开源 java android app 开发（十）广播机制

 文章的目的为了记录使用java 进行android app 开发学习的经历。本职为嵌入式软件开发，公司安排开发app，临时学习，完成app的开发。开发流程和要点有些记忆模糊，赶紧记录，防止忘记。

    相关链接：

开源 java android app 开发（一）开发环境的搭建-优快云博客

开源 java android app 开发（二）工程文件结构-优快云博客

开源 java android app 开发（三）GUI界面布局和常用组件-优快云博客

开源 java android app 开发（四）GUI界面重要组件-优快云博客

开源 java android app 开发（五）文件和数据库存储-优快云博客

开源 java android app 开发（六）多媒体使用-优快云博客

开源 java android app 开发（七）通讯之Tcp和Http-优快云博客

开源 java android app 开发（八）通讯之Mqtt和Ble-优快云博客

开源 java android app 开发（九）后台之线程和服务-优快云博客

开源 java android app 开发（十）广播机制-优快云博客

开源 java android app 开发（十一）调试、发布-优快云博客

开源 java android app 开发（十二）封库.aar-优快云博客

开源 java android app 开发（十三）自定义绘图控件--游戏摇杆

开源 java android app 开发（十四）自定义绘图控件--波形图

开源 java android app 开发（十五）自定义绘图控件--仪表盘

开源 java android app 开发（十六）自定义绘图控件--圆环

推荐链接：

开源C# .net mvc 开发（一）WEB搭建_c#部署web程序-优快云博客

开源 C# .net mvc 开发（二）网站快速搭建_c#网站开发-优快云博客

开源 C# .net mvc 开发（三）WEB内外网访问(VS发布、IIS配置网站、花生壳外网穿刺访问)_c# mvc 域名下不可訪問內網,內網下可以訪問域名-优快云博客

开源 C# .net mvc 开发（四）工程结构、页面提交以及显示_c#工程结构-优快云博客

开源 C# .net mvc 开发（五）常用代码快速开发_c# mvc开发-优快云博客

本章节主要内容是广播机制，广播(Broadcast)是Android四大组件之一，用于实现应用程序内部或应用程序之间的消息传递机制。它基于观察者模式，采用发布/订阅模型，能够实现组件间的解耦通信。

广播分为两个主要部分：广播发送者和广播接收者(BroadcastReceiver)。发送者通过Intent发送广播，接收者通过注册监听特定类型的广播来接收消息。

本章内容如下：

1  2个APP之间进行广播通讯。

2  基于服务和广播通讯的网络文件下载。

一、APP之间的广播通讯(APP1和APP2)

1.1 APP1的界面Activity_main.xml

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

    <Button
        android:id="@+id/btnSendBroadcast"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Send Broadcast"
        android:layout_centerInParent="true"/>
</RelativeLayout>

1.2 APP1的主程序，MainActivity.java

package com.example.Mqtt;


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


public class MainActivity extends AppCompatActivity {

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

        Button btnSendBroadcast = findViewById(R.id.btnSendBroadcast);
        btnSendBroadcast.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 创建Intent并设置Action
                Intent intent = new Intent("com.example.app1.CUSTOM_BROADCAST");
                // 添加数据
                intent.putExtra("message", "Hello from App1!");
                // 发送广播
                sendBroadcast(intent);
            }
        });
    }
}

1.3  APP2的界面activity_main.xml

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

    <TextView
        android:id="@+id/tvBroadcastMessage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Waiting for broadcast..."
        android:layout_centerInParent="true"/>
</RelativeLayout>

1.4  APP2的广播接收类CustomBroadcastReceiver

package com.example.myapplication;


import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Handler;
import android.os.Message;
import android.widget.Toast;

public class CustomBroadcastReceiver extends BroadcastReceiver {

    private Handler handler;

    public CustomBroadcastReceiver(Handler handler) {
        this.handler = handler;
    }
    @Override
    public void onReceive(Context context, Intent intent) {
        // 获取广播中的消息
        String message = intent.getStringExtra("message");
        // 显示Toast消息
        //Toast.makeText(context, "Received: " + message, Toast.LENGTH_LONG).show();
        new Thread(new Runnable() {
            @Override
            public void run() {
                // 子线程操作
                final String result = message;

                // 通过 Handler 发送消息到主线程
                Message msg = handler.obtainMessage();
                msg.obj = result;
                handler.sendMessage(msg);
            }
        }).start();
    }
}

1.5  APP2的主程序，MainActivity.java

package com.example.myapplication;


import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private CustomBroadcastReceiver receiver;
    TextView textView;
    private Handler handler = new Handler(Looper.getMainLooper()) {
        @Override
        public void handleMessage(@NonNull Message msg) {
            super.handleMessage(msg);
            String data = (String) msg.obj;
            updateUI(data);
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = findViewById(R.id.tvBroadcastMessage);
        // 初始化BroadcastReceiver
        receiver = new CustomBroadcastReceiver(handler);

        // 创建IntentFilter并设置Action
        IntentFilter filter = new IntentFilter("com.example.app1.CUSTOM_BROADCAST");

        // 注册BroadcastReceiver
        registerReceiver(receiver, filter);
    }
    public void updateUI(String data) {
        textView.setText(data);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 注销BroadcastReceiver
        unregisterReceiver(receiver);
    }
}

1.6  2个APP运行的效果，点击APP1的按钮，APP2收到消息。

二、基于服务和广播通讯的网络文件下载。该程序稍微复杂，通过服务实现了用户名和密码登录指定的网站登录，成功后跳转到相应页面下载apk程序。在下载过程中计算下载的文件大小，通过广播，更新主界面的文件下载进度条。下载后可以在文件管理中设置安装。在android studio的 device file Explorer中可以看到下载的文件。(注意下载后需要将文件删除，才能再次下载)

2.1  添加库，build.gradle

implementation 'com.squareup.okhttp3:okhttp:4.9.3'
implementation 'com.google.code.gson:gson:2.8.8'

2.2  配置文件中添加权限和服务，

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myapplication" >
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme" >
        <activity android:name=".MainActivity"
            android:exported="true"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:name=".MyService" />
    </application>

</manifest>

2.3  界面文件activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/messageText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Press buttons to interact with the service"
        android:textSize="18sp"
        android:layout_marginBottom="16dp" />

    <Button
        android:id="@+id/startButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start Service"
        android:layout_marginBottom="16dp" />

    <Button
        android:id="@+id/stopButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Stop Service"
        android:layout_marginBottom="16dp" />

    <Button
        android:id="@+id/getMessageButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Get Message from Service" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

2.4  服务MyService

package com.example.myapplication;


import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.Environment;
import android.os.IBinder;
import android.util.Log;


import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.Cookie;
import okhttp3.CookieJar;
import okhttp3.FormBody;
import okhttp3.HttpUrl;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MyService extends Service {

    private static final String TAG = "MyService";
    private final IBinder binder = new LocalBinder(); // Binder 用于通信


    private static final String LOGIN_URL   = "https://www.xxx.com/";
    private static final String exe_URL = "https://xxx.apk";
    private OkHttpClient client;
    long fileSize;
    // 自定义 Binder 类
    public class LocalBinder extends Binder {
        MyService getService() {
            return MyService.this;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        Log.d(TAG, "Service bound");
        return binder;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        Log.d(TAG, "Service created");

        this.client = new OkHttpClient.Builder()
                .cookieJar(new CookieJar() {
                    private final HashMap<String, List<Cookie>> cookieStore = new HashMap<>();

                    @Override
                    public void saveFromResponse(HttpUrl url, List<Cookie> cookies) {
                        cookieStore.put(url.host(), cookies);
                    }

                    @Override
                    public List<Cookie> loadForRequest(HttpUrl url) {
                        List<Cookie> cookies = cookieStore.get(url.host());
                        return cookies != null ? cookies : new ArrayList<>();
                    }
                })
                .build();
    }

    public void login() {
        FormBody formBody = new FormBody.Builder()
                .add("inputEmail3", "")
                .add("inputPassword3","")
                .build();

        Request loginRequest = new Request.Builder()
                .url(LOGIN_URL)
                .post(formBody)
                .build();

        client.newCall(loginRequest).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                Log.e(TAG, "登录请求失败: " + e.getMessage());
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                if (response.isSuccessful()) {
                    Log.d(TAG, "登录成功");
                    String responseData = response.body().string();
                    Log.d(TAG, "登录成功，响应数据: " + responseData);

                    // 登录成功后，跳转到目标网址

                    //redirectToTarget();Login

                    downLoad();
                    /*
                    if (mainActivity != null) {
                        mainActivity.enableDownloadButton();
                        mainActivity.showLoginComplete();
                    }
                    */

                } else {
                    Log.e(TAG, "登录失败，状态码: " + response.code());
                }
            }
        });
    }


    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "Service started");
        login();
        return START_NOT_STICKY;
    }

    public void downLoad() {
        Request targetRequest = new Request.Builder()
                //.url(IMG_URL)
                //.url(IMG_URL)
                .url(exe_URL)
                .build();

        client.newCall(targetRequest).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                Log.e(TAG, "下载请求失败: " + e.getMessage());
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                if (response.isSuccessful()) {
                    fileSize = response.body().contentLength();

                    InputStream inputStream = response.body().byteStream();
                    saveFile(inputStream, "new.apk"); // 保存文件
                    Log.d(TAG, "文件下载成功");

                    //readAndPrintBinaryFile("downloaded_file.zip");
                } else {
                    Log.e(TAG, "下载失败，状态码: " + response.code());
                }
            }
        });
    }


    private void saveFile(InputStream inputStream, String fileName) throws IOException {
        //FileOutputStream outputStream = new FileOutputStream(new File(context.getFilesDir(), fileName));


// 获取 Downloads 目录
        File downloadsDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
// 创建目标文件
        File outputFile = new File(downloadsDir, fileName);
        // 确保目录存在
        if (!downloadsDir.exists()) {
            downloadsDir.mkdirs();
        }

        // 如果文件已存在，先删除
        if (outputFile.exists()) {
            boolean deleted = outputFile.delete();
            if (!deleted) {
                throw new IOException("无法删除已存在的文件: " + outputFile.getAbsolutePath());
            }
        }


        // 写入文件
        FileOutputStream outputStream = new FileOutputStream(outputFile);

        byte[] buffer = new byte[1024];

        int bytesRead;
        long totalBytesRead = 0;
        int lastProgress = 0;

        while ((bytesRead = inputStream.read(buffer)) != -1) {

            //Log.d(TAG, "写入数据");
            outputStream.write(buffer, 0, bytesRead); // 将文件写入本地
            // 计算并更新进度
            totalBytesRead += bytesRead;
            int progress = (int) ((totalBytesRead * 100) / fileSize);
            if (progress > lastProgress) {
                Log.d(TAG, "进度条："+ progress);
                lastProgress = progress;
                Intent progressIntent = new Intent(MainActivity.DOWNLOAD_PROGRESS_ACTION);
                progressIntent.putExtra(MainActivity.PROGRESS_KEY, progress);
                sendBroadcast(progressIntent);
            }

        }
        outputStream.close();
        inputStream.close();
        Log.d(TAG, "文件保存成功: " + fileName);
    }


    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "Service destroyed");
    }

    // 服务提供的公共方法
    public String getMessage() {
        return "Hello from Service!";
    }
}

2.5  主程序 MainActivity.java

package com.example.myapplication;

import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private MyService myService;
    private boolean isBound = false;

    private TextView messageText;
    private Button startButton, stopButton, getMessageButton;


    private ProgressBar progressBar;

    // 定义广播Action
    public static final String DOWNLOAD_PROGRESS_ACTION = "com.example.myapplication.DOWNLOAD_PROGRESS";
    public static final String PROGRESS_KEY = "progress";

    // 广播接收器
    private BroadcastReceiver progressReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            if (intent.getAction() != null && intent.getAction().equals(DOWNLOAD_PROGRESS_ACTION)) {
                int progress = intent.getIntExtra(PROGRESS_KEY, 0);
                progressBar.setProgress(progress);
                messageText.setText("下载进度: " + progress + "%");
            }
        }
    };



    // ServiceConnection 用于绑定服务
    private final ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            Log.d(TAG, "Service connected");
            MyService.LocalBinder binder = (MyService.LocalBinder) service;
            myService = binder.getService();
            isBound = true;
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            Log.d(TAG, "Service disconnected");
            isBound = false;
        }
    };

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

        messageText = findViewById(R.id.messageText);
        startButton = findViewById(R.id.startButton);
        stopButton = findViewById(R.id.stopButton);
        getMessageButton = findViewById(R.id.getMessageButton);

        progressBar = findViewById(R.id.progressBar);

// 注册广播接收器
        IntentFilter filter = new IntentFilter(DOWNLOAD_PROGRESS_ACTION);
        registerReceiver(progressReceiver, filter);


        // 启动服务
        startButton.setOnClickListener(v -> {
            Intent intent = new Intent(MainActivity.this, MyService.class);
            startService(intent); // 启动服务
            bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE); // 绑定服务
        });

        // 停止服务
        stopButton.setOnClickListener(v -> {
            if (isBound) {
                unbindService(serviceConnection); // 解绑服务
                isBound = false;
            }
            Intent intent = new Intent(MainActivity.this, MyService.class);
            stopService(intent); // 停止服务
        });

        // 与服务通信
        getMessageButton.setOnClickListener(v -> {
            if (isBound) {
                String message = myService.getMessage();
                messageText.setText(message);
            } else {
                messageText.setText("Service not bound");
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (isBound) {
            unbindService(serviceConnection); // 解绑服务
            isBound = false;
        }
    }
}

2.6  APP效果图和文件下载位置

文件下载位置