J2me中實現淡入淡出效果
飄飄白雲([email protected])
在J2me中實現淡入淡出效果，據我所知至少有三種方法。
第一種是取得需要變換圖片的像素，依次設置每個象素的alpha通道值,讓它在0~100之間變化。
第二種是修改圖片的調色板數據，讓其在調色板原始數據到255之間變化。
第三種，其實也是利用上面的辦法，先描畫圖片，然後在圖片上覆蓋一個黑色矩形，改變這個黑色矩形透明度就可以實現淡入淡出的效果。
前兩種方法相比較的話，第一種方法運算量是比較大的，而且第一種方法由於midp1.0不支持alpha通道，在一些手機上無法實現。
下面給出第二種方法的示例，在我們開始之前，應該熟悉png文件格式，如果還不是很明白的話，可以google一下，或者查看前面的帖子中的相關連接。
代碼很清楚，下面是源代碼：
------------CODE__START-----------------------
import java.io.DataInputStream;
import java.util.Timer;
import java.util.TimerTask;
import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
/**
* Discription : 修改調色板數據實現淡入淡出效果
* Author : 飄飄白雲([email protected])
* Created date : 2006/07/13 18:06:39
* Modified history :
*/
public class PngFadeInOut extends MIDlet
{
GameCanvas canvas;
Display display;
public PngFadeInOut()
{
super();
try {
display = Display.getDisplay(this);
canvas = new GameCanvas(this);
} catch (Exception e) {}
}
protected void startApp() throws MIDletStateChangeException
{
if( canvas != null ){
display.setCurrent(canvas);
canvas.start();
}
}
protected void pauseApp()
{
canvas.isExit = true;
}
protected void destroyApp( boolean arg0) throws MIDletStateChangeException
{
}
}
class GameCanvas extends Canvas
{
static String imageName = "/fadeInOut.png";
public static final int MAX_TARDINESS = 30;
//---------------------------------------------------
PngFadeInOut app;
boolean isInited = false;
public boolean isExit = false;
Image offImage = null;
public Graphics g = null;
int scrW;
int scrH;
//---------------------------------------------------
int gameMode;
int subMode;
static final int smInit = 0;
static final int smProc = 1;
static final int smEnd = 2;
static final int gmStart = 0;
//---------------------------------------------------
Image testImage = null;
byte[] oldRGBData = null;
byte[] imgData = null;
static final int FADE_IN = 0;
static final int FADE_OUT = 1;
static final int FADE_STEP = 1;
static int fadeType = FADE_IN;
//---------------------------------------------------
//---Timer process
//---------------------------------------------------
TimerTask task;
Timer timer;
int timerDelayTime;
public boolean isTimerRunning;
void startTimer(int delayTime){
timerDelayTime = delayTime;
isTimerRunning = true;
timer = new Timer();
task = new ProcessingRunner();
timer.scheduleAtFixedRate(task, 0, delayTime);
}
public void stopTimer(){
if( task != null )
task.cancel();
isTimerRunning = false;
timer = null;
task = null;
}
//-----------------------------------------------------
class ProcessingRunner extends TimerTask
{
public void run()
{
if( isExit ) {
stopTimer();
app.notifyDestroyed();
}
if (!isTimerRunning || System.currentTimeMillis() -
scheduledExecutionTime() >= timerDelayTime)
{
return;
}
gameMain();
gameDraw();
repaint();
serviceRepaints();
System.gc();
}
}
//-------------------------------------------------
public GameCanvas(MIDlet midlet)
{
app = (PngFadeInOut)midlet;
}
public void start()
{
setFullScreenMode(true);
while (!isShown())
;
if( !isInited ) {
gameInit();
isInited = true;
}
startTimer(MAX_TARDINESS);
}
void gameInit()
{
scrW = getWidth();
scrH = getHeight();
if(g == null || offImage == null) {
offImage = Image.createImage(scrW, scrH);
g = offImage.getGraphics();
}
changeGameMode(gmStart);
}
public void changeGameMode(int gm){
gameMode = gm;
subMode = smInit;
}
//---------------------------------------------------
// 遊戲主邏輯處理
//---------------------------------------------------
void gameMain()
{
if( gameMode == gmStart )
{
if( subMode == smInit )
{
// 取得圖片的二進制數據
imgData = loadFile(imageName);
//保存原始圖片的調色板rgb數據
oldRGBData = getPlteRGBData(imgData);
if( fadeType == FADE_IN) {
// 設置調色板顏色爲白色，淡入效果
for(int i = rgbDataStartPos; i < rgbDataStartPos + rgbDataLength;i++ ) {
imgData[i] = (byte)255;
}