Android简单计时器(转)

原文：http://blog.csdn.net/fwwdn/article/details/7550822

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);
    }
}

运行结果如图所示：

长按计时器弹出上下文菜单选择开始计时：