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Android App后臺(tái)服務(wù)報(bào)告工作狀態(tài)實(shí)例

更新時(shí)間：2014年06月26日 08:44:02 投稿：junjie

這篇文章主要介紹了Android App后臺(tái)服務(wù)報(bào)告工作狀態(tài)實(shí)例,使用LocalBroadcastManager發(fā)送和接收狀態(tài),需要的朋友可以參考下

本節(jié)講運(yùn)行在后臺(tái)服務(wù)里的工作請(qǐng)求，如何向發(fā)送請(qǐng)求者報(bào)告狀態(tài)。推薦用LocalBroadcastManager發(fā)送和接收狀態(tài)，它限制了只有本app才能接收到廣播。

從IntentService匯報(bào)狀態(tài)

從IntentService發(fā)送工作請(qǐng)求狀態(tài)給其他組件，先創(chuàng)建一個(gè)包含狀態(tài)和數(shù)據(jù)的Intent。也可以添加action和URI到intent里。

下一步，調(diào)用 LocalBroadcastManager.sendBroadcast()發(fā)送Intent,應(yīng)用中所有注冊(cè)了接收該廣播的接收器都能收到。LocalBroadcastManager.getInstance()獲取LocalBroadcastManager實(shí)例。

復(fù)制代碼代碼如下:

public final class Constants {

    ...

    // Defines a custom Intent action

    public static final String BROADCAST_ACTION =

        "com.example.android.threadsample.BROADCAST";

    ...

    // Defines the key for the status "extra" in an Intent

    public static final String EXTENDED_DATA_STATUS =

        "com.example.android.threadsample.STATUS";

    ...

}

public class RSSPullService extends IntentService {

...

    /*

     * Creates a new Intent containing a Uri object

     * BROADCAST_ACTION is a custom Intent action

     */

    Intent localIntent =

            new Intent(Constants.BROADCAST_ACTION)

            // Puts the status into the Intent

            .putExtra(Constants.EXTENDED_DATA_STATUS, status);

    // Broadcasts the Intent to receivers in this app.

    LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent);

...

}

下一步是接收廣播并處理。

接收來自IntentService的廣播

接收方式與普通的Broadcast一樣，用一個(gè)BroadcastReceiver的子類，實(shí)現(xiàn)BroadcastReceiver.onReceive()方法

復(fù)制代碼代碼如下:

// Broadcast receiver for receiving status updates from the IntentService

private class ResponseReceiver extends BroadcastReceiver

{

    // Prevents instantiation

    private DownloadStateReceiver() {

    }

    // Called when the BroadcastReceiver gets an Intent it's registered to receive

    @

    public void onReceive(Context context, Intent intent) {

...

        /*

         * Handle Intents here.

         */

...

    }

}

定義好了接收器類以后，定義過濾器，匹配指定的action,categorie,data.

復(fù)制代碼代碼如下:

// Class that displays photos

public class DisplayActivity extends FragmentActivity {

    ...

    public void onCreate(Bundle stateBundle) {

        ...

        super.onCreate(stateBundle);

        ...

        // The filter's action is BROADCAST_ACTION

        IntentFilter mStatusIntentFilter = new IntentFilter(

                Constants.BROADCAST_ACTION);

        // Adds a data filter for the HTTP scheme

        mStatusIntentFilter.addDataScheme("http");

        ...

注冊(cè)方式稍有不同，用LocalBroadcastManager.registerReceiver()。

復(fù)制代碼代碼如下:

  // Instantiates a new DownloadStateReceiver

        DownloadStateReceiver mDownloadStateReceiver =

                new DownloadStateReceiver();

        // Registers the DownloadStateReceiver and its intent filters

        LocalBroadcastManager.getInstance(this).registerReceiver(

                mDownloadStateReceiver,

                mStatusIntentFilter);

        ...

單個(gè)BroadcastReceiver可以處理多種類型的廣播，這個(gè)特性允許你根據(jù)不同的action運(yùn)行不同的代碼，而無需為每個(gè)action定義一個(gè)BroadcastReceiver。

復(fù)制代碼代碼如下:

  /*

         * Instantiates a new action filter.

         * No data filter is needed.

         */

        statusIntentFilter = new IntentFilter(Constants.ACTION_ZOOM_IMAGE);

        ...

        // Registers the receiver with the new filter

        LocalBroadcastManager.getInstance(getActivity()).registerReceiver(

                mDownloadStateReceiver,

                mIntentFilter);

發(fā)送廣播并不會(huì)啟動(dòng)或恢復(fù)Activity.BroadcastReceiver讓Activity能夠接收處理數(shù)據(jù)，包括應(yīng)用在后臺(tái)的時(shí)候，但不會(huì)強(qiáng)制app回到前臺(tái)。如果你要在app在后臺(tái)，對(duì)用戶不可見時(shí)，通知用戶一個(gè)事件發(fā)生，用Notification。絕對(duì)不要啟動(dòng)一個(gè)Activity來響應(yīng)廣播。

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