Usage of Thread, Handler and IntentService

Key points

Thread (thread), Handler (handle), IntentService

Content

When to use threads: When time-consuming tasks need to be performed in the main thread

When the handle is used: Pass the message from the child thread to the main thread.For example: Update UI

Android three ways to open child threads

1. Inherit Thread

 Create a child thread method one inherits the Thread classclass MyThread extends Thread{@Overridepublic void run() {//Simulate time-consuming operationtry {sleep(3000); } catch (InterruptedException e) {e.printStackTrace();}tv_text.setText("123456789");An error will be reported here, because the interface of the ui thread cannot be changed after the thread performs time-consuming operationsOnly the original thread that created a view hierarchy can touch its views.}}MyThread myThread=new MyThread();myThread.start();

//If you want to set the value of tv_text, you need to use the Handler handle

Second, inherit Runnable

Create a child thread method 2 inherit the Runnable classclass MyRunnable implements Runnable{@Overridepublic void run() {try {There is no sleep method in Runnable, so borrow the method in ThreadThread.sleep(3000);String result="123456";Log.i("Runnable:", result);} catch (InterruptedException e) {e.printStackTrace();}}}MyRunnable myRunnable=new MyRunnable();Thread thread=new Thread(myRunnable);thread.start();

Three, use Thread and Runnable at the same time

//Create child thread method 3 Use both Thread and Runnable to create anonymous inner classesnew Thread(new Runnable() {@Overridepublic void run() {try {//Because it is currently in the Runnable interface, we still have to borrow the sleep method of ThreadThread.sleep(3000);String result="Anonymous thread";tv_text.setText(result);} catch (InterruptedException e) {e.printStackTrace();}}}).start();

How to define Handler first:

//This method is outdated, generally adding the parameter Looper.getMainLooper()

//private Handler handler=new handler(){};

private Handler handler=new handler(Looper.getMainLooper){

};

//How to pass the message of the child thread to the child thread?

//In the thread's run()

Message msg=new Message();

msg.what=1;

msg.obj="content"

//0x111 is a hexadecimal number

handler.sendEmptyMessage(0x111);

Receive messages in the main thread

private Handler handler=new handler(Looper.getMainLooper){

handleMessage(Message msg){

if(msg.what==0x111){

String result=(Sring) msg.obj;

tv1.setText(result);

     }

};

IntentService

IntentService is a subclass of Service

The difference between him and the Service is that the Service will not automatically open or close the thread, but the IntentService will open and close automatically.