Android线程问题(Handler+Runnable)让你对线程理解更深刻

 

很多刚学习android的人，都不太熟悉用handler更新主线程ui的具体原理，本文将给你讲述！

public class MainActivity extends Activity {
    Button button;
    TextView textview;
    ProgressBar progressBar;
    MyHandler mhandler;
    MyThread mthread;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        button=(Button)findViewById(R.id.bt);
        textview=(TextView)findViewById(R.id.tv);
        progressBar=(ProgressBar)findViewById(R.id.pb);
        progressBar.setMax(100);
        button.setOnClickListener(new View.OnClickListener() {
            
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                mhandler=new MyHandler();
                mthread=new MyThread();
                new Thread(mthread).start();
                Log.i("++++++++++", "onCreate--The Thread is: "+Thread.currentThread().getId());
            }
        });
    }
    //这里要实现handlermessage方法来处理传过来的msg，要记住是先进先出原则
    class MyHandler extends Handler{
        @Override
        public void handleMessage(Message msg) {
            Log.i("-----", "Handler--The ThreadId is: "+Thread.currentThread().getId());
            super.handleMessage(msg);
            Bundle b1=msg.getData();
            String textStr0=textview.getText().toString();
            String textStr1=b1.getString("textStr");
            MainActivity.this.textview.setText(textStr0+" "+textStr1);
            int i = b1.getInt("barvalue");
            MainActivity.this.progressBar.setProgress(i);
        }
    }
    //再一个新线程里来向主线程发送消息，配合ui更新
    class MyThread implements Runnable {
        int i=1;
        @Override
        public void run() {
            // TODO Auto-generated method stub
            while(i<11){
                Log.i("_+_+_+_+_+","Thread--The ThreadId is: "+Thread.currentThread().getId());
            try {
                Thread.sleep(1000);
                } catch (InterruptedException e) {
                e.printStackTrace();
                }
            Message m=new Message();
            Bundle b =new Bundle();
            b.putString("textStr", "线程运行"+i+"次");
            b.putInt("barValue", i*10);
            i++;
            m.setData(b);
//            通过sendMessage向Handler发送更新UI的消息
            MainActivity.this.mhandler.sendMessage(m);
        }
        }
    }
}

 

这个是运行后的结果，你会看到Oncreate里只会执行一次，剩下的就是子线程与主线程更新ui的一些交互，最后结束。