Android连载24-本地广播和强制下线功能

一、使用本地广播

1.本地广播一个举例

package com.example.broadcasttest2;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
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;
 
 private NetworkChangeReceiver networkChangeReceiver;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  intentFilter = new IntentFilter();
  intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
  networkChangeReceiver = new NetworkChangeReceiver();
  registerReceiver(networkChangeReceiver,intentFilter);
  localBroadcastManager = LocalBroadcastManager.getInstance(this);//获取实例
  
  Button button = (Button) findViewById(R.id.button);
  button.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
    //下面这行代码是用来全局广播的
//    Intent intent = new Intent("com.example.broadcasttest.MY_BROADCAST");
    //下面这行代码是用来本地广播的（也就是app内部传递广播）
    Intent intent = new Intent("com.example.broadcasttest.LOCAL_BROADCAST");
    localBroadcastManager.sendBroadcast(intent);//发送本地广播    
//    sendBroadcast(intent);
    //我们关闭上面一行代码，然后写另一种方法sendOrderedBroadcast,发送有序广播
    sendOrderedBroadcast(intent,null);
   }
  });
  intentFilter = new IntentFilter();
  intentFilter.addAction("com.example.broadcasttest.LOCAL_BROACAST");
  localReceiver = new LocalReceiver();
  localBroadcastManager.registerReceiver(localReceiver,intentFilter);//注册本地广播监听器
  
  
 }
 
 @Override
 protected void onDestroy() {
  super.onDestroy();
//  unregisterReceiver(networkChangeReceiver);
  localBroadcastManager.unregisterRecerver(localReceiver);
  
 }
 
 class NetworkChangeReceiver extends BroadcastReceiver{
  @Override
  public void onReceive(Context context,Intent intent) {
   ConnectivityManager connectionMananger = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
   NetworkInfo networkInfo = connectionMananger.getActiveNetworkInfo();
   if(networkInfo != null && networkInfo.isAvailable()) {
    Toast.makeText(context, "network is available", Toast.LENGTH_SHORT).show();    
   } else {
    Toast.makeText(context, "network is unavailable", Toast.LENGTH_SHORT).show();
   }
   
  }
 }
 
 class LocalReceiver extends BroadcastReceiver {
  @Override
  public void onReceive(Context context,Intent intent) {
   Toast.makeText(context,"received local broadcast",Toast.LENGTH_SHORT).show();
  }
 }
}

通过LocalBroadcastManager的getInstance()方法来获取一个实例，注册广播是用的registerReceiver()方法，传入的参数一个是localReceiver的内部实例，一个是IntentFilter实例。最后在onCreate方法中调用发送广播的方法。
最后我们在按钮的点击事件里面发送一条com.example.broadcasttest.LOCAL_BROADCAST广播，然后在LocalReceiver里面去接收这条广播。

注意点：本地广播是无法通过静态注册的方式来接收的，其实这也完全可以理解，因为静态注册主要就是为了让程序在未启动的时候也能收到广播，而发送本地广播的时候，我们的程序就已经启动了，因为也完全不需要使用静态注册的功能。

2.使用本地广播的优势

（1）程序内部传递，防止机密数据泄露；
（2）其他程序无法将广播发送到我们的程序内部，防止安全漏洞的隐患;
（3）发送本地广播更加高效。

二、实现强制下线功能

1.实现强制下线的逻辑

无论在我们在程序的哪个活动界面，一旦收到强制下线的广播，就跳出来一个界面，必须点击“确认“，然后直接跳转到登录界面。

2.首先创建一个类用于管理所有的活动

package com.example.broadcastbestpractice;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;

public class ActivityCollector {
 
 public static List<Activity> activities = new ArrayList<Activity>();
 
 public static void addActivity(Activity activity) {
  activities.add(activity);
 }
 
 public static void removeActivity(Activity activity) {
  activities.remove(activity);
 }
 
 public static void finishAll() {
  for(Activity activity :activities) {
   if(!activity.isFinishing()) {
    activity.finish();
   }
  }
 }
}

3.创建一个基类`BaseActivity`作为所有活动的父类

package com.example.broadcastbestpractice;

import android.app.Activity;
import android.os.Bundle;

public class BastActivity extends Activity {
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  ActivityCollector.addActivity(this);
 }
 
 @Override
 public void onDestroy() {
  super.onDestroy();
  ActivityCollector.removeActivity(this);
 }
}

4.接着需要建立一个登录页面的布局

<?xml version="1.0" encoding="utf-8"?>
<!-- 
 android:shrinkColumns设置允许被收缩的列序号
 android:strectColumns设置允许被拉伸的列序号 -->
<TableLLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:strectColumns = "1" >
    
    <TableRow>
        <TextView
            android:layout_height = "wrap_content"
            android:text="Account:" />
        
        <EditText
            android:id="@+id/account"
            android:layout_height="wrap_content"
            android:hint="Input your account" />       
    </TableRow>
    
    <TableRow>
        <TextView
            android:layout_height="wrap_content"
            android:text="Password:" />
        
        <EditTest
            android:id="@+id/password"
            android:layout_height="wrap_content"
            android:inputType="textPassword" />        
    </TableRow>
    
    <TableRow>
        <Button
            android:id="@+id/login"
            android:layout_height="wrap_content"
            android:layout_span="2"
            android:text="Login" />
    </TableRow>

</TableLayout>