玩转Android-组件篇-Broadcast Receiver（播音接收器）

Braodcast Receiver顾名思义就是广播接收器，它和时间处理机制类似，但是事件处理机制是程序组件级别的（比如：按钮的单击事件），而广播事件处理机制是系统级别的。我们可以用Intent来启动一个组件，也可以用sendBroadcast()方法发起一个系统级别的事件广播来传递消息。我们同样可以在自己的应用程序中实现Broadcast Receiver来监听和响应广播的Intent。

事件的广播通过创建Intent对象并调用sendBroadcast()方法将广播发出。事件的接受是通过定义一个继承BroadcastReceiver的类来实现的，继承该类后覆盖其onReceive()方法，在该方法中响应时间。

下面是android系统中定义了很多标准的Broadcast Action来响应系统的广播事件。

①ACTION_TIME_CHANGED（时间改变时触发）

②ACTION_BOOT_COMPLETED(系统启动完成后触发)--比如有些程序开机后启动就是用这种方式来实现的

③ACTION_PACKAGE_ADDED（添加包时触发）

④ACTION_BATTERY_CHANGED（电量低时触发）

详细：标准广播ACTION常量

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在这里，要练习3个内容

①自定义Broadcast Receiver

②Notification和NotificationManager的使用

③AlarmManager的使用

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1、首先看一个自定义的广播事件的例子

package org.hualang.broadcast;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class BroadCastTest extends Activity {    /** Called when the activity is first created. */	private static final String MY_ACTION="org.hualang.broadcast.action.MY_ACTION";	private Button btn;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        btn=(Button)findViewById(R.id.button);        btn.setOnClickListener(new OnClickListener()        {			@Override			public void onClick(View arg0) {				// TODO Auto-generated method stub				Intent intent=new Intent();				intent.setAction(MY_ACTION);				intent.putExtra("msg", "同志们好！同志们辛苦啦！");				sendBroadcast(intent);			}        	        });    }}

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MyReceiver.java

package org.hualang.broadcast;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.widget.Toast;public class MyReceiver extends BroadcastReceiver {	@Override	public void onReceive(Context arg0, Intent arg1) {		// TODO Auto-generated method stub		String msg=arg1.getStringExtra("msg");		Toast.makeText(arg0, msg, Toast.LENGTH_LONG).show();	}	}

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注意：在AndroidManifest.xml文件中注册

<receiver android:name="MyReceiver">			<intent-filter>				<action android:name="org.hualang.broadcast.action.MY_ACTION"/>			</intent-filter>		</receiver>

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我们还可以在AndroidManifest.xml文件中注销一个广播接收器，一般在Activity.onResume()方法中使用Context.registerReceiver()方法来注册一个广播接收器，在Activity.onPause()中使用unregisterReceiver(r)方法注销一个广播接收器，例如：

//实例化intent过滤器

IntentFilter filter = new IntentFilte()；

//实例化Receiver

MyReceiver r = new Receiver();

//注册Receiver

registerReceiver(r,filter);

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为了注销一个BroadcastReceiver，应使用Context.unregisterReceiver方法，传入一个BroadcastReceiver实例

//注销

unregisterReceiver(r);

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2、下面的是Notification的例子，比如手机来短信的时候，会在屏幕最上边有一个通知，那个就是Notification

DisplayActivity.java

package org.hualang.notify;import android.app.Activity;import android.app.Notification;import android.app.NotificationManager;import android.app.PendingIntent;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class DisplayActivity extends Activity {	private Button cancelbtn;	private Notification n;	private NotificationManager nm;	private static final int ID=1;	public void onCreate(Bundle savedInstanceState)	{		super.onCreate(savedInstanceState);		setContentView(R.layout.main2);		cancelbtn = (Button)findViewById(R.id.button2);		String service = NOTIFICATION_SERVICE;		nm = (NotificationManager)getSystemService(service);				n = new Notification();		int icon = n.icon =R.drawable.icon;		String tickerText = "喜欢HTC的样子，喜欢defy的配置";		long when = System.currentTimeMillis();		n.icon = icon;		n.tickerText = tickerText;		n.when = when;				Intent intent = new Intent(this,NotifyTest2.class);		PendingIntent pi = PendingIntent.getActivity(this, 0 , intent , 0);		n.setLatestEventInfo(this, "My Title", "My Content", pi);		nm.notify(ID, n);		cancelbtn.setOnClickListener(cancelListener);	}	private OnClickListener cancelListener=new OnClickListener()	{		public void onClick(View v)		{			nm.cancel(ID);		}	};}

?MyReceiver.java

package org.hualang.notify;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;public class MyReceiver extends BroadcastReceiver {	@Override	public void onReceive(Context context, Intent intent) {		// TODO Auto-generated method stub		Intent i=new Intent();		i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);		i.setClass(context,DisplayActivity.class);		context.startActivity(i);	}	}

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NotifyTest2.java

package org.hualang.notify;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class NotifyTest2 extends Activity {    /** Called when the activity is first created. */	private Button btn;	private static final String MY_ACTION="org.hualang.notify.aciton.MY_ACITON";    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        btn=(Button)findViewById(R.id.button);        btn.setOnClickListener(listener);    }    private OnClickListener listener=new OnClickListener()    {    	public void onClick(View v)    	{    		Intent intent=new Intent();    		intent.setAction(MY_ACTION);    		sendBroadcast(intent);    	}    };}

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注册AndroidManifest.xml

<receiver android:name="MyReceiver">			<intent-filter>				<action android:name="org.hualang.notify.aciton.MY_ACITON"/>			</intent-filter>		</receiver>		<activity android:name="DisplayActivity">		</activity>

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运行结果如下：

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3、下面是AlarmManager的例子，它是一个闹钟，感兴趣的朋友可以自己写一个小闹钟

AlarmManager常用的属性和方法

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AlarmTest.java

package org.hualang.alarm;import android.app.Activity;import android.app.AlarmManager;import android.app.PendingIntent;import android.content.Intent;import android.os.Bundle;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class AlarmTest extends Activity {    /** Called when the activity is first created. */	private Button btn1,btn2;	private static final String BC_ACTION="org.hualang.alarm.action.BC_ACTION";    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        btn1 = (Button)findViewById(R.id.button1);        btn2 = (Button)findViewById(R.id.button2);                final AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);        Intent intent = new Intent();        intent.setAction(BC_ACTION);        intent.putExtra("msg", "你该起床了");        final PendingIntent pi = PendingIntent.getBroadcast(AlarmTest.this, 0, intent, 0);        final long time = System.currentTimeMillis();                btn1.setOnClickListener(new OnClickListener()        {        	public void onClick(View v)        	{        		        		am.setRepeating(AlarmManager.RTC_WAKEUP, time, 5*1000, pi);        	}        });        btn2.setOnClickListener(new OnClickListener()        {        	public void onClick(View v)        	{        		am.cancel(pi);        	}        });    }}

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MyReceiver.java

package org.hualang.alarm;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.util.Log;import android.widget.Toast;public class MyReceiver extends BroadcastReceiver {	@Override	public void onReceive(Context context, Intent intent) {		// TODO Auto-generated method stub		String msg=intent.getStringExtra("msg");		Log.v("SERVICE","QIAN----------------------");		Toast.makeText(context, msg, Toast.LENGTH_LONG).show();		Log.v("SERVICE", "HOU-----------------------");	}}

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注册AndroidManifest.xml

<receiver android:name="MyReceiver">			<intent-filter>				<action android:name="org.hualang.alarm.action.BC_ACTION"/>			</intent-filter>		</receiver>

?运行结果：

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?点击设置闹钟后，会每隔5秒弹出一个Toast，点击取消闹钟就不会弹出了

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