Handler communication mechanism

1  PackageCom.example.gp08_day26_handler3;2 3 ImportAndroid.os.Bundle;4 ImportAndroid.os.Handler;5 ImportAndroid.os.Looper;6 ImportAndroid.os.Message;7 Importandroid.app.Activity;8 ImportAndroid.view.Menu;9 ImportAndroid.view.View;Ten  One /** A * The main thread sends messages to child threads -  * @authorQQ -  * the  */ -  Public classMainactivityextendsActivity { -  -     PrivateHandler Handler;//you need to instantiate in a child thread + @Override -     protected voidonCreate (Bundle savedinstancestate) { +         Super. OnCreate (savedinstancestate); A Setcontentview (r.layout.activity_main); at     } -  -      Public voidSendMessage (View v) -     { -         //Click the button to send a message to the child thread -Message msg =Message.obtain (); inMsg.obj = "Hello, hi!"; -         //The message object is put into the MessageQueue object inside the handler, and the MessageQueue reference inside the handler points to Looper in MessageQueue to handler.sendmessage (msg); +     } -     //Creating child Threads the     classMyThreadextendsThread *     { $          Public voidRun ()Panax Notoginseng         { -             //need to have Looper object first theLooper.prepare ();//creates a Looper object and puts the object into the local variable of the thread, creating the MessageQueue object in the Looper constructor method +             //instantiating handler in a child thread, no Looper object in the child thread A              the             //mqueue = mlooper.mqueue; MessageQueue references inside Handler point to Looper objects in MessageQueue +Handler =NewHandler ();//if handler is instantiated directly, the exception is new runtimeexception because there are no Looper objects in the child thread -              $             //let the Looper object iterate through the messages in the MessageQueue $             //The loop reads the message from the queue and, when it reads the message, goes back to call Msg.target.dispatchMessage (msg); -             //There is a target member in the message class, and when the message is sent, the target member is assigned the current handler object - Looper.loop (); the         } -     }Wuyi  the}

mainactivity

Handler communication mechanism