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

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();

Answer 1

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();

Answer 2

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

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

       //stuff that updates ui

    }
});