Question

我在显示JScrollPane中的特定组件时遇到问题。我有水平的JScrollPane与GridLayout（1,0），它包含可变数量的JPanels - 每个包含图像。这就像GIF图像中的帧预览一样。我使用按钮在这些JPanel之间移动（通过更改边框并保持所选择的索引），但我不知道如何强制JScrollPane向我显示JPanel（如果可能的话，将其置于中心位置）

所以我想要这个 enter image description here

强制执行此操作： enter image description here

提前致谢！

编辑：使用scrollRectToVisible()方法

的几乎正常工作的代码

public class MiniatursPanel extends JPanel{


private int indexOfChosenFrame = 0;
private ArrayList<JPanel> frames;
private JScrollPane scrollPane;
private JPanel innerPanel;



public MiniatursPanel(){
    setBorder(BorderFactory.createCompoundBorder(BorderFactory.createRaisedBevelBorder(),BorderFactory.createLoweredBevelBorder()));
    setPreferredSize(new Dimension(1200,170));
    setLayout(null);     
}

public void initialize(){
    int width = GifImageStats.getInstance().getWidth();
    int height = GifImageStats.getInstance().getHeight();
    int numberOfFrames = GifImageStats.getInstance().getNumberOfFrames();

    frames = new ArrayList(numberOfFrames);

    for (int i = 0; i < numberOfFrames; i++) {
        JPanel frameBox = new JPanel();
        frameBox.setLayout(new FlowLayout(FlowLayout.CENTER));
        JButton button = new JButton(String.valueOf(i+1));
        button.setPreferredSize(new Dimension(2*width,2*height));
        button.setBackground(Color.white);
        button.setFocusable(false);
        frameBox.add(button);
        frames.add(frameBox);
    }

    innerPanel = new JPanel();
    innerPanel.setLayout(new GridLayout(1,0,10,10));


    for (JPanel button : frames) {
        innerPanel.add(button);
    }

    scrollPane = new JScrollPane(innerPanel);
    scrollPane.setBounds(10, 10, 1180, 145);
    scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_NEVER);

    highlightFrame(frames.get(0));

    add(scrollPane);
}


public void nextFrame(){
    if (indexOfChosenFrame == frames.size() - 1) {           
        unhighlightFrame(frames.get(indexOfChosenFrame));
        indexOfChosenFrame = 0;
        highlightFrame(frames.get(0));
    }else{
        unhighlightFrame(frames.get(indexOfChosenFrame));
        indexOfChosenFrame++;
        highlightFrame(frames.get(indexOfChosenFrame));
    }
}

public void previousFrame(){
    if (indexOfChosenFrame == 0) {           
        unhighlightFrame(frames.get(0));
        indexOfChosenFrame = frames.size()-1;
        highlightFrame(frames.get(indexOfChosenFrame));
    }else{
        unhighlightFrame(frames.get(indexOfChosenFrame));
        indexOfChosenFrame--;
        highlightFrame(frames.get(indexOfChosenFrame));
    }
}

private void highlightFrame(JPanel frame){
    Rectangle rect = frame.getBounds();
    rect.setBounds(frame.getX()-550, frame.getY(), frame.getWidth()+1050, frame.getHeight());
    innerPanel.scrollRectToVisible(rect);     
    frame.setBorder(BorderFactory.createLineBorder(Color.red,2));
}          

private void unhighlightFrame(JPanel frame){
    frame.setBorder(null);
}

Answer 1

此处的相关方法是JComponent#scrollRectToVisible(Rectangle)。必须在滚动窗格的视口中的组件上调用它。（在您的情况下，这是具有网格布局的面板，其中包含其他子面板）。

传递给此方法的矩形可以是一个子面板的边界。在这种情况下，scoll窗格将执行“最小”滚动，这是使给定矩形可见所必需的。如果要确保相应的子面板位于中心，则可以增加此矩形的大小 - 即，以所需子面板位于中心的方式定义矩形。 / p>

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.Rectangle;
import java.util.ArrayList;
import java.util.List;

import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSpinner;
import javax.swing.SpinnerNumberModel;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;


public class ScrollToVisible
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                createAndShowGUI();
            }
        });
    }

    private static void createAndShowGUI()
    {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        int n = 20;
        final JPanel panel = new JPanel(new GridLayout(1,0));
        final List<JComponent> components = new ArrayList<JComponent>();
        for (int i=0; i<n; i++)
        {
            JComponent component = new JLabel(String.valueOf(i), SwingConstants.CENTER);
            component.setPreferredSize(new Dimension(100,100));
            component.setBorder(BorderFactory.createLineBorder(Color.BLACK));
            components.add(component);
            panel.add(component);
        }
        final JScrollPane scrollPane = new JScrollPane(panel);

        final JSpinner spinner = new JSpinner(new SpinnerNumberModel(0, 0, n-1, 1));
        spinner.addChangeListener(new ChangeListener()
        {
            JComponent selectedComponent = components.get(0);

            @Override
            public void stateChanged(ChangeEvent e)
            {
                selectedComponent.setBorder(BorderFactory.createLineBorder(Color.BLACK));

                int index = (Integer)spinner.getValue();
                JComponent component = components.get(index);
                Rectangle bounds = component.getBounds();

                // This would make the component "just" visible:
                //panel.scrollRectToVisible(bounds);

                // This will center the component:
                int cx = bounds.x + bounds.width / 2;
                int w = scrollPane.getViewport().getWidth();
                Rectangle r = new Rectangle(cx-w/2, bounds.y, w, bounds.height);
                panel.scrollRectToVisible(r);


                selectedComponent = component;
                selectedComponent.setBorder(BorderFactory.createLineBorder(Color.RED));

            }
        });

        f.getContentPane().setLayout(new BorderLayout());
        f.getContentPane().add(scrollPane, BorderLayout.CENTER);
        f.getContentPane().add(spinner, BorderLayout.NORTH);


        f.setSize(800, 300);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

}

编辑：您应不使用setLayout(null)，并且不应对setBounds进行手动调用，你应该很少使用setPreferredSize。并且......当您发布已经非常接近https://stackoverflow.com/help/mcve的代码（或者甚至是从另一篇文章的可运行示例创建的代码）时，您应该使真正运行。重新插入样板代码并浪费一些时间进行调试很烦人，直到你意识到initialize()根本没有被调用...

但是，请根据此更改代码：

private void highlightFrame(JPanel frame){
    Rectangle rect = frame.getBounds();

    int c = rect.x + rect.width / 2; 
    int w = scrollPane.getViewport().getWidth();
    int x = c-w/2;
    rect.setBounds(x, rect.y, w, rect.height);

    innerPanel.scrollRectToVisible(rect);     
    frame.setBorder(BorderFactory.createLineBorder(Color.red,2));
}          

private void unhighlightFrame(JPanel frame){
    frame.setBorder(BorderFactory.createEmptyBorder(2, 2, 2, 2));
}

最重要的是通过设置与“突出显示”边框大小相同的空边框来确保组件的大小正确。

如何强制JScrollPane中的组件显示

1 个答案: