第5章 详解广播机制

本系列学习笔记第5章

前言

打算把android基本知识点写一个系列，旨在把android基础书，例如《Android 第一行代码 第2版》、《爱上android》、《疯狂android讲义》等书的一些知识点记录一下，会持续更新内容，为了方便自己复习，也希望可以帮助到大家！

1、广播机制的简介

android中的广播主要可以分为：
1）标准广播
一种异步执行的广播，在广播发出之后，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，因此它们之间没有任何先后顺序可言。这种广播的效率会比较高，但同时也意味着它是无法被截断的。

2）有序广播
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消息，当这个广播接收器中的逻辑执行完毕之后，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就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。

2、接收系统广播

2.1 动态注册监听网络变化

声明权限

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

MainActivity,java文件

public class MainActivity extends AppCompatActivity {

    private IntentFilter intentFilter;
    private NetworkChangeReceiver receiver;

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

        intentFilter = new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        receiver = new NetworkChangeReceiver();
        registerReceiver(receiver, intentFilter);
    }

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

    class NetworkChangeReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager.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();
            }

        }
    }
}

2.2 更加全面的动态注册监听网络变化

public class NetChangeActivity  extends AppCompatActivity{

    private NetWorkChangeReceiver netWorkChangeReceiver;

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

        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        netWorkChangeReceiver = new NetWorkChangeReceiver();
        registerReceiver(netWorkChangeReceiver,intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (netWorkChangeReceiver != null){
            unregisterReceiver(netWorkChangeReceiver);
        }
    }

    //广播接受者
    class NetWorkChangeReceiver extends BroadcastReceiver{

        private static final int NETTYPE_WIFI = 0x01;
        private static final int NETTYPE_CMWAP = 0x02;
        private static final int NETTYPE_CMNET = 0x03;
        private static final int NETTYPE_NONE = 0x04;
        private int netType = NETTYPE_NONE;

        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "网络状态发生变化："+getNetWorkName(getNetWorkTpye()), Toast.LENGTH_SHORT).show();
        }

        /**
         * 获取当前网络类型
         * @return
         */
        private int getNetWorkTpye(){

            //获取网络管理者
            ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);

            //获取当前网络信息
            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();

            if (networkInfo == null){
                return netType;
            }

            int type = networkInfo.getType();
            if (type == ConnectivityManager.TYPE_MOBILE){

                String extraInfo = networkInfo.getExtraInfo();

                if (!TextUtils.isEmpty(extraInfo)){
                    if (extraInfo.toLowerCase().equals("cmnet")){
                        netType = NETTYPE_CMNET;
                    }else {
                        netType = NETTYPE_CMWAP;
                    }
                }

            }else if (type == ConnectivityManager.TYPE_WIFI){
                netType = NETTYPE_WIFI;
            }

            return netType;
        }

        private String getNetWorkName(int type){

            String netName = "";

            switch (type){
                case NETTYPE_WIFI:
                    netName = "WIFI";
                    break;
                case NETTYPE_CMWAP:
                    netName = "wap网络";
                    break;
                case NETTYPE_CMNET:
                    netName = "net网络";
                    break;
                case NETTYPE_NONE:
                    netName = "无网络";
                    break;
            }

            return netName;
        }
    }
}

2.3 静态注册实现开机启动

声明权限

 <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

注册

 <receiver
            android:name=".BootCompleteReceiver"
            android:enabled="true"
            android:exported="true"
            >
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
        </receiver>

BootCompleteReceiver.java文件

public class BootCompleteReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "手机开机啦！", Toast.LENGTH_SHORT).show();
    }
}

3、发送自定义广播

3.1 发送标准广播

activity_main.xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.broadcastreceivertest.MainActivity">

    <Button
        android:id="@+id/btn_send_broadcast"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:text="发送标准广播"
        android:textColor="@color/colorAccent"
        />

</LinearLayout>

MyBroadcastReceiver.java文件

public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "received in MyBroadcastReceiver", Toast.LENGTH_SHORT).show();
    }
}

注册广播

        <receiver android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true"
            >
            <intent-filter>
                <action android:name="com.example.broadcastreceivertest.MyBroadcastReceiver"/>
            </intent-filter>
        </receiver>

MainActivity.java文件

public class MainActivity extends AppCompatActivity {



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

        Button button = (Button) findViewById(R.id.btn_send_broadcast);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent("com.example.broadcastreceivertest.MyBroadcastReceiver");
                sendBroadcast(intent);
            }
        });

   
    }
}

新建另外一个工程
AnotherBroadcastReceiver.java文件

public class AnotherBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "received in AnotherBroadcastReceiver", Toast.LENGTH_SHORT).show();
    }
}

注册

        <receiver
            android:name=".AnotherBroadcastReceiver"
            android:enabled="true"
            android:exported="true"
            >
            <intent-filter>
                <action android:name="com.example.broadcastreceivertest.MyBroadcastReceiver"/>
            </intent-filter>
        </receiver>

运行俩个项目就可以发现在一个程序里发出的广播，在另外一个程序中也可以收到了

image.png image.png

3.2 发送有序广播

广播是一种可以跨进程的通信方式

在上面代码的基础上修改:
AndroidManifest.xml文件

        <receiver android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true"
            >
            <intent-filter
                android:priority="1000"
                >
                <action android:name="com.example.broadcastreceivertest.MyBroadcastReceiver"/>
            </intent-filter>
        </receiver>

MyBroadcastReceiver.java文件

public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "received in MyBroadcastReceiver", Toast.LENGTH_SHORT).show();
        abortBroadcast();
    }
}

MainActivity.java文件

public class MainActivity extends AppCompatActivity {

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

        Button button = (Button) findViewById(R.id.btn_send_broadcast);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent("com.example.broadcastreceivertest.MyBroadcastReceiver");
                sendOrderedBroadcast(intent,null);
            }
        });

   
    }
}

对广播进行截断之后，现在可以发现另外一个程序就接收不到广播了

image.png

3.3 有序广播的另外一个重载方法

image.png

可以指定接收结果的广播接收者，该广播必须是程序内部，无论前面有多少个广播接收者，哪怕广播被中断，该广播都能接收信息，而且不需要注册

image.png

4、使用本地广播

之前送发送和接收的广播全部属于系统全局广播，即发出的广播可以被其它应用程序接收到，并且我们也可以接收其它应用程序的广播，这样就很容易引起安全性的问题，因此android中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。

image.png

activity_main.xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.broadcastreceivertest.MainActivity">

    <Button
        android:id="@+id/btn_send_broadcast"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:text="发送本地广播"
        android:textColor="@color/colorAccent"
        />

</LinearLayout>

MainActivity.java文件

public class MainActivity extends AppCompatActivity {


    private LocalBroadcastManager localBroadcastManager;
    private LocalReceiver localReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button) findViewById(R.id.btn_send_broadcast);

        localBroadcastManager = LocalBroadcastManager.getInstance(this);

        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("com.example.broadcastreceivertest.Local_Broadcast");
        localReceiver = new LocalReceiver();
        localBroadcastManager.registerReceiver(localReceiver,intentFilter);


        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent("com.example.broadcastreceivertest.Local_Broadcast");
                localBroadcastManager.sendBroadcast(intent);
            }
        });


    }

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

    class LocalReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "接收本地广播", Toast.LENGTH_SHORT).show();
        }
    }

}

5、广播的最佳实践--------实现强制下线功能

ActivityCollector.java文件

public class ActivityCollector {

    public static List<Activity> activities = new ArrayList<>();

    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();
            }
        }
    }

}

BaseActivty.java文件

public class BaseActivity extends AppCompatActivity {


    private ForceOffLineReceiver receiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityCollector.addActivity(this);
    }

    @Override
    protected void onResume() {
        super.onResume();
        IntentFilter filter = new IntentFilter();
        filter.addAction("com.example.broadcastreceivertest.FORCE_OFFLINE");
        receiver = new ForceOffLineReceiver();
        registerReceiver(receiver,filter);

    }

    @Override
    protected void 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("温馨提示：");
            builder.setMessage("你已经被强制下线，请重新登录");
            builder.setCancelable(false);
            builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    ActivityCollector.finishAll();
                    Intent mIntent = new Intent(context,LoginActivity.class);
                    context.startActivity(mIntent);
                }
            });
            builder.show();
        }
    }

}

activity_login.xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="60dp">
        <TextView
            android:layout_width="90dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:textSize="18sp"
            android:text="Account:" />

        <EditText
            android:id="@+id/account"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="center_vertical"/>
    </LinearLayout>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="60dp">
        <TextView
            android:layout_width="90dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:textSize="18sp"
            android:text="Password:" />

        <EditText
            android:id="@+id/password"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="center_vertical"
            android:inputType="textPassword" />
    </LinearLayout>

    <Button
        android:id="@+id/login"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:text="Login" />

</LinearLayout>

LoginActivity.java文件

public class LoginActivity extends BaseActivity {

    private EditText accoutEdit;
    private EditText passwordEdit;
    private Button btnLogin;

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

        accoutEdit = (EditText) findViewById(R.id.account);
        passwordEdit = (EditText) findViewById(R.id.password);
        btnLogin = (Button) findViewById(R.id.login);
        btnLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String account = accoutEdit.getText().toString();
                String password = passwordEdit.getText().toString();

                if (account.equals("admin") && password.equals("123456")){
                    Intent intent = new Intent(LoginActivity.this,ForceOffLineActivtiy.class);
                    startActivity(intent);
                    finish();
                }else {
                    Toast.makeText(LoginActivity.this, "用户名或者密码不正确", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

activity_forceoffline.xml文件

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/btn_off_line"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:text="强制下线"
        android:textColor="@color/colorAccent"
        />

</android.support.constraint.ConstraintLayout>

ForceOffLineActivtiy.java文件

public class ForceOffLineActivtiy extends BaseActivity {

    private Button btnOffLine;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_forceoffline);

        btnOffLine = (Button) findViewById(R.id.btn_off_line);

        btnOffLine.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent("com.example.broadcastreceivertest.FORCE_OFFLINE");
                sendBroadcast(intent);
            }
        });

    }
}

image.png
image.png
image.png

6、广播的实践--------实现桌面快捷方式的创建与删除

public class ShortcutUtils {
    /**
     * 创建快捷方式
     * @param context 上下文
     * @param shortcutName  快捷方式的名称
     * @param iconRes  设置快捷方式图片Res 如 R.drawable.xxx / R.mipmap.xxx
     * @param actionIntent 设置快捷方式动作
     * @param allowRepeat 是否允许重复创建
     */
    public static void addShortcut(Context context, String shortcutName,
                                   int iconRes, Intent actionIntent, boolean allowRepeat){
        Intent shortcutintent = new Intent("com.android.launcher.action.INSTALL_SHORTCUT");
        //是否允许重复创建
        shortcutintent.putExtra("duplicate",allowRepeat);
        //快捷方式的名称
        shortcutintent.putExtra(Intent.EXTRA_SHORTCUT_NAME, shortcutName);
        //设置快捷方式图片
        Parcelable icon = Intent.ShortcutIconResource.fromContext(context.getApplicationContext(), iconRes);
        shortcutintent.putExtra(Intent.EXTRA_SHORTCUT_ICON_RESOURCE, icon);
        //设置快捷方式动作
        shortcutintent.putExtra(Intent.EXTRA_SHORTCUT_INTENT, actionIntent);
        //向系统发送广播
        context.sendBroadcast(shortcutintent);

    }
    /**
     * 创建快捷方式
     * @param context 上下文
     * @param shotcutName 快捷方式的名称
     * @param bitmap 设置快捷方式图片
     * @param actionIntent 设置快捷方式动作
     * @param allowRepeat 是否允许重复创建
     */
    public static void addShortcut(Context context, String shotcutName,
                                   Bitmap bitmap, Intent actionIntent, boolean allowRepeat){
        Intent shortcutintent = new Intent("com.android.launcher.action.INSTALL_SHORTCUT");
        //是否允许重复创建
        shortcutintent.putExtra("duplicate",allowRepeat);
        //快捷方式的名称
        shortcutintent.putExtra(Intent.EXTRA_SHORTCUT_NAME, shotcutName);
        //设置快捷方式图片
        shortcutintent.putExtra(Intent.EXTRA_SHORTCUT_ICON, bitmap);
        //设置快捷方式动作
        shortcutintent.putExtra(Intent.EXTRA_SHORTCUT_INTENT, actionIntent);
        //向系统发送广播
        context.sendBroadcast(shortcutintent);

    }
    /**
     * 删除快捷键
     *
     */
    public static void deleteShortcut(Context context, String name
            ,Intent actionIntent,boolean allowRepeat){
        Intent shortcutintent = new Intent("com.android.launcher.action.UNINSTALL_SHORTCUT");
        //是否循环删除
        shortcutintent.putExtra("duplicate",allowRepeat);
        //快捷方式的名称
        shortcutintent.putExtra(Intent.EXTRA_SHORTCUT_NAME, name);
        //设置快捷方式动作
        shortcutintent.putExtra(Intent.EXTRA_SHORTCUT_INTENT, actionIntent);
        //向系统发送广播
        context.sendBroadcast(shortcutintent);
    }
}

public class MainActivity extends AppCompatActivity {

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

    //删除快捷方式的点击事件
    public void deleteShortCut(View view) {
        Intent intent=new Intent(Intent.ACTION_VIEW);
        intent.setData(Uri.parse("https://www.baidu.com"));
        ShortcutUtils.deleteShortcut(this,"打开百度",intent,false);
    }
    //按钮点击事件 创建快捷方式
    public void addShortCut(View view) {
        //快捷方式打开的意图必须是隐式意图
        Intent intent=new Intent(Intent.ACTION_VIEW);
        intent.setData(Uri.parse("https://www.baidu.com"));

        ShortcutUtils.addShortcut(this,"打开百度",R.mipmap.ic_launcher,intent,false);
    }
}