一、广播发送者&广播接收者介绍
1.广播接收者
广播接收者简单地说就是接收广播意图的Java类,此Java类继承BroadcastReceiver类,重写:
public void onReceive(Context context,Intent intent),其中intent可以获得传递的数据;
广播意图就是通过Context.sendBroadcast(Intent intent)或Context.sendOrderedBroadcast(Intent intent)发送的意图,通过这个语句,能够广播给所有满足条件的组件,比如intent设置了action="com.xiazdong",则所有在AndroidManifest.xml中设置过<action android:name="com.xiazdong"/>的广播接收者都能够接收到广播;
注:onReceive方法必须在10秒内完成,如果没有完成,则抛“Application No Response”当广播接收者onReceive方法需要执行很长时间时,最好将此耗时工作通过Intent发送给Service,由Service完成,并且不能使用子线程解决,因为BroadcastReceiver是接收到广播后才创建的,并且生命周期很短,因此子线程可能在没有执行完就已经被杀死了。
public void onReceive(Context context,Intent intent){
Intent intent = new Intent(context,XxxService.class);
context.startService(intent);
}
2.广播发送者
通常广播发送方就是调用Context.sendBroadcast()的程序,而广播接收者就是继承BroadcastReceiver的程序;
通常广播发送方都是通过隐式意图,这样才能发送给多人;
广播发送方分为普通广播和有序广播;
普通广播:发送方发出后,几乎同时到达多个广播接收者处,某个接收者不能接收到广播后进行一番处理后传给下一个接收者,并且无法终止广播继续传播;Context.sendBroadcast(intent);
有序广播:广播接收者需要提前设置优先级,优先级高的先接收到广播,优先级数值为-1000~1000,在AndroidManifest.xml的<intent-filter android:priority="xxx">设置;比如存在3个广播接收者A、B、C,优先级A>B>C,因此A最先收到广播,当A收到广播后,可以向广播中添加一些数据给下一个接收者(intent.putExtra()),或者终止广播(abortBroadcast());
Context.sendOrderedBroadcast(intent);
二、广播接收者核心代码
同步广播发送方核心代码:
Intent intent = new Intent();
intent.setAction("...");
Context.sendBroadcast(intent);
有序广播发送方核心代码:
Intent intent = new Intent();
intent.setAction("...");
Context.sendOrderedBroadcast(intent,null);
广播接收者核心代码:
public class Receiver extends BroadcastReceiver{
public void onReceive(Context context, Intent intent) {
Bundle bundle = intent.getExtras();
...
}
}
AndroidManifest.xml
<application>
<receiver android:name=".Receiver">
<intent-filter android:priority="1000">
<action android:name="com.xiazdong"/>
</intent-filter>
</receiver>
</application>
三、广播实例
1.同步广播实例
(1)广播发送者:
package com.xiazdong.broadcastsender;
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;
import android.widget.Toast;
public class MainActivity extends Activity {
private Button button;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
button = (Button)this.findViewById(R.id.button);
button.setOnClickListener(listener);
}
private OnClickListener listener = new OnClickListener(){
@Override
public void onClick(View v) {
Intent intent = new Intent();
intent.setAction("com.xiazdong");
intent.putExtra("name", "xiazdong");
MainActivity.this.sendBroadcast(intent);
Toast.makeText(getApplicationContext(), "发送广播成功", Toast.LENGTH_SHORT).show();
}
};
}
(2)广播接收者
package com.xiazdong.broadcastreceiver1;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class Receiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
String name = intent.getExtras().getString("name");
Log.i("Recevier1", "接收到:"+name);
}
}
AndroidManifest.xml
<receiver android:name=".Receiver">
<intent-filter>
<action android:name="com.xiazdong"/>
</intent-filter>
</receiver>
2.有序广播实例
场景说明:
(1)广播发送者
package com.xiazdong.broadcastsender;
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;
import android.widget.Toast;
public class MainActivity extends Activity {
private Button button;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
button = (Button)this.findViewById(R.id.button);
button.setOnClickListener(listener);
}
private OnClickListener listener = new OnClickListener(){
@Override
public void onClick(View v) {
Intent intent = new Intent();
intent.setAction("com.xiazdong");
intent.putExtra("name", "xiazdong");
MainActivity.this.sendOrderedBroadcast(intent, null); //有序广播发送
Toast.makeText(getApplicationContext(), "发送广播成功", Toast.LENGTH_SHORT).show();
}
};
}
(2)广播接收者
Receiver1
package com.xiazdong.broadcastreceiver1;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class Receiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
String name = intent.getExtras().getString("name");
Log.i("Recevier1", "接收到:"+name);
abortBroadcast(); //Receiver1接收到广播后中断广播
}
}
AndroidManifest.xml
<receiver android:name=".Receiver">
<intent-filter android:priority="1000"> <!-- 设置最高优先级 -->
<action android:name="com.xiazdong"/>
</intent-filter>
</receiver>
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