开始下载,创建一个下载线程public void startDownload(DownloadFile file) {downloadFiles.put(file.downloadID, file);DownloadTask task = new DownloadTask(file.downloadID);taskList.add(task);executorService.submit(task);}public void stopAllDownloadTask() {while(taskList.size() != 0){DownloadTask task = taskList.remove(0);// 可以在这里做其他的处理task.stopTask();}// 会停止正在进行的任务和拒绝接受新的任务executorService.shutdownNow();}// 下载任务class DownloadTask implements Runnable {private boolean isWorking = false;private int downloadId;public DownloadTask(int id){this.isWorking = true;this.downloadId = id;}public void stopTask(){this.isWorking = false;}// 更新listview中对应的itempublic void update(DownloadFile downloadFile){Message msg = mHandler.obtainMessage();if(downloadFile.totalSize == downloadFile.downloadSize)downloadFile.downloadState = DOWNLOAD_STATE_FINISH;msg.obj = downloadFile;msg.sendToTarget();}public void run() {// 更新下载文件的状态DownloadFile downloadFile = downloadFiles.get(downloadId);downloadFile.downloadState = DOWNLOAD_STATE_DOWNLOADING;while(isWorking){// 检测是否下载完成if(downloadFile.downloadState != DOWNLOAD_STATE_DOWNLOADING){downloadFiles.remove(downloadFile.downloadID);taskList.remove(this);isWorking = false;break;}//Log.e("", "downloadSize="+downloadFile.downloadSize+"; size="+downloadFile.totalSize);// 这里只是模拟了下载,每一秒更新一次item的下载状态if(downloadFile.downloadSize <= downloadFile.totalSize){this.update(downloadFile);}if(downloadFile.downloadSize < downloadFile.totalSize){try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();downloadFile.downloadState = DOWNLOAD_STATE_PAUSE;this.update(downloadFile);downloadFiles.remove(downloadId);isWorking = false;break;}++ downloadFile.downloadSize;}}}}}
4. 接下来就需要实现listview的adapter了,这里比较重要的一个函数是updateView,这是实现listview局部刷新的关键,通过索引index得到listview中对应位置的子view,然后再更新该view的数据。源码:
package com.alexzhou.downloadfile;import android.content.Context;import android.graphics.drawable.Drawable;import android.os.Handler;import android.os.Message;import android.util.Log;import android.util.SparseArray;import android.view.LayoutInflater;import android.view.View;import android.view.View.OnClickListener;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.Button;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.ListView;import android.widget.TextView;/**author:alexzhou email :zhoujiangbohai@163.comdate :2013-1-27app列表的数据适配器 **/public class AppListAdapter extends BaseAdapter {private SparseArray<AppFile> dataList = null;private LayoutInflater inflater = null;private Context mContext;private DownloadManager downloadManager;private ListView listView;public AppListAdapter(Context context, SparseArray<AppFile> dataList) {this.inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);this.dataList = dataList;this.mContext = context;this.downloadManager = DownloadManager.getInstance();this.downloadManager.setHandler(mHandler);}public void setListView(ListView view){this.listView = view;}@Overridepublic int getCount() {return dataList.size();}@Overridepublic Object getItem(int position) {return dataList.get(position);}@Overridepublic long getItemId(int position) {return position;}// 改变下载按钮的样式private void changeBtnStyle(Button btn, boolean enable){if(enable){btn.setBackgroundResource(R.drawable.btn_download_norm);}else{btn.setBackgroundResource(R.drawable.btn_download_disable);}btn.setEnabled(enable);}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {final ViewHolder holder;if (null == convertView) {holder = new ViewHolder();convertView = inflater.inflate(R.layout.listitem_app, null);holder.layout = (LinearLayout) convertView.findViewById(R.id.gamelist_item_layout);holder.icon = (ImageView) convertView.findViewById(R.id.app_icon);holder.name = (TextView) convertView.findViewById(R.id.app_name);holder.size = (TextView) convertView.findViewById(R.id.app_size);holder.btn = (Button) convertView.findViewById(R.id.download_btn);convertView.setTag(holder);} else {holder = (ViewHolder) convertView.getTag();}// 这里position和app.id的值是相等的final AppFile app = dataList.get(position);//Log.e("", "id="+app.id+", name="+app.name);holder.name.setText(app.name);holder.size.setText((app.downloadSize * 100.0f / app.size) + "%");Drawable drawable = mContext.getResources().getDrawable(R.drawable.app_icon);holder.icon.setImageDrawable(drawable);switch(app.downloadState){case DownloadManager.DOWNLOAD_STATE_NORMAL:holder.btn.setText("下载");this.changeBtnStyle(holder.btn, true);break;case DownloadManager.DOWNLOAD_STATE_DOWNLOADING:holder.btn.setText("下载中");this.changeBtnStyle(holder.btn, false);break;case DownloadManager.DOWNLOAD_STATE_FINISH:holder.btn.setText("已下载");this.changeBtnStyle(holder.btn, false);break;case DownloadManager.DOWNLOAD_STATE_WAITING:holder.btn.setText("排队中");this.changeBtnStyle(holder.btn, false);break;}holder.btn.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {DownloadFile downloadFile = new DownloadFile();downloadFile.downloadID = app.id;downloadFile.downloadState = DownloadManager.DOWNLOAD_STATE_WAITING;app.downloadState = DownloadManager.DOWNLOAD_STATE_WAITING;downloadFile.downloadSize = app.downloadSize;downloadFile.totalSize = app.size;holder.btn.setText("排队中"); changeBtnStyle(holder.btn, false);downloadManager.startDownload(downloadFile);}});return convertView;}static class ViewHolder {LinearLayout layout;ImageView icon;TextView name;TextView size;Button btn;}private Handler mHandler = new Handler() {public void handleMessage(Message msg){DownloadFile downloadFile = (DownloadFile)msg.obj;AppFile appFile = dataList.get(downloadFile.downloadID);appFile.downloadSize = downloadFile.downloadSize;appFile.downloadState = downloadFile.downloadState;// notifyDataSetChanged会执行getView函数,更新所有可视item的数据//notifyDataSetChanged();// 只更新指定item的数据,提高了性能updateView(appFile.id);}};// 更新指定item的数据private void updateView(int index){int visiblePos = listView.getFirstVisiblePosition();int offset = index - visiblePos;//Log.e("", "index="+index+"visiblePos="+visiblePos+"offset="+offset);// 只有在可见区域才更新if(offset < 0) return;View view = listView.getChildAt(offset);final AppFile app = dataList.get(index);ViewHolder holder = (ViewHolder)view.getTag();//Log.e("", "id="+app.id+", name="+app.name);holder.name.setText(app.name);holder.size.setText((app.downloadSize * 100.0f / app.size) + "%");Drawable drawable = mContext.getResources().getDrawable(R.drawable.app_icon);holder.icon.setImageDrawable(drawable);switch(app.downloadState){case DownloadManager.DOWNLOAD_STATE_DOWNLOADING:holder.btn.setText("下载中");this.changeBtnStyle(holder.btn, false);break;case DownloadManager.DOWNLOAD_STATE_FINISH:holder.btn.setText("已下载");this.changeBtnStyle(holder.btn, false);break;}}}
布局文件listitem_app.xml:
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/gamelist_item_layout" android:layout_width="fill_parent" android:layout_height="wrap_content" android:gravity="center_vertical" android:background="@drawable/style_listitem_background" android:paddingBottom="5dp" android:paddingTop="5dp" > <ImageView android:id="@+id/app_icon" android:layout_width="53dip" android:layout_height="53dip" android:layout_marginLeft="5dip" android:adjustViewBounds="false" android:padding="5dp" /> <LinearLayout android:layout_width="match_parent" android:layout_height="60dp" android:layout_marginLeft="5dp" android:layout_weight="1" android:gravity="center_vertical" android:orientation="vertical" > <TextView android:id="@+id/app_name" android:layout_width="wrap_content" android:layout_height="wrap_content" android:singleLine="true" android:text="" android:textColor="#000000" android:textSize="13sp" /> <TextView android:id="@+id/app_size" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="#000000" android:textSize="10sp" /> </LinearLayout> <Button android:id="@+id/download_btn" android:layout_width="55dip" android:layout_height="30dip" android:layout_marginRight="10dip" android:background="@drawable/style_btn_download" android:focusable="false" android:text="@string/download" android:textColor="#ffffffff" android:textSize="12sp" /> </LinearLayout>
listview中item样式文件style_listitem_background.xml:
<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android"> <!-- 没有焦点时的背景颜色 --> <item android:state_window_focused="false" > <shape> <gradient android:startColor="#ffffff" android:endColor="#E3E3E3" android:angle="-90" /> </shape> </item> <!-- 非触摸模式下获得焦点并单击时的背景颜色 --> <item android:state_focused="true" android:state_pressed="true" android:drawable="@drawable/bg_listview_item_selected" /> <!--触摸模式下单击时的背景颜色 --> <item android:state_focused="false" android:state_pressed="true" android:drawable="@drawable/bg_listview_item_selected" /> <!--选中时的背景颜色 --> <item android:state_selected="true" android:drawable="@drawable/bg_listview_item_selected" /> <!--获得焦点时的背景 颜色--> <item android:state_focused="true" android:drawable="@drawable/bg_listview_item_selected" /> </selector>
item中的button样式文件style_btn_download.xml:
<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_pressed="true" android:drawable="@drawable/btn_download_pressed" /> <item android:drawable="@drawable/btn_download_norm" /></selector>
字符文件strings.xml:
<?xml version="1.0" encoding="utf-8"?><resources> <string name="app_name">AndroidDownloadFile</string> <string name="download">下载</string></resources>
5. 最后创建MainActivity.java,源码:
package com.alexzhou.downloadfile; import android.app.Activity;import android.os.Bundle;import android.util.SparseArray;import android.widget.ListView; public class MainActivity extends Activity { private SparseArray<AppFile> appList = new SparseArray<AppFile>(); private ListView listView; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initData(); initUI(); } private void initData() { for(int i =0; i<20; i++) { AppFile app = new AppFile(); app.name = "快玩游戏--" + (i+1); app.size = 100; app.id = i; app.downloadState = DownloadManager.DOWNLOAD_STATE_NORMAL; app.downloadSize = 0; appList.put(app.id, app); } } private void initUI() { listView = (ListView)this.findViewById(R.id.listview); AppListAdapter adapter = new AppListAdapter(this, appList); adapter.setListView(listView); listView.setAdapter(adapter); } @Override protected void onDestroy() { super.onDestroy(); DownloadManager.getInstance().stopAllDownloadTask(); } }
布局文件activity_main.xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="fill_parent"android:layout_height="fill_parent"><ListViewandroid:id="@+id/listview"android:layout_width="fill_parent"android:layout_height="fill_parent"android:fastScrollEnabled="true"/></LinearLayout>
到此为止,代码部分已经全部完成了,下面来看看最终效果图:
这里对比一下分别使用updateView和notifyDataSetChanged时,有什么不一样,看看打印日志:
(1)使用notifyDataSetChanged时,listview可视范围内的所有子项都更新了。
(2)使用updateView时,只更新了指定的子项。
实例源码地址 :http://pan.baidu.com/share/link?shareid=229182&uk=167811495
转载请注明来自:Alex Zhou的程序世界,本文链接:http://codingnow.cn/android/1059.html
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