SeekBar is not incremented properly

Question

I am working on a very simple Android app to convert temperature using SeekBar.

There are 2 seek bars, one to select the temperature in Celsius, and the another one to select temperature in Fahrenheit. They are both initialized in the code as follow:

private SeekBar celsiusSeekbar;
private TextView celsiusValueText;
private SeekBar fahrenheitSeekBar;
private TextView fahrenheitValueText;
private ArrayList<Integer> fahrenheitProgress;
private ArrayList<Integer> celsiusProgress;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    this.celsiusSeekbar = (SeekBar) findViewById(R.id.celsius_seekbar);
    this.fahrenheitSeekBar = (SeekBar) findViewById(R.id.fahrenheit_seekbar);
    this.celsiusValueText = (TextView) findViewById(R.id.celsius_value);
    this.fahrenheitValueText = (TextView) findViewById(R.id.fahrenheit_value);

    this.initCelsiusProgress();
    this.celsiusSeekbar.setMax(200);
    this.celsiusSeekbar.setProgress(100);
    this.celsiusValueText.setText("0°C");
    this.celsiusSeekbar.incrementProgressBy(1);
    this.celsiusSeekbar.setOnSeekBarChangeListener(new CelsiusSeekBarChangedListener());

    this.initFahrenheitProgress();
    this.fahrenheitSeekBar.setMax(360);
    this.fahrenheitSeekBar.setProgress(180);
    this.fahrenheitSeekBar.incrementProgressBy(1);
    this.fahrenheitValueText.setText("32°F");
    this.fahrenheitSeekBar.setOnSeekBarChangeListener(new FahrenheitSeekBarChangedListener());
}

private void initFahrenheitProgress() {
    fahrenheitProgress = new ArrayList<>();
    for(int i = 0; i <= 360; i++)
        fahrenheitProgress.add(i, i - 148);
}

private void initCelsiusProgress(){
    celsiusProgress = new ArrayList<>();
    for(int i = 0; i <= 200; i++)
        celsiusProgress.add(i, i - 100);
}

private int convertCelsiusProgressToValue(int progress){ return celsiusProgress.get(progress); }

private int convertFahrenheitProgressToValue(int progress){ return fahrenheitProgress.get(progress); }

private class CelsiusSeekBarChangedListener implements SeekBar.OnSeekBarChangeListener {

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        System.out.println("progress : " + progress + " | seekbar progresss : " + seekBar.getProgress());
        //Update celsius temperature
        celsiusValueText.setText(convertCelsiusProgressToValue(progress) + "°C");

        //Update fahrenheit temperature
        fahrenheitValueText = (TextView) findViewById(R.id.fahrenheit_value);
        int value = (int) (convertCelsiusProgressToValue(progress) * 1.8 + 32);
        fahrenheitValueText.setText(value + "°F");
        fahrenheitSeekBar.setProgress(fahrenheitProgress.indexOf(new Integer(value)));
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {}

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {}

}

private class FahrenheitSeekBarChangedListener implements SeekBar.OnSeekBarChangeListener {

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        //Update fahrenheit temperature
        fahrenheitValueText.setText(convertFahrenheitProgressToValue(progress) + "°F");

        //Update celsius temperature
        celsiusValueText = (TextView) findViewById(R.id.celsius_value);
        int value = (int) ((convertFahrenheitProgressToValue(progress)-32) / 1.8);
        celsiusValueText.setText(value + "°C");
        celsiusSeekbar.setProgress(celsiusProgress.indexOf(new Integer(value)));
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {}

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {}

}

The first seek bar (for Celsius temperature) is incremented by one between 0°C and -17°C, but then it is incremented by 5 and I don't understand why. Here is a little gif to show you the problem: GIF

I would like the seek bar to be incremented by one every time.

If anyone has an idea to explain why it's not working properly, I'd be very grateful !

Answer 1

I have an idea what might be wrong here. When you are moving your Celsius bar, fahrenheitSeekBar.setProgress(fahrenheitProgress.indexOf(new Integer(value))); this is called at the end, and immediately the onProgressChanged in FahrenheitListener is called (which is then calling celsiusBar.setProgress() and the circle starts).

I suggest wrapping both listeners (onProgressChanged methods) in

if(fromUser){
  //your whole listener
}

fromUser is true if the user makes the change, in the app, thus changes made programatically are gonna be ignored.