如果两个组件大小相同且全屏，则 JLayeredPane 不会绘制低组件

Question

JLayeredPane 如果两个组件大小相同且全屏，则不绘制低组件

软件工作原理：

JFrame <- APanel <- JLayeredPane <-（分层子组件）

• 我的软件是全屏软件。

• APanel 是 BorderLayout 组件。

• JLayeredPane 是 APanel 中的 BorderLayout.CENTER

Panel1 gp = new Panel1(); //Panel1 extends JPanel

gp.setSize(jlp.getSize());

jlp.add(gp);

gp.initializeDisplay(); //starts repaint() loop

jlp.setLayer(gp, 90);

Panel2 lp = new Panel2(); //Panel2 extends JPanel

lp.setSize(jlp.getSize());

lp.initializeDisplay();  //starts repaint() loop

lp.initializeComponents(); //Adds and moves components

jlp.add(lp);

jlp.setLayer(lp, 110);

当我这样制作时，只Panel2显示。Panel1的paintComponent()这个样子的（只需绘制图像）：

g.drawImage(myImage, 0, 0, getWidth(), getHeight(), null);

Panel2包含很多按钮和标签。这个方法解决了这个问题。

Panel1 gp = new Panel1();

gp.setSize(jlp.getSize());

jlp.add(gp);

gp.initializeDisplay();

jlp.setLayer(gp, 90);

Panel2 lp = new Panel2();

lp.setSize(jlp.getWidth() - 1, jlp.getHeight() - 1); //Changed here

lp.initializeDisplay();

lp.initializeComponents();

jlp.add(lp);

jlp.setLayer(lp, 110);

但是这种方法又引起了问题：

Dimension cs = new Dimension(jlp.getWidth() - 1, jlp.getHeight() - 1);

GrassPane gp = new GrassPane();

gp.setSize(cs);

jlp.add(gp);

gp.initializeDisplay();

jlp.setLayer(gp, 90);

LobbyPane lp = new LobbyPane(this);

lp.setSize(cs);

lp.initializeDisplay();

lp.initializeComponents();

jlp.add(lp);

jlp.setLayer(lp, 110);

如果您需要更多信息（例如代码），请添加评论。

Answer 1

当一个不透明组件与另一个组件重叠时，有意跳过绘制完全模糊的组件。当组件被错误地声明为不透明时，这只会成为一个问题。因此，当您实现自己的组件绘制透明图像时，它们应该实现isOpaque()返回false.有趣的是，我仍然可以使用以下代码重现透明组件的重绘问题：JFrame f = new JFrame("Test");JLayeredPane pane = f.getLayeredPane();JButton b = new JButton("Normal Text");b.setHorizontalTextPosition(SwingConstants.LEFT);b.setBounds(20, 20, 300, 100);JLabel l = new JLabel("Overlay");l.setHorizontalTextPosition(SwingConstants.RIGHT);l.setBorder(BorderFactory.createEmptyBorder(4, 4, 4, 4));l.setBounds(20, 20, 300, 100);l.setOpaque(false);pane.add(l);pane.add(b);f.setSize(350, 200);f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);f.setVisible(true);在这里，文本“Overlay”最初可能会也可能不会出现，但是一旦按钮的属性之一发生变化（例如接收焦点或被点击），文本就会消失。问题在于以下属性：System.out.println(pane.isOptimizedDrawingEnabled());将打印true。“优化绘图”意味着在某些情况下可能无法渲染某些子项。正如文档所说：如果此组件平铺其子级，即，如果它可以保证子级不会重叠，则返回 true。当然，JLayeredPane永远不会平铺子项，而是将它们堆叠在一起并且永远不能保证它们不会重叠。尽管如此，出于某种原因，Swing 开发人员还是决定实现以下逻辑：private void validateOptimizedDrawing() {&nbsp; &nbsp; boolean layeredComponentFound = false;&nbsp; &nbsp; synchronized(getTreeLock()) {&nbsp; &nbsp; &nbsp; &nbsp; Integer layer;&nbsp; &nbsp; &nbsp; &nbsp; for (Component c : getComponents()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; layer = null;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if(SunToolkit.isInstanceOf(c, "javax.swing.JInternalFrame") ||&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(c instanceof JComponent &&&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; (layer = (Integer)((JComponent)c).&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;getClientProperty(LAYER_PROPERTY)) != null))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if(layer != null && layer.equals(FRAME_CONTENT_LAYER))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; continue;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; layeredComponentFound = true;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; break;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; if(layeredComponentFound)&nbsp; &nbsp; &nbsp; &nbsp; optimizedDrawingPossible = false;&nbsp; &nbsp; else&nbsp; &nbsp; &nbsp; &nbsp; optimizedDrawingPossible = true;}因此，每当组件不是JComponent实例或没有LAYER_PROPERTY属性时（在使用上述示例中的默认图层时总是如此），尽管实际布局逻辑中没有任何更改，窗格仍会决定优化绘制是可能的。所以当我们改变pane.add(l);pane.add(b);到Object myLayer = JLayeredPane.DEFAULT_LAYER+1;pane.add(l, myLayer);pane.add(b, myLayer);问题将消失，现在System.out.println(pane.isOptimizedDrawingEnabled());将打印false。小心自动装箱。当您使用pane.add(l, JLayeredPane.DEFAULT_LAYER+1);or just 时pane.add(l, 1);，它会调用add(Component comp, int index)而不是所需的add(Component comp, Object constraints).