如何向 JFrame 上的 JComponent 添加滚动功能？

Question

我的 GUI 包含一个扩展 JFrame 的图表 class。我创建了一个名为 DrawingTool 的不同 class，它扩展了 JComponent。 DrawingTool class 就像一个 canvas 区域供用户放置和拖动形状。我还在 JFrame 的底部添加了一个按钮面板，供用户单击各种按钮来选择他们想要的形状和控制操作。我已将按钮面板和 DrawingTool class 的实例添加到图表 class。如何使 canvas 区域 (DrawingTool) 可滚动？我尝试的方式不起作用，我知道我错过了一些东西。

这是图表class:

public class Diagram extends JFrame {
JButton serverButton, vipButton, arrowButton, undoButton, dragButton, loadButton, submitButton;
JButton applicationButton;
int currentAction = 1;
Graphics2D graphSettings;
Color strokeColor = Color.BLUE, fillColor = Color.BLACK;

/**
 * Constructor to generate new diagram with empty drawing board and button
 * panel.
 */
public Diagram() {
    // Define the defaults for the JFrame

    this.setSize(1000, 1000);
    this.setTitle("Diagram Tool");
    //this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JPanel buttonPanel = new JPanel();

    // Swing box that will hold all the buttons

    Box theBox = Box.createHorizontalBox();

    // Make all the buttons in makeButtons by calling helper function

    serverButton = makeButtons("Server", 2);
    vipButton = makeButtons("VIPs", 3);
    arrowButton = makeButtons("Arrow", 4);
    undoButton = makeButtons("Undo", 5);
    dragButton = makeButtons("Drag", 6);
    loadButton = makeButtons("Load", 11);
    applicationButton = makeButtons("Application", 8);
    submitButton = makeButtons("Submit", 12);

    // Add the buttons to the box

    theBox.add(serverButton);
    theBox.add(vipButton);
    theBox.add(applicationButton);
    theBox.add(arrowButton);
    theBox.add(undoButton);
    theBox.add(dragButton);
    theBox.add(loadButton);
    theBox.add(submitButton);

    // Add the box of buttons to the panel



    buttonPanel.add(theBox);

    // Position the buttons in the bottom of the frame

    JPanel container=new JPanel();
    container.add(new DrawingBoard(),BorderLayout.CENTER);
    JScrollPane jsp=new JScrollPane(container);
    this.add(buttonPanel, BorderLayout.SOUTH);
    this.add(jsp);

    // Make the drawing area take up the rest of the frame

    // Show the frame

    this.setVisible(true);
}

这是绘图板class:

private class DrawingBoard extends JComponent implements MouseListener, MouseMotionListener {
    //declare variables

    /**
     * Constructor to initialize the drawing board
     */
    public DrawingBoard() {
        addMouseListener(this);
        addMouseMotionListener(this);

    //  initializeCanvas();
    }
   //Rest of the code for DrawingBoard 
  }

这是现在的样子。我想让灰色 canvas 区域可滚动。

图表图像

Answer 1

MadProgrammer 在评论中说的很对。您需要设置一些信息，以便您的 ScrollPanel 知道如何表现。它本身的尺寸是多少，里面的元件尺寸等等

所以通常您会有一个 ContentPane，并且在其内部显示您的内容。要创建可滚动窗格，您只需将 ScrollPane 放在 ContentPane 中，然后为您的 ScrollPane 设置一个视口。我使用的一点代码功能齐全：

contentPane = new JPanel();
setContentPane(contentPane);
contentPane.setLayout(null);

JScrollPane scrollPane = new JScrollPane();

//Vertical and Horizontal scroll bar policy is set to choose when the scroll will be visible    scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED);
    scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
scrollPane.setBounds(0, 217, 414, 505);
scrollPane.setPreferredSize(new Dimension(414, 414));

JPanel viewport = new JPanel();
viewport.setLayout(null);
viewport.setBounds(0, 0, 414, 505);

//Create your components here, then:
//viewport.add(component)

viewport.setPreferredSize(new Dimension(414, 150));
scrollPane.setViewportView(viewport);
contentPane.add(scrollPane);

你放在 ViewPort 里面的任何东西将自动滚动，如果它的大小大于 PreferredSize。

请注意，我提供的所有尺寸仅供参考。

如何向 JFrame 上的 JComponent 添加滚动功能？

How to add scrolling feature to a JComponent on a JFrame?

java

user-interface

swing

jcomponent

jframe