Android学习总结——本地广播机制

   为了简单解决广播的安全性问题，Android引入了一套本地广播机制，使用这个机制发出的广播只能在程序的内部进行传递，只能接受来自本应用程序发出的广播。否则当我们发送一些携带关键数据的广播可能被截获，一些恶意程序也可能向我们的广播接收器中发送各种垃圾广播。

用法如下：（主要就是使用LocalBroadcastManager来对广播进行管理，并提供注册广播和发送广播的方法）。

package com.example.xch.localbroadcast;

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.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private IntentFilter intentFilter;
    private Button sendBroadcast;
    private LocalReceiver localReceiver;
    private LocalBroadcastManager localBroadcastManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        localBroadcastManager=LocalBroadcastManager.getInstance(this);//通过getInstance()得到LocalBroadcastManager的实例

        sendBroadcast=(Button) findViewById(R.id.sendBroadcast);
        sendBroadcast.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //发送本地广播
                Intent intent=new Intent("com.example.LOCAL_BROADCAST");
                localBroadcastManager.sendBroadcast(intent);
            }
        });
        //注册本地广播监听器
        intentFilter=new IntentFilter();
        intentFilter.addAction("com.example.LOCAL_BROADCAST");
        localReceiver=new LocalReceiver();
        localBroadcastManager.registerReceiver(localReceiver,intentFilter);
    }
    class LocalReceiver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context,"接受到本地广播",Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        localBroadcastManager.unregisterReceiver(localReceiver);//关闭广播
    }
}