Android之Handler

1.Handler默认情况下与主线程处于同一线程

public class MainActivity extends Activity {

    private Button startButton = null;
    private Button endButton = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        startButton = (Button) findViewById(R.id.startButton);
        endButton = (Button) findViewById(R.id.endButton);

        startButton.setOnClickListener(new StartButtonListener());
        endButton.setOnClickListener(new EndButtonListener());

        /*
         * if (savedInstanceState == null) {
         * getSupportFragmentManager().beginTransaction() .add(R.id.container,
         * new PlaceholderFragment()).commit(); }
         */
    }

    class StartButtonListener implements OnClickListener {
        @Override
        public void onClick(View v) {
            System.out.println(Thread.currentThread().getId() + " Start");
            handler.post(updateThread);
        }
    }

    class EndButtonListener implements OnClickListener {
        @Override
        public void onClick(View v) {
            System.out.println(Thread.currentThread().getId() + " End");
            handler.removeCallbacks(updateThread);
        }
    }

    Handler handler = new Handler();
    Runnable updateThread = new Runnable() {
        @Override
        public void run() {
            System.out
                    .println(Thread.currentThread().getId() + " UpdateThread");
            handler.postDelayed(updateThread, 3000);
        }
    };

2.通过Handler实现进度条

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    tools:context="com.example.mars_1200_progressbarhandler.MainActivity"
    tools:ignore="MergeRootFrame" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="hello" />

    <ProgressBar
        android:id="@+id/bar"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:visibility="gone" />

    <Button
        android:id="@+id/startButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="start" />

</LinearLayout>

public class MainActivity extends Activity {

    ProgressBar bar = null;
    Button startButton = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        System.out.println("主线程ID："+Thread.currentThread().getId());
        bar = (ProgressBar) findViewById(R.id.bar);
        startButton = (Button) findViewById(R.id.startButton);
        startButton.setOnClickListener(new ButtonListener());
        /*
         * if (savedInstanceState == null) {
         * getSupportFragmentManager().beginTransaction() .add(R.id.container,
         * new PlaceholderFragment()).commit(); }
         */
    }

    class ButtonListener implements OnClickListener {
        @Override
        public void onClick(View v) {
            bar.setVisibility(View.VISIBLE);
            updateBarHandler.post(updateThread);
        }
    }

    //使用匿名内部类
    Handler updateBarHandler = new Handler() {
        //可传递参数
        @Override
        public void handleMessage(Message msg) {
            bar.setProgress(msg.arg1);
            updateBarHandler.post(updateThread);
        }
    };

    //线程类，该类使用匿名内部类的方式进行声明
    Runnable updateThread = new Runnable() {
        int i = 0;
        @Override
        public void run() {
            System.out.println("Begin Thread");
            System.out.println("Handler线程ID："+Thread.currentThread().getId());
            i = i + 10;
            //得到一个消息，Message类是有Android操作系统提供的
            Message msg = updateBarHandler.obtainMessage();
            //将msg对象的arg1参数的值设置为i，用arg1和arg2这两个
            //成员变量传递值，优点是消耗性能小
            msg.arg1 = i;
            try {
                Thread.sleep(1000);
            } catch (Exception e) {
                e.printStackTrace();
            }
            updateBarHandler.sendMessage(msg);
            if (i >= 100) {
                updateBarHandler.removeCallbacks(updateThread);
            }
        }
    };

3.Handler通过post执行Runnable(还是与主线程处于同一线程)

public class MainActivity extends Activity {
    private Handler handler = new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //handler线程和主线程在同一线程
        handler.post(r);
        /*Thread t=new Thread(r);
        t.start();*/
        
        System.out.println("activity-->" + Thread.currentThread().getId());
        System.out.println("activityname-->" + Thread.currentThread().getId());
        /*
         * if (savedInstanceState == null) {
         * getSupportFragmentManager().beginTransaction() .add(R.id.container,
         * new PlaceholderFragment()).commit(); }
         */
    }

    Runnable r = new Runnable() {
        @Override
        public void run() {
            System.out.println("handler-->" + Thread.currentThread().getId());
            System.out.println("handlername-->"
                    + Thread.currentThread().getName());
            try {
                Thread.sleep(10000);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    };

4.通过HandlerThread执行线程，并可通过Bundle传递参数

public class MainActivity02 extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_activity02);

        System.out.println(Thread.currentThread().getId());
        //生成一个HandlerThread对象，实现了使用Looper来处理消息队列的功能，这个类由Android提供
        HandlerThread handlerThread=new HandlerThread("handler_Thread");
        handlerThread.start();
        MyHandler myHandler=new MyHandler(handlerThread.getLooper());
        Message msg=myHandler.obtainMessage();
        msg.obj="abc";//通过obj存储数据
        Bundle b=new Bundle();
        b.putInt("age", 20);
        b.putString("name", "Jhon");
        msg.setData(b);//通过Bundle存储数据
        msg.sendToTarget();//将msg发送到目标对象，所谓的目标对象就是生成该msg的Handler
        /*if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }*/
    }

    class MyHandler extends Handler{
        public MyHandler(){
            
        }
        public MyHandler(Looper looper){
            super(looper);
        }
        @Override
        public void handleMessage(Message msg){
            System.out.println(msg.obj);
            Bundle b=msg.getData();
            System.out.println(b.getInt("age"));
            System.out.println(b.getString("name"));
            System.out.println("handleMessage:"+Thread.currentThread().getId());
        }
    }