java - 我想我的 jframe 在这个程序中是正确的，但不确定

Question

我认为这个程序中的 jframe 是正确的，但是为什么当我运行它时什么也没有出现？ 我有两个不同的类(class)，这是我的第一个。只需忽略最后一个方法，我将在其中绘制一个带有圆圈的矩形作为红绿灯。

这是我的代码。

package trafficlight;

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

public class TrafficLight {

private int goDuration;
private int stopDuration;
private int warnDuration;

public enum State {STOP, GO, WARN};
public Color GO_COLOR = Color.green;
public Color STOP_COLOR = Color.red;
public Color OFF_COLOR = Color.darkGray;
public Color WARNING_COLOR = Color.yellow;
private State currentState;


public TrafficLight() {
goDuration =  2;
stopDuration = 2;
warnDuration =1;
currentState =  State.GO;
}

public void changeLight(){
if(currentState  == State.GO){
        currentState = State.WARN;
}
if(currentState == State.WARN){
        currentState = State.STOP;
}
if(currentState == State.STOP){
        currentState = State.GO;
}
}


public int getGoDuration() {
    return goDuration;
}

public void setGoDuration(int goDuration) {
    this.goDuration = goDuration;
}

public int getStopDuration() {
    return stopDuration;
}

public void setStopDuration(int stopDuration) {
    this.stopDuration = stopDuration;
}

public int getWarnDuration() {
    return warnDuration;
}

public void setWarnDuration(int warnDuration) {
    this.warnDuration = warnDuration;
}

public State getCurrentState() {
    return currentState;
}

public void setCurrentState(State currentState) {
    this.currentState = currentState;
}
public int getCurrentDuration(){
    int duration = 0;
    if (currentState == State.STOP){
        duration = stopDuration;
    }
    if (currentState == State.GO){
        duration = goDuration;
    }
    if (currentState == State.WARN){
        duration = warnDuration;
    }
    return duration;
}
public void draw(Graphics canvas) {
    canvas.drawRect(125,185,100,250);
    canvas.drawOval(145,200,60,60);
    canvas.drawOval(145,280,60,60);
    canvas.drawOval(145,360,60,60);

    if (currentState == State.STOP){

    }


}

}

这是我的第二堂课。

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

public class TrafficLightDriver extends JFrame {

private static TrafficLight light;

public void message() {
}

public static void main(String[] args) {
    TrafficLightDriver myFrame = new TrafficLightDriver();
    int delay, answer;
    String valueString;

    do {
        valueString = JOptionPane.showInputDialog("What is the green light delay? (1.. 10)");
        light.setGoDuration(Integer.parseInt(valueString));
        valueString = JOptionPane.showInputDialog("What is the yellow light delay? (1.. 10)");
        light.setWarnDuration(Integer.parseInt(valueString));
        valueString = JOptionPane.showInputDialog("What is the red light delay? (1.. 10)");
        light.setStopDuration(Integer.parseInt(valueString));
        for (int i = 1; i <= 10; i++) {
            delay = light.getCurrentDuration();
            Wait.manySec(delay);
            light.changeLight();
            myFrame.repaint();
        }
        answer = JOptionPane.showConfirmDialog(null, "Would you like to run the light again?",
                null, JOptionPane.YES_NO_OPTION);
    } while (answer == JOptionPane.YES_OPTION);
    System.exit(0);
}

@Override
public void paint(Graphics canvas) {
    light.draw(canvas);
}

public TrafficLightDriver() {  //constructor
    setSize(350, 600);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    light = new TrafficLight();
    setVisible(true);
}
}

这是我的等待类(class)

package trafficlight;

public class Wait {

public static void oneSec() {
    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        System.err.println(e);
    }
}

public static void manySec(long s) {
    try {
        Thread.sleep(s * 1000);
    } catch (InterruptedException e) {
        System.err.println(e);
    }
}

public static void tenthOfSec(long s) {
    try {
        Thread.sleep(s * 100);
    } catch (InterruptedException e) {
        System.err.println(e);
    }
}
}

Answer 1

1. 您应该避免重写顶级容器的paint，相反，您应该使用JPanel之类的东西并重写它的paintComponent方法。
2. 绘制过程是一系列串联的方法，所有这些方法都相互构建以生成输出，一旦破坏此更改，就会出现伪影和不规则现象。确保始终调用 super.paintXxx
来尊重绘制链
3. Swing 是一个单线程框架。也就是说，有一个线程负责处理系统内的所有事件，包括重绘请求。这意味着，如果您出于任何原因阻止该线程，您将无法处理任何新事件，这将使您的程序看起来好像已挂起。您还需要确保对 UI 的任何更新都是在此线程的上下文中进行的。

从通读开始

• Concurrency in Swing
• Performing Custom Painting
• Painting in AWT and Swing

现在，我不知道您的 Wait 类是如何工作的，所以我无法评论该部分，但是您的 TrafficLight 不会更新自身以反射(reflect)它的情况目前状态...

已更新...

您还有两个非常令人困惑的 main 方法。应用程序逻辑似乎位于 TrafficLightDriver 中，您应该确保在执行程序时正在运行此类。

您的 changeLight 方法存在逻辑问题

public void changeLight(){
    if(currentState  == State.GO){
        currentState = State.WARN;
    }
    if(currentState == State.WARN){
        currentState = State.STOP;
    }
    if(currentState == State.STOP){
        currentState = State.GO;
    }
}

基本上，这意味着......

如果 currentState 为 GO，则将 currentState 设置为 WARN...
如果 currentState 为 WARN，则将 currentState 设置为 STOP...
如果 currentState 为 STOP，则将 currentState 设置为 GO...

鉴于默认状态是 GO，当您调用此方法时，状态永远不会更改为 GO 之外的任何状态。相反，您应该使用 if-else 语句

public void changeLight() {
    if (currentState == State.GO) {
        currentState = State.WARN;
    } else if (currentState == State.WARN) {
        currentState = State.STOP;
    } else if (currentState == State.STOP) {
        currentState = State.GO;
    }
}

已更新

渲染灯光本身很大程度上取决于个人喜好，例如，我可能会想做类似的事情......

switch (getCurrentState()) {
    case GO:
        canvas.setColor(GO_COLOR);
        canvas.drawOval(145,360,60,60);
        break;
    case WARN:
        canvas.setColor(WARNING_COLOR);
        canvas.drawOval(145,280,60,60);
        break;
    case STOP:
        canvas.setColor(STOP_COLOR);
        canvas.drawOval(145,200,60,60);
        break;
}
canvas.setColor(OFF_COLOR);
canvas.drawRect(125,185,100,250);
canvas.drawOval(145,200,60,60);
canvas.drawOval(145,280,60,60);
canvas.drawOval(145,360,60,60);

这将填充处于 Activity 状态的灯光，但随后将其他所有内容渲染到顶部，因此灯光始终处于轮廓中