不推荐使用Handler(Handler.Callback) [英] Handler(Handler.Callback) is deprecated

问题描述

不建议使用Handler(android.os.Handler.Callback)，而是应该使用什么?

Handler(android.os.Handler.Callback) is deprecated what should I use instead?

Handler handler = new Handler(new Handler.Callback() {
    @Override
    public boolean handleMessage(@NonNull Message message) {
        switch(message.what) {
            case READ_MESSAGE:
                byte[] readBuff = (byte[]) message.obj;
                String tempMessage = new String(readBuff, 0, message.arg1);
                readMsg.setText(tempMessage);
                break;
        }
        return true;
    }
});

推荐答案

从API级别30开始，不推荐使用2个构造函数.

From API level 30, there are 2 constructors are deprecated.

• Handler()

Handler(Handler.)

Google在下面解释了原因.

Google explains the reason below.

在过程中隐式选择一个弯针处理程序的构造可能会导致错误，而这些错误会静默地进行操作丢失(如果处理程序不期望新任务并退出)，则崩溃(如果有时在没有Looper的线程上创建处理程序，活动)或竞争条件(与处理程序相关联的线程)与作者所期望的不一样.相反，请使用执行程序或使用Looper#getMainLooper明确指定Looper，{linkandroid.view.View#getHandler}或类似名称.如果隐式线程需要本地行为以实现兼容性，请使用newHandler(Looper.myLooper()，callback)使读者可以清楚地看到它.

Implicitly choosing a Looper during Handler construction can lead to bugs where operations are silently lost (if the Handler is not expecting new tasks and quits), crashes (if a handler is sometimes created on a thread without a Looper active), or race conditions, where the thread a handler is associated with is not what the author anticipated. Instead, use an Executor or specify the Looper explicitly, using Looper#getMainLooper, {link android.view.View#getHandler}, or similar. If the implicit thread local behavior is required for compatibility, use new Handler(Looper.myLooper(), callback) to make it clear to readers.

解决方案1:使用执行器

1..在主线程中执行代码.

1. Execute code in the main thread.

// Create an executor that executes tasks in the main thread. 
Executor mainExecutor = ContextCompat.getMainExecutor(this);

// Execute a task in the main thread
mainExecutor.execute(new Runnable() {
    @Override
    public void run() {
        // You code logic goes here.
    }
});

2..在后台线程中执行代码

2. Execute code in a background thread

// Create an executor that executes tasks in a background thread.
ScheduledExecutorService backgroundExecutor = Executors.newSingleThreadScheduledExecutor();

// Execute a task in the background thread.
backgroundExecutor.execute(new Runnable() {
    @Override
    public void run() {
        // Your code logic goes here.
    }
});

// Execute a task in the background thread after 1 second.
backgroundExecutor.schedule(new Runnable() {
    @Override
    public void run() {
        // Your code logic goes here
    }
}, 1, TimeUnit.SECONDS);

注意:请记住在使用后关闭执行程序.

Note: Remember to shut down the executor after using.

backgroundExecutor.shutdown(); // or backgroundExecutor.shutdownNow();

3..在后台线程中执行代码并更新主线程上的UI.

3. Execute code in a background thread and update UI on the main thread.

// Create an executor that executes tasks in the main thread. 
Executor mainExecutor = ContextCompat.getMainExecutor(this);

// Create an executor that executes tasks in a background thread.
ScheduledExecutorService backgroundExecutor = Executors.newSingleThreadScheduledExecutor();

// Execute a task in the background thread.
backgroundExecutor.execute(new Runnable() {
    @Override
    public void run() {
        // Your code logic goes here.
        
        // Update UI on the main thread
        mainExecutor.execute(new Runnable() {
            @Override
            public void run() {
                // You code logic goes here.
            }
        });
    }
});

解决方案2:通过使用以下构造函数之一明确指定Looper.

Solution 2: Specify a Looper explicitly by using one of the following constructors.

• Handler(Looper)

1..在主线程中执行代码

1. Execute code in the main thread

1.1.带有Looper的处理程序

1.1. Handler with a Looper

Handler mainHandler = new Handler(Looper.getMainLooper());

1.2 带有Looper和Handler.Callback的处理程序

1.2 Handler with a Looper and a Handler.Callback

Handler mainHandler = new Handler(Looper.getMainLooper(), new Handler.Callback() {
    @Override
    public boolean handleMessage(@NonNull Message message) {
        // Your code logic goes here.
        return true;
    }
});

2..在后台线程中执行代码

2. Execute code in a background thread

2.1.带有Looper的处理程序

2.1. Handler with a Looper

// Create a background thread that has a Looper
HandlerThread handlerThread = new HandlerThread("HandlerThread");
handlerThread.start();

// Create a handler to execute tasks in the background thread.
Handler backgroundHandler = new Handler(handlerThread.getLooper()); 

2.2.带有Looper和Handler.Callback的处理程序

2.2. Handler with a Looper and a Handler.Callback

// Create a background thread that has a Looper
HandlerThread handlerThread = new HandlerThread("HandlerThread");
handlerThread.start();

// Create a handler to execute taks in the background thread.
Handler backgroundHandler = new Handler(handlerThread.getLooper(), new Handler.Callback() {
    @Override
    public boolean handleMessage(@NonNull Message message) {
        // Your code logic goes here.
        return true;
    }
});

注意:请记住在使用后释放线程.

Note: Remember to release the thread after using.

handlerThread.quit(); // or handlerThread.quitSafely();

3..在后台线程中执行代码并更新主线程上的UI.

3. Execute code in a background thread and update UI on the main thread.

// Create a handler to execute code in the main thread
Handler mainHandler = new Handler(Looper.getMainLooper());

// Create a background thread that has a Looper
HandlerThread handlerThread = new HandlerThread("HandlerThread");
handlerThread.start();

// Create a handler to execute in the background thread
Handler backgroundHandler = new Handler(handlerThread.getLooper(), new Handler.Callback() {
    @Override
    public boolean handleMessage(@NonNull Message message) {
        // Your code logic goes here.
        
        // Update UI on the main thread.
        mainHandler.post(new Runnable() {
            @Override
            public void run() {
                
            }
        });
        
        return true;
    }
});

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