Custom inline SeekBarPreference - how to set SeekBar progress on the 1st run?

问题

I have prepared a simple test project for my question at GitHub.

In my project there is a custom inline SeekBarPreference, which mostly works fine (its summary is updated when seekbar is being dragged and it saves integer value):

However there is a problem:

On the very 1st run of the app (you might need to uninstall my app when you try see the error again) the progress of the SeekBar is not set (but the summaries are set):

My question is: how to fix this issue in my code?

I have tried adding mSeekBar.setProgress(mProgress) in different spots of SeekBarPreference.java, but just can't find the correct place for that code.

Below are excerpts from my source code (in case Stackoverflow ever outlives GitHub) -

MainActivity.java:

PreferenceManager.setDefaultValues(this, R.xml.preferences, false);

getFragmentManager().beginTransaction()
    .addToBackStack(null)
    .replace(R.id.root, new PrefFragment(), "prefs")
    .commit();

PrefFragment.java:

@Override
public void onResume() {
    super.onResume();

    SharedPreferences prefs = getPreferenceManager().getSharedPreferences();
    // set the summaries from saved values
    onSharedPreferenceChanged(prefs, SEEK_1);
    onSharedPreferenceChanged(prefs, SEEK_2);
    prefs.registerOnSharedPreferenceChangeListener(this);
}

@Override
public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {

    if (SEEK_1.equals(key)) {
        int i1 = prefs.getInt(key, DEFAULT_1);
        mSeek1.setSummary("$ " + i1);
    } else if (SEEK_2.equals(key)) {
        int i2 = prefs.getInt(key, DEFAULT_2);
        mSeek2.setSummary("$ " + i2);
    }       
}

SeekBarPreference.java (the complete source code):

public class SeekBarPreference extends Preference implements OnSeekBarChangeListener {

    private SeekBar mSeekBar; // FIXME how to set its progress?
    private int mProgress;

    public SeekBarPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected View onCreateView(ViewGroup parent) {
        LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View view = inflater.inflate(R.layout.preference_seekbar, parent, false);
        // can also be done in onBindView, does not work either
        mSeekBar = (SeekBar) view.findViewById(R.id.seekbar);
        mSeekBar.setProgress(mProgress);
        mSeekBar.setOnSeekBarChangeListener(this);
        return view;
    }

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        if (!fromUser)
            return;

        setValue(progress);
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {
        // not used
    }

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {
        // not used
    }

    @Override
    protected void onSetInitialValue(boolean restoreValue, Object defaultValue) {
        setValue(restoreValue ? getPersistedInt(mProgress) : (Integer) defaultValue);
    }

    public void setValue(int value) {
        if (shouldPersist()) {
            persistInt(value);
        }

        if (value != mProgress) {
            mProgress = value;
            notifyChanged();
        }
    }
}

UPDATE:

What I have unsuccessfully tried sofar -

1) Adding the following lines to the onCreateView() method:

    int progress = getPersistedInt(mProgress); // shows 0 in debugger
    mSeekBar.setProgress(progress);

2) Adding the following lines to the setValue() method:

    if (value != mProgress) {
        mProgress = value;
        mSeekBar.setProgress(mProgress);
        notifyChanged();
    }

Alas this does not work, the progress of the mSeekBar stays at 0.

Also, there is a SeekBarPreference by Google - but I don't understand how it works there (or if it works at all).

回答1:

You need to override onGetDefaultValue in SeekBarPreference.

Try this:

@Override
protected Object onGetDefaultValue(TypedArray a, int index) {
    return a.getInt(index, 0);
}

回答2:

When you instantiate

mSeek1 = (SeekBarPreference) findPreference(SEEK_1);

private int mProgress; is 0

So probably it will help if you add a setter in the SeekBarPreference for mProgress and set its value:

mSeek1 = (SeekBarPreference) findPreference(SEEK_1);
mSeek1.setMProgress(valueIhopeIsKnownAtThisMonent);

回答3:

SOLUTION: It's a Bug in ProgressBar!

finally... I think I found the solution...

this does not work as one would expect:

seekBar.setMax(50);
seekBar.setProgress(20);
seekBar.setMax(20);
seekBar.setProgress(20);

The setProgress(...) seems to not trigger the update on the drawable if the same value is passed again. But it's not triggered during the setMax, too. So the update is missing. Seems like a Bug in the android ProgressBar! This took me about 8 hours now.. lol :D

To solve this, I'm just doing a bar.setProgress(0) before each update... this is only a workaround, but it works for me as expected:

seekBar.setMax(50);
seekBar.setProgress(20);
seekBar.setProgress(0); // <--
seekBar.setMax(20);
seekBar.setProgress(20);

回答4:

Add this code before you call mSeekBar.setProgress(mProgress); :

String preferenceSummary = this.getSummary().toString();
preferenceSummary = preferenceSummary.replace("$ ", "");
mProgress = Integer.valueOf(preferenceSummary);

来源：https://stackoverflow.com/questions/30170384/custom-inline-seekbarpreference-how-to-set-seekbar-progress-on-the-1st-run

标签

android

android-preferences

seekbar

android-seekbar

seekbarpreference