Java：JScrollPane装满后会消失

我想查看一些有关程序某些对象的信息.为此,我将为其每个信息创建一个JPanel.这些面板打包在一起,并添加到ScrollPane中.

如果只有几个对象,则效果很好,因此无需滚动即可显示所有信息.一旦有更多,整个面板就会以最小化的方式消失.

很抱歉,我无法提取一个小的代码段来重现该错误.我使它尽可能的小.所以我必须给你三个班：

程序：创建对象的TreeMap并对其进行处理.在这里,它只是初始化一个整数列表.

   import java.util.TreeMap;




   public class Program {


// Set ObjectNumber here!
static int numberObjects = 32;


static TreeMap<Integer, Integer> objects = new TreeMap<Integer, Integer>();

static TestFrame frame;

public static void main(String[] args) {

    init();

}

public static void init() {

    for (int i=0; i < numberObjects; i++) {
        objects.put(i, i);
    }

    frame = new TestFrame(objects);

    frame.repaint();

}


}

TestFrame：它扩展了JFrame,将其自身设置为最大化并设置了Border Layout.之后,它从我的类TestPanel向东部添加一个JPanel.

 import java.awt.BorderLayout;

 import java.awt.Dimension;

 import java.awt.Frame;

 import java.util.TreeMap;

 import java.awt.GridLayout;

 import java.awt.Toolkit;

 import java.util.TreeMap;


 import javax.swing.JFrame;


 public class TestFrame extends JFrame {


TreeMap<Integer, Integer> objects;

TestPanel testPanel;

public TestFrame(TreeMap<Integer, Integer> objects) {

    this.objects = objects;
    setTitle("Program");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    this.setExtendedState(Frame.MAXIMIZED_BOTH);

    init();

}

public void init() {

    setLocationRelativeTo(null);
    setLayout(new BorderLayout());

    testPanel = new TestPanel(objects);
    this.add(testPanel, BorderLayout.EAST);

    setVisible(true);

}


 }

TestPanel：它扩展了JPanel.遍历所有对象,并将带有整数值的标签添加到数组名称[].然后再为每个对象创建一个仅用于此对象的面板,添加一个带有文本“ Name：”和名称[] -array中的标签的面板.与GridBagLayout.
现在,它将对象的所有面板打包在一个面板“ innerPanel”中.这将添加到滚动窗格.滚动窗格被添加到类(TestPanel)中.

import java.util.TreeMap;


import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.SwingConstants;


import java.awt.Font;

import java.awt.Graphics;

import java.awt.GridBagConstraints;

import java.awt.GridBagLayout;

import java.awt.GridLayout;

import java.awt.Label;


import javax.swing.BorderFactory;


public class TestPanel extends JPanel {

GridBagConstraints gridBagConstraints = new GridBagConstraints();

TreeMap<Integer, Integer> objects;

Label[] names;

JPanel[] objectPanel;

JPanel innerPanel;

Font fontLabelName = new Font("Arial", Font.BOLD, 20);



public TestPanel (TreeMap<Integer, Integer> objects) {

    this.objects = objects;

    names = new Label[objects.size()];

    objectPanel = new JPanel[objects.size()];

    this.setLayout(new GridBagLayout());

    for(int i=0; i<objects.size(); i++) {
        Label tempLabel = new Label(Integer.toString(objects.get(i)), SwingConstants.LEFT);
        tempLabel.setFont(fontLabelName);
        names[i]=tempLabel;
    }

    for (int i=0; i<objects.size(); i++) {

        JPanel tempPanel = new JPanel();
        tempPanel.setLayout(new GridBagLayout());
        objectPanel[i] = tempPanel;

        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        gridBagConstraints.gridheight = 1;
        Label nameLabel = new Label("Name: ", SwingConstants.LEFT);
        nameLabel.setFont(fontLabelName);
        objectPanel[i].add(nameLabel, gridBagConstraints);

        gridBagConstraints.gridx = 2;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        gridBagConstraints.gridheight = 1;
        objectPanel[i].add(names[i], gridBagConstraints);
    }

    innerPanel = new JPanel();
    innerPanel.setLayout(new GridLayout(0,1));

    for (int i = 0; i<objects.size(); i++) {
        innerPanel.add(objectPanel[i]);
    }

    JScrollPane scrollPane = new JScrollPane(innerPanel);
    // scrollPane.setBorder( BorderFactory.createEmptyBorder() );
    scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

    this.add(scrollPane);

}

}

如屏幕截图所示,在我的屏幕分辨率为31个对象的情况下,效果很好.但是,如果我使用32个对象,则滚动窗格几乎消失了.

31 objects

32 objects

如果有人可以帮助我解决问题或链接匹配的帖子,我将非常感谢-我在Google /搜索中找不到任何帖子.

解决方法:

尝试在TestPanel中设置其他布局.如果要在面板中仅添加一个对象(案例中为scollpane),并且希望该对象占据面板的所有空间,则BorderLayout是一个不错的选择.

this.setLayout(new BorderLayout());

标签：swing,jpanel,jscrollpane,java
来源： https://codeday.me/bug/20191119/2033491.html