安卓广播BroadcastReceiver机制《第一行代码笔记》

安卓广播BroadcastReceiver机制《第一行代码笔记》

标准广播概念

是一种完全异步执行的广播，在广播发出以后，所有的广播接收器几乎都会在同一时刻接收到这条广播信息，因此他们之间没有先后顺序可言，这样的广播效率会比较高，但同时意味着它是无法被截断的，标准的广播流程如图

标准广播流程图.jpg

有序广播概念

是一种同步执行的广播，在广播发出之后，同一时刻只会有一个广播接收器能够收到这条广播信息，当这个广播接收器逻辑执行完后，广播才会继续传递。所以此时的广播接收器是有先后顺序的，优先级高的广播接收器可以先收到广播信息，并且前面的广播接收器还可以截断正在传递的广播，这样后面的广播接收器就无法收到广播信息了,有序广播的流程如图

有序广播流程图.jpg

动态注册监听网络变化

MainActivity类

package com.yinhao.broadcasttest;

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;

public class MainActivity extends AppCompatActivity {

    private NetworkChangeReceiver receiver;
    private IntentFilter intentFilter;
    

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

        intentFilter = new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");//action是添加相应的广播的方法
        receiver = new NetworkChangeReceiver();
        registerReceiver(receiver, intentFilter);
    }

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

定义一个类集成自BroadcastReceiver

package com.yinhao.broadcasttest;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.util.Log;
import android.widget.Toast;

/**
 * Created by yinhao on 2017/9/11.
 */

public class NetworkChangeReceiver extends BroadcastReceiver {
    private static final String TAG = "NetworkChangeReceiver";

    @Override
    public void onReceive(Context context, Intent intent) {
        //专门管理网络连接的系统服务类
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        //得到NetworkInfo的实例
        NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
        if (networkInfo != null && networkInfo.isAvailable()) {//是否有网络的方法
            Toast.makeText(context, "网络可用", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(context, "网络不可用", Toast.LENGTH_SHORT).show();
        }
    }
}

最后加上权限

静态注册实现开机启动

写一个类继承自BroadcastReceiver

package com.yinhao.broadcasttest;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.widget.Toast;

/**
 * Created by yinhao on 2017/9/12.
 */

public class BootCompleteReceiver extends BroadcastReceiver {
    private static final String TAG = "BootCompleteReceiver";
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "Boot Complete", Toast.LENGTH_LONG).show();

        //Log.i(TAG, "onReceive: Boot Complete");
    }
}

在这里注意下，静态注册必须要在manifest中注册,application下

添加接收开机启动状态权限和相应的action(在上面的代码已经注明)

发送自定义广播

1.自定义一个类继承自BroadcastReceiver

2.记得要在manifest中注册，不过这次intent-filter标签下action标签的name值要写自己创建的这个类，比如在这里我的类名MyBroadcastReceiver,那么name值可以写为：

其实这样定义name值方便自己，里面的值只要是唯一的，你定义什么都可以。

如何发送呢？
我们可以写一个按钮点击事件，当我们点击按钮时：

Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("com.yinhao.broadcasttest.MyBroadcastReceiver");
                sendBroadcast(intent);
            }
        });

这样我们就完成了发送自定义广播。

发送有序广播

我们需要新建另一个项目,定义一个类继承自BroadcastReceiver，在Manifest里添加上一个项目自定义的receiver的name值

这样当我们上一个项目里面的按钮时，就会弹出两个Toast

我们如何判断这是一个有序广播呢

我们可以在第一个项目中添加一个值，priority，这是优先权的意思

我们在MainActiviy中sendBroadcast()方法修改为sendOrderBroadcast()

sendOrderedBroadcast(intent,null);//第一个参数是intent，第二个是跟权限有关的字符串

这样即为发送一个有序广播，而且MyBroadcastReceiver因为优先值高，Toast会优先显示。
最后我们可以在MyBroadcastReceiver中添加一个方法，abortBroadcast()

public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "received in MyBroadcastReceiver", Toast.LENGTH_SHORT).show();
        abortBroadcast();//将这条广播截断，后面的广播接收器将无法再收到此条广播
    }
}

这样当我们点击按钮时，只会弹出一个Toast了，因为此方法将后面的广播截断了，原因是我们之前定义了优先级。

发送本地广播

因为安全性的问题，让别的应用无法访问此应用的广播

新建一个类继承自BroadcastReceiver，因为与上面的一些代码，所以不多展开展示

public class MainActivity extends AppCompatActivity {

  
    private IntentFilter intentFilter;
    private LocalBroadcastManager localBroadcastManager;
    private LocalReceiver localReceiver;

    @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 View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("com.yinhao.broadcasttest.LocalReceiver");
                localBroadcastManager.sendBroadcast(intent);//发送本地广播
            }
        });

        intentFilter = new IntentFilter();
        intentFilter.addAction("com.yinhao.broadcasttest.LocalReceiver");
        localReceiver = new LocalReceiver();
        localBroadcastManager.registerReceiver(localReceiver, intentFilter);//注册本地广播
    }

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

实现强制下线Demo

MainActivity

package com.yinhao.broadcastreceiverbestpractice;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends BaseActivity {

    private Button forceOffline;

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

R.layout.activity_main

LoginActivity

package com.yinhao.broadcastreceiverbestpractice;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class LoginActivity extends BaseActivity {

    private EditText accountEdit;
    private EditText passwordEdit;
    private Button login;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        accountEdit = (EditText) findViewById(R.id.account);
        passwordEdit = (EditText) findViewById(R.id.password);
        login = (Button) findViewById(R.id.login);
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String account = accountEdit.getText().toString();
                String password = passwordEdit.getText().toString();
                if (account.equals("admin") && password.equals("123456")) {
                    startActivity(new Intent(LoginActivity.this, MainActivity.class));
                    finish();
                } else {
                    Toast.makeText(LoginActivity.this, "account or password invalid", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

activity_login

BaseActivity

package com.yinhao.broadcastreceiverbestpractice;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.PersistableBundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

/**
 * Created by yinhao on 2017/9/12.
 */

public class BaseActivity extends AppCompatActivity {

    private ForceOfflineReceiver receiver;
    private static final String TAG = "BaseActivity";

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState, @Nullable PersistableBundle persistentState) {
        super.onCreate(savedInstanceState, persistentState);
        ActivityCollector.addActivity(this);
    }

    @Override
    protected void onResume() {
        Log.i(TAG, "onResume: ");
        super.onResume();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("com.yinhao.broadcastreceiverbestpractice.FORCE_OFFLINE");
        receiver = new ForceOfflineReceiver();
        registerReceiver(receiver, intentFilter);
    }

    @Override
    protected void onPause() {
        Log.i(TAG, "onPause: ");
        super.onPause();
        if (receiver != null) {
            unregisterReceiver(receiver);
            receiver = null;
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        ActivityCollector.removeActivity(this);
    }

    class ForceOfflineReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(final Context context, Intent intent) {
            AlertDialog.Builder builder = new AlertDialog.Builder(context);
            builder.setTitle("Warning");
            builder.setMessage("You are force to be offline. Please try to login again.");
            builder.setCancelable(false);//将对话框设置为不可取消
            builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    ActivityCollector.finishAll();//销毁活动
                    context.startActivity(new Intent(context, LoginActivity.class));//重新启动到登录界面
                }
            });
            builder.show();
        }
    }
}

ActivityCollector

package com.yinhao.broadcastreceiverbestpractice;

import android.app.Activity;

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

/**
 * Created by yinhao on 2017/9/12.
 */

public class ActivityCollector {
    public static List activities = new ArrayList<>();

    public static void addActivity(Activity activity) {
        activities.add(activity);
    }

    public static void removeActivity(Activity activity) {
        activities.add(activity);
    }

    public static void finishAll() {
        for (Activity activity : activities) {
            activity.finish();
        }
    }
}

因为始终需要保证处于栈顶的活动才能接收到这条强制下线的广播，非栈顶的活动不应该也没有必要去接收这条广播。当一个活动失去栈顶时，自动取消广播接收器的注册。