Custom Preference with a StringSet

Question

I have a list of folders I'd like to display in a preference as a list of strings. I'm storing the folders via SharedPreferences.Editor.putStringSet(). The user can click a row to remove that entry.

I'm not sure how to display the values in a custom Preference; a ListView would be ideal. The built in preferences don't support this use case and Preference.getPersistedStringSet is hidden "pending API approval", apparently for years, so a custom Preference won't work easily.

I could use a delimited string with a static helper method within the custom Preference to ensure a call to SharedPreferences.Editor.putString() (instead of putStringSet) is formatted properly, but that's a bit sloppy. Any better ideas?

Answer 1

So I created a custom DialogPreference as the existing views would have been a poor/confusing user experience. It will actually link to (and requires) a StringSet preference key and allow the user to remove entries. You could modify the onClick to have it behave differently.

public class RemovableListPreference extends DialogPreference implements OnClickListener
{
    private static final String androidns="http://schemas.android.com/apk/res/android";

    private ListView mListView;
    private ArrayAdapter<String> mAdapter = new ArrayAdapter<>(getContext(), android.R.layout.simple_list_item_1);
    private TextView mSplashText,mValueText;
    private String mPreferenceKey;
    private Context mContext;

    private String mDialogMessage;

    public RemovableListPreference(Context context, AttributeSet attrs) {

        super(context,attrs);
        mContext = context;

        // Message attribute for the alert dialog
        int mDialogMessageId = attrs.getAttributeResourceValue(androidns, "dialogMessage", 0);
        if(mDialogMessageId == 0)
            mDialogMessage = attrs.getAttributeValue(androidns, "dialogMessage");
        else
            mDialogMessage = mContext.getString(mDialogMessageId);

        // Key attribute for the view, used to automatically update the preferences
        int preferenceId = attrs.getAttributeResourceValue(androidns, "key", -1);
        if (preferenceId == -1)
            throw new RuntimeException(RemovableListPreference.class.getSimpleName() + " requires a preference key (android:key)");
        else
            mPreferenceKey = mContext.getString(preferenceId);
    }

    @Override
    protected View onCreateDialogView() {

        LinearLayout.LayoutParams params;
        LinearLayout layout = new LinearLayout(mContext);
        layout.setOrientation(LinearLayout.VERTICAL);
        layout.setPadding(6,6,6,6);

        mSplashText = new TextView(mContext);
        if (mDialogMessage != null)
            mSplashText.setText(mDialogMessage);
        layout.addView(mSplashText);

        mValueText = new TextView(mContext);
        mValueText.setGravity(Gravity.CENTER_HORIZONTAL);
        mValueText.setTextSize(32);
        params = new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.MATCH_PARENT);
        layout.addView(mValueText, params);

        mListView = new ListView(mContext);
        mListView.setDivider(getDivider());

        mListView.setAdapter(mAdapter);
        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener()
        {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id)
            {
                mAdapter.remove(mAdapter.getItem(position));
            }
        });
        layout.addView(mListView, new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));

        return layout;
    }

    public void setEntries(Set<String> entries)
    {
        mAdapter.clear();
        mAdapter.addAll(entries);
    }

    @Override
    public void showDialog(Bundle state) {

        super.showDialog(state);

        SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(mContext);
        Set<String> excludedFolders = pref.getStringSet(mContext.getString(R.string.KEY_EXCLUDED_FOLDERS), new HashSet<String>());
        mAdapter.clear();
        mAdapter.addAll(excludedFolders);

        Button positiveButton = ((AlertDialog) getDialog()).getButton(AlertDialog.BUTTON_POSITIVE);
        positiveButton.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        if (mPreferenceKey != null)
        {
            SharedPreferences.Editor editor = PreferenceManager.getDefaultSharedPreferences(mContext).edit();
            Set<String> rows = new HashSet<>();
            for (int i = 0; i < mAdapter.getCount(); ++i)
            {
                rows.add(mAdapter.getItem(i));
            }
            editor.putStringSet(mPreferenceKey, rows);
            editor.apply();
        }
        ((AlertDialog) getDialog()).dismiss();
    }

    private Drawable getDivider() {
        int[] attrs = { android.R.attr.listDivider };
        TypedArray a = mContext.obtainStyledAttributes(attrs);
        Drawable divider = a.getDrawable(0);
        a.recycle();

        return divider;
    }
}

Ex. header:

<com.anthonymandra.widget.RemovableListPreference
    android:key="@string/KEY_EXCLUDED_FOLDERS"
    android:negativeButtonText=""
    android:title="@string/excludedFolders"
    android:summary="@string/excludedSummary"
    android:dialogTitle="@string/excludedFolders"
    android:dialogMessage="@string/excludedMessage"/>