Java swing，滚动条不适用于绝对布局 [英] Java swing, scrollbar does not working with absolute layout

问题描述

我想有一个固定大小的jpanel，而jscrollpane中也没有布局管理器(这也将没有布局管理器).我不能使用任何布局管理器，因为我需要在用户点击的位置创建一个矩形/圆形(并允许所有创建的润饰剂进行拖放)

I want to have a jpanel with fixed size without layout manager in jscrollpane (which will be also without layout manager). I cant use any layout manager because i need to create an rectangle/circle at a location where user clicks (and allow drag & drop for all the created emelents)

    setLocationRelativeTo(null);
    setSize(300,300);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setName("dnd test");


    int v=ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED;
    int h=ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED;


    JScrollPane scroll = new JScrollPane(panel,v,h);
    scroll.setLayout(null);
    scroll.setPreferredSize(new Dimension(1000, 1000));
    scroll.setBounds(0, 0, 1000, 1000);
    panel = buildComponentOnAbsoluteLayout(new JPanel(),scroll,0,0,500,500);
    panel.setBackground(Color.darkGray);
    panel.setSize(350,350);
    panel.setLayout(null);
    buildComponentOnAbsoluteLayout(new JButton("button 1"),panel,10,10,120,30);
    buildComponentOnAbsoluteLayout(new JButton("button 1"),panel,50,50,120,30);

    add(scroll);
    setVisible(true);

    public static  <T extends JComponent> T buildComponentOnAbsoluteLayout(T t,Container holder,int x, int y,int width, int heigth){
        t.setBounds(x,y,width,heigth);
        holder.add(t);
    return t;
}

滚动条将永远不会弹出.

Scrollbar will never pop up.

推荐答案

我不能使用任何布局管理器，因为我需要在用户点击的位置创建一个矩形/圆形(并允许所有创建的润饰剂进行拖放)

I cant use any layout manager because i need to create an rectangle/circle at a location where user clicks (and allow drag & drop for all the created emelents)

好吧，您不能使用JDK中的标准布局管理器，但是是的，您应该使用布局管理器，因为布局管理器不仅可以设置组件的位置.

Well, you can't use a standard layout manager from the JDK, but yes you SHOULD be using a layout manager because a layout manager does more than just set the location of a component.

滚动条将永远不会弹出.

Scrollbar will never pop up.

无法进行滚动，因为基于添加到面板的组件，面板没有合适的首选尺寸.

Your scrolling doesn't work because the panel doesn't have a proper preferred size based on the components added to the panel.

查看拖动版式，这是一个设计的版式管理器以此目的.它可以随机放置，但仍可以计算出首选大小，因此可以滚动.

Check out the Drag Layout which is a layout manager designed for this purpose. It allows random placement but it still calculates a preferred size so scrolling will work.

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