处理程序（）

处理程序（处理程序.回调）

谷歌在下面解释了原因。

在Handler构建过程中隐式选择Looper可能会导致错误，其中操作会静默丢失（如果Handler不期望新的任务和退出）、崩溃（如果有时在没有Looper活动的线程上创建处理程序）或竞争条件，其中处理程序关联的线程不是作者预期的。相反，使用执行器或显式指定Looper，使用Looper#getMainLooper、{link android. view.View#getHandler}或类似方法。如果兼容性需要隐式线程本地行为，请使用new Handler（Looper.myLooper（）、callback）向读者明确说明。

解决方案1：使用执行器

1、在主线程执行代码。

// 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

// 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：使用后记得关闭执行器。

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

3.在后台线程执行代码，在主线程更新UI。

// 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：使用以下构造函数之一显式指定Looper。

>

处理程序（循环）

处理程序（循环，处理程序。回调）

1、在主线程执行代码

1.1。带有Looper的处理程序

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

1.2带有Looper和Handler. Callback的处理程序

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

2.1。带有Looper的处理程序

// 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

// 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：使用后记得松开线程。

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

3.在后台线程执行代码，在主线程更新UI。

// 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;
    }
});