Seekbar progress update

Question

Background: I have one activity, with a Textview and a button. Clicking the button runs SetValue() which opens a dialog that contains a Seekbar, which in turn sets the value for the textview. Here's the code:

    public void SetValue(View view){
    ShowDialog();
    }


    public void ShowDialog() {

    final AlertDialog.Builder popDialog = new AlertDialog.Builder(this);
    final SeekBar seek = new SeekBar(this);
    int value = 0;
    try {
        value = Integer.parseInt(tv.getText().toString());
    } catch(NumberFormatException nfe) {
       System.out.println("Could not parse " + nfe);
    } 

    seek.setProgress(value);
    seek.setMax(100);
    popDialog.setView(seek);
    seek.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {

    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser){
    //Update textview value
    tv.setText("Value : " + progress);
    }
        public void onStartTrackingTouch(SeekBar arg0) {
        // TODO Auto-generated method stub
        }
        public void onStopTrackingTouch(SeekBar seekBar) {
        // TODO Auto-generated method stub
        }
    });
    // Button 
    popDialog.setPositiveButton("OK", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
            }
            });
    popDialog.create();
    popDialog.show();
    }

So it works fine, displaying the initial textview progress, and lets me update it with the seekbar.

Problem: After initially setting the value, if I try to use the method again to change the text, the progress on the seekbar starts at 0 every time, when it should be at the previously selected value/current textview value.

Also, I can set a max value for the bar, can I set a min value? Ie -100? How do I set a range for the seekbar?

Thanks for all advice!

Update 1: I initialized the variable at the start of the class, so that eliminated the int value = 0; line, but the problem persists - the seekbar always opens with the progress at the original text value of the textview.

Answer 1

First of all, you need to persist your value when the user finishes 'seeking' the SeekBar. We do this in onStopTrackingTouch:

public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser){
    //Update textview value
    tv.setText("Value : " + progress);
}
public void onStartTrackingTouch(SeekBar arg0) {
    // TODO Auto-generated method stub
}
public void onStopTrackingTouch(SeekBar seekBar) {
    // Update your preferences only when the user has finished moving the seek bar
    SharedPreferences prefs = getContext().getSharedPreferences("mySharedPrefsFilename", Context.MODE_PRIVATE);
    // Don't forget to call commit() when changing preferences.
    prefs.edit().putInt("seekBarValue", seekBar.getProgress()).commit();
}

Now you want to display this persisted value whenever the dialog is created - so you'll need to retrieve it. You can do this like this:

int value = 0;
SharedPreferences prefs = getContext().getSharedPreferences("mySharedPrefsFilename", Context.MODE_PRIVATE);
value = prefs.getInt("seekBarValue", 0); // 0 is default

seek.setProgress(value);

// You also need to update your TextView to show the saved value
tv.setText("Value : " + value);

You can wrap the access to the SharedPreferences in a class; this is one way to ensure you're using the same preferences file name ("mySharedPrefsFilename" in this example) and the same preference keys to store/retrieve the value ("seekbarValue" in this example).