在气垫船的所有 cmets 旁边
图形上下文在组件之间共享。 super.paintComponent 的任务之一是在绘制之前“清理”图形上下文。
这就是为什么您会看到两个版本的按钮...
我也会做一些不同的事情。随着时间的推移，这应该有助于可扩展性和重用性，同时也会稍微减少逻辑。
我会...
- 将形状抽象为具有最低要求的基本“形状”类，例如填充和描边颜色、位置、大小、描边等，并且知道如何绘制自身。
- 我将创建某种模型，使您能够分离和定义责任边界。 “管理”形状不是组件的责任，它只关心在其表面上绘制它们。同样，组件并不关心“形状”是什么，它只想知道如何绘制它们......
- 我会使用
Actions 来简单地创建这些形状并将它们添加到模型中...
我只创建了一个三角形（除了位置和大小之外，它没有其他属性），但我相信你会明白的……（ps 你需要提供自己的三角形图标为了行动;))
public class DrawMe {
public static void main(String[] args) {
new DrawMe();
}
public DrawMe() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
DrawModel model = new DefaultDrawModel();
model.addElement(new Triangle(new Rectangle(10, 10, 100, 100)));
DrawPane drawPane = new DrawPane(model);
JToolBar toolBar = new JToolBar();
toolBar.add(new AddTriangleAction(model));
frame.add(toolBar, BorderLayout.NORTH);
frame.add(drawPane);
frame.setSize(400, 400);
frame.setVisible(true);
}
});
}
/**
* Simple action used to add triangles to the model...the model acts
* as a bridge between the action and the UI.
*/
protected class AddTriangleAction extends AbstractAction {
private DrawModel model;
public AddTriangleAction(DrawModel model) {
// Supply your own icon
putValue(SMALL_ICON, new ImageIcon(getClass().getResource("/shape_triangle.png")));
this.model = model;
}
public DrawModel getModel() {
return model;
}
@Override
public void actionPerformed(ActionEvent e) {
// Randomly add the triangles...
int x = (int)(Math.random() * 400);
int y = (int)(Math.random() * 400);
model.addElement(new Triangle(new Rectangle(x, y, 100, 100)));
}
}
/**
* This is the background pane, from which the draw pane extends...
*/
protected class BackgroundPane extends JPanel {
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
int x = getWidth() / 2;
int y = getHeight() / 2;
Graphics2D g2d = (Graphics2D) g.create();
RadialGradientPaint rgp = new RadialGradientPaint(
new Point(x, y),
Math.max(getWidth(), getHeight()),
new float[]{0f, 1f},
new Color[]{Color.GRAY, Color.WHITE}
);
g2d.setPaint(rgp);
g2d.fill(new Rectangle(0, 0, getWidth(), getHeight()));
g2d.setBackground(Color.BLACK);
g2d.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
g2d.dispose();
}
}
/**
* This is a simple model, I stole the list model because it was quicker
* and easier to demonstrate (don't need to write all the listeners)
*/
public interface DrawModel extends ListModel<DrawMeShape> {
public void addElement(DrawMeShape shape);
public void removeElement(DrawMeShape shape);
}
/**
* A default implementation of the DrawModel...
*/
public class DefaultDrawModel extends DefaultListModel<DrawMeShape> implements DrawModel {
@Override
public void removeElement(DrawMeShape shape) {
removeElement((Object)shape);
}
}
/**
* The actually "canvas" that shapes are rendered to
*/
protected class DrawPane extends BackgroundPane {
// Should provide ability to setModel...
private DrawModel model;
public DrawPane(DrawModel model) {
this.model = model;
model.addListDataListener(new ListDataListener() {
@Override
public void intervalAdded(ListDataEvent e) {
repaint();
}
@Override
public void intervalRemoved(ListDataEvent e) {
repaint();
}
@Override
public void contentsChanged(ListDataEvent e) {
repaint();
}
});
}
public DrawModel getModel() {
return model;
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Draw the shapes from the model...
Graphics2D g2d = (Graphics2D) g.create();
DrawModel model = getModel();
for (int index = 0; index < model.getSize(); index++) {
DrawMeShape shape = model.getElementAt(index);
shape.paint(g2d, this);
}
g2d.dispose();
}
}
/**
* A abstract concept of a shape. Personally, if I was doing it, I would
* generate an interface first, but this is just a proof of concept...
*/
public abstract class DrawMeShape {
private Rectangle bounds;
public void setBounds(Rectangle bounds) {
this.bounds = bounds;
}
public Rectangle getBounds() {
return bounds;
}
protected abstract Shape getShape();
/**
* The shape knows how to paint, but it needs to know what to paint...
* @param g2d
* @param parent
*/
public void paint(Graphics2D g2d, JComponent parent) {
g2d = (Graphics2D) g2d.create();
Rectangle bounds = getBounds();
Shape shape = getShape();
g2d.translate(bounds.x, bounds.y);
g2d.setColor(Color.DARK_GRAY);
g2d.fill(shape);
g2d.setColor(Color.BLACK);
g2d.draw(shape);
g2d.dispose();
}
}
/**
* An implementation of a Triangle shape...
*/
public class Triangle extends DrawMeShape {
public Triangle(Rectangle bounds) {
setBounds(bounds);
}
@Override
protected Shape getShape() {
// This should be cached ;)
Path2D path = new Path2D.Float();
Rectangle bounds = getBounds();
path.moveTo(bounds.width / 2, 0);
path.lineTo(bounds.width, bounds.height);
path.lineTo(0, bounds.height);
path.lineTo(bounds.width / 2, 0);
path.closePath();
return path;
}
}
}
画得好……