java - JFrame 滚动条和 Canvas

Question

我在尝试向具有 Canvas 的 JFrame 添加水平滚动条时遇到问题。我在 Canvas 上绘制图像，有时这些图像会超出屏幕，因此我需要一个滚动条以使用户能够看到它们。

这是代码中的关键部分，如果需要任何其他代码，请告诉我，我会编辑。

有人能指出我做错了什么吗？

非常感谢J

public class TheFrame extends JFrame {

private static ThePanel canvas;
private String deckImagesToUse;

/**
 * The constructor creates a Frame ready to display the cards
 */
public TheFrame(String cardImgFile) {


    // Calls the constructor in the JFrame superclass passing up the name to 
    // display in the title
    super("Window title");

    //Using users choice of cards
    deckImagesToUse = cardImgFile;

    // When you click on the close window button the window will be closed
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // This has North, East, South, West and center positions for components
    setLayout(new BorderLayout());

    // This is what we will draw on (see the inner class below)
    canvas = new ThePanel();
    setSize(700, 300);
    this.add(canvas, BorderLayout.CENTER);

    //Scroll Bar
    JScrollPane scrollPane = new JScrollPane(canvas);
    //scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
    this.getContentPane().add(scrollPane);
    int desiredWidth = (Pack.cardsInPlay.size() * 70);
    Dimension d = new Dimension(desiredWidth,300);
    canvas.setPreferredSize(d);

    setVisible(true); // Display the window


}

Answer 1

canvas = new ThePanel();
setSize(700, 300);
this.add(canvas, BorderLayout.CENTER);

设置大小并添加到 this 是徒劳的，因为稍后的滚动 Pane 会忽略它。

当您的图像大于 JScrollPane 时，只需调用 canvas.setPreferredSize(imageWidth, imageHeight);