why thread creation is failed?

Question

I want to turn on/off the flash light in infinite loop, so when it turned on it should wait for 5 seconds and then turned off then wait 5 seconds to turned on again, and so on... how I can do that?

here is my code:

b2.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        // TODO Auto-generated method stub

                    //  num = Integer.parseInt(n.getText().toString());

                        while(bl){

                             if(camera == null){

                                 new Thread(new Runnable() {
                                        @Override
                                        public void run() {
                                            try {
                                                Thread.sleep(5000);
                                            } catch (InterruptedException e) {
                                                e.printStackTrace();
                                            }
                                            runOnUiThread(new Runnable() {
                                                @Override
                                                public void run() {
                                                    turnOn();
                                                }
                                            });
                                        }
                                    }).start();
                                }

                             else{

                                 new Thread(new Runnable() {
                                        @Override
                                        public void run() {
                                            try {
                                                Thread.sleep(5000);
                                            } catch (InterruptedException e) {
                                                e.printStackTrace();
                                            }
                                            runOnUiThread(new Runnable() {
                                                @Override
                                                public void run() {
                                                    turnOff();
                                                }
                                            });
                                        }
                                    }).start();
                                }
                        }

                    }
                });

Answer 1

I would recommend not using Threads in order to achieve this. Why not use the Runnable class and post it with a delay via a Handler? For example:

Handler handler = new Handler(); // make this a member variable of your class
boolean isOn = false; // make this a member variable of your class

final Runnable flashRunnable = new Runnable() {
    @Override
    public void run() {
        if (isOn) {
            turnOff();
            isOn = false;
        } else {
            turnOn();
            isOn = true;
        }
        handler.postDelayed(flashRunnable, 5000);
    }
};

handler.postDelayed(flashRunnable, 5000);

If you need to run the code inside the Runnable on the UI thread, you even call postDelayed on a View instead of creating a Handler

Answer 2

Try something like so, using Executors instead of (ugly) Thread.sleep():

boolean cameraOn = true

final Runnable runnable = new Runnable() {
    @Override
    public void run() {
        // your logic here:
        // if (cameraOn) ...
        // else ...
        // cameraOn = !cameraOn
    }
};

Executors.newScheduledThreadPool(1).schedule(new Runnable() {

    @Override
    public void run() {
        runnable.run();
    }

}, 5, TimeUnit.SECONDS);