CODEWITHSUNDEEP
androidmultithreading
František Jeřábek
František Jeřábek

Reputation: 663

Handler Thread: Only one Looper may be created per thread

I am trying to use Handler and HandlerThread from foreground service to execute task on new thread. But when I call HandlerThread.run() I get java.lang.RuntimeException: Only one Looper may be created per thread

I am starting the thread using this code:

networkThread = new HandlerThread("Network Thread");
    if(networkThread.getLooper() == null)
        networkThread.run();

handler = new Handler(networkThread.getLooper());
handler.postDelayed(updateTask, 1000);

Upvotes: 2

Views: 1321

Answers (1)

Son Truong
Son Truong

Reputation: 14173

In android each Thread has only one Looper, when you use HandlerThread, it creates a Looper when you start the handler thread.

HandlerThread is just a java Thread which has a Looper.

Root cause: Your code is not correct.

Solution: Change your code

From

networkThread = new HandlerThread("Network Thread");
    if(networkThread.getLooper() == null)
        networkThread.run();

handler = new Handler(networkThread.getLooper());
handler.postDelayed(updateTask, 1000);

To

// Create and start a handler thread.
networkThread = new HandlerThread("Network Thread");
networkThread.start(); 

handler = new Handler(networkThread.getLooper()); // The calling thread must wait until a Looper has been created in the handler thread.

// Post your task to handler thread to process
handler.postDelayed(updateTask, 1000);

Upvotes: 2

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