我试图缩放图像以适合我GUI中的JPanel。每当我在JFrame中创建一个ImagePanel
的新实例时,我会得到一个异常,因为宽度和高度均为0.但是,我忽略了getPreferredSize()
,因此宽度和高度看起来应该是非零值。当为JPanel缩放图像时,宽度和高度必须为非零
public class ImagePanel extends JPanel {
private Image image;
public ImagePanel() {
try {
image = ImageIO.read(new File("resources/opening.jpg"));
image = scaleImage(image);
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(image, 0, 0, this);
}
public void setImage(Image i) {
image = scaleImage(i);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(500, 500);
}
public Image scaleImage(Image i) {
return i.getScaledInstance(getWidth(), getHeight(), Image.SCALE_SMOOTH);
}
}
这里是堆栈跟踪:
Exception in thread "main" java.lang.IllegalArgumentException: Width (0) and height (0) must be non-zero
at java.awt.image.ReplicateScaleFilter.<init>(ReplicateScaleFilter.java:102)
at java.awt.image.AreaAveragingScaleFilter.<init>(AreaAveragingScaleFilter.java:77)
at java.awt.Image.getScaledInstance(Image.java:172)
at ImagePanel.scaleImage(ImagePanel.java:40)
at ImagePanel.<init>(ImagePanel.java:18)
at GUIFrame.<init>(GUIFrame.java:44)
at main.main(main.java:6)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
你可以显示堆栈跟踪吗? – MordechayS
@MordechayS是的,我刚刚添加了栈跟踪 – tpm900
'getPreferredSize()'是一个请求,而不是一个保证。当你第一次创建'JPanel'时,它不是组件层次结构的一部分,所以它没有机会调整大小。在面板添加到父容器并进行布局后,您需要调用'scaleImage'。或者,您可以使用首选大小作为参数,而不是实际大小。 – resueman