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我正在爲我的學士論文設計一個程序，根據z位置（電纜中的位置）顯示鋼絲繩的內部幾何形狀。最終變量不斷變化，但不應該
爲了測試我一塊電纜的「穿行」，用這段代碼（sl是股名單，已經初始化，即正常工作）：
Cable c = new Cable(sl);
ImageFrame ts = new ImageFrame(c);
try {
while (location <2) {
location = location + 0.01;
Thread.sleep(100);
c.update(location);
ts.repaint();
}
System.exit(0);
} catch (InterruptedException e) {
e.printStackTrace();
}
電纜功能update只是應重新計算電纜的幾何形狀。我的班線有所有這些股股的名單，以及這update功能呢，只是調用更新功能：
public void update(double z) {
for(int i=0;i<strandList.size() ;i++) {
strandList.get(i).updateStrand(z);
}
}
對象Strand看起來是這樣的：
public abstract class Strand {
Punt middenCable;
final Punt nulpoint_midden;
Punt midden;
Double angle;
Double d_to_core;
Image img;
int img_size;
BufferedImage bf;
/**
*
* @param c centre of the cable
* @param p middle of the strand
* @param ang angle at this point
* @param dtc distance to core
* @param i image
*/
public Strand(Punt c,Punt p,Image i) {
nulpoint_midden = p; //location of strand at z=0
middenCable =c;
midden = p; // for drawing
img = i;
img_size = 135; //TODO adapt
bf = new BufferedImage(img_size, img_size, BufferedImage.TRANSLUCENT);
bf.getGraphics().drawImage(img, 0, 0, null);
}
/**
* angle goed zetten tov de z
* @param z
*/
abstract public void updateStrand(Double z);
public void paint(Graphics g){
g.setColor(Color.RED); //cirkels rood
//rotate around itself
int x = (int) (this.midden.getX() - img_size/2 );
int y = (int) (this.midden.getY() - img_size/2);
int st = (int) this.img_size;
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(Color.RED);
AffineTransform at = new AffineTransform();
at.setToRotation(Math.toRadians(angle), midden.getX(), midden.getY());
g2d.setTransform(at);
g2d.drawImage(bf, x, y, null);
g2d.dispose();
}
在繪畫功能以一定的角度圍繞自身旋轉。但問題是抽象函數「更新鏈」。這個應該做的是改變平底球Midden的座標到它實際上的位置。參數nulpoint_midden應該不是變化並且是恆定的，用於計算。對象類型外鏈（延伸鏈）的updatestrand就像下面：
import java.awt.Image;
public class OuterStrand extends Strand{
private double rotateconstant1 = 10; //tweaken tot perfecte laylength
private double rotateconstant2 = (2*Math.PI/34); //tweaken tot perfecte laylength
public OuterStrand(Punt c,Punt p, Image i) {
super(c, p,i);
}
@Override
public void updateStrand(Double z) {
// midden updaten
double xpoint = nulpoint_midden.getX(); //original point
double ypoint = nulpoint_midden.getY(); //original point
double cCableX = super.middenCable.getX();
double cCableY = super.middenCable.getY();
double dx = nulpoint_midden.getX() - cCableX;
double dy = ypoint - cCableY;
System.out.println(xpoint+ " " +ypoint) ;
double curangle = Math.atan2(dy, dx);
double dist = Math.sqrt(dx*dx + dy*dy);
double dangle = rotateconstant2 * z;
double x1 = cCableX + dist * Math.cos(dangle + curangle);
double y1 = cCableY + dist * Math.sin(dangle + curangle);
super.midden.setX(x1);
super.midden.setY(y1);
// rotate around itself
super.angle = z * Math.PI * rotateconstant1;
}
}
所以中的println給出XPOINT和ypoint，這應該是恆定的。但實際上，它會改變（所以平底球nulpoint_midden改變值）。我有沒有想法爲什麼這個值改變。這裏是我的打印：
> 500.0 200.0
> 500.55439838802135 200.00051226305845
> 501.66318759079536 200.00461035702926
> 503.32632406233347 200.0184412864145
> 505.54367148773895 200.0512248625842
> 508.3149156018249 200.11525184075379
> 511.63945065512087 200.22587972200301
> 515.5162375992163 200.40152475227
> 519.9436341271526 200.66364828540742
> 524.9191967987913 201.03673531535162
> 530.439455611731 201.54826262515832
> 536.4996615512757 202.22865365075 (etcetera)
由於這個值變化，表示是不正確的。由於走過電纜，它應該以恆定的速度旋轉，但實際上正在加速。
對於長時間的解釋我很抱歉，但如果有人看到我的錯誤，並告訴我我做錯了什麼，那將會很棒。謝謝！
你可以添加「Punt」類的完整源代碼嗎？ – iMysak 2013-05-05 20:53:36