Android入門筆記之BroadcastReceiver

Android入門筆記之BroadcastReceiver

<1>簡介

廣播接收者（BroadcastReceiver）用於異步接收廣播Intent，廣播Intent的發送是通過調用Context.sendBroadcast()、Context.sendOrderedBroadcast()或者Context.sendStickyBroadcast()來實現的。通常一個廣播Intent可以被訂閱了此Intent的多個廣播接收者所接收。

<2>關鍵步驟

第一步：要想實現一個廣播機制，就必須實現一個類，這個類繼承於BroadcastReceiver並重寫onReceive()方法。

事件響應的實現應在onReceive方法中實現。

第二步：訂閱感興趣的廣播Intent，訂閱方法有兩種：
第一種：使用代碼進行訂閱
IntentFilter filter = newIntentFilter("android.provider.Telephony.SMS_RECEIVED");
IncomingSMSReceiver receiver = new IncomingSMSReceiver();
registerReceiver(receiver, filter);
第二種：在AndroidManifest.xml文件中的<application>節點裏進行註冊:
<intent-filter>是一個過濾器。

在發送廣播過程中，如果某個BroadCastReceiver的Action和這裏的Action相符合，則啓動，接受廣播。

生命週期：

每次廣播到來時,會重新創建BroadcastReceiver對象,並且調用onReceive()方法,執行完以後,該對象即被銷燬.當onReceive()方法在10秒內沒有執行完畢，Android會認爲該程序無響應.所以在BroadcastReceiver裏不能做一些比較耗時的操作,否側會彈出ANR(Application NoResponse)的對話框.。

 

<3>出現的問題

       Toast千萬不要不要忘記show啊

<4>代碼及解釋

       BroadcastActivity.java:

package com.test;

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 BroadcastActivity extends Activity{
	/**   
	 * @ProjectName:  [androidtest] 
	 * @Package:      [com.func.BroadcastActivity.java]  
	 * @ClassName:    [BroadcastActivity]   
	 * @Description:    
	 * @Author:       [gmj]   
	 * @CreateDate:   [2013-9-9 下午7:18:59]   
	 * @Version:      [v1.0] 
	 */
	public static final String MY_ACTION = "gmj";
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		Button but = (Button) findViewById(R.id.broadcastButton);
		but.setOnClickListener(new OnClickListener(){

			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				
				Intent intent = new Intent();
				intent.setAction(MY_ACTION);
				intent.putExtra("msg", "hello");
				sendBroadcast(intent);
				Toast.makeText(BroadcastActivity.this, "broadcast ", Toast.LENGTH_LONG).show();
			}
			
		});
	}
}

BroadRceiver.java:

package com.test;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class BroadReceiver extends BroadcastReceiver{
	/**   
	 * @ProjectName:  [androidtest] 
	 * @Package:      [com.func.BroadReceiver.java]  
	 * @ClassName:    [BroadReceiver]   
	 * @Description:    
	 * @Author:       [gmj]   
	 * @CreateDate:   [2013-9-9 下午7:31:28]   
	 * @Version:      [v1.0] 
	 */
	
	public BroadReceiver(){
		System.out.println("receive");
	}
	
	@Override
	public void onReceive(Context arg0, Intent arg1) {
		// TODO Auto-generated method stub
		System.out.println("onReceive");
		Toast.makeText(arg0, "the action is" + arg1.getAction() + "and msg is" + arg1.getStringExtra("msg"), Toast.LENGTH_LONG).show();
	}

}