java - 如何在 JPanel 更新时使 JScrollPane 滚动

Question

我正在尝试实现一个 JPanel(添加到 JScrollPane 中)。这个想法是在 JPanel 上绘制一系列矩形。其中一个矩形具有不同的颜色。这个想法是，当应用程序运行时，我应该能够添加更多这些矩形(如果需要)或在当前绘制的矩形之间移动。我有左/右移动按钮，可以让我在矩形之间移动。现在的问题是，当我可以在按钮之间移动时，但 JPanel 更新时 JScrollPane 不会移动。如下图所示，假设我位于值为 [a] 的矩形中，其颜色为橙色。现在我可以向左或向右移动，但 JScrollPane 保持不变。如何让 JScrollPane 随矩形移动？ The panel screenshot

我有一个执行所有绘图的文件 (TapeArea) 和一个将 3 个 TapeArea 实例捆绑在一起的文件 (TapePanel)。

import java.awt.Color;
import javax.swing.Timer;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowListener;
import java.awt.font.FontRenderContext;
import java.awt.geom.Rectangle2D;
import java.awt.geom.RoundRectangle2D;


import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.border.Border;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.TitledBorder;

public class TapeArea extends JPanel {

    private final Color BG_COLOR = new Color(200,200,200);
    private final Color DEFAULT_CELL_COLOR = Color.white;
    private final Color CURRENT_CELL_COLOR = Color.orange;
    private final Color CELL_INDEX_COLOR = new Color(0, 130, 0);
    private final int FONT_STYLE = Font.BOLD;
    private final String FONT_NAME = "Monotype";
    private final double INITIAL_OFFSET = -1.5;


    int cellWidth = 40;
    int cellHeight = 40;
    int fontSize = 20;
    boolean tapeInit = false;
    int leftMostCell = 0, rightMostCell = 0;
    double newLeftCellWidth = 0, newRightCellWidth = 0;
    boolean newLeftCell = false, newRightCell = false;
    Color currentTextColor = Color.black;
    double offset = INITIAL_OFFSET;
    int origin = 0;

    Dimension areaSize;
    int filler;
    Tape tape;
    FlowLayout layout;

    int x   = 10;   //Start Drawing from X=10   
    int delay   = 500;  //milliseconds

    public TapeArea(Tape t){
        tape = t;
        layout = new FlowLayout();
        setLayout(layout);
        setPreferredSize(new Dimension(1200,50));


//       ActionListener counter = new ActionListener() {
//              public void actionPerformed(ActionEvent evt) 
//              { 
//                  stepOneTapeCell();
//                    repaint();
//                    x++;
//              }};
//           new Timer(delay, counter).start();
    }




    public void paintComponent(Graphics g){
        int i,drawPos;
        int yAlign;
        int fontScalingFactor;
        int stringWidth, stringHeight;
        int index = 0, startAt, cellsToDraw, currentPosition;
        int tapeLength;
        String symbol;
        FontRenderContext DEFAULT_FONT_RENDER_CONTEXT =
                new FontRenderContext(null, false, false);
        Rectangle2D charBounds;

        Graphics2D g2d = (Graphics2D) g;
        super.paintComponent(g2d);

        if(tape == null)
            return;


        g2d.setColor(BG_COLOR);
        g2d.fillRect(0,0,getWidth(), getHeight());

        tapeLength = tape.getSize();

        if(areaSize != null)
            if(areaSize.width != getSize().width || areaSize.height != getSize().height)
                tapeInit = false;

        areaSize = getSize();
        yAlign = areaSize.height / 2;

        cellWidth = getHeight() - 2;
        if(cellWidth > 40) {
            cellWidth = 40;
        }
        cellHeight = cellWidth;
        fontSize = cellWidth / 2;



        if(newLeftCell) {
            startAt = 1;
            cellsToDraw = tapeLength - 1;
            currentPosition = 0;
        } else if(newRightCell) {
            startAt = 0;
            cellsToDraw = tapeLength - 1;
            currentPosition = tapeLength - 2;
        } else {
            startAt = 0;
            cellsToDraw = tapeLength;
            currentPosition = tape.getCurrentPosition();
        }
        currentPosition = tape.getCurrentPosition();

        //determine the number of cells to left and right on the tape
        if(!tapeInit){
            for(filler = 0; cellWidth * (1 + 2*filler) <= areaSize.width; filler++);
            filler += 2;

            leftMostCell = currentPosition - filler;
            rightMostCell = leftMostCell + 2*filler;

            while(-leftMostCell < rightMostCell - tapeLength - 1 && 0 < rightMostCell - tapeLength - 1) {
                leftMostCell--;
                rightMostCell--;
            }
            while(-leftMostCell > rightMostCell - tapeLength + 1 && leftMostCell < 0) {
                leftMostCell++;
                rightMostCell++;
            }

        }//end of if(!tapeInit)



        if(origin != tape.getOrigin()){
            leftMostCell++;
            rightMostCell++;
        }
        origin = tape.getOrigin();
        tapeInit = true;

        //draw tape cells
        for(drawPos = 0, i = leftMostCell; i <= rightMostCell; i++, drawPos++){

            //what symbol to be drawn on the cell
            if(i >= 0 && i < tapeLength)
                symbol = (String) tape.getSymbolAt(i);
            else
                symbol = tape.getFillSymbol();

            //indicate current tape cell by coloring it
            if(i == currentPosition)
                g2d.setColor(CURRENT_CELL_COLOR);
            else 
                g2d.setColor(DEFAULT_CELL_COLOR);

            g2d.fillRect((int)((newLeftCellWidth + drawPos + offset) * cellWidth), yAlign - cellHeight/2, 
                       cellWidth, cellHeight);

            g2d.setColor(Color.black);
            g2d.drawRoundRect((int)((newLeftCellWidth + drawPos + offset) * cellWidth), yAlign - cellHeight/2, 
                       cellWidth, cellHeight, 10, 10);

            //draw symbols on cells
            charBounds = g.getFont().getStringBounds(symbol, 
                     DEFAULT_FONT_RENDER_CONTEXT);

            stringWidth  = (int)Math.ceil(charBounds.getWidth());
            stringHeight = (int)Math.ceil(charBounds.getHeight());

            //if symbol is multi-character, font may be adjusted so it will fit
            fontScalingFactor = (int)Math.ceil((double)stringWidth/(double)cellWidth);
            g.setFont(new Font(FONT_NAME, FONT_STYLE, fontSize/fontScalingFactor));

            charBounds = g.getFont().getStringBounds(symbol, 
                                 DEFAULT_FONT_RENDER_CONTEXT);

            stringWidth  = (int)Math.ceil(charBounds.getWidth());
            stringHeight = (int)Math.ceil(charBounds.getHeight());

            if(i == tape.getCurrentPosition()) {
                g.setColor(currentTextColor);
            }

            g.drawString(symbol, 
                 (int)((newLeftCellWidth + drawPos + 0.5 + offset) * cellWidth - (stringWidth/2)), 
                     (int)(yAlign + (stringHeight/4)));

            g.setFont(new Font(FONT_NAME, Font.PLAIN, fontSize/(2 * fontScalingFactor)));
            g.setColor(CELL_INDEX_COLOR);

            g.drawString(Integer.toString(i - origin), 
                     (int)((newLeftCellWidth + drawPos + 0.3 + offset) * cellWidth - (stringWidth/2)), 
                     (int)(yAlign + 0.45 * cellHeight));
            index++;

        }//end of for() drawing tape cells



    }

    void setTapeData(String m, Tape p){
        p.removeAllTapeData();
        p.addDataToTape(m);
    }


    void stepOneTapeCell(String direction){
        switch(direction){
        case "L":
            if(tape.getCurrentPosition() > tape.getOrigin()){
                tape.setCurrentPosition(tape.getCurrentPosition() - 1);
                revalidate();
                repaint();
            }
            //tape.shiftLeft();
            break;
        case "R":
            if(tape.getCurrentPosition() < tape.getSize()-1){
                tape.setCurrentPosition(tape.getCurrentPosition() + 1);
                revalidate();
                repaint();
            }
//          tape.setCurrentPosition(tape.getCurrentPosition() + 1);
//          repaint();
//          tape.shiftRight();
//          repaint();
            break;
        }   
    }


}//end of class TapePanel

TapePanel 文件:

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.border.Border;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.TitledBorder;

public class TapePanel extends JPanel implements MyJPanel{

    private final int ROWS = 3;
    private final int COLS = 1;
    private final int TAPE_ORIGINAL_POSITION = 0;
    private int NUM_TAPES = 3;
    GridLayout layout;
    Tape [] tapes;
    TapeArea [] tapeArea;
    JScrollPane sp1, sp2, sp3;

    Border blackLine, border,margin;
    TitledBorder title;

    public TapePanel(Tape t1, Tape t2, Tape t3){

        tapes = new Tape[NUM_TAPES];
        tapes[0] = t1;
        tapes[1] = t2;
        tapes[2] = t3;
        initiateComps();
        addCompsToLayout();
    }


    public void initiateComps() {
        // TODO Auto-generated method stub
        layout = new GridLayout(ROWS,COLS);
        setLayout(layout);

        blackLine = BorderFactory.createLineBorder(Color.BLACK);
        title = BorderFactory.createTitledBorder(blackLine,"Tapes");
        title.setTitleJustification(TitledBorder.LEFT);
        border = title.getBorder();
        margin = new EmptyBorder(15,15,15,15);
        title.setBorder(new CompoundBorder(margin,border));
        setBorder(title);

        tapeArea = new TapeArea[NUM_TAPES];
        tapeArea[0] = new TapeArea(tapes[0]);
        tapeArea[1] = new TapeArea(tapes[1]);
        tapeArea[2] = new TapeArea(tapes[2]);

        sp1 = new JScrollPane(tapeArea[0],JScrollPane.VERTICAL_SCROLLBAR_NEVER,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        sp1.setPreferredSize(new Dimension(200,70));
        sp2 = new JScrollPane(tapeArea[1],JScrollPane.VERTICAL_SCROLLBAR_NEVER,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        sp2.setPreferredSize(new Dimension(200,70));
        sp3 = new JScrollPane(tapeArea[2],JScrollPane.VERTICAL_SCROLLBAR_NEVER,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        sp3.setPreferredSize(new Dimension(200,70));

        //setBorder(new EmptyBorder(20,15,15,15));
    }

    @Override
    protected void paintComponent(Graphics g) {
        // TODO Auto-generated method stub
        super.paintComponent(g);

    }
    void repaintTapeArea(){
        for(int i = 0; i < NUM_TAPES;i++){
            tapeArea[i].revalidate();
            tapeArea[i].repaint();
        }

    }

    void resetAllTapes(){

        for(int i = 0; i < NUM_TAPES; i++){
            tapeArea[i].setTapeData("", tapes[i]);
            tapeArea[i].tape.setCurrentPosition(TAPE_ORIGINAL_POSITION);
        }

    }
    void setTapeData(String m, Tape p, int tapeNumber){
        tapeArea[tapeNumber].setTapeData(m, p);
    }

    void stepOneCell(int tapeNumber, String direction){
        tapeArea[tapeNumber].stepOneTapeCell(direction);
    }

    @Override
    public void addCompsToLayout() {
        // TODO Auto-generated method stub
        add(sp1);
        add(sp2);
        add(sp3);
    }


    @Override
    public void addComponent(Component comp, int zone, int row, int col, int width, int height) {
        // TODO Auto-generated method stub

    }

    public static void main(String [] args){

            JFrame f = new JFrame();
            f.add(new TapePanel(new Tape("a b c d"),new Tape("a b c d"),new Tape("a b")));
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setVisible(true);

            f.pack();

    }
}

磁带只是一个简单的链表。

Answer 1

I only get 14 rectangles on the screen that I can move over with. If i add more than that, then they will not be visible.

仅当添加到滚动 Pane 的组件的首选大小大于滚动 Pane 的大小时，才会发生滚动。

您需要重写自定义绘画面板的 getPreferredSize() 方法，以反射(reflect)每个矩形覆盖的区域。

因此，当您向右或向下移动矩形时，您可能需要调整首选尺寸。