安卓学习第9课——计时器chronometer

package com.example.chronometer;

import android.app.Activity;
import android.os.Bundle;
import android.os.SystemClock;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Chronometer;
import android.widget.Chronometer.OnChronometerTickListener;

public class MainActivity extends Activity {
Chronometer ch;
Button start;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ch=(Chronometer) findViewById(R.id.test);
        start=(Button) findViewById(R.id.start);
        start.setOnClickListener(new OnClickListener(){

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                //设置开始计时时间
            ch.setBase(SystemClock.elapsedRealtime());
            //启动计时器
            ch.start();
            start.setEnabled(false);
            }    
        });
        ch.setOnChronometerTickListener(new OnChronometerTickListener(){

            @Override
            public void onChronometerTick(Chronometer chronometer) {
                // TODO Auto-generated method stub
                //如果从计时开始到现在超过了20s
                if(SystemClock.elapsedRealtime()-ch.getBase()>20*1000){
                    ch.stop();
                    start.setEnabled(true);
                }
            }
            
        });
    }

    
}