Intent 和 PendingIntent 区别

长平狐 发布于 2013/01/06 11:16
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intent 英文意思是意图,pending 表示即将发生或来临的事情。 
PendingIntent 这个类用于处理即将发生的事情,比如在通知Notification中用于跳转页面,但不是马上跳转。 

Intent 是及时启动,intent 随所在的activity 消失而消失。 

PendingIntent 可以看作是对intent的包装,通常通过getActivity,getBroadcast,getService来得到pendingintent的实例,当前activity并不能马上启动它所包含的intent,而是在外部执行 pendingintent 时,调用intent的。正由于pendingintent中保存有当前App的Context,使它赋予外部App一种能力,使得外部App可以如同当前App一样的执行pendingintent里的 Intent, 就算在执行时当前App已经不存在了,也能通过存在pendingintent里的Context照样执行Intent。另外还可以处理intent执行后的操作。PendingIntent常和alermanger 和notificationmanager一起使用。 

Intent一般是用作Activity、Sercvice、BroadcastReceiver之间传递数据;而Pendingintent一般用在 Notification上,可以理解为延迟执行的intent,PendingIntent是对Intent一个包装。

PendingIntent pIntent = PendingIntent.getActivity(this, 0, new Intent(this, NotifyActivity.class), 0);

详见代码:

private void showNotify(){
		PendingIntent pIntent = PendingIntent.getActivity(this, 0, new Intent(this, NotifyActivity.class), 0);	// pendingIntent
		
		Notification notify = new Notification();
		notify.icon = R.drawable.ic_launcher;
		notify.tickerText = "您有一条新消息";
		notify.defaults = Notification.DEFAULT_SOUND;
		notify.when = System.currentTimeMillis();
		notify.vibrate = new long[]{0, 50, 100, 150};
		notify.contentIntent = pIntent;
		notify.setLatestEventInfo(this, "通知", "http://blog.csdn.net/sunboy_2050", pIntent);	// context, title, msg, pendingIntent
		
		NotificationManager manager = (NotificationManager)getSystemService(this.NOTIFICATION_SERVICE);
		manager.notify(0, notify);
	}

通知结果:




GSM网络中android发送短信示例

private void showNotify222(){
		String phone = "13212341234";
		String msg = "http://blog.csdn.net/sunboy_2050";
		
		PendingIntent pIntent = PendingIntent.getBroadcast(this, 0, new Intent("com.homer.pendingintent.pendingbroadcast"), 0);		// pendingIntent
		
		SmsManager manager = SmsManager.getDefault();
		if(msg.length() > 70) {		// split msg length 
			List<String> msgList = manager.divideMessage(msg);
			for (String msg2 : msgList) {
				manager.sendTextMessage(phone, null, msg2, pIntent, null);		// destinationAddress, scAddress, text, sentIntent, deliveryIntent
			}
		} else {
			manager.sendTextMessage(phone, null, msg, pIntent, null);
		}
	}


AndroidManifest.xml 中 Application 节点内注册广播:

        <receiver android:name=".PendingReceiver">
            <intent-filter>
                <action android:name="com.homer.pendingintent.pendingbroadcast" />
            </intent-filter>
        </receiver>

PendingReceiver 类 主要处理 PendingIntent广播的事情,即发送短信成功后的提醒,实现如下:

public class PendingReceiver extends BroadcastReceiver {
	@Override
	public void onReceive(Context context, Intent intent) {
		if(intent.getAction().equals("com.homer.pendingintent.pendingbroadcast")) {
			Toast.makeText(context, "Test PendingIntent Success", Toast.LENGTH_LONG).show();
		}
	}
}

AndroidManifest.xml 根节点下,添加短信发送权限:

<uses-permission android:name="android.permission.SEND_SMS" />


运行结果:



代码下载


代码解释: 

PendingIntent 是一个Intent的描述(封装),可以把这个描述交给别的程序,别的程序根据这个描述在后面的时间做自己安排做的事情 (By giving a PendingIntent to another application, you are granting it the right to perform the operation you have specified as if the other application was yourself,就相当于PendingIntent代表了Intent。

本例中别的程序就是发送短信的程序,短信发送成功后要把intent广播出去

SmsManager.sendTextMessage(String destinationAddress, String scAddress, String text, PendingIntent sentIntent, PendingIntent deliveryIntent)

1)PendingIntent sentIntent:当短信发出时,成功的话sendIntent会把其内部的描述的intent广播出去,否则产生错误代码并通过android.app.PendingIntent.OnFinished进行回调,这个参数最好不为空,否则会存在资源浪费的潜在问题;

2)PendingIntent deliveryIntent:是当消息已经传递给收信人后所进行的PendingIntent广播。

如果BroadcastReveiver注册接收相应的消息,你就会收到相应的Intent,这时候就可以根据Intent的Action,执行相应的动作,这就是上面说的in the future的含义;

可以获得PendingIntent实例的静态方法

  • public static PendingIntent getActivity(Context context, int requestCode, Intent intent, int flags)  
  • public static PendingIntent getActivities(Context context, int requestCode, Intent[] intents, int flags)
  • public static PendingIntent getService(Context context, int requestCode, Intent intent, int flags) 
  • public static PendingIntent getBroadcast(Context context, int requestCode, Intent intent, int flags)

flags参数有四个:

1) FLAG_ONE_SHOT :this PendingIntent can only be used once. If set, after send() is called on it, it will be automatically canceled for you and any future attempt to send through it will fail.

2) FLAG_UPDATE_CURRENT :if the described PendingIntent already exists, then keep it but its replace its extra data with what is in this new Intent. This can be used if you are creating intents where only the extras change, and don't care that any entities that received your previous PendingIntent will be able to launch it with your new extras even if they are not explicitly given to it.

3) FLAG_NO_CREATE :if the described PendingIntent does not already exist, then simply return null instead of creating it.

4) FLAG_CANCEL_CURRENT :if the described PendingIntent already exists, the current one is canceled before generating a new one. You can use this to retrieve a new PendingIntent when you are only changing the extra data in the Intent; by canceling the previous pending intent, this ensures that only entities given the new data will be able to launch it. If this assurance is not an issue, consider FLAG_UPDATE_CURRENT.

FLAG_UPDATE_CURRENT 这个简单解释一下,就是当存在时,先把原来的取消,然后创建一个新的,在AlarmManager服务时修改一个闹铃,用的比较笨的的方法,先取消然后重新注册,其实加上这个参数就行了。要注意的是,这个只更新extra data,不会修改其他内容,不能new一个Intent,还有就是如果你的Intent中需要传递Id或者其他数据,一定要用这个flags或者FLAG_CANCEL_CURRENT,曾经一直接收不到Id,查了半天原来是这个原因


上面4个flag中最经常使用的是FLAG_UPDATE_CURRENT,因为Intent有更新的时候需要用到这个flag去更新你的描述(确切的说是更新extra data),否则组件在下次事件发生或时间到达的时候extras永远是第一次Intent的extras,使用FLAG_CANCEL_CURRENT也能做到更新extras,只不过是先把前面的extras清除,另外FLAG_CANCEL_CURRENT和FLAG_UPDATE_CURRENT的区别在于能否新new一个Intent,FLAG_CANCEL_CURRENT能够新new一个Intent,而FLAG_UPDATE_CURRENT则不能,只能使用第一次的Intent。
 

还有一个问题就是怎么区分PendingIntent,主要是取消的时候要用到requestCode区分,但系统还是根据Intent的Action去区分的,如果Intent设置了Class,classData,取消的时候Intent一定要设置要相同的,不然取消不掉就可能出现取消后Alarm还会响的问题,PendingIntent用的地方蛮多的,像 Notifications, AlarmManager等都会用到。。。

查看PendingIntent 类可以看到许多的Send函数,就是PendingIntent在进行被赋予的相关的操作。



参考推荐:

PendingIntent(Android Developer)

PendingIntent与Intent区别

android发送短信



原文链接:http://blog.csdn.net/sunboy_2050/article/details/8333593
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