Android简单计时器

本文利用ContextMenu(上下文菜单),Chronometer实现简单计数器。

Main.xml:

    <?xml version="1.0" encoding="utf-8"?>  
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:orientation="vertical"  
    android:layout_width= "fill_parent"  
    android:layout_height = "fill_parent"  
    android:gravity = "center_horizontal"  
    >  
    <Chronometer  
    android:id ="@+id/chronometer"  
    android:layout_width="wrap_content"  
    android:layout_height="wrap_content"  
    android:format="%s"  
    android:textSize="80px"  
    android:textColor="#00FF00"  
    />  
    </LinearLayout >   

/layout/menu/context_menu.xml：

    <?xml version="1.0" encoding="utf-8"?>  
    <menu xmlns:android="http://schemas.android.com/apk/res/android">  
        <item android:id="@+id/timer_start" android:title=" 开始计时 " />  
        <item android:id="@+id/timer_stop" android:title=" 终止计时 " />  
        <item android:id="@+id/timer_reset" android:title=" 清零 " />  
    </menu>  

主Activity:

    public class MainActivity extends Activity {  
        private Chronometer timer;  
        @Override  
        public void onCreate(Bundle savedInstanceState)  
        {  
            super.onCreate(savedInstanceState);  
            setContentView(R.layout.main);  
            // 获得计时器对象  
            timer = (Chronometer)this.findViewById(R.id.chronometer);  
            //长按计时器时，出现上下文菜单  
            this.registerForContextMenu(timer);  
        }  
        //创建上下文菜单  
        @Override  
        public void onCreateContextMenu(ContextMenu menu, View v,  
                ContextMenuInfo menuInfo)  
        {  
            super.onCreateContextMenu(menu, v, menuInfo);  
            // ContextMenu的Item不支持Icon，所以不用再资源文件中，为它们设定图标  
            if (v.getId() == R.id.chronometer)  
            {  
                //加载xml菜单布局文件  
                this.getMenuInflater().inflate(R.menu.context_menu, menu);  
                // 设定头部图标  
                menu.setHeaderIcon(R.drawable.icon);   
                // 设定头部标题  
                menu.setHeaderTitle(" 计时器控制选项 ");  
            }  
        }  
        //选择菜单项后的响应  
        @Override  
        public boolean onContextItemSelected(MenuItem item)  
        {  
            switch (item.getItemId())  
            {  
            case R.id.timer_start:  
                // 将计时器清零  
                timer.setBase(SystemClock.elapsedRealtime());   
                //开始计时  
                timer.start();  
                break;  
            case R.id.timer_stop:  
                //停止计时  
                timer.stop();  
                break;  
            case R.id.timer_reset:  
                //将计时器清零  
                timer.setBase(SystemClock.elapsedRealtime());   
                break;  
            }  
            return super.onContextItemSelected(item);  
        }  
    }  

转载自：http://blog.csdn.net/fwwdn/article/details/7550822