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Posted on 2005-11-16 18:19 让变化成为计划的一部分 阅读(494) 评论(0) 编辑 收藏 所属分类: J2ME
请参考java.util.TimerTask.
TimerTask is something like Timer in VisualBasic. You can sepcify a time period in milliseconds
for your requirement"一幅LOGO显示完以后，几秒种自动显示下一幅LOGO".
Here is an sample code.
  public void testTimer()  {
 MyTimerTask myTimerTask = new MyTimerTask();
Timer timer = new Timer();
timer.schedule(myTimerTask, 5000, 10000); //wait for 5 seconds and then call the function every
10 seconds
 }
class MyTimerTask extends TimerTask {
  public void run() {
//This method will be called every 10 Seconds
Image im = Image.createImage(imageData, 0, imageData.length);
if(im == null)
System.out.println("NULL IMAGE");
System.out.println("The Size of the Byte Array is:" +imageData);
if(frm.size() > 0)
for(int i = 0; i < frm.size(); i++)
frm.delete(i);
frm.append(im);
disp.setCurrent(frm);
 }
}
另外，对于你所说的是不是应该叫做SplashScreen，那么国外曾经有人给出这么一个例子，虽然不是周期性地显示一张又一张的图片，而是利用TimerTask周期性地repaint画布，画出一种Splash Screen的感觉，你可以参考：
import java.util.*;
import javax.microedition.lcdui.*;
public class WaitCanvas
extends Canvas {
private int mCount, mMaximum;
private int mInterval;
private int mWidth, mHeight, mX, mY, mRadius;
private String mMessage;
public WaitCanvas() {
mCount = 0;
mMaximum = 36;
mInterval = 100;
mWidth = getWidth();
mHeight = getHeight();
// Calculate the radius.
int halfWidth = (mWidth - mRadius) / 2;
int halfHeight = (mHeight - mRadius) / 2;
mRadius = Math.min(halfWidth, halfHeight);
// Calculate the location.
mX = halfWidth - mRadius / 2;
mY = halfHeight - mRadius / 2;
// Create a Timer to update the display.
TimerTask task = new TimerTask() {
public void run() {
mCount = (mCount + 1) % mMaximum;
repaint();
}
};
Timer timer = new Timer();
timer.schedule(task, 0, mInterval);
}
public void setMessage(String s) {
mMessage = s;
repaint();
}
public void paint(Graphics g) {
int theta = -(mCount * 180 / mMaximum);
// Clear the whole screen.
g.setColor(255, 255, 255);
g.fillRect(0, 0, mWidth, mHeight);
// Now draw the pinwheel.
g.setColor(0, 0, 0);
g.drawArc(mX, mY, mRadius, mRadius, 0, 360);
g.fillArc(mX, mY, mRadius, mRadius, theta + 20, 20);
//g.fillArc(mX, mY, mRadius, mRadius, theta + 60, 60);
//g.fillArc(mX, mY, mRadius, mRadius, theta + 90, 90);
//g.fillArc(mX, mY, mRadius, mRadius, theta + 120, 120);
// Draw the message, if there is a message.
if (mMessage != null)
g.drawString(mMessage, mWidth / 2, mHeight,
Graphics.BOTTOM | Graphics.HCENTER);
}
}
上面那个是利用TimerTask自动定时填充图形来展示Splash Screen的，那么下面这个就是显示图片来Splash Screen了：
import java.util.*;
import javax.microedition.lcdui.*;
public class Splash extends Canvas {
private Display display;
private Displayable next;
private Timer timer=new Timer();
public Splash (Display display,Displayable next) {
this.display=display;
this.next=next;
display.setCurrent(this);
}
protected void showNotify () {
timer.schedule( new TimerTask () { public void run() {
displayNext(); }},8000);
}
protected void hideNotify() {
timer.cancel();
}
protected void keyPressed (int keycode) {
displayNext();
}
protected void pointerPressed (int x, int y) {
displayNext();
}
private void displayNext() {
display.setCurrent(next);
}
protected void paint (Graphics g) {
int height=this.getHeight();
int width=this.getWidth();
// fill background as white
g.setColor(0xFFFFFF);
g.fillRect(0,0,width,height);
Image logo=null;
try {
logo=Image.createImage("/images/logo.png");
} catch (Exception ignore) {}
g.drawImage(logo,width/2,height/2,g.HCENTER|g.VCENTER);
}
}
here's the calling method in your midlet(it passes the Display and current Displayable):
/** *//**
* This shows the splash
*/
private void showSplash () {
new Splash (display,MenuList);
}
还有一种办法是利用currentTimeMillis。 无非就是利用System.currentTimeMillis()+2000先行计算出什么时间该显示 后一幅图片了，如果靠while循环不断检测发现时间到了，就换那张图片。
private boolean showImage;
void someMethod()
{
long time = System.currentTimeMillis()+2000;
showImage = true;
while(System.currentTimeMillis()<time)
{
repaint();
serviceRepaints();
}
showImage = false;
}
public void paint()
{
if(showImage)
g.drawImage(img,offsetX,MAX_Y/2,g.LEFT|g.VCENTER);
}
efei说：
“你要做的无非就是一个延时，过一定时间就换一幅图片。至于怎么来判断这个延时，方法多种多样，用线程，用TimerTask，用System.currentTimeMillis()，基本上都一样
个人比较倾向于使用线程作为固定的时钟脉冲来驱动游戏。
对于System.currentTimeMillis()，我只能告诉你两点，一是它的作用是取得当前时间，二呢，用这个方法如果只是简单比较时间，那么如果中断游戏，过一段时间再恢复，就会存在问题。
”
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