JFrame不更新背景顏色

我在計算器類中更新JFrame的背景顏色時遇到問題。「frame.getContentPane（）。setBackground（Color.BLACK）;」方法調用不更新幀的背景顏色外觀。相反，背景顏色保持不變;灰白色。該代碼相當容易找到位於第一個方法「public void addComponents」。先謝謝你。JFrame不更新背景顏色

import javax.swing.*; 

import java.awt.*; 
import java.awt.event.*; 

public class Calculator extends JFrame implements ActionListener { 
    private static final long serialVersionUID = 1L; 

    public static JFrame frame = new JFrame("Calculator"); 
    public JPanel panel = new JPanel(new GridLayout(6,0,4,4)); 
    public double currentNumber, nextNumber, total; 
    public boolean numberPresent = false; 
    public boolean addition = false, subtraction = false, multiplication = false, division = false; 

    public void addComponents(int x, int y) { 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.setSize(x,y); 
     frame.getContentPane().setBackground(Color.BLACK); 
     frame.setLocationRelativeTo(null); 
     frame.setResizable(false); 

     JButton button1 = new JButton("0"); 
     button1.addActionListener(this); 
     button1.setActionCommand("ZERO"); 
     button1.setPreferredSize(new Dimension(20,20)); 

     JButton button2 = new JButton("1"); 
     button2.addActionListener(this); 
     button2.setActionCommand("ONE"); 
     button2.setPreferredSize(new Dimension(20,20)); 

     JButton button3 = new JButton("2"); 
     button3.addActionListener(this); 
     button3.setActionCommand("TWO"); 
     button3.setPreferredSize(new Dimension(20,20)); 

     JButton button4 = new JButton("3"); 
     button4.addActionListener(this); 
     button4.setActionCommand("THREE"); 
     button4.setPreferredSize(new Dimension(20,20)); 

     JButton button5 = new JButton("4"); 
     button5.addActionListener(this); 
     button5.setActionCommand("FOUR"); 
     button5.setPreferredSize(new Dimension(20,20)); 

     JButton button6 = new JButton("5"); 
     button6.addActionListener(this); 
     button6.setActionCommand("FIVE"); 
     button6.setPreferredSize(new Dimension(20,20)); 

     JButton button7 = new JButton("6"); 
     button7.addActionListener(this); 
     button7.setActionCommand("SIX"); 
     button7.setPreferredSize(new Dimension(20,20)); 

     JButton button8 = new JButton("7"); 
     button8.addActionListener(this); 
     button8.setActionCommand("SEVEN"); 
     button8.setPreferredSize(new Dimension(20,20)); 

     JButton button9 = new JButton("8"); 
     button9.addActionListener(this); 
     button9.setActionCommand("EIGHT"); 
     button9.setPreferredSize(new Dimension(20,20)); 

     JButton button10 = new JButton("9"); 
     button10.addActionListener(this); 
     button10.setActionCommand("NINE"); 
     button10.setPreferredSize(new Dimension(20,20)); 

     JButton button11 = new JButton("CLEAR"); 
     button11.addActionListener(this); 
     button11.setActionCommand("CLEAR"); 
     button11.setPreferredSize(new Dimension(20,20)); 

     JButton button12 = new JButton("+"); 
     button12.addActionListener(this); 
     button12.setActionCommand("+"); 
     button12.setPreferredSize(new Dimension(20,20)); 

     JButton button13 = new JButton("-"); 
     button13.addActionListener(this); 
     button13.setActionCommand("-"); 
     button13.setPreferredSize(new Dimension(20,20)); 

     JButton button14 = new JButton("x"); 
     button14.addActionListener(this); 
     button14.setActionCommand("x"); 
     button14.setPreferredSize(new Dimension(20,20)); 

     JButton button15 = new JButton("/"); 
     button15.addActionListener(this); 
     button15.setActionCommand("/"); 
     button15.setPreferredSize(new Dimension(20,20)); 

     JButton button16 = new JButton("="); 
     button16.addActionListener(this); 
     button16.setActionCommand("="); 
     button16.setPreferredSize(new Dimension(20,20)); 

     panel.add(button8); 
     panel.add(button9); 
     panel.add(button10); 
     panel.add(button5); 
     panel.add(button6); 
     panel.add(button7); 
     panel.add(button2); 
     panel.add(button3); 
     panel.add(button4); 
     panel.add(button1); 
     panel.add(button12); 
     panel.add(button13); 
     panel.add(button16); 
     panel.add(button14); 
     panel.add(button15); 
     panel.add(button11); 

     frame.setContentPane(panel); 
     frame.setVisible(true); 
    } 

    public void actionPerformed(ActionEvent ea) { 
     String action = ea.getActionCommand(); 
      if (numberPresent = true && action.equals("ZERO")) { 
       nextNumber = currentNumber; 
       currentNumber = 0; 
       System.out.print("0"); 
      } 
      if (numberPresent = false && action.equals("ZERO")) { 
       currentNumber = 0; 
       numberPresent = true; 
       System.out.print("0"); 
      } 
      if (numberPresent = true && action.equals("ONE")) { 
       nextNumber = currentNumber; 
       currentNumber = 1; 
       System.out.print("1"); 
      } 
      if (numberPresent = false && action.equals("ONE")) { 
       currentNumber = 1; 
       numberPresent = true; 
       System.out.print("1"); 
      } 
      if (numberPresent = true && action.equals("TWO")) { 
       nextNumber = currentNumber; 
       currentNumber = 2; 
       System.out.print("2"); 
      } 
      if (numberPresent = false && action.equals("TWO")) { 
       currentNumber = 2; 
       numberPresent = true; 
       System.out.print("2"); 
      } 
      if (numberPresent = true && action.equals("THREE")) { 
       nextNumber = currentNumber; 
       currentNumber = 3; 
       System.out.print("3"); 
      } 
      if (numberPresent = false && action.equals("THREE")) { 
       currentNumber = 3; 
       numberPresent = true; 
       System.out.print("3"); 
      } 
      if (numberPresent = true && action.equals("FOUR")) { 
       nextNumber = currentNumber; 
       currentNumber = 4; 
       System.out.print("4"); 
      } 
      if (numberPresent = false && action.equals("FOUR")) { 
       currentNumber = 4; 
       numberPresent = true; 
       System.out.print("4"); 
      } 
      if (numberPresent = true && action.equals("FIVE")) { 
       nextNumber = currentNumber; 
       currentNumber = 5; 
       System.out.print("5"); 
      } 
      if (numberPresent = false && action.equals("FIVE")) { 
       currentNumber = 5; 
       numberPresent = true; 
       System.out.print("5"); 
      } 
      if (numberPresent = true && action.equals("SIX")) { 
       nextNumber = currentNumber; 
       currentNumber = 6; 
       System.out.print("6"); 
      } 
      if (numberPresent = false && action.equals("SIX")) { 
       currentNumber = 6; 
       numberPresent = true; 
       System.out.print("6"); 
      } 
      if (numberPresent = true && action.equals("SEVEN")) { 
       nextNumber = currentNumber; 
       currentNumber = 7; 
       System.out.print("7"); 
      } 
      if (numberPresent = false && action.equals("SEVEN")) { 
       currentNumber = 7; 
       numberPresent = true; 
       System.out.print("7"); 
      } 
      if (numberPresent = true && action.equals("EIGHT")) { 
       nextNumber = currentNumber; 
       currentNumber = 8; 
       System.out.print("8"); 
      } 
      if (numberPresent = false && action.equals("EIGHT")) { 
       currentNumber = 8; 
       numberPresent = true; 
       System.out.print("8"); 
      } 
      if (numberPresent = true && action.equals("NINE")) { 
       nextNumber = currentNumber; 
       currentNumber = 9; 
       System.out.print("9"); 
      } 
      if (numberPresent = false && action.equals("NINE")) { 
       currentNumber = 9; 
       numberPresent = true; 
       System.out.print("9"); 
      } 
      if (action.equals("CLEAR")) { 
       currentNumber = 0; 
       nextNumber = 0; 
       total = 0; 
       System.out.println("CLEARED"); 
      } 
      if (action.equals("=")) { 
       numberPresent = false; 
       if (addition) { 
        System.out.println(" = " + (currentNumber + nextNumber)); 
        total = (currentNumber + nextNumber); 
        currentNumber = total; 
        addition = false; 
       } 
       if (subtraction) { 
        System.out.println(" = " + (nextNumber - currentNumber)); 
        total = (currentNumber - nextNumber); 
        currentNumber = total; 
        subtraction = false; 
       } 
       if (multiplication) { 
        System.out.println(" = " + (currentNumber * nextNumber)); 
        total = (currentNumber * nextNumber); 
        currentNumber = total; 
        multiplication = false; 
       } 
       if (division) { 
        System.out.println(" = " + (nextNumber/ currentNumber)); 
        total = (nextNumber/currentNumber); 
        currentNumber = total; 
        division = false; 
       } 
      } 
      if (action.equals("+")) { 
       addition = true; 
       System.out.print(" + "); 
      } 
      else if (action.equals("-")) { 
       subtraction = true; 
       System.out.print(" - "); 
      } 
      else if (action.equals("x")) { 
       multiplication = true; 
       System.out.print(" x "); 
      } 
      else if (action.equals("/")) { 
       division = true; 
       System.out.print("/"); 
      } 
    } 

    public static void main(String[] args) { 
     System.out.println("Only handles 1 digit inputs at once. *Almost* Fully Functional"); 
     Calculator calc = new Calculator(); 
     calc.addComponents(260, 325); 
    } 
}

來源

2014-07-19 Ryan Kelly

哇..它不應該需要大約280 LOC顯示「無法設置BG」！爲了更快地獲得更好的幫助，請發佈[MCVE]（http://stackoverflow.com/help/mcve）（最小，完整，可驗證示例）。 –

1）請參閱[我是否應避免使用Swing中的set（Preferred | Maximum | Minimum）Size方法？]（http://stackoverflow.com/q/7229226/418556）（是）。按鈕是使用大字體或給按鈕大利潤。對於方形按鈕，擴展組件或使用方形圖標（並且不包含文本）。 2）另請參閱[工作計算器]（http://stackoverflow.com/a/7441804/418556）。 –

我會記住任何未來的問題。感覺就像展示整個編碼部分，以降低背景顏色變化抑制的可能性。事實證明，這只是一個菜鳥的錯誤，它可能會在幾秒鐘的閱讀和「Ctrl + X」+「Ctrl + V」中被阻止。我會盡量保持簡短，以便將來解決問題。 –

會發生什麼情況是您在將面板作爲內容窗格添加到框架之前設置了框架的ContentPane的背景顏色。

這裏的解決方案：

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.GridLayout; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import javax.swing.*; 

public class Calculator extends JFrame implements ActionListener { 

    private static final long serialVersionUID = 1L; 

    public static JFrame frame = new JFrame("Calculator"); 
    public JPanel panel = new JPanel(new GridLayout(6,0,4,4)); 
    public double currentNumber, nextNumber, total; 
    public boolean numberPresent = false; 
    public boolean addition = false, subtraction = false, multiplication = false, division = false; 

    public void addComponents(int x, int y) { 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.setSize(x,y); 

     frame.setLocationRelativeTo(null); 
     frame.setResizable(false); 

     JButton button1 = new JButton("0"); 
     button1.addActionListener(this); 
     button1.setActionCommand("ZERO"); 
     button1.setPreferredSize(new Dimension(20,20)); 

     JButton button2 = new JButton("1"); 
     button2.addActionListener(this); 
     button2.setActionCommand("ONE"); 
     button2.setPreferredSize(new Dimension(20,20)); 

     JButton button3 = new JButton("2"); 
     button3.addActionListener(this); 
     button3.setActionCommand("TWO"); 
     button3.setPreferredSize(new Dimension(20,20)); 

     JButton button4 = new JButton("3"); 
     button4.addActionListener(this); 
     button4.setActionCommand("THREE"); 
     button4.setPreferredSize(new Dimension(20,20)); 

     JButton button5 = new JButton("4"); 
     button5.addActionListener(this); 
     button5.setActionCommand("FOUR"); 
     button5.setPreferredSize(new Dimension(20,20)); 

     JButton button6 = new JButton("5"); 
     button6.addActionListener(this); 
     button6.setActionCommand("FIVE"); 
     button6.setPreferredSize(new Dimension(20,20)); 

     JButton button7 = new JButton("6"); 
     button7.addActionListener(this); 
     button7.setActionCommand("SIX"); 
     button7.setPreferredSize(new Dimension(20,20)); 

     JButton button8 = new JButton("7"); 
     button8.addActionListener(this); 
     button8.setActionCommand("SEVEN"); 
     button8.setPreferredSize(new Dimension(20,20)); 

     JButton button9 = new JButton("8"); 
     button9.addActionListener(this); 
     button9.setActionCommand("EIGHT"); 
     button9.setPreferredSize(new Dimension(20,20)); 

     JButton button10 = new JButton("9"); 
     button10.addActionListener(this); 
     button10.setActionCommand("NINE"); 
     button10.setPreferredSize(new Dimension(20,20)); 

     JButton button11 = new JButton("CLEAR"); 
     button11.addActionListener(this); 
     button11.setActionCommand("CLEAR"); 
     button11.setPreferredSize(new Dimension(20,20)); 

     JButton button12 = new JButton("+"); 
     button12.addActionListener(this); 
     button12.setActionCommand("+"); 
     button12.setPreferredSize(new Dimension(20,20)); 

     JButton button13 = new JButton("-"); 
     button13.addActionListener(this); 
     button13.setActionCommand("-"); 
     button13.setPreferredSize(new Dimension(20,20)); 

     JButton button14 = new JButton("x"); 
     button14.addActionListener(this); 
     button14.setActionCommand("x"); 
     button14.setPreferredSize(new Dimension(20,20)); 

     JButton button15 = new JButton("/"); 
     button15.addActionListener(this); 
     button15.setActionCommand("/"); 
     button15.setPreferredSize(new Dimension(20,20)); 

     JButton button16 = new JButton("="); 
     button16.addActionListener(this); 
     button16.setActionCommand("="); 
     button16.setPreferredSize(new Dimension(20,20)); 

     panel.add(button8); 
     panel.add(button9); 
     panel.add(button10); 
     panel.add(button5); 
     panel.add(button6); 
     panel.add(button7); 
     panel.add(button2); 
     panel.add(button3); 
     panel.add(button4); 
     panel.add(button1); 
     panel.add(button12); 
     panel.add(button13); 
     panel.add(button16); 
     panel.add(button14); 
     panel.add(button15); 
     panel.add(button11); 
     frame.setContentPane(panel); 
     frame.getContentPane().setBackground(Color.BLACK);//Set The Background color after adding the panel 
     frame.setVisible(true); 
    } 

     @Override 
     @SuppressWarnings("DeadBranch") 
     public void actionPerformed(ActionEvent ea) { 
     String action = ea.getActionCommand(); 
      if (numberPresent = true && action.equals("ZERO")) { 
       nextNumber = currentNumber; 
       currentNumber = 0; 
       System.out.print("0"); 
      } 
      if (numberPresent = false && action.equals("ZERO")) { 
       currentNumber = 0; 
       numberPresent = true; 
       System.out.print("0"); 
      } 
      if (numberPresent = true && action.equals("ONE")) { 
       nextNumber = currentNumber; 
       currentNumber = 1; 
       System.out.print("1"); 
      } 
      if (numberPresent = false && action.equals("ONE")) { 
       currentNumber = 1; 
       numberPresent = true; 
       System.out.print("1"); 
      } 
      if (numberPresent = true && action.equals("TWO")) { 
       nextNumber = currentNumber; 
       currentNumber = 2; 
       System.out.print("2"); 
      } 
      if (numberPresent = false && action.equals("TWO")) { 
       currentNumber = 2; 
       numberPresent = true; 
       System.out.print("2"); 
      } 
      if (numberPresent = true && action.equals("THREE")) { 
       nextNumber = currentNumber; 
       currentNumber = 3; 
       System.out.print("3"); 
      } 
      if (numberPresent = false && action.equals("THREE")) { 
       currentNumber = 3; 
       numberPresent = true; 
       System.out.print("3"); 
      } 
      if (numberPresent = true && action.equals("FOUR")) { 
       nextNumber = currentNumber; 
       currentNumber = 4; 
       System.out.print("4"); 
      } 
      if (numberPresent = false && action.equals("FOUR")) { 
       currentNumber = 4; 
       numberPresent = true; 
       System.out.print("4"); 
      } 
      if (numberPresent = true && action.equals("FIVE")) { 
       nextNumber = currentNumber; 
       currentNumber = 5; 
       System.out.print("5"); 
      } 
      if (numberPresent = false && action.equals("FIVE")) { 
       currentNumber = 5; 
       numberPresent = true; 
       System.out.print("5"); 
      } 
      if (numberPresent = true && action.equals("SIX")) { 
       nextNumber = currentNumber; 
       currentNumber = 6; 
       System.out.print("6"); 
      } 
      if (numberPresent = false && action.equals("SIX")) { 
       currentNumber = 6; 
       numberPresent = true; 
       System.out.print("6"); 
      } 
      if (numberPresent = true && action.equals("SEVEN")) { 
       nextNumber = currentNumber; 
       currentNumber = 7; 
       System.out.print("7"); 
      } 
      if (numberPresent = false && action.equals("SEVEN")) { 
       currentNumber = 7; 
       numberPresent = true; 
       System.out.print("7"); 
      } 
      if (numberPresent = true && action.equals("EIGHT")) { 
       nextNumber = currentNumber; 
       currentNumber = 8; 
       System.out.print("8"); 
      } 
      if (numberPresent = false && action.equals("EIGHT")) { 
       currentNumber = 8; 
       numberPresent = true; 
       System.out.print("8"); 
      } 
      if (numberPresent = true && action.equals("NINE")) { 
       nextNumber = currentNumber; 
       currentNumber = 9; 
       System.out.print("9"); 
      } 
      if (numberPresent = false && action.equals("NINE")) { 
       currentNumber = 9; 
       numberPresent = true; 
       System.out.print("9"); 
      } 
      if (action.equals("CLEAR")) { 
       currentNumber = 0; 
       nextNumber = 0; 
       total = 0; 
       System.out.println("CLEARED"); 
      } 
      if (action.equals("=")) { 
       numberPresent = false; 
       if (addition) { 
        System.out.println(" = " + (currentNumber + nextNumber)); 
        total = (currentNumber + nextNumber); 
        currentNumber = total; 
        addition = false; 
       } 
       if (subtraction) { 
        System.out.println(" = " + (nextNumber - currentNumber)); 
        total = (currentNumber - nextNumber); 
        currentNumber = total; 
        subtraction = false; 
       } 
       if (multiplication) { 
        System.out.println(" = " + (currentNumber * nextNumber)); 
        total = (currentNumber * nextNumber); 
        currentNumber = total; 
        multiplication = false; 
       } 
       if (division) { 
        System.out.println(" = " + (nextNumber/ currentNumber)); 
        total = (nextNumber/currentNumber); 
        currentNumber = total; 
        division = false; 
       } 
      } 
      switch (action) { 
       case "+": 
        addition = true; 
        System.out.print(" + "); 
        break; 
       case "-": 
        subtraction = true; 
        System.out.print(" - "); 
        break; 
       case "x": 
        multiplication = true; 
        System.out.print(" x "); 
        break; 
       case "/": 
        division = true; 
        System.out.print("/"); 
        break; 
      } 
    } 

    public static void main(String[] args) { 
     System.out.println("Only handles 1 digit inputs at once. *Almost* Fully Functional"); 
     Calculator calc = new Calculator(); 
     calc.addComponents(260, 325); 
    } 
}

來源

2014-07-19 03:59:25

我還替換了比較動作與開關的if條件。 –

謝謝！我真的不知道我怎麼能忽視這樣一個簡單的解決方案......我甚至沒有將面板添加到框架（facepalm）。菜鳥錯誤哈哈哈！感謝「case＆break」創新。我忘了所有關於： –

不客氣:) –

JFrame不更新背景顏色

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