MultipleChoicePreference.java

package com.mcxiaoke.apptoolkit.preference;

import android.app.AlertDialog.Builder;
import android.content.Context;
import android.content.DialogInterface;
import android.preference.ListPreference;
import android.util.AttributeSet;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

/**
 * Similar to a ListPreference, but uses a multi-choice list and saves the value as a comma-separated string.
 *
 * @author nlawson
 */
public class MultipleChoicePreference extends ListPreference {

    public static final String DELIMITER = ",";
    boolean[] checkedDialogEntryIndexes;

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

    public MultipleChoicePreference(Context context) {
        super(context);
    }

    @Override
    protected void onPrepareDialogBuilder(Builder builder) {

        // convert comma-separated list to boolean array

        String value = getValue();
        Set<String> commaSeparated = new HashSet<String>(Arrays.asList(value.split(DELIMITER)));

        CharSequence[] entryValues = getEntryValues();
        final boolean[] checked = new boolean[entryValues.length];
        for (int i = 0; i < entryValues.length; i++) {
            checked[i] = commaSeparated.contains(entryValues[i]);
        }

        builder.setMultiChoiceItems(getEntries(), checked, new DialogInterface.OnMultiChoiceClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int which, boolean isChecked) {
                checked[which] = isChecked;
            }
        });
        builder.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int which) {

                checkedDialogEntryIndexes = checked;

				/*
                 * Clicking on an item simulates the positive button
                 * click, and dismisses the dialog.
                 */
                MultipleChoicePreference.this.onClick(dialog, DialogInterface.BUTTON_POSITIVE);
                dialog.dismiss();

            }
        });
    }

    @Override
    protected void onDialogClosed(boolean positiveResult) {

        if (positiveResult && checkedDialogEntryIndexes != null) {
            String value = createValueAsString(checkedDialogEntryIndexes);
            if (callChangeListener(value)) {
                setValue(value);
            }
        }
    }

    private String createValueAsString(boolean[] checked) {
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < checked.length; i++) {
            if (checked[i]) {
                sb.append(getEntryValues()[i]).append(DELIMITER);
            }
        }
        return sb.length() == 0 ? "" : sb.substring(0, sb.length() - 1);
    }
}