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page.title=Responding to a Refresh Request
trainingnavtop=true
@jd:body
<div id="tb-wrapper">
<div id="tb">
<!-- table of contents -->
<h2>This lesson teaches you to</h2>
<ol>
<li><a href="#RespondRefresh">Respond to the Refresh Gesture</a></li>
<li><a href="#RespondAction">Respond to the Refresh Action</a>
</ol>
<h2>Sample App</h2>
<ul>
<li><a href="{@docRoot}samples/SwipeRefreshLayoutBasic/index.html">
SwipeRefreshLayoutBasic</a></li>
</ul>
</div>
</div>
<p>
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.
</p>
<h2 id="RespondRefresh">Respond to the Refresh Gesture</h2>
<p>
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.
</p>
<p>
To respond to the refresh gesture in your app, implement the {@link
android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener} interface and
its {@link
android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener#onRefresh
onRefresh()} method. The {@link
android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener#onRefresh
onRefresh()} method is invoked when the user performs a swipe gesture.
</p>
<p>
You should put the code for the actual update
operation in a separate method, and call that update method from your {@link
android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener#onRefresh
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.
</p>
<p>
Your update method calls {@link
android.support.v4.widget.SwipeRefreshLayout#setRefreshing
setRefreshing(false)} when it has finished updating the data. Calling this
method instructs the {@link android.support.v4.widget.SwipeRefreshLayout} to
remove the progress indicator and update the view contents.
</p>
<p>
For example, the following code implements {@link
android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener#onRefresh
onRefresh()} and invokes the method {@code myUpdateOperation()} to update the
data displayed by the {@link android.widget.ListView}:
</p>
<pre>/*
* 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();
}
}
);</pre>
<h2 id="RespondAction">Respond to the Refresh Action</h2>
<p>
If the user requests a refresh by using the action bar, the system calls the
{@link android.support.v4.app.Fragment#onOptionsItemSelected
onOptionsItemSelected()} method. Your app should respond to this call by
displaying the progress indicator and refreshing the app's data.
</p>
<p>
To respond to the refresh action, override {@link
android.support.v4.app.Fragment#onOptionsItemSelected
onOptionsItemSelected()}. In your override method, trigger the {@link
android.support.v4.widget.SwipeRefreshLayout} progress indicator by calling
{@link android.support.v4.widget.SwipeRefreshLayout#setRefreshing
setRefreshing()} with the value {@code 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
{@link android.support.v4.widget.SwipeRefreshLayout#setRefreshing
setRefreshing(false)} to remove the refresh progress indicator.
</p>
<p>The following code shows how to respond to the request action:
</p>
<pre>/*
* 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);
}</pre>
<p class="note">
<strong>Note:</strong> When the user triggers a refresh with a swipe action as
described in <a href="#RespondRefresh">Respond to the Refresh Gesture</a>,
you do not need to call {@link
android.support.v4.widget.SwipeRefreshLayout#setRefreshing setRefreshing()}.
The {@link
android.support.v4.widget.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 <em>other than</em> a swipe gesture,
you need to explicitly turn the progress indicator on with {@link
android.support.v4.widget.SwipeRefreshLayout#setRefreshing setRefreshing()}.
The method which actually refreshes the data calls {@link
android.support.v4.widget.SwipeRefreshLayout#setRefreshing
setRefreshing(false)} to signal that the update is finished.
</p>
|
