Android “Only the original thread that created a view hierarchy can touch its views.” error in for loop

Question

I am trying to run the for loop in every half second.The loop is changing something in the view every time it is called,but the changes are made by another class i.e Speedometer.

Thread thread=new Thread(){
        @Override
        public void run() {
            float i;
            try {

                for ( i = 0; i <= 100; i++) {
                            Speedometer1.onSpeedChanged(Speedometer1.getCurrentSpeed(i) + 8);
                            Speedometer2.onSpeedChanged(Speedometer2.getCurrentSpeed(i) + 8);
                            Speedometer3.onSpeedChanged(Speedometer3.getCurrentSpeed(i) + 8);
                            Speedometer4.onSpeedChanged(Speedometer4.getCurrentSpeed(i) + 8);
                            Speedometer5.onSpeedChanged(Speedometer5.getCurrentSpeed(i) + 8);
                            Speedometer6.onSpeedChanged(Speedometer6.getCurrentSpeed(i) + 8);


                    sleep(500);
                }
            }
            catch (InterruptedException e)
            {e.printStackTrace();}
        }
    };thread.start();

refer [Android “Only the original thread that created a view hierarchy can touch its views.”](http://stackoverflow.com/questions/5161951/android-only-the-original-thread-that-created-a-view-hierarchy-can-touch-its-vi) — Ravi, Aug 03 '16 at 12:17

score 24 · Accepted Answer · answered Aug 03 '16 at 12:18

That's because any view can be only modify in the main thread or ui Thread. Try running onSpeedChanged() using runOnUiThread(). Like this:

    Thread thread=new Thread(){
    @Override
    public void run() {
        float i;
        try {

            for ( i = 0; i <= 100; i++) {
                runOnUiThread(new Runnable() {
                    public void run() {
                        Speedometer1.onSpeedChanged(Speedometer1.getCurrentSpeed(i) + 8);
                        Speedometer2.onSpeedChanged(Speedometer2.getCurrentSpeed(i) + 8);
                        Speedometer3.onSpeedChanged(Speedometer3.getCurrentSpeed(i) + 8);
                        Speedometer4.onSpeedChanged(Speedometer4.getCurrentSpeed(i) + 8);
                        Speedometer5.onSpeedChanged(Speedometer5.getCurrentSpeed(i) + 8);
                        Speedometer6.onSpeedChanged(Speedometer6.getCurrentSpeed(i) + 8)

                    }

                });


                sleep(500);
            }
        }
        catch (InterruptedException e)
        {e.printStackTrace();}
    }
};thread.start();

Running perfectly... Thanks alot – Ariel Aug 06 '16 at 18:17 — Ariel, Aug 06 '16 at 18:17

score 13 · Answer 2 · answered Aug 03 '16 at 12:18

13

You should update the UI Components in runOnUIThread.Sample code is

runOnUiThread(new Runnable() {
     @Override
     public void run() {

       //stuff that updates ui

    }
});

answered Aug 03 '16 at 12:18

Mujammil Ahamed

1,454
4
24
50

2

thanks so much, it worked! – bboydflo May 22 '17 at 11:42

score 10 · Answer 3 · answered Aug 03 '16 at 12:21

You should update your UI on the UI thread.

For that, create a handler in your onCreate() method:

private Handler mHandler;

@Override
public void onCreate() {
    mHandler = new Handler();
    // ...
}

Then call the handler in your separate thread to execute it on the main thread:

mHandler.post(new Runnable() {
    @Override
    public void run() {
        // Update your UI
    }
});

score 0 · Answer 4 · answered Aug 03 '16 at 12:20

You cannot modify View objects from outside the main thread. Even though your Speedometer class is making the changes, it is running in the secondary thread you have created.

You could create a Runnable and post with deejay to a Handler created by the main thread, or use other similar techniques to accomplish the same.

Android “Only the original thread that created a view hierarchy can touch its views.” error in for loop

4 Answers4