ButtonGroup.java

/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx.scenes.scene2d.ui;

import com.badlogic.gdx.utils.Array;

/**
 * Manages a group of buttons to enforce a minimum and maximum number of checked buttons. This enables "radio button"
 * functionality and more. A button may only be in one group at a time.
 * 
 * @author Nathan Sweet
 */
public class ButtonGroup {
	private final Array<Button> buttons = new Array();
	private Array<Button> checkedButtons = new Array(1);
	private int minCheckCount, maxCheckCount = 1;
	private boolean uncheckLast = true;
	private Button lastChecked;

	public ButtonGroup() {
		minCheckCount = 1;
	}

	public ButtonGroup(Button... buttons) {
		minCheckCount = 0;
		add(buttons);
		minCheckCount = 1;
	}

	public void add(Button button) {
		if (button == null)
			throw new IllegalArgumentException("button cannot be null.");
		button.buttonGroup = null;
		boolean shouldCheck = button.isChecked() || buttons.size < minCheckCount;
		button.setChecked(false);
		button.buttonGroup = this;
		buttons.add(button);
		if (shouldCheck)
			button.setChecked(true);
	}

	public void add(Button... buttons) {
		if (buttons == null)
			throw new IllegalArgumentException("buttons cannot be null.");
		for (int i = 0, n = buttons.length; i < n; i++)
			add(buttons[i]);
	}

	public void remove(Button button) {
		if (button == null)
			throw new IllegalArgumentException("button cannot be null.");
		button.buttonGroup = null;
		buttons.removeValue(button, true);
	}

	public void remove(Button... buttons) {
		if (buttons == null)
			throw new IllegalArgumentException("buttons cannot be null.");
		for (int i = 0, n = buttons.length; i < n; i++)
			remove(buttons[i]);
	}

	/** Sets the first {@link TextButton} with the specified text to checked. */
	public void setChecked(String text) {
		if (text == null)
			throw new IllegalArgumentException("text cannot be null.");
		for (int i = 0, n = buttons.size; i < n; i++) {
			Button button = buttons.get(i);
			if (button instanceof TextButton && text.equals(((TextButton) button).getText())) {
				button.setChecked(true);
				return;
			}
		}
	}

	/**
	 * Called when a button is checked or unchecked.
	 * 
	 * @return true if the new state should be allowed.
	 */
	protected boolean canCheck(Button button, boolean newState) {
		if (button.isChecked == newState)
			return false;

		if (!newState) {
			// Keep button checked to enforce minCheckCount.
			if (checkedButtons.size <= minCheckCount)
				return false;
			checkedButtons.removeValue(button, true);
		} else {
			// Keep button unchecked to enforce maxCheckCount.
			if (maxCheckCount != -1 && checkedButtons.size >= maxCheckCount) {
				if (uncheckLast) {
					int old = minCheckCount;
					minCheckCount = 0;
					lastChecked.setChecked(false);
					minCheckCount = old;
				} else
					return false;
			}
			checkedButtons.add(button);
			lastChecked = button;
		}

		return true;
	}

	/** Sets all buttons' {@link Button#isChecked()} to false, regardless of {@link #setMinCheckCount(int)}. */
	public void uncheckAll() {
		int old = minCheckCount;
		minCheckCount = 0;
		for (int i = 0, n = buttons.size; i < n; i++) {
			Button button = buttons.get(i);
			button.setChecked(false);
		}
		minCheckCount = old;
	}

	/** @return the first checked button, or null. */
	public Button getChecked() {
		if (checkedButtons.size > 0)
			return checkedButtons.get(0);
		return null;
	}

	public Array<Button> getAllChecked() {
		return checkedButtons;
	}

	public Array<Button> getButtons() {
		return buttons;
	}

	/** Sets the minimum number of buttons that must be checked. Default is 1. */
	public void setMinCheckCount(int minCheckCount) {
		this.minCheckCount = minCheckCount;
	}

	/** Sets the maximum number of buttons that can be checked. Set to -1 for no maximum. Default is 1. */
	public void setMaxCheckCount(int maxCheckCount) {
		this.maxCheckCount = maxCheckCount;
	}

	/**
	 * If true, when the maximum number of buttons are checked and an additional button is checked, the last button to
	 * be checked is unchecked so that the maximum is not exceeded. If false, additional buttons beyond the maximum are
	 * not allowed to be checked. Default is true.
	 */
	public void setUncheckLast(boolean uncheckLast) {
		this.uncheckLast = uncheckLast;
	}
}