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Posted on 2005-11-16 18:19 讓變化成為計劃的一部分 閱讀(500) 評論(0) 編輯 收藏 所屬分類: J2ME
請參考java.util.TimerTask.
TimerTask is something like Timer in VisualBasic. You can sepcify a time period in milliseconds
for your requirement"一幅LOGO顯示完以后，幾秒種自動顯示下一幅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，對于你所說的是不是應該叫做SplashScreen，那么國外曾經有人給出這么一個例子，雖然不是周期性地顯示一張又一張的圖片，而是利用TimerTask周期性地repaint畫布，畫出一種Splash Screen的感覺，你可以參考：
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);
}
}
上面那個是利用TimerTask自動定時填充圖形來展示Splash Screen的，那么下面這個就是顯示圖片來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);
}
還有一種辦法是利用currentTimeMillis。 無非就是利用System.currentTimeMillis()+2000先行計算出什么時間該顯示 后一幅圖片了，如果靠while循環不斷檢測發現時間到了，就換那張圖片。
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說：
“你要做的無非就是一個延時，過一定時間就換一幅圖片。至于怎么來判斷這個延時，方法多種多樣，用線程，用TimerTask，用System.currentTimeMillis()，基本上都一樣
個人比較傾向于使用線程作為固定的時鐘脈沖來驅動游戲。
對于System.currentTimeMillis()，我只能告訴你兩點，一是它的作用是取得當前時間，二呢，用這個方法如果只是簡單比較時間，那么如果中斷游戲，過一段時間再恢復，就會存在問題。
”
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