The difference between invalidate and Postinvalidate in Android

Note: This article is a personal study excerpt, the original address: http://www.cnblogs.com/tt_mc/archive/2012/01/30/2332023.html

There are two sets of methods for updating view in Android, one for invalidate and the other for Postinvalidate, where the former is used in the UI thread itself, while the latter is used in non-UI threads.
Android provides the Invalidate method for interface refresh, but invalidate cannot be called directly in the thread because he is violating the single-threaded model: Android UI operations are not thread-safe, and these operations must be called in the UI thread.

There are two kinds of interface refresh methods that can be used in Android programs, namely, using handler and using Postinvalidate () to refresh the interface in thread.

1, using invalidate () to refresh the interface
Instantiate an handler object and override the Handlemessage method call invalidate () to implement the interface refresh, while the thread updates the message through the SendMessage send interface.

To open a thread in OnCreate ()

New Thread (New Gamethread ()). Start ();

Instantiate a handler

Handler MyHandler = new Handler () {
Receive Message post processing
public void Handlemessage (Message msg) {
Switch (msg.what) {
Case Activity01.refresh:
Mgameview.invalidate (); Refresh Interface
Break
}

Super.handlemessage (msg);
}
};

Class Gamethread implements Runnable {
public void Run () {
while (! Thread.CurrentThread (). isinterrupted ()) {
Message message = new Message ();
Message.what = Activity01.refresh;
Send Message
Activity01.this.myHandler.sendMessage (message);
try {
Thread.Sleep (100);
} catch (Interruptedexception e) {
Thread.CurrentThread (). interrupt ();
}
}
}

}

2, use Postinvalidate () to refresh the interface
The use of postinvalidate is relatively simple, do not need to handler, directly in the thread call Postinvalidate.

Class Gamethread implements Runnable {
public void Run () {
while (! Thread.CurrentThread (). isinterrupted ()) {
try {
Thread.Sleep (100);
} catch (Interruptedexception e) {
Thread.CurrentThread (). interrupt ();
}

Use Postinvalidate to update the interface directly in the thread
Mgameview.postinvalidate ();
}
}
}

View class Postinvalidate () method source code is as follows, it is also used to handler:

1. public void Postinvalidate () {
2. postinvalidatedelayed (0);
3. }
5. public void postinvalidatedelayed (long delaymilliseconds) {
6. We try only with the attachinfo because there's no point in invalidating
7. If we is not a attached to our window
8. if (mattachinfo! = null) {
9. Message msg = Message.obtain ();
10. Msg.what = attachinfo.invalidate_msg;
11. Msg.obj = this;
12. MAttachInfo.mHandler.sendMessageDelayed (msg, delaymilliseconds);
13. }
14. }

In addition to OnCreate () is running on the UI thread, in fact, most of the other methods are running on the UI thread, in fact, as long as you do not open a new thread, your code is basically running on the UI thread.

The difference between invalidate and Postinvalidate in Android