BroadcastReceiver简介和用法实例，两种注册方式 （二）

一.BroadcastReceiver简介?

???BraodcastReceiver(广播接收器)是为了实现系统广播而提供的一种组件，它和事件处理机制类似，但是事件处理机制是程序组件级别的，而广播事件处理机制是系统级别的。比如，我们可以发出一种广播来测试手机电量的变化，这时候就可以定义一个BraodcastReceiver来接受广播，当手机电量较低时提示用户。我们既可以用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BroadcastReceiver来监听和响应广播的Intent。

?? 在程序中使用BraodcastReceiver是比较简单的。首先要定义一个类继承BraodcastReceiver，并且覆盖onReceiver()方法来响应事件。然后注册在程序中BraodcastReceiver。最后构建Intent对象调用sendBroadcast()方法将广播发出。

二.BroadcastReceiver的注册方式

?1.静态注册方式

???静态注册方式是在AndroidManifest.xml的application里面定义receiver并设置要接收的action。静态注册方式的特点：不管改应用程序是否处于活动状态，都会进行监听，比如某个程序时监听内存?的使用情况的，当在手机上安装好后，不管改应用程序是处于什么状态，都会执行改监听方法中的内容。

下面是具体的例子：

MainActivity.java

package?com.android.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?MainActivity?extends?Activity{ ?
????//定义action常量 ?
????protected?static?final?String?ACTION?=?"com.android.broadcast.RECEIVER_ACTION"; ?
????//定义Button对象 ?
????private?Button?btnBroadcast; ?
????@Override?
????public?void?onCreate(Bundle?savedInstanceState){ ?
????????super.onCreate(savedInstanceState); ?
????????setContentView(R.layout.main); ?
????????btnBroadcast=(Button)findViewById(R.id.btnBroadcast); ?
????????//为按钮设置单击监听器 ?
????????btnBroadcast.setOnClickListener(new?OnClickListener(){ ?
????????????@Override?
????????????public?void?onClick(View?v){ ?
????????????????//实例化Intent ?
????????????????Intent?intent=new?Intent(); ?
????????????????//设置Intent的action属性 ?
????????????????intent.setAction(ACTION); ?
????????????????//发出广播 ?
????????????????sendBroadcast(intent); ?
????????????} ?
????????}); ?
????} ?
}?

在“com.android.broadcast”包中定义一个MyReceiver类，继承于BroadcastReceiver，覆盖onReceive()方法。

MyReceiver.java

package?com.android.broadcast; ?
?
import?android.content.BroadcastReceiver; ?
import?android.content.Context; ?
import?android.content.Intent; ?
import?android.util.Log; ?
?
public?class?MyReceiver?extends?BroadcastReceiver{ ?
???//定义日志标签 ?
????private?static?final?String?TAG?=?"Test"; ?
????@Override?
????public?void?onReceive(Context?context,?Intent?intent){ ?
????????//输出日志信息 ?
????????Log.i(TAG,?"MyReceiver?onReceive--->"); ?
????} ?
} ?

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"?
????>?
????<Button?
????????android:id="@+id/btnBroadcast"?
????????android:layout_width="match_parent"?
????????android:layout_height="wrap_content"?
????????android:text="发送Broadcast"?
????????/>?
</LinearLayout>?

在AndroidManifest.xml配置文件中16~20行声明receiver

<?xml?version="1.0"?encoding="utf-8"?>?
<manifest?xmlns:android="http://schemas.android.com/apk/res/android"?
??????package="com.android.broadcast"?
??????android:versionCode="1"?
??????android:versionName="1.0">?
????<uses-sdk?android:minSdkVersion="10"?/>?
?
????<application?android:icon="@drawable/icon"?android:label="@string/app_name">?
????????<activity?android:name=".MainActivity"?
??????????????????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="MyReceiver">?
????????????<intent-filter>?
????????????????<action?android:name="com.android.broadcast.RECEIVER_ACTION"/>?
????????????</intent-filter>?
????????</receiver>?
????</application>?
</manifest>?

效果图：

?

?当我们点击按钮的时候，程序会调用onReceive()方法，LogCat输出信息如下：

?2.动态注册方式

?? 动态注册方式在activity里面调用函数来注册，和静态的内容差不多。一个形参是receiver，另一个是IntentFilter，其中里面是要接收的action。动态注册方式特点：在代码中进行注册后，当应用程序关闭后，就不再进行监听。

下面是具体的例子：

?MainActivity.java

package?com.android.broadcast; ?
?
import?android.app.Activity; ?
import?android.content.Intent; ?
import?android.content.IntentFilter; ?
import?android.os.Bundle; ?
import?android.view.View; ?
import?android.view.View.OnClickListener; ?
import?android.widget.Button; ?
?
public?class?MainActivity?extends?Activity{ ?
????//定义Action常量 ?
????protected?static?final?String?ACTION?=?"com.android.broadcast.RECEIVER_ACTION"; ?
????private?Button?btnBroadcast; ?
????private?Button?registerReceiver; ?
????private?Button?unregisterReceiver; ?
????private?MyReceiver?receiver; ?
????@Override?
????public?void?onCreate(Bundle?savedInstanceState){ ?
????????super.onCreate(savedInstanceState); ?
????????setContentView(R.layout.main); ?
????????btnBroadcast=(Button)findViewById(R.id.btnBroadcast); ?
????????//创建事件监听器 ?
????????btnBroadcast.setOnClickListener(new?OnClickListener(){ ?
????????????@Override?
????????????public?void?onClick(View?v){ ?
????????????????Intent?intent=new?Intent(); ?
????????????????intent.setAction(ACTION); ?
????????????????sendBroadcast(intent); ?
????????????} ?
????????}); ?
???????? ?
????????registerReceiver=(Button)findViewById(R.id.btnregisterReceiver); ?
????????//创建事件监听器 ?
????????registerReceiver.setOnClickListener(new?OnClickListener(){ ?
????????????@Override?
????????????public?void?onClick(View?v){ ?
????????????????receiver=new?MyReceiver(); ?
????????????????IntentFilter?filter=new?IntentFilter(); ?
????????????????filter.addAction(ACTION); ?
????????????????//动态注册BroadcastReceiver ?
????????????????registerReceiver(receiver,?filter); ?
????????????} ?
????????}); ?
???????? ?
????????unregisterReceiver=(Button)findViewById(R.id.btnunregisterReceiver); ?
????????//创建事件监听器 ?
????????unregisterReceiver.setOnClickListener(new?OnClickListener(){ ?
????????????@Override?
????????????public?void?onClick(View?v){ ?
????????????????//注销BroadcastReceiver ?
????????????????unregisterReceiver(receiver); ?
????????????} ?
????????}); ?
????} ?
}?

?在“com.android.broadcast”包中定义一个MyReceiver类，继承于BroadcastReceiver，覆盖onReceive()方法。

MyReceiver.java

package?com.android.broadcast; ?
?
import?android.content.BroadcastReceiver; ?
import?android.content.Context; ?
import?android.content.Intent; ?
import?android.util.Log; ?
?
public?class?MyReceiver?extends?BroadcastReceiver{ ?
????//定义日志标签 ?
????private?static?final?String?TAG?=?"Test"; ?
????@Override?
????public?void?onReceive(Context?context,?Intent?intent){ ?
????????//输出日志信息 ?
????????Log.i(TAG,?"MyReceiver?onReceive--->"); ?
????} ?
} ?

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"?
????>?
????<Button?
????????android:id="@+id/btnBroadcast"?
????????android:layout_width="match_parent"?
????????android:layout_height="wrap_content"?
????????android:text="发送广播"?
????????/>?
????<Button?
????????android:id="@+id/btnregisterReceiver"?
????????android:layout_width="match_parent"?
????????android:layout_height="wrap_content"?
????????android:text="注册广播接收器"?
????????/>?
????<Button?
????????android:id="@+id/btnunregisterReceiver"?
????????android:layout_width="match_parent"?
????????android:layout_height="wrap_content"?
????????android:text="注销广播接听器"?
????????/>?
</LinearLayout>?

效果图：

?

①当我们首先点击按钮的时候，因为程序没有注册BraodcastReceiver，所以LogCat没有输出任何信息。

②当我们先点击再点击按钮的时候，这时程序会动态的注册BraodcastReceiver，之后会调用onReceive()方法，LogCat输出信息如下：

?

?③当我们点击按钮的时候，这时程序会注销BraodcastReceiver，再点击，LogCat没有输出任何信息。

三.BroadcastReceiver?的生命周期

???一个BroadcastReceiver 对象只有在被调用onReceive(Context, Intent)的才有效的，当从该函数返回后，该对象就无效的了，结束生命周期。

?

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