Android Handler之线程交互

通过前面的学习，我们知道如果在Activity中创建一个Handler = new Handler() ，如果不指定参数的的话，默认会绑定Main Thread的looper。 如果我们在创建的过程中，指定了某一个线程的looper，如new Handler(mHandlerThread.getLooper()) ,就会绑定另外一个线程的looper，既然这样，我们就可以利用这2个Handler来做线程的交互

package com.example.user.hanlder_02;
 
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Message;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
 
public class MainActivity extends Activity {
    private static final int MSG_TO_THREAD = 0;
    private static final int MSG_TO_MAIN_THREAD = 1;
    private HandlerThread mHandlerThread;
    private static Handler mUiHandler, mHandler;
    private TextView mTextView;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
    }
 
    private void init() {
        mTextView = (TextView) findViewById(R.id.tv);
        //创建默认与Main Thread绑定的Handler
        mUiHandler = new Handler(){
            @Override
            public void handleMessage(Message msg) {
                int what = msg.what;
                if(MSG_TO_MAIN_THREAD == what){
                    Person person = (Person) msg.obj;
                    Log.d("david",Thread.currentThread() + " handle message @2");
                    mTextView.setText(person.toString());
                }
            }
        };
 
        mHandlerThread = new HandlerThread("MyHandlerThread");
        mHandlerThread.start();
 
        //创建与HandlerThread loopper绑定的handler
        mHandler = new Handler(mHandlerThread.getLooper()){
            @Override
            public void handleMessage(Message msg) {
                int what = msg.what;
                if(MSG_TO_THREAD == what) {
                    Log.d("david", Thread.currentThread() + " handle message @1");
                    Message message = mUiHandler.obtainMessage();
                    Person person  = new Person("David",24);
                    message.obj = person;
                    message.what = MSG_TO_MAIN_THREAD;
                    //在子线程中，向MainThread发送消息
                    mUiHandler.sendMessage(message);
                }
            }
        };
    }
 
    @Override
    protected void onResume() {
        super.onResume();
        Message msg = mHandler.obtainMessage();
        msg.what = MSG_TO_THREAD;
        //向子线程发送消息，一般我们会执行一些耗时的操作
        mHandler.sendMessage(msg);
    }
 
    class Person{
        public String name;
        public int age;
 
        public Person(String name, int age){
            this.name = name;
            this.age = age;
        }
        @Override
        public String toString() {
            return "Name = " + name + " ,Age = " + age;
        }
    }
}

可以看到在onResume方法中，我们利用mHandler向HandlerThread发送消息，这里呢，可以让HandlerThread来做一些耗时操作，耗时操作完成了，就可以向Main Thread发送消息，这个时候我们就可以利用与Main Thread绑定的mUIHandler来发送消息，具体请看代码，基本上没太多可说，前面几篇文章已经讲述的很清楚

至此，Handler分析已经完毕，nice or not~