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我正在尝试根据随机数字数组绘制图片。到目前为止,我已经取得了部分成功,因为背景颜色(白色)确实出现了。
但是,画不出来。相反,我只看到白色背景和这个错误:
PixelAvatarGen
XphnX
Black and white or 8-bit color?
0 = B&W, 1 = 8bit
1
Print name to make into avatar.
2
5:2:7:0:3:6:7:0:6:7:7:3:1:4:0:6:5:1:7:4:0:0:5:6:6:3:0:2:3:7:2:4:7:5:4:2:3:6:0:1:4:1:6:4:1:1:1:5:7:5:1:5:4:0:4:5:1:5:6:0:5:4:6:0:0:6:0:0:0:6:7:5:2:6:4:0:1:1:1:7:0:2:1:4:0:2:3:3:3:3:2:6:6:2:6:4:2:7:5:4:7:3:3:3:1:5:1:6:1:3:4:6:0:1:1:2:5:7:4:1:0:2:4:4:4:6:3:7:7:1:0:6:3:6:3:7:6:5:2:5:5:3:5:3:5:4:4:7:0:5:7:4:2:4:5:7:1:0:3:2:7:7:2:3:5:5:2:7:5:6:6:7:4:3:0:7:4:7:1:0:0:7:4:4:3:7:6:0:4:2:7:6:7:3:2:4:2:7:3:0:5:6:6:7:7:2:2:0:2:5:7:6:5:1:0:6:1:5:2:0:7:0:7:0:4:1:0:3:4:3:7:7:4:4:2:7:0:7:4:7:1:6:1:4:4:2:4:7:3:0:4:4:6:6:3:5:
Drawing11
Exception in thread "AWT-EventQueue-0" Drawing11
java.lang.NullPointerException
at xphnx.pixelgen.Screen.paintComponent(Screen.java:25)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JLayeredPane.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paintToOffscreen(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paint(Unknown Source)
at javax.swing.RepaintManager.paint(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at java.awt.GraphicsCallback$PaintCallback.run(Unknown Source)
at sun.awt.SunGraphicsCallback.runOneComponent(Unknown Source)
at sun.awt.SunGraphicsCallback.runComponents(Unknown Source)
at java.awt.Container.paint(Unknown Source)
at java.awt.Window.paint(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.access$700(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at xphnx.pixelgen.Screen.paintComponent(Screen.java:25)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintToOffscreen(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paint(Unknown Source)
at javax.swing.RepaintManager.paint(Unknown Source)
at javax.swing.JComponent._paintImmediately(Unknown Source)
at javax.swing.JComponent.paintImmediately(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.access$700(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
这是程序的完整输出。 0 = B&W 之后的“1”和“Print name to...”之后的“2”是用户输入。
这里是 Screen.java:
public class Screen extends JPanel {
String[] pixels;
Color[] proxlol;
public Screen(String[] in1, Color[] in2) {
in1 = pixels;
in2 = proxlol;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
this.setBackground(Color.WHITE);
int row = 1, column = 1, row10, column10;
for(int i = 0; i != 256; i++) {
System.out.println("Drawing" + row + column);
g.setColor(proxlol[i]);
if(i == 17 ||
i == 33 ||
i == 49 ||
i == 65 ||
i == 81 ||
i == 97 ||
i == 113 ||
i == 129 ||
i == 145 ||
i == 161 ||
i == 177 ||
i == 193 ||
i == 209 ||
i == 225 ||
i == 241
){
row++;
column = 1;
}
row10 = row*10;
column10 = column*10;
g.fillRect(row10, column10, 10, 10);
System.out.println("Done drawing" + row + column);
column++;
}
}
}
如有需要,Main.java和 Arranger.java在 pastebin 上。
我以前对 Swing 没有什么经验。怎么回事?
最佳答案
您永远不会为您的类变量 proxlol
赋值。
public class Screen extends JPanel {
String[] pixels;
Color[] proxlol;
public Screen(String[] in1, Color[] in2) {
in1 = pixels;
in2 = proxlol;
}
}
您将未初始化的类变量分配(无效)给输入参数 in2
。因此,在您的绘画方法中,当您引用颜色数组时,您会得到一个 NPE。
关于尝试绘制时出现java NullPointerException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13420685/
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