/*
*
*
* Copyright 1990-2007 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 only, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License version 2 for more details (a copy is
* included at /legal/license.txt).
*
* You should have received a copy of the GNU General Public License
* version 2 along with this work; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
* information or have any questions.
*/
package javax.microedition.lcdui.game;
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.Graphics;
/**
* A Layer is an abstract class representing a visual element of a game.
* Each Layer has position (in terms of the upper-left corner of its visual
* bounds), width, height, and can be made visible or invisible.
* Layer subclasses must implement a {@link #paint(Graphics)} method so that
* they can be rendered.
* <p>
* The Layer's (x,y) position is always interpreted relative to the coordinate
* system of the Graphics object that is passed to the Layer's paint() method.
* This coordinate system is referred to as the <em>painter's</em> coordinate
* system. The initial location of a Layer is (0,0).
*
* <p>
**/
public abstract class Layer {
/**
* Creates a new Layer with the specified dimensions.
*
* This constructor is declared package scope to
* prevent developers from creating Layer subclasses
*
* By default, a Layer is visible and its upper-left
* corner is positioned at (0,0).
* @param width The width of the layer, in pixels
* @param height The height of the layer, in pixels
*
*/
Layer(int width, int height) {
setWidthImpl(width);
setHeightImpl(height);
}
/**
* Sets this Layer's position such that its upper-left corner
* is located at (x,y) in the painter's coordinate system.
* A Layer is located at (0,0) by default.
* <br>
* @param x the horizontal position
* @param y the vertical position
* @see #move
* @see #getX
* @see #getY
*
*/
public void setPosition(int x, int y) {
this.x = x;
this.y = y;
}
/**
* Moves this Layer by the specified horizontal and vertical distances.
* <br>
* The Layer's coordinates are subject to wrapping if the passed
* parameters will cause them to exceed beyond Integer.MAX_VALUE
* or Integer.MIN_VALUE.
* @param dx the distance to move along horizontal axis (positive
* to the right, negative to the left)
* @param dy the distance to move along vertical axis (positive
* down, negative up)
* @see #setPosition
* @see #getX
* @see #getY
*
*/
public void move(int dx, int dy) {
x += dx;
y += dy;
}
/**
* Gets the horizontal position of this Layer's upper-left corner
* in the painter's coordinate system.
* <p>
* @return the Layer's horizontal position.
* @see #getY
* @see #setPosition
* @see #move
*
*/
public final int getX() {
return x;
}
/**
* Gets the vertical position of this Layer's upper-left corner
* in the painter's coordinate system.
* <p>
* @return the Layer's vertical position.
* @see #getX
* @see #setPosition
* @see #move
*
*/
public final int getY() {
return y;
}
/**
* Gets the current width of this layer, in pixels.
* @return the width in pixels
* @see #getHeight
*
**/
public final int getWidth() {
return width;
}
/**
* Gets the current height of this layer, in pixels.
* @return the height in pixels
* @see #getWidth
*
**/
public final int getHeight() {
return height;
}
/**
* Sets the visibility of this Layer. A visible Layer is rendered when
* its {@link #paint(Graphics)} method is called; an invisible Layer is
* not rendered.
* @param visible <code>true</code> to make the <code>Layer</code> visible,
* <code>false</code> to make it invisible
* @see #isVisible
*
*/
public void setVisible(boolean visible) {
this.visible = visible;
}
/**
* Gets the visibility of this Layer.
* @return <code>true</code> if the <code>Layer</code> is visible,
* <code>false</code> if it is invisible.
* @see #setVisible
*
*/
public final boolean isVisible() {
return visible;
}
/**
* Paints this Layer if it is visible. The upper-left corner of the Layer
* is rendered at it's current (x,y) position relative to the origin of
* the provided Graphics object. Applications may make use of Graphics
* clipping and translation to control where the Layer is rendered and to
* limit the region that is rendered.
* <P>
* Implementations of this method are responsible for checking if this
* Layer is visible; this method does nothing if the Layer is not
* visible.
* <p>
* The attributes of the Graphics object (clip region, translation,
* drawing color, etc.) are not modified as a result of calling this
* method.
*
* @param g the graphics object for rendering the <code>Layer</code>
* @throws NullPointerException if <code>g</code> is <code>null</code>
*/
public abstract void paint(Graphics g);
/**
* Sets the current width of this layer, in pixels. The Layer's width is
* used to determine its bounds for rendering purposes.
* @param width The width in pixels
* @throws IllegalArgumentException if the specified width is less than 0
* @see #setHeightImpl
* @see #getHeight
* @see #getWidth
*
**/
void setWidthImpl(int width) {
if (width < 0) {
throw new IllegalArgumentException();
}
this.width = width;
}
/**
* Sets the current height of this layer, in pixels. The Layer's height
* is used to determine its bounds for rendering purposes.
* @param height The height in pixels
* @throws IllegalArgumentException if the specified height is less than 0
* @see #setWidthImpl
* @see #getHeight
* @see #getWidth
*
**/
void setHeightImpl(int height) {
if (height < 0) {
throw new IllegalArgumentException();
}
this.height = height;
}
/**
* position of layer in x offset
*/
int x; // = 0;
/**
* position of layer in y offset
*/
int y; // = 0;
/**
* width of layer
*/
int width; // = 0;
/**
* height of layer
*/
int height; // = 0;
/**
* If the Layer is visible it will be drawn when <code>paint</code>
* is called.
*/
boolean visible = true;
}
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