如何获取JList的大小?

时间:2013-10-05 21:27:58

标签: swing jlist

我正在尝试从其单元格渲染器getListCellRendererComponent()方法中获取JList的宽度。

我得到的疏远行为是,只要它被放大,我得到正确的宽度,但是对于小于原始宽度的尺寸,我总是得到它在第一次绘制时的宽度。

这适用于list.getWidth(),list.getSize(),list.getBounds()和list.getCellBounds()。 将包含ScrollPanel的列表的宽度与parent.getxxxxx()一起使用可以正常工作。

顺便说一下,这个JList上没有设置min / max / preferredSize。

此时我不知所措..

修改
因此,似乎在调整大小时不会重新验证包含的ScrollPanel。不应该自动调用revalidate()吗?请注意,这不是以编程方式完成的任何操作,而只是用户执行的鼠标框架调整大小。

编辑2:
是的,好吧,JList的几何有一些复杂的内在性,在一天结束时与实际屏幕真实状态完全无关。任何对后者感兴趣的人都可以更好地获取包含ScrollPane的ViewPort并查询(getWidth,getHaight,getSize,getBounds)。

编辑3
这是根据要求的SSCCE。虽然不是很短暂,但我想保留Netbeans的布局代码,以防它对这个问题产生影响。有了这个,我得到一个667的JList宽度,这似乎与最长项目的长度有些相关(在667它开始显示末尾的省略号)。 只要视口的宽度为667,jlists宽度就会开始跟踪视口的宽度。缩小时,此跟踪在667处停止并保持不变。

package com.dafquest.operator.mvc;

import java.awt.Component;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JLabel;
import javax.swing.JList;

public class JListSSCCE extends javax.swing.JFrame {

    public JListSSCCE() {
        initComponents();
    }

    @SuppressWarnings("unchecked")
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        jList1 = new javax.swing.JList();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setName("Form");

        jPanel1.setName("jPanel1");

        jScrollPane1.setHorizontalScrollBarPolicy(javax.swing.ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        jScrollPane1.setName("jScrollPane1");

        jList1.setModel(new javax.swing.AbstractListModel() {
            String[] strings = { "This is this Jlist's Item 1", "A shorter Item 2", "For some reason Item 3 seems to be longer", "Certainly issue whith item 3 must be a mirage, Item 4 *is* a really long item", "Item 5" };
            public int getSize() { return strings.length; }
            public Object getElementAt(int i) { return strings[i]; }
        });
        jList1.setCellRenderer(new MyCellRenderer());
        jList1.setName("jList1");
        jScrollPane1.setViewportView(jList1);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 330, Short.MAX_VALUE)
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 110, Short.MAX_VALUE)
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );

        pack();
    }                        

    public static void main(String args[]) {
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(JListSSCCE.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }

        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new JListSSCCE().setVisible(true);
            }
        });
    }

    private javax.swing.JList jList1;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;

    private class MyCellRenderer extends DefaultListCellRenderer {

        @Override
        public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {

            JLabel comp = (JLabel) super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
            String widths = "(SPViewPort: " + list.getParent().getWidth()
                    + ", Jlist: " + list.getWidth()
                    + ", Cell: " + comp.getWidth()
                    + ", CellPref: " + comp.getPreferredSize().width + ") ";
            comp.setText(widths + comp.getText());

            // Lets see after adding text, might be that JList width is equal
            // tho longest item's preferred width?
            widths = "(SPViewPort: " + list.getParent().getWidth()
                    + ", Jlist: " + list.getWidth()
                    + ", Cell: " + comp.getWidth()
                    + ", CellPref: " + comp.getPreferredSize().width + ") ";
            System.out.println(widths);

            return comp;
        }
    }
}

1 个答案:

答案 0 :(得分:1)

问题在于您有效地更改了列表的大小要求而未通知它: - )

以下是您的渲染器已修改以演示行为:

  • 最初,就是在列表显示之前,它的ui-delegate测量每个项目的大小要求并为每个单元格缓存那些
  • 那时,视口和列表的大小均为0:添加的textlength为somefixedChars + 2
  • 该列表是一个Scrollable并将其prefScrollableSize报告为其首选
  • scrollPane始终在其prefScrollableSize上调整列表大小,如果更大则滚动
  • 显示后,list / viewport的大小> 0将最大长度项的实际prefSize更改为somefixedChars + 2* digitsOfSize
  • ui不知道这个变化,因此它的pref及其prefScrollable及其实际都没有更新

解决方案取决于您的实际用例:您需要找到一种方法来强制ui使其大小缓存无效。 SwingX' JXList有一个方法,如:

xList.invalidateCellSizeCache();

对于核心,您可以通过重新设置固定大小来破解:

list.setFixedCellWidth(somearbitraryValue);
list.setFixedCellWidth(-1);

要使用的渲染器:

private class MyCellRenderer extends DefaultListCellRenderer {

    private int zeroPref;

    @Override
    public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {

        JLabel comp = (JLabel) super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
        String widths = "(SPViewPort: " + list.getParent().getWidth()
                + ", Jlist: " + list.getWidth()
                + ", CellPref: " + comp.getPreferredSize().width + ") ";
        comp.setText(widths + comp.getText());
        if (list.getWidth() == 0) {
            // keep track of the pref for a zero sized list/viewport 
            zeroPref = Math.max(comp.getPreferredSize().width, zeroPref);
        }
        //list is sized to its initial pref
        widths = //"index: " + index 
                "initial: " + zeroPref
                + "(SPViewPort: " + list.getParent().getWidth()
                + ", Jlist: " + list.getWidth()
                + ", CellPref: " + comp.getPreferredSize().width + ") ";
        System.out.println(widths);

        return comp;
    }
}