安卓开发之简单计时器

功能：Menu包括 计时、停止、清零

          长按计时器控件 弹出上下文菜单  包括开始计时、终止计时、清零

重点：长按计时器弹出上下文菜单。 

//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.main, menu);              // 设定头部图标               menu.setHeaderIcon(R.drawable.ic_launcher);               // 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();             return true;        case R.id.timer_stop:              //停止计时               timer.stop();              return true;        case R.id.timer_reset:              //将计时器清零               timer.setBase(SystemClock.elapsedRealtime());               return true;         }         return false;        //return super.onContextItemSelected(item);      }  

 

MainActivuty.java

package com.example.timer1;import android.os.Bundle;import android.os.SystemClock;import android.app.Activity;import android.view.ContextMenu;import android.view.ContextMenu.ContextMenuInfo;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.Chronometer;public class MainActivity extends Activity {    private Chronometer timer;        final static int menu_start = Menu.FIRST;final static int menu_stop = Menu.FIRST+1;final static int menu_setting = Menu.FIRST+2;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_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.main, menu);              // 设定头部图标               menu.setHeaderIcon(R.drawable.ic_launcher);               // 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();             return true;        case R.id.timer_stop:              //停止计时               timer.stop();              return true;        case R.id.timer_reset:              //将计时器清零               timer.setBase(SystemClock.elapsedRealtime());               return true;         }         return false;        //return super.onContextItemSelected(item);      }  public boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.//getMenuInflater().inflate(R.menu.main, menu);menu.add(0,menu_start,0,"计时");menu.add(0,menu_stop,1,"停止");menu.add(0,menu_setting,2,"清零");return true;}public boolean onOptionsItemSelected(MenuItem item) {// TODO Auto-generated method stub//return super.onOptionsItemSelected(item);switch(item.getItemId()){case menu_start: // 将计时器清零               timer.setBase(SystemClock.elapsedRealtime());               //开始计时               timer.start();  return true;case menu_stop://停止计时               timer.stop();  return true;case menu_setting: timer.setBase(SystemClock.elapsedRealtime());            return true;}return false;}}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context=".MainActivity" >    <TextView        android:id="@+id/textView1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/hello_world" />    <Chronometer        android:id="@+id/chronometer"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_centerVertical="true"        android:layout_marginLeft="23dp"        android:layout_toRightOf="@+id/textView1"        android:format="%s"        android:textColor="#00FF00"        android:textSize="80px" /></RelativeLayout>

main.xml

<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>