ApiDemos 之 AlarmManager

 

AlarmManager的使用机制有的称呼为全局定时器，有的称呼为闹钟。通过对它的使用，个人觉得叫全局定时器比较合适，其

 

实它的作用和Timer有点相似。都有两种相似的用法：（1）在指定时长后执行某项操作（2）周期性的执行某项操作。

 

AlarmManager对象配合Intent使用，可以定时的开启一个Activity,发送一个BroadCast,或者开启一个Service.

 

 

下面的代码详细的介绍了两种定时方式的使用：

 

（1）在指定时长后执行某项操作：

 

MainAct.java:

 

 

public class MainAct extends Activity {
	Toast mToast;
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Button btn = (Button)findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				Intent intent = new Intent("oneshot");
				PendingIntent pintent = PendingIntent.getBroadcast(MainAct.this, 0, intent, 0);
				//根据传入的NAME来取得对应的Object，然后转换成相应的服务对象
				AlarmManager am = (AlarmManager)MainAct.this.getSystemService(ALARM_SERVICE);
				
				Calendar canlender = Calendar.getInstance();//获取日历的实例
				canlender.setTimeInMillis(System.currentTimeMillis());// 代表当前时间的日历  
				canlender.add(canlender.SECOND, 30);// 将时间设置为现在的30s以后  （定时时间）
				//设置并启动定时器
				am.set(AlarmManager.RTC_WAKEUP, canlender.getTimeInMillis(), pintent);
				if (mToast != null) {
		                mToast.cancel();
	            }
	            mToast = Toast.makeText(MainAct.this, "one shot alarm will go off in 30 seconds.",
	                    Toast.LENGTH_LONG);
	            //弹出Toast，用于提示定时任务已经开启
	            mToast.show();
	        }
		});
        
    }
}

 

 清单文件：

 

 

 <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".MainAct"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
		<receiver android:name=".OneShotAlarm">
			<intent-filter>
				<action android:name="oneshot"/>
			</intent-filter>
		</receiver>
    </application>

 

OneShotAlarm.java：

 

 

public class OneShotAlarm extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        Toast.makeText(context, R.string.one_shot_received, Toast.LENGTH_SHORT).show();
    }
}

 

（2）周期性的执行某项操作

 

start repeating AlarmManager:

 

  Button btn1 = (Button)findViewById(R.id.btn1);
        btn1.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				Intent intent = new Intent("repeating");
	            PendingIntent sender = PendingIntent.getBroadcast(MainAct.this,
	                    0, intent, 0);
	            
	            // We want the alarm to go off 30 seconds from now.
	            //系统启动到目前为止的时间
	            long firstTime = SystemClock.elapsedRealtime();
	            firstTime += 15*1000;

	            // Schedule the alarm!
	            AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);
	           
	            //public void setRepeating (int type, long triggerAtTime, long interval, PendingIntent operation)
	            //以15秒一个周期发送广播...
	            am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP,
	                            firstTime, 15*1000, sender);

	            // Tell the user about what we did.
	            if (mToast != null) {
	                mToast.cancel();
	            }
            mToast = Toast.makeText(MainAct.this, "已启动周期性计时器~",
	                    Toast.LENGTH_LONG);
	            mToast.show();
	        }
		});

 

 

stop repeating Alarm:

 

 

 Button btn2 = (Button)findViewById(R.id.btn2);
        btn2.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				 Intent intent = new Intent("repeating");
		            PendingIntent sender = PendingIntent.getBroadcast(MainAct.this,
		                    0, intent, 0);
		            
		            AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);
		            am.cancel(sender);

		            // Tell the user about what we did.
		            if (mToast != null) {
		                mToast.cancel();
		            }
		            mToast = Toast.makeText(MainAct.this, "alarm canceled",
		                    Toast.LENGTH_LONG);
		            mToast.show();
			}
		});