Question

我是Java图形的新手，我试图创建一个简单的十字路口GUI界面，上面有4个红绿灯，当我使用我创建的以下类时 - 我得到一个窗口它上面有一个大的灰色矩形（我假设因为我没有在中心分配一个红绿灯，它已经填充了默认的灰色背景），我如何控制JFrame中心的大小？

这就是我想要实现的目标：

这就是我得到的：

这是JFrame类。

import java.awt.*;
import javax.swing.*;

public class CrossroadInterface extends JFrame /*implements IAppInterface*/ {
private static final int WIDTH_OF_WINDOW = 400;
private static final int HEIGHT_OF_WINDOW = 400;

//Panels
TrafficLight tLightW, tLightC, tLightE, tLightS, tLightN;

//Other
public CrossroadInterface() {
    super("My Crossroad");
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setSize(WIDTH_OF_WINDOW, HEIGHT_OF_WINDOW);
    this.setVisible(true);
    createInterface();
}

public void createInterface () {    
    tLightW = new TrafficLight();
    tLightE = new TrafficLight();
    tLightS = new TrafficLight();
    tLightN = new TrafficLight();
    this.add(tLightW, BorderLayout.WEST);
    this.add(tLightN, BorderLayout.NORTH);
    this.add(tLightE, BorderLayout.EAST);
    this.add(tLightS, BorderLayout.SOUTH);
 }
}

这是Jpanel类。

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.GridLayout;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class TrafficLight extends JPanel {
    private final Color offRed = new Color(128, 0, 0);
    private final Color offGreen = new Color(0, 96, 0);
    private static final int CAR_DIAMETER = 50;
    private static final int PERSON_HEIGHT = 100;
    private static final int PERSON_WIDTH = 50;
    private int status;
    public TrafficLight() {
        super();
        this.setSize(CAR_DIAMETER, 120);
        this.setBackground(Color.BLACK);
        status = 0;
        this.setVisible(true);
    }
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(offRed);
        g.fillOval(this.getX(), this.getY(), CAR_DIAMETER, CAR_DIAMETER);
        g.setColor(offGreen);
        g.fillOval(this.getX(), this.getY()+CAR_DIAMETER, CAR_DIAMETER, CAR_DIAMETER);
        g.setColor(offRed);
        g.fillRect(this.getX(), this.getY()+CAR_DIAMETER+PERSON_HEIGHT, PERSON_WIDTH, PERSON_HEIGHT);
        g.setColor(offGreen);
        g.fillRect(this.getX(), this.getY()+CAR_DIAMETER+2*PERSON_HEIGHT, PERSON_WIDTH, PERSON_HEIGHT);
        //drawIlluminatedLights(g);
        System.out.println(this.getX()+" "+this.getY());
    }
}

编辑：继Hovercraft充满鳗鱼＆＃39;建议，这是我的新课程：

import java.awt.*;
import javax.swing.*;

public class CrossroadInterface extends JFrame /*implements IAppInterface*/ {
private static final int WIDTH_OF_WINDOW = 900;
private static final int HEIGHT_OF_WINDOW = 900;

//Panels
TrafficLight tLightW, tLightC, tLightE, tLightS, tLightN;

//Other
public CrossroadInterface() {
    super("My Crossroad");
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setSize(WIDTH_OF_WINDOW, HEIGHT_OF_WINDOW);
    setLayout(new GridLayout(3,3));
    createInterface();
}

public void createInterface () {    
    tLightW = new TrafficLight();
    tLightE = new TrafficLight();
    tLightS = new TrafficLight();
    tLightN = new TrafficLight();
    this.add(new JPanel());
    this.add(tLightW);
    this.add(new JPanel());
    this.add(tLightN);
    this.add(new JPanel());
    this.add(tLightE);
    this.add(new JPanel());
    this.add(tLightS);
    this.setVisible(true);
 }
}

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

import javax.swing.JPanel;

public class TrafficLight extends JPanel {
    private final Color offRed = new Color(128, 0, 0);
    private final Color offGreen = new Color(0, 96, 0);
    private static final int CAR_DIAMETER = 50;
    private static final int PERSON_HEIGHT = 50;
    private static final int PERSON_WIDTH = 50;
    private int status;
    public TrafficLight() {
        super();
        status = 0;
        this.setPreferredSize(new Dimension(CAR_DIAMETER,2*CAR_DIAMETER+2*PERSON_HEIGHT));
        this.setVisible(true);
    }
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(offRed);
        g.fillOval(100, 50, CAR_DIAMETER, CAR_DIAMETER);
        g.setColor(offGreen);
        g.fillOval(100, 50+CAR_DIAMETER, CAR_DIAMETER, CAR_DIAMETER);
        g.setColor(offRed);
        g.fillRect(100, 50+CAR_DIAMETER+PERSON_HEIGHT, PERSON_WIDTH, PERSON_HEIGHT);
        g.setColor(offGreen);
        g.fillRect(100, 50+CAR_DIAMETER+2*PERSON_HEIGHT, PERSON_WIDTH, PERSON_HEIGHT);
        //drawIlluminatedLights(g);
    }
}

Answer 1

你的问题不是JFrame的中心太大，而是因为你周围的JPanel的大小太小了。了解大多数Swing布局管理器都尊重组件首选大小，并使用它来设置组件的大小。您的其他问题包括

使用getX()和getY()放置图纸。这些值给出了JPanel在其容器中的位置，但这不会帮助您放置绘图，因为当您在JPanel中绘制时，绘图的位置相对于JPanel内的像素位置而不是其容器放置，因此使用这些方法会搞砸你。
在添加所有组件之前调用JFrame的setVisible(true) 。这可能无法显示所有组件。

使您的TrafficLight类扩展JPanel。使用单个JPanel完成所有绘图并使TrafficLight类不从任何Swing组件扩展而是扩展为逻辑类，你会好得多。给它一个public void draw(Graphics2D g2)方法，你可以在绘图JPanel的paintComponent方法中调用它。

例如：

import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.RenderingHints; import java.awt.Shape; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.geom.Ellipse2D; import java.util.ArrayList; import java.util.EnumMap; import java.util.List; import java.util.Map; import java.util.Random; import javax.swing.*; @SuppressWarnings("serial") public class CrossRoads2 extends JPanel { private static final int PREF_W = 400; private static final int PREF_H = PREF_W; private static final int TIMER_DELAY = 100; List<TrafficLight2> lights = new ArrayList<>(); public CrossRoads2() { // create a timer to randomly change traffic light state // and start it new Timer(TIMER_DELAY, new TimerListener()).start(); // create 4 TrafficLight2 objects and place them at 4 // compass locations, and add to lights ArrayList int x = (PREF_W - TrafficLight2.getWidth()) / 2; int y = 0; lights.add(new TrafficLight2(x, y)); x = 0; y = (PREF_H - TrafficLight2.getHeight()) / 2; lights.add(new TrafficLight2(x, y)); x = (PREF_W - TrafficLight2.getWidth()); lights.add(new TrafficLight2(x, y)); x = (PREF_W - TrafficLight2.getWidth()) / 2; y = (PREF_H - TrafficLight2.getHeight()); lights.add(new TrafficLight2(x, y)); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); // cast g into a Graphics2 object Graphics2D g2 = (Graphics2D) g; // for smooth rendering g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); // iterate through the ArrayList, calling the draw method on each light for (TrafficLight2 light : lights) { light.draw(g2); } } @Override public Dimension getPreferredSize() { if (isPreferredSizeSet()) { return super.getPreferredSize(); } // give our JPanel a decent size return new Dimension(PREF_W, PREF_H); } // ActionListener that randomly changes the LightState of each traffic light private class TimerListener implements ActionListener { private Random random = new Random(); @Override public void actionPerformed(ActionEvent e) { for (TrafficLight2 light : lights) { // random number 0 to 2 int randomIndex = random.nextInt(LightState.values().length); // get one of the LightStates using the index above LightState lightState = LightState.values()[randomIndex]; // set our light to this state light.setLightState(lightState); } repaint(); } } private static void createAndShowGui() { CrossRoads2 mainPanel = new CrossRoads2(); JFrame frame = new JFrame("Cross Roads"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.getContentPane().add(mainPanel); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokeLater(() -> createAndShowGui()); } }

class TrafficLight2 { private static final int ELLIPSE_W = 40; private static final int GAP = 4; private int x; private int y; private LightState lightState = LightState.RED; // what color is bright // map to hold our 3 ellipses, each one corresponding to a LightState private Map<LightState, Shape> lightMap = new EnumMap<>(LightState.class); public TrafficLight2(int x, int y) { // create 3 ellipses, one each for RED, YELLOW, GREEN // place each one below the previous // associate each one with one of our RED, YELLOW, or GREEN LightStates // putting the Ellipse into the map with the light state as key this.x = x; this.y = y; int tempX = x + GAP; int tempY = y + GAP; lightMap.put(LightState.RED, new Ellipse2D.Double(tempX, tempY, ELLIPSE_W, ELLIPSE_W)); tempY += ELLIPSE_W + GAP; lightMap.put(LightState.YELLOW, new Ellipse2D.Double(tempX, tempY, ELLIPSE_W, ELLIPSE_W)); tempY += ELLIPSE_W + GAP; lightMap.put(LightState.GREEN, new Ellipse2D.Double(tempX, tempY, ELLIPSE_W, ELLIPSE_W)); } // called by JPanel's paintComponent public void draw(Graphics2D g2) { // iterate through the 3 LightStates for (LightState ltSt : LightState.values()) { // if the ltSt in the for loop is this traffic light's LightState // then the display color should be bright Color c = ltSt == lightState ? ltSt.getColor() : // other wise the display color should be very dark ltSt.getColor().darker().darker().darker(); g2.setColor(c); g2.fill(lightMap.get(ltSt)); // fill the oval with color g2.setColor(Color.BLACK); g2.draw(lightMap.get(ltSt)); // draw a black border } } public int getX() { return x; } public int getY() { return y; } public LightState getLightState() { return lightState; } public void setLightState(LightState lightState) { this.lightState = lightState; } // static method for the width of our traffic lights public static int getWidth() { return 2 * GAP + ELLIPSE_W; } // static method for the height of our traffic lights public static int getHeight() { return 4 * GAP + 3 * ELLIPSE_W; } }

// enum that encapsulates the 3 possible states of the traffic light enum LightState { RED("Red", Color.RED), YELLOW("Yellow", Color.YELLOW), GREEN("Green", Color.GREEN); private LightState(String text, Color color) { this.text = text; this.color = color; } private String text; private Color color; public String getText() { return text; } public Color getColor() { return color; } }

在Java上扩展JFrame的类上绘画

1 个答案: