基于MIDP1.0实现屏幕滚动

王朝other·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

本例介绍了一个常用的编程技巧,就是如何基于MIDP1.0实现屏幕的滚动效果。在MIDP2.0可以借助LayerManager的的“可视窗口”来实现。MIDP1.0通过变化坐标系来实现屏幕的滚动效果,只要借助Graphics.translate()方法。

package com.j2medev.translate;

import javax.microedition.midlet.*;

import javax.microedition.lcdui.*;

public class Translate extends MIDlet

{

PRivate Display display; // The display

private TranslateCanvas canvas; // Canvas

public Translate()

{

display = Display.getDisplay(this);

canvas = new TranslateCanvas(this);

}

protected void startApp()

{

display.setCurrent( canvas );

}

protected void pauseApp()

{ }

protected void destroyApp( boolean unconditional )

{ }

public void exitMIDlet()

{

destroyApp(true);

notifyDestroyed();

}

}

/*

* TranslateCanvas.java

*

* Created on 2005年12月1日, 下午10:15

*

* To change this template, choose Tools Options and locate the template under

* the Source Creation and Management node. Right-click the template and choose

* Open. You can then make changes to the template in the Source Editor.

*/

package com.j2medev.translate;

import javax.microedition.lcdui.Canvas;

import javax.microedition.lcdui.Command;

import javax.microedition.lcdui.CommandListener;

import javax.microedition.lcdui.Displayable;

import javax.microedition.lcdui.Graphics;

import javax.microedition.lcdui.Image;

class TranslateCanvas extends Canvas implements CommandListener {

private Command cmExit;

private Translate midlet;

private Image im = null;

private int translatex = 0, translatey = 0;

public TranslateCanvas(Translate midlet) {

this.midlet = midlet;

cmExit = new Command("Exit", Command.EXIT, 1);

addCommand(cmExit);

setCommandListener(this);

try {

//创建图片

im = Image.createImage("/img.png");

} catch (Java.io.IOException e) {

System.err.println("Unable to locate or read .png file");

}

}

protected void paint(Graphics g) {

if (im != null) {

//清屏

g.setColor(255, 255, 255);

g.fillRect(0, 0, getWidth(), getHeight());

//变换坐标,请参考Graphics.translate(x,y)方法说明

g.translate(translatex, translatey);

//总是在原点处画图片,由于前面变换了坐标 看起来同样图片会动起来

g.drawImage(im, 0, 0, Graphics.LEFT Graphics.TOP);

}

}

public void commandAction(Command c, Displayable d) {

if (c == cmExit)

midlet.exitMIDlet();

}

protected void keyPressed(int keyCode) {

switch (getGameAction(keyCode)) {

case UP:

break;

case DOWN:

break;

case LEFT:

// 图片右边缘已经到达屏幕最右边

System.out.println(translatex);

System.out.println(im.getWidth());

if (translatex + im.getWidth() < getWidth())

return;//直接返回

else

translatex -= 2;

break;

case RIGHT:

// 滚动到图片的左边缘

if (translatex>getWidth()-2)

return;

else

translatex += 2;

break;

}

repaint();

}

}

下载源码变换坐标

(出处:http://www.knowsky.com)

 
 
 
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