下拉刷新控件(5)SwipeRefreshLayout官方教程(下)响应刷新事件

　　http://developer.android.com/training/swipe/respond-refresh-request.html

　　This lesson shows you how to update your app when the user requests a manual refresh, whether the user triggers the refresh with a swipe gesture or by using the action bar refresh action.

Respond to the Refresh Gesture

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　　When the user makes a swipe gesture, the system displays the progress indicator and calls your app's callback method. Your callback method is responsible for actually updating the app's data.

　　To respond to the refresh gesture in your app, implement the SwipeRefreshLayout.OnRefreshListenerinterface and its onRefresh() method. The onRefresh() method is invoked when the user performs a swipe gesture.

　　You should put the code for the actual update operation in a separate method, and call that update method from your onRefresh() implementation. That way, you can use the same update method to perform the update when the user triggers a refresh from the action bar.

　　Your update method calls setRefreshing(false) when it has finished updating the data. Calling this method instructs the SwipeRefreshLayout to remove the progress indicator and update the view contents.

For example, the following code implements onRefresh() and invokes the method myUpdateOperation()to update the data displayed by the ListView:

 /*
  * Sets up a SwipeRefreshLayout.OnRefreshListener that is invoked when the user
  * performs a swipe-to-refresh gesture.
  */
 mySwipeRefreshLayout.setOnRefreshListener(
     new SwipeRefreshLayout.OnRefreshListener() {
         @Override
         public void onRefresh() {
             Log.i(LOG_TAG, "onRefresh called from SwipeRefreshLayout");

             // This method performs the actual data-refresh operation.
             // The method calls setRefreshing(false) when it's finished.
             myUpdateOperation();
         }
     }
 );

Respond to the Refresh Action

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　　If the user requests a refresh by using the action bar, the system calls the onOptionsItemSelected()method. Your app should respond to this call by displaying the progress indicator and refreshing the app's data.

　　To respond to the refresh action, override onOptionsItemSelected(). In your override method, trigger theSwipeRefreshLayout progress indicator by calling setRefreshing() with the value true, then perform the update operation. Once again, you should be doing the actual update in a separate method, so the same method can be called whether the user triggers the update with a swipe or by using the action bar. When the update has finished, call setRefreshing(false) to remove the refresh progress indicator.

　　The following code shows how to respond to the request action:

 /*
  * Listen for option item selections so that we receive a notification
  * when the user requests a refresh by selecting the refresh action bar item.
  */
 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
     switch (item.getItemId()) {

         // Check if user triggered a refresh:
         case R.id.menu_refresh:
             Log.i(LOG_TAG, "Refresh menu item selected");

             // Signal SwipeRefreshLayout to start the progress indicator
             mySwipeRefreshLayout.setRefreshing(true);

             // Start the refresh background task.
             // This method calls setRefreshing(false) when it's finished.
             myUpdateOperation();

             return true;
     }

     // User didn't trigger a refresh, let the superclass handle this action
     return super.onOptionsItemSelected(item);

 }

Note:

　　When the user triggers a refresh with a swipe action as described in Respond to the Refresh Gesture, you do not need to call setRefreshing(). The SwipeRefreshLayout widget takes care of displaying the progress indicator and removing it when the update has finished. However, if the update is triggered by any means other than a swipe gesture, you need to explicitly turn the progress indicator on with setRefreshing(). The method which actually refreshes the data calls setRefreshing(false) to signal that the update is finished.