repaint方法不使用的Java

Question

我有這樣的代碼，我希望它重新繪製，這樣，當用戶進入它打印出的加速和油耗的細節（在另一個類計算），我可以看到它的作品，因爲我有system.out.println顯示的值，但他們沒有更新到我的JFrame。

窗口（）被調用在另一個類另一個構造，JFrame中打開不錯，但不更新

任何想法？

感謝

public class Vehicle extends JFrame { 

    protected static double horsepower; 
    protected static double aerodynamics; 
    protected static double weight; 
    protected static double acceleration; 
    protected static double topspeed; 
    protected double fuelconsumption; 
    protected String userHorsepower; 
    protected String userWeight; 
    protected String userTopspeed; 
    protected String userInput = "No Current Selection"; 

    JPanel panel = new JPanel(); 
    JButton Van = new JButton("Add Van"); 



    public Vehicle(double horsepower, double weight, double aerodynamics, double topspeed){ 
     super(); 
    } 

    public void window(){ 

     JButton Van = new JButton("Add Van Car"); 
     Van.addActionListener(new ActionListener(){ 
      public void actionPerformed(ActionEvent e) { 

       userHorsepower = JOptionPane.showInputDialog("Enter Horsepower"); 
       horsepower = Double.parseDouble(userHorsepower); 
       userWeight = JOptionPane.showInputDialog("Enter Weight"); 
       weight = Double.parseDouble(userWeight); 
       userTopspeed = JOptionPane.showInputDialog("Enter Topspeed"); 
       topspeed = Double.parseDouble(userTopspeed); 
       aerodynamics = 0.9; 
       userInput = "Van"; 
       TestConsumption.printVan(); 
       repaint(); 
       return; 

      }}); 

     JButton SportCar = new JButton("Add Sports Car"); 
     SportCar.addActionListener(new ActionListener(){ 
      public void actionPerformed(ActionEvent e) { 
         userHorsepower = JOptionPane.showInputDialog("Enter Horsepower"); 
         horsepower = Double.parseDouble(userHorsepower); 
         userWeight = JOptionPane.showInputDialog("Enter Weight"); 
         weight = Double.parseDouble(userWeight); 
         userTopspeed = JOptionPane.showInputDialog("Enter Topspeed"); 
         topspeed = Double.parseDouble(userTopspeed); 
         aerodynamics = 0.5; 
         userInput = "Sports Car"; 
         TestConsumption.printCar(); 
         panel.repaint(); 
      }}); 

     JLabel userChoice = new JLabel(userInput); 
     JLabel accel = new JLabel("Acceleration: " + acceleration); 
     JLabel fuel = new JLabel("Fuel Consumption: " + fuelconsumption); 

     panel.setLayout(new GridLayout(5,5,0,0)); 
     panel.add(Van); 
     panel.add(SportCar); 
     panel.add(userChoice); 
     panel.add(accel); 
     panel.add(fuel); 
     add(panel); 
     pack(); 
     setTitle("Title Here"); 
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     setResizable(true); 
     setSize(300,200); 
     setLocationRelativeTo(null); 
     setVisible(true); 
     repaint(); 
    } 

窗口被稱爲這個類

public class TestConsumption extends Vehicle { 

    public TestConsumption(double horsepower, double weight, double aerodynamics, double topspeed) { 
     super(horsepower, weight, aerodynamics, topspeed); 
    } 

    public static void main(String [] args){ 

     Vehicle vh = new Vehicle(500, 500, 500, 500); 
     vh.window(); 
    } 


    public static void printCar(){ 
     Vehicle Car = new SportCar(horsepower,weight,aerodynamics,topspeed); 

     Car.acceleration(); 
     Car.showFuelConsumption(); 
    } 

    public static void printVan(){ 

     Vehicle FirstVan = new Van(horsepower,weight,aerodynamics,topspeed); 

     FirstVan.acceleration(); 
     FirstVan.showFuelConsumption(); 
    } 
} 

Answer 1

至於我們可以看到，你永遠更新的JLabel文本。計算該標籤的新對應值後，您需要在每個JLabel上撥打setText。

然而，在您的情況，您JLabel對象作爲window()方法的局部範圍變量創建的，所以他們不再容易獲得（在技術上有訪問他們，因爲你將他們添加到您的JPanel的方式，但這是不必要的繁瑣）。

由於TestConsumption.printVan()顯然是用來計算加速和油耗，使生活更輕鬆，我建議促進JLabel accel和JLabel fuel實例變量，然後制定個體化的方法來計算TestConsumption兩個值。所以你的動作事件可能看起來像這樣：

sportCar.addActionListener(new ActionListener(){ 
    public void actionPerformed(ActionEvent e) { 
     userHorsepower = JOptionPane.showInputDialog("Enter Horsepower"); 
     horsepower = Double.parseDouble(userHorsepower); 

     userWeight = JOptionPane.showInputDialog("Enter Weight"); 
     weight = Double.parseDouble(userWeight); 

     userTopspeed = JOptionPane.showInputDialog("Enter Topspeed"); 
     topspeed = Double.parseDouble(userTopspeed); 

     aerodynamics = 0.5; 
     userInput = "Sports Car"; 

     // These static methods would be added to your TestConsumption class 
     acceleration = TestConsumption.calculateAcceleration(...whatever params required for this calculation...); 
     fuelConsumption = TestConsumption.calculateFuelConsumption(...whatever params required for this calculation...); 

     accel.setText("Acceleration: " + acceleration); 
     fuel.setText("Fuel Consumption: " + fuelConsumption); 

     panel.repaint(); 
}}); 

或者，你不必將JLabels提升爲實例變量;只要你之前在window()方法頂部聲明accel和fuel你兩個按鈕設置了ActionListener，他們將在通過actionPerformed方法的範圍機箱中的事件動作來訪問。

一些旁註：

請記住，變量名的Java命名慣例是，以小寫字母開頭他們。所以，你的Van和SportCar變量應該是van和sportCar。在我的例子中，我已經寫下了它們。雖然它不會造成任何問題，但從語法上講，它很難一眼就知道是否正在查看類或變量名。

據我所知，您的TestConsumption類不需要延長Vehicle。它不是一輛車;它似乎既是你的應用程序的起點，又是一個輔助類（靜態方法）。

這似乎是學校裏的功課，所以我不能肯定你是否已經明確告訴以這種方式來設計你的程序，但是從設計的角度來看，你在你的組合概念「視圖」和「模型「在一起。 A JFrame不是車輛;它是一個窗口，用於幫助表示數據的視圖元素。您可能會發現它將通過提取特定於車輛的字段和方法（如acceleration,topspeed等）將其清理到一個名爲Vehicle的單獨類中，然後您可以使用SportCar和Van進行子類化（正如您似乎按照TestConsumption中的指示進行）。您的JFrame子類（我們可以稱其爲MainWindow或其他類似的東西），只負責更新其數據表示（在本例中爲我們的accel和fuel JLabel）。

Answer 2

呼叫window()在constructor Vehicle(double horsepower, double weight, double aerodynamics, double topspeed)