SeekBar值未在while循环中实现

Question

I am trying to create a flashlight app with a strobe (blink) effect which I can change with a SeekBar (to change the frequency of the strobe).My goal is that I would be able to change the frequency while it's ON (blinking) and if the Seekbar value goes to 0 the Flash should be ON(without strobe/blinking) . My problem is that I can turn it ON (with a Switch Btn, but if I increase the frequency once I am not able to turn OFF the strobe (but the Flash is still ON without blinking) with the Seekbar . If I put the Seekbar value to 0 it's still blinking with the lowest frequency.

I would be so glad if you could help me.

Code: public class MainActivity extends AppCompatActivity {

Camera cam;
Parameters camParams;
boolean hasCam;
int freq;
StroboRunner sr;
Thread t;
SeekBar seekBar;

Switch mySwitch;
SeekBar skBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mySwitch = (Switch) findViewById(R.id.mySwitch);
    // set the Switch to off
    mySwitch.setChecked(false);
    //now you need a listener to check changes in state
    mySwitch.setOnCheckedChangeListener(new OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            turnOnOff(isChecked);
        }
    });
    skBar = (SeekBar) findViewById(R.id.seekBar);
    skBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            freq = progress;
        }
        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {
        }
        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
        }
    });
}
@Override
protected void onResume() {
    super.onResume();
    try {
        cam = Camera.open();
        camParams = cam.getParameters();
        cam.startPreview();
        hasCam = true;
    }catch(Exception e){
    }
}
private void turnOnOff(boolean on){
    if(on) {
        if(freq != 0){
            sr = new StroboRunner();
            t = new Thread(sr);
            t.start();
            return;
        }else{
            camParams.setFlashMode(Parameters.FLASH_MODE_TORCH);
        }
    }else if(!on){
        if(t != null){
            sr.stopRunning = true;
            t =null;
            return;
        }else{
            camParams.setFlashMode(Parameters.FLASH_MODE_OFF);
        }
    }
    cam.setParameters(camParams);
    cam.startPreview();
}
private class StroboRunner implements Runnable {
    boolean stopRunning = false;
    @Override
    public void run() {
        Camera.Parameters paramsOn = cam.getParameters();
        Camera.Parameters paramsOff = camParams;
        paramsOn.setFlashMode(Parameters.FLASH_MODE_TORCH);
        paramsOff.setFlashMode(Parameters.FLASH_MODE_OFF);
        try {
            while (!stopRunning) {
                cam.setParameters(paramsOn);
                cam.startPreview();
                Thread.sleep((100 - freq)*1);
                cam.setParameters(paramsOff);
                cam.startPreview();
                Thread.sleep((100 - freq)*1);

            }
        }catch(Exception e){
            }
        }
    }

}

Answer 1

The problem is rather simple but easy to overlook: You have two variables named freq , one in StroboRunner and one in MainActivity .

The one in MainActivity is always updated when the progress bar changes, but the code inside StroboRunner uses the local freq variable. And that one is only updated when you turn the strobe on, right after creating a new StroboRunner ( sr.freq = freq; ). That's why it works again after you turn the strobe off and on again.

If I'm not completely mistaken, you should be able to fix this by just getting rid of the freq variable inside the StroboRunner class and the line sr.freq = freq;

Answer 2

I finally found out how to fix it. Now it works perfect (Flashlight with Strobe effect, also works when the screen is locked!)