diff options
Diffstat (limited to 'core/java/android')
| -rw-r--r-- | core/java/android/os/Handler.java | 34 |
1 files changed, 27 insertions, 7 deletions
diff --git a/core/java/android/os/Handler.java b/core/java/android/os/Handler.java index 9af9edae9a3f..a99bdabee137 100644 --- a/core/java/android/os/Handler.java +++ b/core/java/android/os/Handler.java @@ -28,15 +28,14 @@ import java.lang.reflect.Modifier; * A Handler allows you to send and process {@link Message} and Runnable * objects associated with a thread's {@link MessageQueue}. Each Handler * instance is associated with a single thread and that thread's message - * queue. When you create a new Handler, it is bound to the thread / - * message queue of the thread that is creating it -- from that point on, - * it will deliver messages and runnables to that message queue and execute - * them as they come out of the message queue. - * + * queue. When you create a new Handler it is bound to a {@link Looper}. + * It will deliver messages and runnables to that Looper's message + * queue and execute them on that Looper's thread. + * * <p>There are two main uses for a Handler: (1) to schedule messages and * runnables to be executed at some point in the future; and (2) to enqueue * an action to be performed on a different thread than your own. - * + * * <p>Scheduling messages is accomplished with the * {@link #post}, {@link #postAtTime(Runnable, long)}, * {@link #postDelayed}, {@link #sendEmptyMessage}, @@ -114,7 +113,18 @@ public class Handler { * * If this thread does not have a looper, this handler won't be able to receive messages * so an exception is thrown. + * + * @deprecated Implicitly choosing a Looper during Handler construction can lead to bugs + * where operations are silently lost (if the Handler is not expecting new tasks and quits), + * crashes (if a handler is sometimes created on a thread without a Looper active), or race + * conditions, where the thread a handler is associated with is not what the author + * anticipated. Instead, use an {@link java.util.concurrent.Executor} or specify the Looper + * explicitly, using {@link Looper#getMainLooper}, {link android.view.View#getHandler}, or + * similar. If the implicit thread local behavior is required for compatibility, use + * {@code new Handler(Looper.myLooper())} to make it clear to readers. + * */ + @Deprecated public Handler() { this(null, false); } @@ -128,7 +138,17 @@ public class Handler { * so an exception is thrown. * * @param callback The callback interface in which to handle messages, or null. - */ + * + * @deprecated Implicitly choosing a Looper during Handler construction can lead to bugs + * where operations are silently lost (if the Handler is not expecting new tasks and quits), + * crashes (if a handler is sometimes created on a thread without a Looper active), or race + * conditions, where the thread a handler is associated with is not what the author + * anticipated. Instead, use an {@link java.util.concurrent.Executor} or specify the Looper + * explicitly, using {@link Looper#getMainLooper}, {link android.view.View#getHandler}, or + * similar. If the implicit thread local behavior is required for compatibility, use + * {@code new Handler(Looper.myLooper(), callback)} to make it clear to readers. + */ + @Deprecated public Handler(@Nullable Callback callback) { this(callback, false); } |