Question

摘要：我目前正在进行模拟出租车的小程序实验室练习，它必须显示速度，燃料，票价和行驶距离，也是驾驶室的大帐篷被占用或空置。它有按钮，为用户提供交互。问题：我使用了一个线程用于票价，距离和燃料以及另一个用于选框的线程，但为什么我的选框连续闪烁？

Answer 1

没有代码，这真的是任何人的猜测，但不管我会不会被刺伤。我的猜测是你直接在JApplet的paint(...)方法中绘图，从而失去了Swing双缓冲的所有可能的收益。如果是这样，那么更改它并绘制JApplet正在显示的JPanel的paintComponent(...)方法。

如果这没有帮助，那么请考虑给我们足够的信息，以便我们不必猜测。您可能希望填写我们如何进行线程处理，并向我们保证您必须遵守Swing线程规则并仅在事件线程上更新Swing组件。

修改
你的代码：

import java.awt.*; import java.awt.event.ActionEvent; import javax.swing.JApplet; import javax.swing.*; import java.awt.event.ActionListener; import java.io.*; import javax.swing.border.Border; /** * * @author IC */ public class taxiCab extends JApplet implements ActionListener { private JTextField speed, distance, fare, fuel, ov, full, tf, tf_fuel, tf_speed; private JButton butt, start, butt_pass, butt_sUp, butt_sDown, butt_refuel; private JLabel label; private JPanel main, north, south, south_left, south_right, center, center_content, north_speed, north_distance, north_fuel, north_fare; private Container contain; private int speedVal, distanceVal, passval, thread_sleep, status_width, fuel_width; private float fuelVal, fareVal; private Graphics g; private String status; private Font font2 = new Font("Kozuka Gothic Pro B", Font.BOLD, 60); private Border border2 = BorderFactory.createLineBorder(Color.black, 3); private Border border1 = BorderFactory.createLineBorder(Color.black, 1); private final int width_ = 500; private final int height_ = 300; Thread thread1 = new trd1(); Thread thread2 = new trd2(); /** * Initialization method that will be called after the applet is loaded into * the browser. */ public void init() { setSize(width_,height_); status = new String(); status = "VACANT"; status_width = -330; Border border3 = BorderFactory.createLineBorder(Color.black, 5); thread1 = new trd1(); thread2.start(); thread2.suspend(); contain = new Container(); contain = getContentPane(); main = new JPanel(new BorderLayout()); north = new JPanel(new GridLayout(2,2)); north.setBackground(Color.blue); north_speed = new JPanel(); tf_speed = new JTextField(10); tf_speed.setBorder(border1); tf_speed.setText("Speed"); tf_speed.setHorizontalAlignment(JTextField.CENTER); tf_speed.setBackground(Color.CYAN); tf_speed.setEditable(false); speed = new JTextField(10); speed.setBorder(border1); speed.setEditable(false); speed.setText("-"); speed.setHorizontalAlignment(JTextField.CENTER); north_speed.add(tf_speed); north_speed.add(speed); north_distance = new JPanel(); tf = new JTextField(10); tf.setBorder(border1); tf.setText("Distance"); tf.setHorizontalAlignment(JTextField.CENTER); tf.setBackground(Color.CYAN); tf.setEditable(false); distance = new JTextField(10); distance.setBorder(border1); distance.setEditable(false); distance.setText("-");//<----------------------------------distance distance.setHorizontalAlignment(JTextField.CENTER); north_distance.add(tf); north_distance.add(distance); north_fuel = new JPanel(); tf_fuel = new JTextField(10); tf_fuel.setBorder(border1); tf_fuel.setText("Fuel"); tf_fuel.setHorizontalAlignment(JTextField.CENTER); tf_fuel.setBackground(Color.CYAN); tf_fuel.setEditable(false); fuel = new JTextField(10); fuel.setBorder(border1); fuel.setEditable(false); fuel.setText("-"); fuel.setHorizontalAlignment(JTextField.CENTER); north_fuel.add(tf_fuel); north_fuel.add(fuel); north_fare = new JPanel(); tf = new JTextField(10); tf.setBorder(border1); tf.setText("Fare"); tf.setHorizontalAlignment(JTextField.CENTER); tf.setBackground(Color.CYAN); tf.setEditable(false); fare = new JTextField(10); fare.setBorder(border1); fare.setEditable(false); fare.setText("-"); fare.setHorizontalAlignment(JTextField.CENTER); north_fare.add(tf); north_fare.add(fare); north.add(north_speed); north.add(north_distance); north.add(north_fuel); north.add(north_fare); center = new JPanel(new BorderLayout(3,3)); center_content = new JPanel(new GridLayout(2,1,0,15)); ov = new JTextField(20); ov.setText(""); ov.setBackground(Color.yellow); ov.setEditable(false); ov.setBorder(border2); full = new JTextField(20); full.setHorizontalAlignment(JTextField.CENTER); full.setText("FUELMeter"); full.setIgnoreRepaint(true); full.setFont(font2); full.setBorder(border2); center_content.add(ov); center_content.add(full); center.add(center_content, "Center"); center_content.setBackground(Color.yellow); label = new JLabel(" "); center.add(label, "North"); label = new JLabel(" "); center.add(label, "West"); label = new JLabel(" "); center.add(label, "South"); label = new JLabel(" "); center.add(label, "East"); south = new JPanel(new BorderLayout()); south_left = new JPanel(new GridLayout(2,1)); butt_sUp = new JButton("Speed Up"); butt_sUp.setBorder(border1); butt_sUp.addActionListener(this); butt_sUp.setEnabled(false); south_left.add(butt_sUp); butt_sDown = new JButton("Speed Down"); butt_sDown.setBorder(border1); butt_sDown.addActionListener(this); butt_sDown.setEnabled(false); south_left.add(butt_sDown); south_right = new JPanel(new GridLayout(2,1)); butt_pass = new JButton("Passenger In"); butt_pass.setBorder(border1); butt_pass.addActionListener(this); butt_pass.setEnabled(false); south_right.add(butt_pass); butt_refuel = new JButton("Refuel"); butt_refuel.setBorder(border1); butt_refuel.addActionListener(this); butt_refuel.setEnabled(false); south_right.add(butt_refuel); butt = new JButton("Start"); butt.setBorder(border1); butt.addActionListener(this); south.add(butt, "Center"); south.add(south_left, "West"); south.add(south_right, "East"); north.setBorder(border1); center.setBorder(border1); south.setBorder(border1); center.setBackground(Color.yellow); main.add(north, "North"); main.add(center, "Center"); main.add(south, "South"); main.setBorder(border1); //main.setIgnoreRepaint(true); contain.add(main); contain.setVisible(true); //contain.setIgnoreRepaint(true); } public void paint(Graphics g){ super.paint(g); g.setColor(Color.black); g.setFont(font2); g.drawString(status, status_width, 140); g.setColor(Color.yellow); g.fillRect(2,82,12,70); g.fillRect(getWidth()-14,82,12,70); g.setColor(Color.black); g.fillRect(0,82,2,70); g.setColor(Color.GREEN); g.fillRect(17,(getHeight()/2)+20,fuel_width,getHeight()-(83+(getHeight()/2))); main.setBorder(border1); } public void actionPerformed(ActionEvent e) { if(e.getActionCommand() == "Start"){ butt.setLabel("Stop"); butt_pass.setEnabled(true); fuelVal = 50.00f; distanceVal = 0; fareVal = 40.00f; speedVal = 0; fuel.setText(String.valueOf(fuelVal) + " L"); distance.setText(String.valueOf(distanceVal) + " km"); fare.setText("Php " + String.valueOf(fareVal)); speed.setText(String.valueOf(speedVal) + " kph"); thread1 = new trd1(); thread1.start(); thread2 = new trd2(); thread2.start(); //BufferedWriter bw;<----------------------------------------------- } else if(e.getActionCommand() == "Stop"){ butt.setLabel("Start"); butt_pass.setEnabled(false); butt_sUp.setEnabled(false); butt_sDown.setEnabled(false); butt_refuel.setEnabled(false); butt_pass.setLabel("Passenger In"); thread1.stop(); } else if(e.getActionCommand() == "Speed Up"){ if(speedVal == 0){ speedVal+=25; speed.setText(String.valueOf(speedVal) + " kph"); butt_sDown.setEnabled(true); tf_speed.setText("Speed"); thread1 = new trd1(); thread1.start(); } else if(speedVal == 275){ speedVal+=25; speed.setText(String.valueOf(speedVal) + " kph"); //butt_sUp.setEnabled(false); tf_speed.setText("MAX SPEED"); } else{ speedVal+=25; speed.setText(String.valueOf(speedVal) + " kph"); } } else if(e.getActionCommand() == "Speed Down"){ repaint(); if(speedVal==25){ speedVal-=25; speed.setText(String.valueOf(speedVal) + " kph"); tf_speed.setText("S T O P P E D"); butt_sDown.setEnabled(false); } else if(speedVal == 300){ speedVal-=25; speed.setText(String.valueOf(speedVal) + " kph"); tf_speed.setText("Speed"); butt_sUp.setEnabled(true); } else{ speedVal-=25; speed.setText(String.valueOf(speedVal) + " kph"); } } else if(e.getActionCommand() == "Passenger In"){ butt_pass.setLabel("Passenger Out"); fareVal = 40.0f; fare.setText("Php " + String.valueOf(fareVal)); butt_sUp.setEnabled(true); butt_sDown.setEnabled(true); butt_refuel.setEnabled(true); speedVal = 25; speed.setText(String.valueOf(speedVal) + " kph"); status = "OCCUPIED"; thread1 = new trd1(); thread1.start(); } else if(e.getActionCommand() == "Passenger Out"){ status = "VACANT"; butt_pass.setLabel("Passenger In"); thread1.stop(); } else if(e.getActionCommand() == "Refuel"){ if(fuelVal == 0.0f){ fuelVal = 50.00f; fuel.setText(String.valueOf(fuelVal)); tf_fuel.setBackground(Color.cyan); tf_fuel.setText("Fuel"); fuel_width = (int)((getWidth()-34)*fuelVal/50f); thread1 = new trd1(); thread1.start(); } else{ fuelVal = 50.00f; fuel.setText(String.valueOf(fuelVal) + " L"); } } } public class trd1 extends Thread implements Runnable { public void run(){ if(fuelVal>0.00f || speedVal>0){ for(;;){ try { Thread.sleep(50000/speedVal); if(fuelVal == 0.00f || speedVal == 0) thread1.stop(); distanceVal++; fareVal += 1.00; fuelVal -=.25f; fuel_width = (int)((getWidth()-34)*fuelVal/50f); repaint(); distance.setText(String.valueOf(distanceVal)+" km"); fuel.setText(String.valueOf(fuelVal)+" L"); fare.setText("P " + String.valueOf(fareVal)); } catch (InterruptedException e) { } } } } } public class trd2 extends Thread implements Runnable { //tf_fuel = new JTextField(15); public void run(){ for(int b = 0;;b++){ try { Thread.sleep(10); status_width +=1; if(status_width == getWidth()) status_width = -330; repaint(); if(fuelVal == 0.0f){ if(b%2==0){ tf_fuel.setBackground(Color.red); tf_fuel.setText("R E F U E L"); } else{ tf_fuel.setBackground(Color.cyan); tf_fuel.setText("R E F U E L"); } } } catch (InterruptedException e) { } } } } }

是的，我猜错了：你是直接在JApplet中绘画的。正如我最初所说，不要这样做。事实上，学习正确学习的最佳方法是阅读教程：

Lesson: Performing Custom Painting (the basics)

Painting in AWT and Swing (for more advanced concepts)

您的代码中还有很多其他错误，包括使用==来比较字符串而不是equals(...)或equalsIgnoreCase(...)方法，并尝试调用{{1直接。永远不要那样做。也不要在paint或paintComponent中设置组件的边框。您还要在后台线程中设置组件的文本和背景颜色，并从Swing事件线程中设置 - 这是间歇性和难以调试的线程错误的两个潜在原因。你只想在Swing事件线程上做这些事情。

当我使用多个线程重绘时，为什么我的applet会闪烁？

1 个答案: