意向廣播沒有收到的活動

Question

我試圖在2個活動之間廣播意圖。如下圖所示

mFiltersView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
      public void onItemClick(AdapterView<?> parent, View v, int position, long id) { 

       CameraFiltersFactory effect = (CameraFiltersFactory) v.findViewById(R.id.filteredImage).getTag(); 
       final Intent previewIntent = new Intent(FiltersActivity.this, PreviewActivity.class);  
       startActivityForResult(previewIntent, 0); 

       effect.save(new GPUImage.OnPictureSavedListener() { 

        @Override public void onPictureSaved(Uri uri) {  
         final Intent ImageIntent = new Intent(); 
         ImageIntent.setData(uri);  
         ImageIntent.setAction("com.test.FILTER_RENDERED"); 
         sendBroadcast(ImageIntent); 
        } 
       }); 

在PreviewActivity我需要註冊所述接收器和使用IntentFiter趕上意圖，並檢查它

意圖是從FilterActivity發送到PreviewActivity。

public class PreviewActivity extends Activity { 

    ReceiveMessages myReceiver = null; 
    Boolean myReceiverIsRegistered = false; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     myReceiver = new ReceiveMessages(); 
     if (!myReceiverIsRegistered) { 
      // registerReceiver(myReceiver, new IntentFilter()); 
      registerReceiver(myReceiver, new IntentFilter("com.test.FILTER_RENDERED")); 

      myReceiverIsRegistered = true; 
     } 
    .... 

    @Override 
    protected void onResume(){ 
     super.onResume(); 
     if (!myReceiverIsRegistered) { 
      registerReceiver(myReceiver, new IntentFilter("com.test.FILTER_RENDERED")); 
      myReceiverIsRegistered = true; 
     } 
    } 

    @Override 
    protected void onStop() { 
     super.onStop(); 
     if (myReceiverIsRegistered) { 
      unregisterReceiver(myReceiver); 
      myReceiverIsRegistered = false; 
     } 
    } 


    @Override 
    protected void onNewIntent(Intent intent) { 
     super.onNewIntent(intent); 
     Intent mNewIntent = intent; 

     Bundle bundle = null; 
     String fragment = null; 
     if (intent != null) { 
      mImagePreviewUri = mNewIntent.getData(); 
      if(mImagePreviewUri!=null) { 
       mCameraActionsView.setEnabled(true); 
       mImagePreview.setImageURI(mImagePreviewUri); 
      } 
     } 
    } 

    public class ReceiveMessages extends BroadcastReceiver 
    { 
     @Override 
     public void onReceive(Context context, Intent intent) 
     { 
      String action = intent.getAction(); 
      if(action.equalsIgnoreCase("com.test.FILTER_RENDERED")){ 
       if (intent != null) { 
        mImagePreviewUri = intent.getData(); 
        if(mImagePreviewUri!=null) { 
         mCameraActionsView.setEnabled(true); 
         mImagePreview.setImageURI(mImagePreviewUri); 
        } 
       } 
      } 
     } 
    } 

} 

不幸的是，其意圖是永遠不會被活動<

任何想法得到爲什麼，的onReceive沒有被觸發？

Answer 1

當廣播從您的FilterActivity發送到您的PreviewActivity時，預覽活動中的BroadcastReceiver尚未註冊以接收任何廣播並因此錯過了它。正常廣播需要在廣播時註冊接收器以便接收它。它不會停留並等待您的接收器註冊。在你的代碼中，接收者只有在你的PreviewActivity出現在前臺，例如OnResume方法中後才被註冊，然後廣播已經消失。此外，您的接收器在onStop中取消註冊，即PreviewActivity一進入後臺即可。所以，當預覽活動不在前臺時，所有後續廣播都會被忽略，直到再次調用onResume。如果您將使用StickyBroadcast而不是普通廣播，則廣播將可用並由您的接收器接收。但是StickyBroadcasts存在安全隱患，因爲它的使用已被棄用。