Send messages between the Android main thread and thread

By analyzing the Activity source code, we know that each Activity has a logoff, so the main thread does not need to call Logoff When receiving messages. prepare () and logoff. loop (), but the thread does not contain Looper. When the thread wants to receive messages from its own thread, it needs to call Looper. prepare () and logoff. loop (). The following example shows how to send a Message between the main thread and thread.
 

01 import android. app. Activity;

02 import android. OS. Bundle;

03 import android. OS. Handler;

04 import android. OS. Message;

05 import android. widget. Toast;

06

07 /**

08 * this class is the main thread. It sends a Message to the thread every two seconds. After receiving the Message, the thread sends a Message to the main thread, after receiving the Message, the main thread Toast the Message content.

09 * org. fneg. HandlerTestActivity. java

10 * Create at: 9:39:19

11 * @ author: feng

12 * Email: fengcunhan@gmail.com

13 *

14 */

15 public class HandlerTestActivity extends Activity {

16 private Handler uiHandler;

17 private threadwithlow.thread;

18 private Runnable showRunable;

19 @ Override

20 public void onCreate (Bundle savedInstanceState ){

21 super. onCreate (savedInstanceState );

22 setContentView (R. layout. main );

23 uiHandler = new Handler (){

24 @ Override

25 public void handleMessage (Message msg ){

26 switch (msg. what ){

27 case Messages. MSG_HELLO:

28 Toast. makeText (HandlerTestActivity. this, (String) msg. obj, Toast. LENGTH_SHORT). show ();

29 break;

30

31}

32}

33 };

34 thread = new ThreadWithLooper (uiHandler );

35

36 thread. start ();

37 showRunable = new Runnable (){

38

39 @ Override

40 public void run (){

41 // send a Message to the thread

42 thread. getHandler (). sendEmptyMessage (Messages. MSG_HELLO );

43 uiHandler. postDelayed (this, 2*1000 );

44}

45 };

46 uiHandler. post (showRunable );

47

48}

49

50 @ Override

51 protected void onStop (){

52 super. onStop ();

53 uiHandler. removeCallbacks (showRunable );

54}

55}

01 import android. OS. Handler;

02 import android. OS. logoff;

03 import android. OS. Message;

04

05 /**

06 * send a message from the thread to the UI thread (main thread)

07 * org. fneg. threadwithlow.java

08 * Create at: 4:58:11

09 * @ author: feng <br/>

10 * Email: fengcunhan@gmail.com

11 *

12 */

13 public class threadwithlow.extends Thread {

14 private Handler handler;

15

16 private Handler uiHandler;

17

18 public ThreadWithLooper (Handler mHandler ){

19 this. uiHandler = mHandler;

20 // initialize Handler. After receiving the Message sent by the main thread, a Message is returned to the main thread. The Message content is a string and the current time.

21 handler = new Handler (){

22

23 @ Override

24 public void handleMessage (Message msg ){

25 switch (msg. what ){

26 case Messages. MSG_HELLO:

27 Message message = new Message ();

28 message. what = Messages. MSG_HELLO;

29 message. obj = "Yes! I get a hello "+ System. currentTimeMillis ();

30 uiHandler. sendMessage (message );

31 break;

32

33}

34}

35

36 };

37}

38

39 public Handler getHandler (){

40 return handler;

41}

42

43 public void setHandler (Handler handler ){

44 this. handler = handler;

45}

46

47 @ Override

48 public void run (){

49 logoff. prepare ();

50

51 logoff. loop ();

52}

53

54

55}

01 /**

02 *

03 * org. fneg. Messages. java

04 * Create at: 4:51:20

05 * @ author: feng

06 * Email: fengcunhan@gmail.com

07 *

08 */

09 public class Messages {

10 public static final int MSG_HELLO = 0X1;

11}