Android中使用LocalBroadcastManager发送进程内广播

分类：Android, Java 阅读 (2,924) Add comments

3月 182016

转载请注明原文地址：http://bcoder.com/java/use-localbroadcastmanager-to-broadcast-messages-in-process

　　LocalBroadcastManager是support v4包里提供的一个组件，它只负责进程内发送广播和接收消息，它的优点如下：

广播消息只在进程内发送，不会造成数据泄露
只接收进程内的广播消息，不会有广播方面的安全问题
比全局的广播效率更高

　　LocalBroadcastManager的实现原理：我们通常都是通过LocalBroadcastManager.getInstance(Context context)来获得它的实例的，通过查看LocalBroadcastManager的代码，笔者发现它的实现并不复杂，它其实是一个单实例对象，那么我们在整个进程内使用的其实是一个LocalBroadcastManager对象，这个单实例对象负责注册消息和分发消息。

　　了解了一下它的原理，下面我们就用一个小demo来使用一下它吧：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.administrator.androidtest.LocalBroadCastMgrActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Text"
        android:id="@+id/tvReceiver"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Send"
        android:id="@+id/button24"
        android:layout_below="@+id/tvReceiver"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="94dp"
        android:onClick="onBtnSendClick" />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:paddingBottom="@dimen/activity_vertical_margin"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

tools:context="com.example.administrator.androidtest.LocalBroadCastMgrActivity">

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="New Text"

android:id="@+id/tvReceiver"

android:layout_alignParentTop="true"

android:layout_centerHorizontal="true" />

<Button

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Send"

android:id="@+id/button24"

android:layout_below="@+id/tvReceiver"

android:layout_centerHorizontal="true"

android:layout_marginTop="94dp"

android:onClick="onBtnSendClick" />

</RelativeLayout>

package com.example.administrator.androidtest;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.support.v4.content.LocalBroadcastManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class LocalBroadCastMgrActivity extends Activity {
    LocalBroadcastManager localBroadcastManager;
    MyMsgReceiver myMsgReceiver;

    TextView tvReceiver ;

    public static String BROADCAST_ACTION = "com.bcoder.test.localbroadcast";
    public static String INTENTEXTRA_MYWEBSITE = "mywebsite";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_local_broad_cast_mgr);

        tvReceiver = (TextView) findViewById(R.id.tvReceiver);
    }

    @Override
    protected void onStart() {
        super.onStart();
        myMsgReceiver = new MyMsgReceiver();
        IntentFilter intentFilter = new IntentFilter(BROADCAST_ACTION);
        localBroadcastManager = LocalBroadcastManager.getInstance(this);
        //注册广播消息接收器
        localBroadcastManager.registerReceiver(myMsgReceiver, intentFilter);
    }

    @Override
    protected void onStop() {
        //删除已注册的广播
        localBroadcastManager.unregisterReceiver(myMsgReceiver);
        super.onStop();
    }

    public void onBtnSendClick(View v){
        Intent intent = new Intent(BROADCAST_ACTION);
        intent.putExtra(INTENTEXTRA_MYWEBSITE, "http://svn1.bcoder.com");
        //在其他Activity或者服务中使用时可以直接使用LocalBroadcastManager.getInstance，不用再定义变量
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
    }

    //定义自己的广播接收类
    class MyMsgReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            if(null != intent && null != intent.getStringExtra(INTENTEXTRA_MYWEBSITE)){
                tvReceiver.setText(String.format("我的网站: %s", intent.getStringExtra(INTENTEXTRA_MYWEBSITE)));
            }
        }
    }
}

package com.example.administrator.androidtest;

import android.app.Activity;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.content.IntentFilter;

import android.support.v4.content.LocalBroadcastManager;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.TextView;

public class LocalBroadCastMgrActivity extends Activity {

LocalBroadcastManager localBroadcastManager;

MyMsgReceiver myMsgReceiver;

TextView tvReceiver ;

public static String BROADCAST_ACTION = "com.bcoder.test.localbroadcast";

public static String INTENTEXTRA_MYWEBSITE = "mywebsite";

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_local_broad_cast_mgr);

tvReceiver = (TextView) findViewById(R.id.tvReceiver);

}

@Override

protected void onStart() {

super.onStart();

myMsgReceiver = new MyMsgReceiver();

IntentFilter intentFilter = new IntentFilter(BROADCAST_ACTION);

localBroadcastManager = LocalBroadcastManager.getInstance(this);

//注册广播消息接收器

localBroadcastManager.registerReceiver(myMsgReceiver, intentFilter);

}

@Override

protected void onStop() {

//删除已注册的广播

localBroadcastManager.unregisterReceiver(myMsgReceiver);

super.onStop();

}

public void onBtnSendClick(View v){

Intent intent = new Intent(BROADCAST_ACTION);

intent.putExtra(INTENTEXTRA_MYWEBSITE, "http://svn1.bcoder.com");

//在其他Activity或者服务中使用时可以直接使用LocalBroadcastManager.getInstance，不用再定义变量

LocalBroadcastManager.getInstance(this).sendBroadcast(intent);

}

//定义自己的广播接收类

class MyMsgReceiver extends BroadcastReceiver{

@Override

public void onReceive(Context context, Intent intent) {

if(null != intent && null != intent.getStringExtra(INTENTEXTRA_MYWEBSITE)){

tvReceiver.setText(String.format("我的网站: %s", intent.getStringExtra(INTENTEXTRA_MYWEBSITE)));

}

　　注意事项：

Android桌面组件和app不在一个进程内，不能使用LocalBroadcastManager进行广播
LocalBroadcastManager注册的消息只有使用LocalBroadcastManager发送才能接收到，同样LocalBroadcastManager发出的消息只有它注册的消息才能接收
LocalBroadcastManager和全局广播可以同时使用，以便于和其它的app进行通讯

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