Android多进程开发 - 在 APP 中启动多个进程（最简单实现）、查看进程、多进程下 Application 多次创建、多进程下单例模式失效

一、在 APP 中启动多个进程（最简单实现）

1、Service

public class MyServiceA extends Service {

public static final String TAG = MyServiceA.class.getSimpleName();

@Override
public void onCreate() {
super.onCreate();
Log.i(TAG, "MyServiceA 启动");
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
}

public class MyServiceB extends Service {

public static final String TAG = MyServiceB.class.getSimpleName();

@Override
public void onCreate() {
super.onCreate();
Log.i(TAG, "MyServiceB 启动");
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
}

2、AndroidManifest

• AndroidManifest.xml

<service
android:name=".service.MyServiceA"
android:exported="false"
android:process=":MyServiceA" />

<service
android:name=".service.MyServiceB"
android:exported="false"
android:process=":MyServiceB" />

• 注：不建议将process 配置为 .MyServiceA，这样进程名就会变为 【包名】.MyServiceA

3、Activity Code

startService(new Intent(this, MyServiceA.class));
startService(new Intent(this, MyServiceB.class));

new Handler().postDelayed(() -> CommonTool.printAllProcesses(this.getApplicationContext()), 5 * 1000);

# 输出结果

MyServiceA 启动
MyServiceB 启动
总进程数: 3
进程名: com.my.androidadvance, PID: 29146, UID: 10246
进程名: com.my.androidadvance:MyServiceB, PID: 29271, UID: 10246
进程名: com.my.androidadvance:MyServiceA, PID: 29263, UID: 10246

二、查看进程

1、通过 ps 命令查看进程

ps -ef

ps -ef | grep 【包名】

2、通过 ActivityManager 查看进程

• 通过 ActivityManager 查看进程，但是，只能查看调用者自身的进程

public static void printAllProcesses(Context context) {
ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);

List<ActivityManager.RunningAppProcessInfo> runningAppProcesses = activityManager.getRunningAppProcesses();

if (runningAppProcesses == null) {
Log.e("printAllProcesses", "进程列表为 null");
return;
}

Log.i("ProcessCheck", "总进程数: " + runningAppProcesses.size());

for (ActivityManager.RunningAppProcessInfo runningAppProcessInfo : runningAppProcesses) {
Log.i("printAllProcesses",
"进程名: " + runningAppProcessInfo.processName + ", " +
"PID: " + runningAppProcessInfo.pid + ", " +
"UID: " + runningAppProcessInfo.uid);
}
}

CommonTool.printAllProcesses(this)

// 或者
CommonTool.printAllProcesses(this.getApplicationContext())

三、多进程下 Application 多次创建

1、基本介绍

• 每个进程都会单独初始化一个 Application 实例，每个进程启动时都会调用一次 onCreate 方法，需要根据进程名做不同初始化

2、演示

public class MyApplication extends Application {

public static final String TAG = MyApplication.class.getSimpleName();

public MyApplication() {
Log.i(TAG, "MyApplication 构造函数被调用");
}

@Override
public void onCreate() {
super.onCreate();

String processName = getProcessName();
Log.i(TAG, "onCreate, processName: " + processName);
}
}

# 输出结果

MyApplication 构造函数被调用
onCreate, processName: com.my.androidadvance

MyApplication 构造函数被调用
onCreate, processName: com.my.androidadvance:MyServiceA
MyServiceA 启动

MyApplication 构造函数被调用
onCreate, processName: com.my.androidadvance:MyServiceB
MyServiceB 启动

总进程数: 3
进程名: com.my.androidadvance, PID: 30763, UID: 10246
进程名: com.my.androidadvance:MyServiceB, PID: 30814, UID: 10246
进程名: com.my.androidadvance:MyServiceA, PID: 30808, UID: 10246

四、多进程下单例模式失效

1、Singleton

• SimpleSingleton.java

public class SimpleSingleton {

public static final String TAG = SimpleSingleton.class.getSimpleName();

private String data = "no data";

private static SimpleSingleton simpleSingleton = new SimpleSingleton();

private SimpleSingleton() {
Log.d(TAG, "单例创建，进程 ID：" + android.os.Process.myPid());
}

public static SimpleSingleton getInstance() {
return simpleSingleton;
}

public void setData(String data) {
this.data = data;
Log.d(TAG, "进程 " + android.os.Process.myPid() + " 设置数据：" + data);
}

public String getData() {
Log.d(TAG, "进程 " + android.os.Process.myPid() + " 读取数据：" + data);
return data;
}
}

2、Service

public class MyServiceA extends Service {

public static final String TAG = MyServiceA.class.getSimpleName();

@Override
public void onCreate() {
super.onCreate();
Log.i(TAG, "MyServiceA 启动");

new Handler(Looper.getMainLooper()).postDelayed(() -> {
SimpleSingleton simpleSingleton = SimpleSingleton.getInstance();
String data = simpleSingleton.getData();

Log.i(TAG, "MyServiceA 从 SimpleSingleton 读取数据：" + data);
}, 9 * 1000);
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
}

public class MyServiceB extends Service {

public static final String TAG = MyServiceB.class.getSimpleName();

@Override
public void onCreate() {
super.onCreate();
Log.i(TAG, "MyServiceB 启动");

new Handler(Looper.getMainLooper()).postDelayed(() -> {
SimpleSingleton simpleSingleton = SimpleSingleton.getInstance();
String data = simpleSingleton.getData();

Log.i(TAG, "MyServiceB 从 SimpleSingleton 读取数据：" + data);
}, 9 * 1000);
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
}

3、Activity Code

startService(new Intent(this, MyServiceA.class));
startService(new Intent(this, MyServiceB.class));

new Handler().postDelayed(() -> CommonTool.printAllProcesses(this.getApplicationContext()), 3 * 1000);

new Handler().postDelayed(() -> {
SimpleSingleton simpleSingleton = SimpleSingleton.getInstance();
simpleSingleton.setData("test content");

Log.i(TAG, "主进程向 SimpleSingleton 写入数据");
}, 6 * 1000);

# 输出结果

MyServiceA 启动

MyServiceB 启动

总进程数: 3
进程名: com.my.androidadvance, PID: 10962, UID: 10246
进程名: com.my.androidadvance:MyServiceB, PID: 11015, UID: 10246
进程名: com.my.androidadvance:MyServiceA, PID: 11009, UID: 10246

单例创建，进程 ID：10962
进程 10962 设置数据：test content
主进程向 SimpleSingleton 写入数据

单例创建，进程 ID：11009
进程 11009 读取数据：no data
MyServiceA 从 SimpleSingleton 读取数据：no data

单例创建，进程 ID：11015
进程 11015 读取数据：no data
MyServiceB 从 SimpleSingleton 读取数据：no data