要检查下载管理器是否下载了文件，必须实现BroatcastReceiver.

To check whether the download manager downloaded the file, you must implements your BroatcastReceiver.

@Override
public void onReceive(Context context, Intent intent) {
    String action = intent.getAction();
    if (action.equals(DownloadManager.ACTION_DOWNLOAD_COMPLETE)) {
        DownloadManager.Query query = new DownloadManager.Query();
        query.setFilterById(intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, 0));
        DownloadManager manager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
        Cursor cursor = manager.query(query);
        if (cursor.moveToFirst()) {
            if (cursor.getCount() > 0) {
                int status = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));
                if (status == DownloadManager.STATUS_SUCCESSFUL) {
                    String file = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME));
                    // So something here on success
                } else {
                    int message = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_REASON));
                    // So something here on failed.
                }
            }
        }
    }
}

但是，我不确定您是否可以通过编程方式安装APK.出于安全原因，我认为您不能.对于应用程序更新，我认为您应该使用Google版本控制.当您使用其他版本号重新部署您的应用程序时，用户应能够自动更新(除非用户在Google Play上关闭).希望这会有所帮助.

However, I am not sure whether you can install the APK programmatically. For security reason, I don't think you can. For application update, I think you should use google versioning control. When you re-deploy your app using different version number, the users should able to update automatically (unless user turn off at google play). Hope that this will help.

更新

您不需要调用我提到的方法.您只需要在清单xml文件中声明广播接收器，下载完成后，DownloadManager将在调用.xml如下所示:

You do not need to call the method that I mention. You just need to declare your broadcast receiver at your manifest xml file and DownloadManager will call at when download complete. The xml look something like below:

    <receiver
        android:name=".BroadcastReceiver"
        android:enabled="true"
        android:exported="true" >
        <intent-filter>
            <action android:name="android.intent.action.DOWNLOAD_COMPLETE" />
            <action android:name="android.intent.action.DOWNLOAD_NOTIFICATION_CLICKED" />
        </intent-filter>
    </receiver>