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