一、廣播寄件者&廣播接收者介紹
1.廣播接收者
廣播接收者簡單地說就是接收廣播意圖的Java類,此Java類繼承BroadcastReceiver類,重寫:
public void onReceive(Context context,Intent intent),其中intent可以獲得傳遞的資料;
廣播意圖就是通過Context.sendBroadcast(Intent intent)或Context.sendOrderedBroadcast(Intent intent)發送的意圖,通過這個語句,能夠廣播給所有滿足條件的組件,比如intent設定了action="com.xiazdong",則所有在AndroidManifest.xml中設定過<action android:name="com.xiazdong"/>的廣播接收者都能夠接收到廣播;
注:onReceive方法必須在10秒內完成,如果沒有完成,則拋“Application No Response”當廣播接收者onReceive方法需要執行很長時間時,最好將此耗時工作通過Intent發送給Service,由Service完成,並且不能使用子線程解決,因為BroadcastReceiver是接收到廣播後才建立的,並且生命週期很短,因此子線程可能在沒有執行完就已經被殺死了。
public void onReceive(Context context,Intent intent){Intent intent = new Intent(context,XxxService.class);context.startService(intent);}
2.廣播寄件者
通常廣播發送方就是調用Context.sendBroadcast()的程式,而廣播接收者就是繼承BroadcastReceiver的程式;
通常廣播發送方都是通過隱式意圖,這樣才能發送給多人;
廣播發送方分為普通廣播和有序廣播;
同步廣播:發送方發出後,幾乎同時到達多個廣播接收者處,某個接收者不能接收到廣播後進行一番處理後傳給下一個接收者,並且無法終止廣播繼續傳播;Context.sendBroadcast(intent);
有序廣播:廣播接收者需要提前設定優先權,優先順序高的先接收到廣播,優先順序數值為-1000~1000,在AndroidManifest.xml的<intent-filter android:priority="xxx">設定;比如存在3個廣播接收者A、B、C,優先順序A>B>C,因此A最先收到廣播,當A收到廣播後,可以向廣播中添加一些資料給下一個接收者(intent.putExtra()),或者終止廣播(abortBroadcast());Context.sendOrderedBroadcast(intent);
二、廣播接收者核心代碼
同步廣播發送方核心代碼:
Intent intent = new Intent();intent.setAction("...");Context.sendBroadcast(intent);
有序廣播發送方核心代碼:
Intent intent = new Intent();intent.setAction("...");Context.sendOrderedBroadcast(intent,null);
廣播接收者核心代碼:
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、廣播執行個體
1.同步廣播執行個體
情境說明:
(1)廣播寄件者:
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;private OnClickListener listener = new OnClickListener(){@Overridepublic void onClick(View v) {Intent intent = new Intent();intent.setAction("com.xiazdong");intent.putExtra("name", "xiazdong");MainActivity.this.sendBroadcast(intent);Toast.makeText(getApplicationContext(), "發送廣播成功", Toast.LENGTH_SHORT).show();}};@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); button = (Button)this.findViewById(R.id.button); button.setOnClickListener(listener); }}
(2)廣播接收者
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 {@Overridepublic 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>
結果:
2.有序廣播執行個體
情境說明:
(1)廣播寄件者
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;private OnClickListener listener = new OnClickListener(){@Overridepublic void onClick(View v) {Intent intent = new Intent();intent.setAction("com.xiazdong");intent.putExtra("name", "xiazdong");MainActivity.this.sendOrderedBroadcast(intent, null);//有序廣播發送Toast.makeText(getApplicationContext(), "發送廣播成功", Toast.LENGTH_SHORT).show();}};@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); button = (Button)this.findViewById(R.id.button); button.setOnClickListener(listener); }}
(2)廣播接收者
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 {@Overridepublic void onReceive(Context context, Intent intent) {String name = intent.getExtras().getString("name");Log.i("Recevier1", "接收到:"+name);abortBroadcast();//Receiver1接收到廣播後中斷廣播}}
AndroidManifest.xml
<receiver android:name=".Receiver"> <intent-filter android:priority="1000"><!-- 設定最高優先順序 --> <action android:name="com.xiazdong"/> </intent-filter> </receiver>