[android开发入门]初识BroadcastReceiver

来源：互联网发布：ftp需要开放的端口编辑：程序博客网时间：2024/06/13 16:57

作者：sundroid

个人站点：sundroid.cn 邮箱： hfutsnjc@163.com 微博：http://weibo.com/Sundroid

Android系统引入了一种信息传播机制-BroadcastReceiver，这是一种广泛应用于程序之间传输信息的方式，在系统运行过程中会产生很多的系统通知，比如地域变换、电量不足，BroadcastReceiver就相当于收音机，而许许多多的广播台就是消息的发送者，它们通过特定的频率（Action相同），来接受和发送内容。

在Android系统中发送和接收工作分别由sendBroadcast(Intent intent)方法和注册的BroadcastReceiver类来完成，并且只有发送sendBroadcast(Intent intent)和在manifests中
BroadcastReceiver注册的action一致，才可以正确接收信息。

MainActivity

package cn.sundroid.broadcast;import android.app.Activity;import android.content.Intent;import android.support.v7.app.ActionBarActivity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.Button;public class MainActivity extends Activity {    private Button send;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        send = (Button) findViewById(R.id.send);        send.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent();                //设置广播内容                intent.putExtra("CONTENT","test broadcast");                //设置广播的action                intent.setAction("cn.sundroid.broadcast");                //发送广播                sendBroadcast(intent);            }        });    }}

Receiver

package cn.sundroid.broadcast;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.util.Log;public class Receiver extends BroadcastReceiver {    /**     *     * @param context     * @param intent     */    @Override    public void onReceive(Context context, Intent intent) {        Log.i("RECEIVER",intent.getStringExtra("CONTENT"));    }}

OtherReceiver

package cn.sundroid.broadcast;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.util.Log;public class OtherReceiver extends BroadcastReceiver {    @Override    public void onReceive(Context context, Intent intent) {        // TODO: This method is called when the BroadcastReceiver is receiving        Log.i("OTHERRECEIVER", intent.getStringExtra("CONTENT"));    }}

mainfest

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="cn.sundroid.broadcast" >    <application        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:theme="@style/AppTheme" >        <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=".Receiver"            android:enabled="true"            android:exported="true" >            <intent-filter>                <action android:name="cn.sundroid.broadcast" />            </intent-filter>        </receiver>        <receiver            android:name=".OtherReceiver"            android:enabled="true"            android:exported="true" >            <intent-filter>                <action android:name="cn.sundroid.receiver" />            </intent-filter>        </receiver>    </application></manifest>

我们可以看出结果中打印的Log为"RECEIVER"+test broadcast，这里的调用的BroadcastReceiver为Receiver，而不是OtherReceiver，就是因为OtherReceiver在manifests里面注册的anction和sendBroadcast(Intent intent)里面设置的Action不一致的结果，那么如果Receiver和OtherReceiver在manifests里都设置相同的action，结果会如何呢？

这里就不必再做解释了吧！

后台服务还可以查看初识Service

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