自定义JScrollBar-Thumb已绘制，但不会移动

问题描述

我决定在秋千和定制绘画组件的材料上再深入一些.最近几天，我在StackOverFlow和其他论坛上阅读了大量文章，API文档和问题.但是在理解这个概念时，我仍然遇到一些基本问题.

I decided to dive a little bit deeeper in the materia of swing and custom painting components.The last few days I read tons of articles, API-documentations and questions here on StackOverFlow and other forums. But still I got some basic problems in understanding the concept.

我想做的事情:基本上，我想为自己的Swing GUI设计一些组件.设计自定义JButton并没有太多问题.我只是在paint.net中创建了一个自定义图像，创建了一个ImageIcon并使JButton.setIcon(ImageIcon)正常工作.如果我想自定义JSlider的Thumb，则使用相同的故事.我在这里找到了一个非常有趣的解决方案.它只是覆盖了默认拇指，什么都没有，然后在第二步中，将用于"Slider.horizo​​ntalThumbIcon"的自定义ImageIcon(通过ClassLoader使用我的自定义createImageIcon类)放到UIManger.

What I want to do: Basically, I want to design some components for my own Swing GUI. I don't have much problems designing a custom JButton. I just create an custom Image in paint.net, create an ImageIcon and make JButton.setIcon(ImageIcon), that works fine. Same story if I want to customize the Thumb of a JSlider. I found a very funny solution here. It just overrides the default-thumb with nothing and in a second step it puts a custom ImageIcon (using my custom createImageIcon-class via ClassLoader) for the "Slider.horizontalThumbIcon" to the UIManger.

UIManager.getLookAndFeelDefaults().put("Slider.horizontalThumbIcon", new Icon(){

    public int getIconHeight() {
        return 0;
    }

    public int getIconWidth() {
        return 0;
    }

    public void paintIcon(Component c, Graphics g, int x, int y) {
       //do nothing
    }
});

和

UIManager.getLookAndFeelDefaults().put("Slider.horizontalThumbIcon",
                                        createImageIcon("images/slider.png"));

但是现在问题开始了.如果我没看错，则ScrollBar的拇指不是Icon，因此我必须创建一个扩展BasicScrollBarUI的"CustomScrollBarUI"类.此外，我不需要任何箭头键.好的，所以我做了以下工作(从这里的一些示例代码中再次激发了我的灵感):

But now the problem starts. If I'm not wrong, the thumb of a ScrollBar is not an Icon, so I have to create an own "CustomScrollBarUI"-class which extends BasicScrollBarUI. Further I don't wanted any arrow-keys. OK, so I did the following (inspiring me again from some sample code from here):

public class CustomScrollBarUI extends BasicScrollBarUI {

    private ImageIcon img;

    protected JButton createZeroButton() {
        JButton button = new JButton("zero button");
        Dimension zeroDim = new Dimension(0,0);
        button.setPreferredSize(zeroDim);
        button.setMinimumSize(zeroDim);
        button.setMaximumSize(zeroDim);
        return button;
    }


    protected JButton createDecreaseButton(int orientation) {
        return createZeroButton();
    }


    protected JButton createIncreaseButton(int orientation) {
        return createZeroButton();
    }


    protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) {
        BufferedImage img = new LoadBackgroundImage("images/slider.png").getImage();
        g.drawImage(img, 0, 0, new Color(255,255,255,0), null);
    }


    protected void setThumbBounds(int x, int y,int width,int height){
          super.setThumbBounds(x, y, 14, 14);
    }


    protected Rectangle getThumbBounds(){
          return new     Rectangle(super.getThumbBounds().x,super.getThumbBounds().y,14,14);
    }


        protected Dimension getMinimumThumbSize(){
        return new Dimension(14,14);
    }


    protected Dimension getMaximumThumbSize(){
        return new Dimension(14,14);
    }
}

LoadBackGroundImage是一个自己的类，它通过ClassLoader创建BufferedImage.滚动条的拇指现在是我自定义的"slider.png"，但它没有移动.如果我将其向下拖动，则窗格会滚动，但是拇指会停留在他的位置.由于我还不了解所有机制，因此我阅读了有关paintImage方法的信息.在那里，您必须提交一个ImageObserver，我不十分了解它的功能.我在网上找到了多个提交null的代码示例(就像我一样)，但是我认为这不适用于必须移动(并重新粉刷)的图像.我该如何解决?如果我在paintThumb方法中绘制普通图形，则可以正常工作，但是一旦绘制图像，它便不会移动.

The LoadBackGroundImage is an own class, which creates a BufferedImage via ClassLoader. The thumb of the scrollbar is now my custom "slider.png", BUT it doesn't move. If I drag it down, the pane scrolls, but the thumb remains at his place.Due that I haven't understood all the mechanism yet, I read about the paintImage-method. There you have to commit an ImageObserver, whose function I don't really understand. I found various code examples on the net committing null (like I do), but i think this doesn't work for images that have to be moved (and so repainted). How can I solve this? If I paint a normal graphic in the paintThumb-method, it works fine, but as soon that I paint an Image, it doesn't move.

我希望有人能帮助我.预先感谢.

I'm hope somebody can help me. Thanks in advance.

推荐答案

在您的特定情况下-您始终在同一位置绘制图像:

In your specific case - you are always painting image @ the same location:

protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) {
    BufferedImage img = new LoadBackgroundImage("images/slider.png").getImage();
    g.drawImage(img, 0, 0, new Color(255,255,255,0), null);
}

"0，0"在滚动条坐标系中(左上角为零)是"x，y"坐标.

"0, 0" here is "x, y" coordinates in scroll bar coordinates system (which zero is placed in top left corner).

您可以使用paintThumb方法(矩形thumbBounds)接收指向当前拇指位置的拇指边界-只需使用这些值在适当的位置上绘制图像即可.

You recieve thumb bounds in paintThumb method (Rectangle thumbBounds) which points to current thumb location - just use those values to paint image on a proper place.

如果您的拇指图像大小不适合收到的thumbBounds，则可以在其中计算其中点和中心图像.不过，这只是一个例子-您可以按照自己喜欢的任何其他方式来做.

In case your thumb image size does not fit recieved thumbBounds you could calculate its middle point and center image at it. Thats just an example though - you can do it in any other way you like.

而且我想补充一点，在各种UI中几乎所有分离的绘制方法都放置在同一坐标系中，因此您始终必须使用接收到的坐标/边界/...来放置要绘制的内容或对其进行计算靠你自己.

And i would like to add that almost every separated paint-method in various UI's are placed in the same coordinate system, so you always have to use recieved coordinates/bounds/... to place what you are painting OR calculate it on your own.

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