每天进步一点-----全局大喇叭Broadcast

public class MainActivity extends BaseActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button forceOffline = (Button) findViewById(R.id.force_offline);
        forceOffline.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(
                        "com.example.broadcastbestpractice.FORCE_OFFLINE");
                sendBroadcast(intent);
            }
        });
    }

}

import android.app.AlertDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.view.WindowManager;

public class ForceOfflineReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, Intent intent) {
        AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(context);
        dialogBuilder.setTitle("Warning");
        dialogBuilder.setMessage("You are forced to be offline. Please try to login again.");
        dialogBuilder.setCancelable(false);
        dialogBuilder.setPositiveButton("OK",
                new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        ActivityCollector.finishAll();
                        Intent intent = new Intent(context, LoginActivity.class);
                        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                        context.startActivity(intent);
                    }
                });
        AlertDialog alertDialog = dialogBuilder.create();
        alertDialog.getWindow().setType(
                WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
        alertDialog.show();
    }

}

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 3     package="com.example.broadcastbestpractice"
 4     android:versionCode="1"
 5     android:versionName="1.0" >
 6
 7     <uses-sdk
 8         android:minSdkVersion="14"
 9         android:targetSdkVersion="17" />
10
11     <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
12
13     <application
14         android:allowBackup="true"
15         android:icon="@drawable/ic_launcher"
16         android:label="@string/app_name"
17         android:theme="@style/AppTheme" >
18         <activity
19             android:name=".LoginActivity"
20             android:label="@string/app_name" >
21             <intent-filter>
22                 <action android:name="android.intent.action.MAIN" />
23
24                 <category android:name="android.intent.category.LAUNCHER" />
25             </intent-filter>
26         </activity>
27         <activity android:name=".MainActivity" >
28         </activity>
29
30         <receiver android:name=".ForceOfflineReceiver" >
31             <intent-filter>
32                 <action android:name="com.example.broadcastbestpractice.FORCE_OFFLINE" />
33             </intent-filter>
34         </receiver>
35     </application>
36
37 </manifest>

本地广播：

　　前面我们发送和接收的广播全部都是属于系统全局广播，即发出的广播可以被其他任何 的任何应用程序接收到，并且我们也可以接收来自于其他任何应用程序的广播。这样就很容 易会引起安全性的问题，比如说我们发送的一些携带关键性数据的广播有可能被其他的应用程序截获，或者其他的程序不停地向我们的广播接收器里发送各种垃圾广播。 为了能够简单地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够在应用程序的内部进行传递，并且广播接收器也只能接收来自本应用 程序发出的广播，这样所有的安全性问题就都不存在了。

package com.example.broadcasttest;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.support.v4.content.LocalBroadcastManager;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {

    private IntentFilter intentFilter;

    private LocalReceiver localReceiver;

    private LocalBroadcastManager localBroadcastManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        localBroadcastManager = LocalBroadcastManager.getInstance(this);
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(
                        "com.example.broadcasttest.LOCAL_BROADCAST");
                localBroadcastManager.sendBroadcast(intent);
            }
        });
        intentFilter = new IntentFilter();
        intentFilter.addAction("com.example.broadcasttest.LOCAL_BROADCAST");
        localReceiver = new LocalReceiver();
        localBroadcastManager.registerReceiver(localReceiver, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        localBroadcastManager.unregisterReceiver(localReceiver);
    }

    class LocalReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "received local broadcast",
                    Toast.LENGTH_SHORT).show();
        }

    }

}