如何更新Java swing背景图？
正如您所看到的这些图片，背景网格线和黑色矩形在菜单项关闭后不会更新。我怎样才能更新它？在 C# 中，有一个事件处理程序可以使其自动更新，但我是 Java swing GUI 应用程序的新手。
这是代码：
public void paint(Graphics g) {
super.paintComponents(g);
MainDisplayForm mD = new MainDisplayForm();
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLACK);
int gridWidth = 1240;
int gridHeight = 400;
g2.fillRect(20, 50, gridWidth, gridHeight);
g2.setColor(Color.darkGray);
paintGrid(g2,gridWidth, gridHeight);
g2.setColor(Color.red);
Line2D line = new Line2D.Float(20, 50, 250, 260);
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
//g2.draw(line); //pending
g2.dispose();
}
private void paintGrid(Graphics g, int gridWidth, int gridHeight)
{
for(int i=20; i<gridWidth+20; i=i+10)
{
g.drawLine(i, 50, i, gridHeight+49);
}
for(int i=50; i<gridHeight+50; i=i+10)
{
g.drawLine(20, i, 1259, i);
}
}
//感谢您的评论！这是要添加的事件处理程序。 必须将其添加到网格上绘制的每个 memu 项目
private void jMenu2MenuDeselected(javax.swing.event.MenuEvent evt) {
repaint();
}
As you see these picture, the background grid lines and black rectangle are not updated after the menu item is closed. How can I update it? In C# there is an event handler to make it updated automatically, but I am newbie to Java swing GUI application.
Here is the code:
public void paint(Graphics g) {
super.paintComponents(g);
MainDisplayForm mD = new MainDisplayForm();
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLACK);
int gridWidth = 1240;
int gridHeight = 400;
g2.fillRect(20, 50, gridWidth, gridHeight);
g2.setColor(Color.darkGray);
paintGrid(g2,gridWidth, gridHeight);
g2.setColor(Color.red);
Line2D line = new Line2D.Float(20, 50, 250, 260);
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
//g2.draw(line); //pending
g2.dispose();
}
private void paintGrid(Graphics g, int gridWidth, int gridHeight)
{
for(int i=20; i<gridWidth+20; i=i+10)
{
g.drawLine(i, 50, i, gridHeight+49);
}
for(int i=50; i<gridHeight+50; i=i+10)
{
g.drawLine(20, i, 1259, i);
}
}
//Thanks for comments!! Here is the event handler to add.
This must be added to every memu item drawn over the grid
private void jMenu2MenuDeselected(javax.swing.event.MenuEvent evt) {
repaint();
}
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评论（3）
不要重写paint()并调用super.paintComponents()。
自定义绘制是通过重写 JPanel（或 JComponent）的 PaintComponent() 方法来完成的，然后您将调用 super.paintComponent()。
如果您需要更多帮助，请发布您的 SSCCE 来演示问题。
Don't override paint() and invoke super.paintComponents().
Custom painting is done by overriding the paintComponent() method of a JPanel (or JComponent) and then you would invoke super.paintComponent().
If you need more help then post your SSCCE demonstrating the problem.
使用
repaint()刷新/更新组件。何时使用
repaint()？将某些组件添加到面板/框架或操作某些组件后，例如，当您更改 Swing 中组件的位置/属性时动画，调用
repaint()它会为你完成这项工作。实际上，它触发了对调用组件的update()方法的调用。Use
repaint()for refreshing/updating the components.When to use
repaint()?After you add some components to a panel/frame or manipulate some components, for example when you change the locations/properties of components in a Swing animation, call
repaint()and it will do the job for you. Actually, it triggers a call forupdate()method of the calling component.当菜单关闭时，调用重新打印到窗口。
不要调用
paint(getGraphics())。相反，调用repaint()因为这会通知超级组件它也需要重绘。When the menu is closed call reprint to the window.
Don't call
paint(getGraphics()). Instead callrepaint()because this informs the super component that it needs to redraw as well.