DragListener.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.utils;

import com.badlogic.gdx.Input.Buttons;
import com.badlogic.gdx.scenes.scene2d.InputEvent;
import com.badlogic.gdx.scenes.scene2d.InputListener;

/**
 * Detects mouse or finger touch drags on an actor. A touch must go down over the actor and a drag won't start until it
 * is moved outside the {@link #setTapSquareSize(float) tap square}. Any touch (not just the first) will trigger this
 * listener. While pressed, other touch downs are ignored.
 * 
 * @author Nathan Sweet
 */
public class DragListener extends InputListener {
	private float tapSquareSize = 14, touchDownX = -1, touchDownY = -1;
	private int pressedPointer = -1;
	private int button;
	private boolean dragging;
	private float deltaX, deltaY;

	public boolean touchDown(InputEvent event, float x, float y, int pointer, int button) {
		if (pressedPointer != -1)
			return false;
		if (pointer == 0 && this.button != -1 && button != this.button)
			return false;
		pressedPointer = pointer;
		touchDownX = x;
		touchDownY = y;
		return true;
	}

	public void touchDragged(InputEvent event, float x, float y, int pointer) {
		if (pointer != pressedPointer)
			return;
		if (!dragging && (Math.abs(touchDownX - x) > tapSquareSize || Math.abs(touchDownY - y) > tapSquareSize)) {
			dragging = true;
			dragStart(event, x, y, pointer);
			deltaX = x;
			deltaY = y;
		}
		if (dragging) {
			deltaX -= x;
			deltaY -= y;
			drag(event, x, y, pointer);
			deltaX = x;
			deltaY = y;
		}
	}

	public void touchUp(InputEvent event, float x, float y, int pointer, int button) {
		if (pointer == pressedPointer) {
			if (dragging)
				dragStop(event, x, y, pointer);
			dragging = false;
			pressedPointer = -1;
		}
	}

	public void dragStart(InputEvent event, float x, float y, int pointer) {
	}

	public void drag(InputEvent event, float x, float y, int pointer) {
	}

	public void dragStop(InputEvent event, float x, float y, int pointer) {
	}

	/** Returns true if a touch has been dragged outside the tap square. */
	public boolean isDragging() {
		return dragging;
	}

	public void setTapSquareSize(float halfTapSquareSize) {
		tapSquareSize = halfTapSquareSize;
	}

	public float getTapSquareSize() {
		return tapSquareSize;
	}

	public float getTouchDownX() {
		return touchDownX;
	}

	public float getTouchDownY() {
		return touchDownY;
	}

	/** Returns the amount on the x axis that the touch has been dragged since the last drag event. */
	public float getDeltaX() {
		return deltaX;
	}

	/** Returns the amount on the y axis that the touch has been dragged since the last drag event. */
	public float getDeltaY() {
		return deltaY;
	}

	public int getButton() {
		return button;
	}

	/**
	 * Sets the button to listen for, all other buttons are ignored. Default is {@link Buttons#LEFT}. Use -1 for any
	 * button.
	 */
	public void setButton(int button) {
		this.button = button;
	}
}