JScrollPane的：后重新验证

我的问题滚动位置很相似，这一个：JScrollPane的：后重新验证

Set the vertical scroll to current position after revalidate

不同的是，我不想卷回至0，而是从更新前我救的位置子组件如下：

final int oldPos = scrollPanel.getVerticalScrollBar().getValue(); 
removeAll(); // Removes all components from the JPanel 
add(mList()); // Adds a bunch of content 
revalidate(); 
SwingUtilities.invokeLater(new Runnable() 
{ 
    @Override 
    public void run() 
    { 
     ml.getVerticalScrollBar().setValue(oldPos); 
    } 
});

此代码获取另一componenent的鼠标移动侦听器触发因此它被称为相当频繁。

即使最初jscrollpane滚动到顶部有时oldPos不为零，导致窗格向下滚动，尽管设置了该值。

即使我用力滚动到顶部，只要登录oldPos价值，它并不总是0：

final int oldPos = scrollPanel.getVerticalScrollBar().getValue(); 
removeAll(); 
add(mList()); 
revalidate(); 
SwingUtilities.invokeLater(new Runnable() 
{ 
    @Override 
    public void run() 
    { 
     System.out.println(oldPos); // Sometimes this is > 2000 
     ml.getVerticalScrollBar().setValue(0); // scroll to the top 
    } 
});

我想如果oldPos = ...代码先前执行的invokeLater的块之前执行这种情况被调用。我怎样才能解决这个问题？

更新：

我创建了一个SSCCE的建议通过@mKorbel：

更新2：我更新了SSCCE允许的JTextArea/JLabel的之间的切换，启用/禁用的重新绑定监听器，并在jTextArea和从jTextArea继承的自定义类之间切换，覆盖scrollRectToVisible方法。

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.Component; 
import java.awt.Dimension; 
import java.awt.Rectangle; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.awt.event.MouseEvent; 
import java.awt.event.MouseMotionAdapter; 

import javax.swing.Box; 
import javax.swing.BoxLayout; 
import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.JSplitPane; 
import javax.swing.JTextArea; 
import javax.swing.ScrollPaneConstants; 
import javax.swing.SwingUtilities; 

public class Main { 
    static class MyTextArea extends JTextArea { 
    @Override 
    public void scrollRectToVisible(final Rectangle aRect) { 
     // supress scrollToRect in textarea 
    } 
    } 

    static final Box inner = Box.createVerticalBox(); 

    // if the jtextarea should contain text 
    private static boolean textEnabled = true; 
    private static boolean usejLabel = false; 
    private static boolean useRebinding = false; 
    private static boolean useLock = true; 
    private static boolean customTextarea = false; 

    private static boolean _locked = false; 

    public static void main(final String[] args) { 
    final JFrame frame = new JFrame(); 

    final JPanel insideScroll = insideScroll(); 
    final JScrollPane scrollpane = new JScrollPane(insideScroll); 
    scrollpane.setAutoscrolls(false); 
    scrollpane 
     .setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER); 
    final JPanel rightPanel = new JPanel(); 
    rightPanel.setPreferredSize(new Dimension(300, 300)); 

    final MouseMotionAdapter listener = new MouseMotionAdapter() { 

     @Override 
     public void mouseDragged(final MouseEvent e) { 
     super.mouseDragged(e); 
     final boolean rebind = useRebinding; 

     final MouseMotionAdapter self = this; 
     if (rebind) { 
      rightPanel.removeMouseMotionListener(self); 
     } 
     final int pos = scrollpane.getVerticalScrollBar().getValue(); 
     if (!useLock || !_locked) { 
      if (useLock) { 
      _locked = true; 
      } 
      update(); 
      SwingUtilities.invokeLater(new Runnable() { 

      @Override 
      public void run() { 
       if (rebind) { 
       rightPanel.addMouseMotionListener(self); 
       } 
       if (useLock) { 
       _locked = false; 
       } 
      } 
      }); 
     } 

     } 
    }; 
    rightPanel.addMouseMotionListener(listener); 

    // Add labels describing the problem 
    rightPanel.setLayout(new BoxLayout(rightPanel, BoxLayout.PAGE_AXIS)); 
    final JButton toggleButton = new JButton("Toggle text"); 
    final JButton toggleButtonLabel = new JButton("Toggle JLable/JTextArea"); 
    final JButton toggleButtonRebind = new JButton("Turn rebinding on"); 
    final JButton toggleButtonCustomTextArea = new JButton(
     "Toggle Custom Textarea"); 
    rightPanel.add(toggleButton); 
    rightPanel.add(toggleButtonLabel); 
    rightPanel.add(toggleButtonRebind); 
    rightPanel.add(toggleButtonCustomTextArea); 
    rightPanel 
     .add(new JLabel(
      "<html>If the text is disabled, you can press/drag<br> your mouse on on right side of the<br> window and the scrollbar will<br> stay in its position.")); 

    rightPanel 
     .add(new JLabel(
      "<html><br/>If the text is enabled, the scrollbar<br> will jump around when dragging<br> on the right side.")); 

    rightPanel 
     .add(new JLabel(
      "<html><br/>The problem does not occur when using JLabels instead of JTextArea")); 

    // enable/disable the text when the button is clicked. 
    toggleButton.addActionListener(new ActionListener() { 
     @Override 
     public void actionPerformed(final ActionEvent e) { 
     textEnabled = !textEnabled; 
     update(); 
     } 
    }); 

    toggleButtonLabel.addActionListener(new ActionListener() { 
     @Override 
     public void actionPerformed(final ActionEvent e) { 
     usejLabel = !usejLabel; 
     update(); 
     } 
    }); 
    toggleButtonRebind.addActionListener(new ActionListener() { 
     @Override 
     public void actionPerformed(final ActionEvent e) { 
     useRebinding = !useRebinding; 
     toggleButtonRebind.setText(useRebinding ? "Turn rebinding off" 
      : "Turn rebinding on"); 
     update(); 
     } 
    }); 
    toggleButtonCustomTextArea.addActionListener(new ActionListener() { 
     @Override 
     public void actionPerformed(final ActionEvent e) { 
     customTextarea = !customTextarea; 
     update(); 
     } 
    }); 

    final JSplitPane split = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, 
     scrollpane, rightPanel); 

    frame.add(split); 

    // initialize the scrollpane content 
    update(); 

    frame.pack(); 
    frame.setVisible(true); 

    frame.setLocationRelativeTo(null); 

    } 

    // initializes the components inside the scrollpane 
    private static JPanel insideScroll() { 
    final JPanel panel = new JPanel(); 
    panel.setLayout(new BorderLayout()); 
    panel.add(inner, BorderLayout.NORTH); 

    return panel; 
    } 

    // replaces all components inside the scrollpane 
    private static void update() { 
    inner.removeAll(); 

    for (int i = 0; i < 30; i++) { 
     inner.add(buildRow(i)); 
    } 

    inner.revalidate(); 
    } 

    // build a single component to be inserted into the scrollpane 
    private static JPanel buildRow(final int i) { 
    final JPanel row = new JPanel(); 

    final Color bg = i % 2 == 0 ? Color.DARK_GRAY : Color.LIGHT_GRAY; 

    row.setBackground(bg); 
    row.setPreferredSize(new Dimension(300, 80)); 
    row.setLayout(new BorderLayout()); 

    row.add(textarea(bg), BorderLayout.CENTER); 

    return row; 
    } 

    // build the textarea to be inserted into the cells in the scroll pane 
    private static Component textarea(final Color bg) { 
    final String text = String.format("%d", (int) (1000 * Math.random())) 
     + " Lorem ipsum dolor si amet. Lorem ipsum dolor si amet. Lorem ipsum dolor si amet"; 
    if (usejLabel) { 
     final JLabel textarea = new JLabel(); 

     textarea.setBackground(bg); 
     if (textEnabled) { 
     textarea.setText(text); 
     } 

     return textarea; 
    } else { 
     final JTextArea textarea; 
     if (customTextarea) { 
     textarea = new MyTextArea(); 
     textarea.setDisabledTextColor(Color.cyan); 

     } else { 
     textarea = new JTextArea(); 
     textarea.setDisabledTextColor(Color.black); 

     } 

     textarea.setEnabled(false); 
     textarea.setLineWrap(true); 
     textarea.setBackground(bg); 
     textarea.setEditable(false); 
     if (textEnabled) { 
     textarea.setText(text); 
     } 

     return textarea; 
    } 

    } 
}

通过这样做，我意识到，只有当jscroll包含有自己的文字设置为一个字符串的JTextArea元素出现问题。在我真正的应用程序中，我需要自动换行的textareas，但即使禁用换行也会出现问题。

来源

2015-07-12 Laszlo Korte

我该如何解决这个问题？ ==为了更好地帮助发布SSCCE/MVCE，短，可运行，可编译 – mKorbel

考虑使用['scrollRectToVisible']（http://docs.oracle.com/javase/7/docs/api/javax/swing/JComponent。 HTML＃scrollRectToVisible（java.awt中。矩形））你想要滚动的组件 – MadProgrammer

@MadProgrammer如何获得矩形？ –

我找到了解决方案。整个问题不是JScrollPane本身，但如果文本不适合，JTextArea会自动调用scrollRectToVisible。这个调用通过视图层次传播到JScrollPane，导致它滚动到textarea。

在我的情况下，我有30 + JTextareas不断变化的文本，这发生相当的offen。

我的解决方案是创建一个继承自JTextArea的自定义类，并用空实现重写scrollRectToVisible方法。

这里是工作示例：

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.Component; 
import java.awt.Dimension; 
import java.awt.Rectangle; 
import java.awt.event.MouseEvent; 
import java.awt.event.MouseMotionAdapter; 

import javax.swing.Box; 
import javax.swing.BoxLayout; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.JSplitPane; 
import javax.swing.JTextArea; 
import javax.swing.ScrollPaneConstants; 

public class Main { 
    // custom Textarea class 
    static class MyTextArea extends JTextArea { 
    @Override 
    public void scrollRectToVisible(final Rectangle aRect) { 
     // supress scrollToRect in textarea 
    } 
    } 

    static final Box inner = Box.createVerticalBox(); 

    public static void main(final String[] args) { 
    final JFrame frame = new JFrame(); 

    final JPanel insideScroll = insideScroll(); 
    final JScrollPane scrollpane = new JScrollPane(insideScroll); 
    scrollpane.setAutoscrolls(false); 
    scrollpane 
    .setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER); 
    final JPanel rightPanel = new JPanel(); 
    rightPanel.setPreferredSize(new Dimension(300, 300)); 

    final MouseMotionAdapter listener = new MouseMotionAdapter() { 

     @Override 
     public void mouseDragged(final MouseEvent e) { 
     super.mouseDragged(e); 

     update(); 
     } 
    }; 
    rightPanel.addMouseMotionListener(listener); 

    // Add labels describing the problem 
    rightPanel.setLayout(new BoxLayout(rightPanel, BoxLayout.PAGE_AXIS)); 

    final JSplitPane split = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, 
     scrollpane, rightPanel); 

    frame.add(split); 

    // initialize the scrollpane content 
    update(); 

    frame.pack(); 
    frame.setVisible(true); 

    frame.setLocationRelativeTo(null); 

    } 

    // initializes the components inside the scrollpane 
    private static JPanel insideScroll() { 
    final JPanel panel = new JPanel(); 
    panel.setLayout(new BorderLayout()); 
    panel.add(inner, BorderLayout.NORTH); 

    return panel; 
    } 

    // replaces all components inside the scrollpane 
    private static void update() { 
    inner.removeAll(); 

    for (int i = 0; i < 30; i++) { 
     inner.add(buildRow(i)); 
    } 

    inner.revalidate(); 
    } 

    // build a single component to be inserted into the scrollpane 
    private static JPanel buildRow(final int i) { 
    final JPanel row = new JPanel(); 

    final Color bg = i % 2 == 0 ? Color.DARK_GRAY : Color.LIGHT_GRAY; 

    row.setBackground(bg); 
    row.setPreferredSize(new Dimension(300, 80)); 
    row.setLayout(new BorderLayout()); 

    row.add(textarea(bg), BorderLayout.CENTER); 

    return row; 
    } 

    // build the textarea to be inserted into the cells in the scroll pane 
    private static Component textarea(final Color bg) { 
    final String text = String.format("%d", (int) (1000 * Math.random())) 
     + " Lorem ipsum dolor si amet. Lorem ipsum dolor si amet. Lorem ipsum dolor si amet"; 

    final JTextArea textarea = new MyTextArea(); 
    textarea.setDisabledTextColor(Color.cyan); 

    textarea.setEnabled(false); 
    textarea.setLineWrap(true); 
    textarea.setBackground(bg); 
    textarea.setEditable(false); 
    textarea.setText(text); 

    return textarea; 
    } 

}

更新：我只是碰到这种其他的线程来与禁用JTextArea中的自动滚动一个更好的解决方案 - 没有子：

Java/Swing : JTextArea in a JScrollPane, how to prevent auto-scroll?

来源

2015-07-13 09:20:42

JScrollPane的：后重新验证

回答

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