Downloadmanager in android

最新推荐文章于 2024-04-18 14:06:00 发布

原创最新推荐文章于 2024-04-18 14:06:00 发布 · 2.1k 阅读

2 ·

CC 4.0 BY-SA版权

android 专栏收录该内容

90 篇文章

订阅专栏

本文介绍如何使用Android中的DownloadManager进行文件下载，包括创建下载任务、设置下载参数、查询下载进度及状态等操作，并提供了监听下载进度和下载完成的方法。

Downloadmanager使用

DownloadManager是android提供的一个下载管理器

缺点：不支持断点续传

使用方法:

创建实例:

DownloadManager manager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);

创建下载任务:

DownloadManager.Request request = new DownloadManager.Request(Uri.parse(URL));
//指定保存地址
request.setDestinationInExternalPublicDir("chuyi", "meizhi.apk");
//设置允许下载的网络状况
request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);
//设置通知栏的行为
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
//通过id唯一标识此下载任务
long id = manager.enqueue(request);

删除下载任务:
```
manager.remove(id);
```

查询下载任务:

DownloadManager.Query query = new DownloadManager.Query();
query.setFilterById(id);
Cursor cursor = manager.query(query);

if(cursor.moveToFirst()){
    String filename = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME));
    String fileUri = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
    Toast.makeText(context,"下载完成...name:"+filename+",uri:"+fileUri,Toast.LENGTH_SHORT).show();
}else {
  //TODO
}
cursor.close();

查询下载进度:

DownloadManager.Query query = new DownloadManager.Query().setFilterById(downloadId);
Cursor c = null;
try {
    c = downloadManager.query(query);
    if (c != null && c.moveToFirst()) {
        int downloadedBytes = c.getInt(c.getColumnIndexOrThrow(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
        int totalBytes = c.getInt(c.getColumnIndexOrThrow(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
        int state = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
    }
} finally {
    if (c != null) {
        c.close();
    }
}

监听下载结束通知:

可以通过接收DownloadManager.ACTION_DOWNLOAD_COMPLETE广播来监听下载结束的通知

IntentFilter filter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);
    mReceiver = new BroadcastReceiver(){
      public void onReceive(Context c,Intent i){
          long downId = i.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID,-1);
      }
    }
    context.registerReceiver(mReceiver,filter);

监听下载进度:

主要有三种方案：1.FileReceiver 2.ContentObserver 3.定时任务

class DownloadChangeObserver extends ContentObserver {

public DownloadChangeObserver(){
    super(handler);
}

@Override
public void onChange(boolean selfChange) {
    //查询进度
}

}
//in activity
private DownloadChangeObserver downloadObserver;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.download_manager_demo);
……
downloadObserver = new DownloadChangeObserver();
}

@Override
protected void onResume() {
    super.onResume();
    /** observer download change **/
    getContentResolver().registerContentObserver(DownloadManagerPro.CONTENT_URI, true,
                                                 downloadObserver);
}

@Override
protected void onPause() {
    super.onPause();
    getContentResolver().unregisterContentObserver(downloadObserver);
}

上面这种做法可能对性能有些损耗，因为会不断触发onChange

推荐使用ScheduledExecutorService

public static ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(3);
Runnable command = new Runnable() {

    @Override
    public void run() {
        updateView();
    }
};
scheduledExecutorService.scheduleAtFixedRate(command, 0, 3, TimeUnit.SECONDS);

参考资料：