How to solve Handler() deprecated?

Question

Could anyone know, how to fix the deprecated warning or any alternate solution for this.

Handler().postDelayed({
    context?.let {
        //code
    }
}, 30         


        

Answer 1

The deprecated function is that constructor for Handler. Use Handler(Looper.myLooper()) .postDelayed(runnable, delay) instead

Answer 2

use this

Looper.myLooper()?.let {
    Handler(it).postDelayed({
        //Your Code
    },2500)
}

Answer 3

Provide a looper in the Handler Constructor

Handler(Looper.getMainLooper())

Answer 4

Use it for Java

new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
    @Override
    public void run() {
        // Your Code
    }
}, 3000);

Use it for Kotlin

Handler(Looper.getMainLooper()).postDelayed({
    // Your Code
}, 3000)

Answer 5

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

• Handler()

• Handler(Handler.Callback)

Google explains the reason below.

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.

Solution 1: Use an Executor

1. Execute code in the main thread.

Java

// 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.
    }
});

Kotlin

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

// Execute a task in the main thread
mainExecutor.execute {
    // You code logic goes here.
}

2. Execute code in a background thread

Java

// 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 3 seconds.
backgroundExecutor.schedule(new Runnable() {
    @Override
    public void run() {
        // Your code logic goes here
    }
}, 3, TimeUnit.SECONDS);

Kotlin

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

// Execute a task in the background thread.
backgroundExecutor.execute {
    // Your code logic goes here.
}

// Execute a task in the background thread after 3 seconds.
backgroundExecutor.schedule({
    // Your code logic goes here
}, 3, TimeUnit.SECONDS)

Note: Remember to shut down the executor after using.

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

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

Java

// 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.
            }
        });
    }
});

Kotlin

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

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

// Execute a task in the background thread.
backgroundExecutor.execute {
    // Your code logic goes here.

    // Update UI on the main thread
    mainExecutor.execute {
        // You code logic goes here.
    }
}

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

• Handler(Looper)

• Handler(Looper, Handler.Callback)

1. Execute code in the main thread

1.1. Handler with a Looper

Java

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

Kotlin

val mainHandler = Handler(Looper.getMainLooper())

1.2 Handler with a Looper and a Handler.Callback

Java

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

Kotlin

val mainHandler = Handler(Looper.getMainLooper(), Handler.Callback {
    // Your code logic goes here.
    true
})

2. Execute code in a background thread

2.1. Handler with a Looper

Java

// 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()); 

Kotlin

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


// Create a handler to execute tasks in the background thread.
val backgroundHandler = Handler(handlerThread.looper)

2.2. Handler with a Looper and a Handler.Callback

Java

// 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;
    }
});

Kotlin

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


// Create a handler to execute taks in the background thread.
val backgroundHandler = Handler(handlerThread.looper, Handler.Callback {
    // Your code logic goes here.
    true
})

Note: Remember to release the thread after using.

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

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

Java

// 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;
    }
});

Kotlin

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

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

// Create a handler to execute in the background thread
val backgroundHandler = Handler(handlerThread.looper, Handler.Callback {
    // Your code logic goes here.

    // Update UI on the main thread.
    mainHandler.post {
        
    }
    true
})

Answer 6

Use Executor instead of handler for more info Executor.
To achieve post delay use ScheduledExecutorService:

ScheduledExecutorService worker = Executors.newSingleThreadScheduledExecutor();
Runnable runnable = () -> {
    public void run() {
        // Do something
    }
};
worker.schedule(runnable, 2000, TimeUnit.MILLISECONDS);