Handler under android developing

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=""
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <ProgressBar android:layout_height="wrap_content"
        android:layout_width="fill_parent" style="?android:attr/progressBarStyleHorizontal"
        android:id="@+id/progressBar"
        android:visibility="gone"
        ></ProgressBar>
    <Button android:text="Start" android:id="@+id/startButton"
        android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
    <Button android:text="End" android:id="@+id/endButton"
        android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
</LinearLayout>

package cn.youhap.handler;

    import android.app.Activity;
    import android.os.Bundle;
    import android.os.Handler;
    import android.os.Message;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.ProgressBar;

    public class HandlerTestDriveActivity extends Activity {
        /** Called when the activity is first created. */

        private ProgressBar progressBar;
        private Button startButton;
        private Button endButton;
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            progressBar = (ProgressBar)findViewById(R.id.progressBar);
            startButton = (Button)findViewById(R.id.startButton);
            endButton = (Button)findViewById(R.id.endButton);
            startButton.setOnClickListener(new StartButtonListener());
            endButton.setOnClickListener(new EndButtonListener());
            enableStartButton();
        }

        class StartButtonListener implements OnClickListener{
            @Override
            public void onClick(View arg0) {
                progressBar.setVisibility(View.VISIBLE);
                updateHandler.post(updateThread);//线程被加入线程队列
                disableStartButton();
            }

        }

        private void enableStartButton(){
            startButton.setEnabled(true);
            endButton.setEnabled(false);
        }

        private void disableStartButton(){
            startButton.setEnabled(false);
            endButton.setEnabled(true);
        }

        private void initProgressBar(){
            progressBar.setVisibility(View.GONE);
            progressBar.setProgress(0);
        }

        class EndButtonListener implements OnClickListener{

            @Override
            public void onClick(View arg0) {
                updateHandler.removeCallbacks(updateThread);
                initProgressBar();
                enableStartButton();
            }

        }

        Handler updateHandler = new Handler(){

            @Override
            public void handleMessage(Message msg) {
                progressBar.setProgress(msg.arg1);
                updateHandler.post(updateThread); //线程再次被加入线程队列
            }

        };

        Runnable updateThread = new Runnable(){
            int i = 0;
            @Override
            public void run() {
                i += 10;
                Message msg = updateHandler.obtainMessage();
                msg.arg1 = i;

                try {
                    Thread.sleep(1000L);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                updateHandler.sendMessage(msg);//消息队列
                if (i >= progressBar.getMax()){
                    i = 0;
                    msg.arg1 = 0;
                    initProgressBar();
                    enableStartButton();
                    updateHandler.removeCallbacks(updateThread);
                    updateHandler.removeMessages(msg.arg1);
                }

            }
        };
    }