Android UI ProgressBar跟Timer的使用

package cn.jinyejun.ui_progressbardemo;import java.util.Timer;import java.util.TimerTask;import android.os.Bundle;import android.support.v7.app.ActionBarActivity;import android.widget.ProgressBar;public class MainActivity extends ActionBarActivity {	private ProgressBar pb =null;	private Timer timer = null;	private TimerTask timerTask = null;	private int progress = 0;	@Override	protected void onCreate(Bundle savedInstanceState) {		super.onCreate(savedInstanceState);		setContentView(R.layout.activity_main);				pb = (ProgressBar) findViewById(R.id.progressBar);			}		@Override	protected void onResume() {		super.onResume();		startTimer();	}		@Override	protected void onStop() {		super.onStop();		stopTimer();	}		/**	 * 启动计时器	 */	private void startTimer(){		if(timer == null){			timer = new Timer();			timerTask =  new TimerTask() {								@Override				public void run() {					progress+=1;					pb.setProgress(progress);				}			};			timer.schedule(timerTask, 1000,50);					}	}	/**	 * 关闭计时器并释放资源	 */	private void stopTimer(){		if(timer !=null){			timerTask.cancel();			timer.cancel();						timerTask = null;			timer = null;		}	}}

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