Question

 public class FadingLayer extends JPanel {

    public FadingLayer(JPanel panel) {
        // when set to "insets 0 0 0 0", shows the FadingPanel without fading.
        setLayout(new MigLayout("insets 1 0 0 0"));  
        add(panel,"dock center");
        setOpaque(false);
    }

    @Override
    public void paintComponent(Graphics arg0) {
        Graphics2D graphics = (Graphics2D) arg0;
        AlphaComposite alpha = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity);
        graphics.setComposite(alpha);
        graphics.setColor(getBackground());
        graphics.fillRect(0, 0, getWidth(), getHeight());
    }
}

这是我正在放置一些褪色效果的面板。使用swing的Timer类更新不透明度。问题是当所有insets值都设置为0时，计时器工作，但我只看到最终结果没有任何淡入淡出效果。但即使其中一个插图被设置为某个非零值，我也可以看到褪色效果。怎么了，请帮帮忙？

编辑： 当面板（添加到FadingPanel）获取完整区域时，会发生这种情况。这是将FadingPanel设置为 - ＆gt;

的时间

 setLayout(new BorderLayout());
 add(panel,BorderLayout.CENTER);

或

setLayout(new MigLayout("insets 0 0 0 0"));
add(panel,"dock center");

Answer 1

SagarDabas的回答是正确的，我只想做一些小评论

public void paintComponent(Graphics arg0) {
    Graphics2D graphics = (Graphics2D) arg0;
    AlphaComposite alpha = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity);
    graphics.setComposite(alpha);
    graphics.setColor(getBackground());
    graphics.fillRect(0, 0, getWidth(), getHeight());
}

操作图形上下文时必须非常小心。上面的代码将影响它之后绘制的所有组件（保留应用的alpha组合）

更好的方法是在开始之前复制图形。

public void paintComponent(Graphics arg0) {
    Graphics2D graphics = (Graphics2D) arg0.create();
    // paint as normal
    graphics.dispose();
}

当插入物为零时，褪色不起作用

1 个答案: