本文档介绍了当用户请求手动刷新时如何更新您的应用,无论是通过滑动操作还是使用操作栏刷新操作触发的刷新。
响应刷新手势
当用户执行下拉刷新手势时,系统会显示进度指示器并调用您的应用的回调方法。您的回调方法负责更新应用的数据。
要在您的应用中响应刷新手势,请实现 SwipeRefreshLayout.OnRefreshListener
接口及其 onRefresh()
方法。onRefresh()
方法在用户执行滑动操作时调用。
将实际更新操作的代码放在单独的方法中,最好是在 ViewModel
中,然后在您的 onRefresh()
实现中调用该更新方法。这样,当用户通过滑动或操作栏触发刷新时,您都可以使用相同的更新方法执行更新。
在您的更新方法中,数据更新完成后,请调用 setRefreshing(false)
。调用此方法会指示 SwipeRefreshLayout
移除进度指示器并更新 View 内容。
例如,以下代码实现了 onRefresh()
并调用了 myUpdateOperation()
方法来更新 ListView
显示的数据
Kotlin
// Sets up a SwipeRefreshLayout.OnRefreshListener that invokes when // the user performs a swipe-to-refresh gesture. mySwipeRefreshLayout.setOnRefreshListener { Log.i(LOG_TAG, "onRefresh called from SwipeRefreshLayout") // This method performs the actual data-refresh operation and calls // setRefreshing(false) when it finishes. myUpdateOperation() }
Java
// Sets up a SwipeRefreshLayout.OnRefreshListener that is invoked when // the user performs a swipe-to-refresh gesture. mySwipeRefreshLayout.setOnRefreshListener(() -> { Log.i(LOG_TAG, "onRefresh called from SwipeRefreshLayout"); // This method performs the actual data-refresh operation and calls // setRefreshing(false) when it finishes. myUpdateOperation(); } );
响应刷新操作
如果用户通过操作栏请求刷新,系统会调用 onOptionsItemSelected()
方法。您的应用会响应此调用,显示进度指示器并刷新应用的数据。
要响应刷新操作,请覆盖 onOptionsItemSelected()
。在您的覆盖方法中,通过调用 setRefreshing()
并传入值 true
来触发 SwipeRefreshLayout
进度指示器,然后执行更新操作。将实际更新放在单独的方法中,以便用户无论是通过滑动还是操作栏触发更新,都可以调用同一方法。更新完成后,调用 setRefreshing(false)
以移除刷新进度指示器。
以下代码展示了如何响应请求操作
Kotlin
// Listen for option item selections to receive a notification when the user // requests a refresh by selecting the refresh action bar item. override fun onOptionsItemSelected(item: MenuItem): Boolean { when (item.itemId) { // Check whether the user triggers a refresh: R.id.menu_refresh -> { Log.i(LOG_TAG, "Refresh menu item selected") // Signal SwipeRefreshLayout to start the progress indicator. mySwipeRefreshLayout.isRefreshing = true // Start the refresh background task. This method calls // setRefreshing(false) when it finishes. myUpdateOperation() return true } } // User doesn't trigger a refresh. Let the superclass handle this action. return super.onOptionsItemSelected(item) }
Java
// Listen for option item selections to 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 whether the user triggers 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 finishes. myUpdateOperation(); return true; } // User doesn't trigger a refresh. Let the superclass handle this action. return super.onOptionsItemSelected(item); }