複数のJPanelsにCardLayoutを使用して何も表示しない

Question

私は単純な（そして偽の）コンピュータ消費電力計算機を作っています。私はカードレイアウトを使用して複数のパネルを配置していますが、実行すると何も表示されない小さなウィンドウがあります。ここに私の長いコードがあります。私はそれを1つのクラスにまとめました。

package my.Project; 

import java.awt.*; 
import java.awt.event.*; 
import java.io.IOException; 
import java.net.URI; 
import java.net.URISyntaxException; 
import java.text.DecimalFormat; 
import javax.swing.*; 


public class MainProject extends JFrame { 

CardLayout cl; 

int motherboardP, oddP, hddP, ssdP, fanP, cpuP, gpuP, monitorP, hoursint; 
int ramNum, hddNum, ssdNum, fanNum, gpuNum; 
double ramP, totalP, powerPerYear; 
public float tariff = (float) 0.2180; 
public float costRM; 

JPanel mainPage, secondPage, thirdPage, results; 
//JPanel panelCont; 
JLabel title, icon, motherboard, ram, numram, 
     numssd, numhdd, odd, numfan, cpu, gpu, 
     numgpu, monitor, hours, outage, peryear, 
     costyear, watt, kwatt, rm; 

JButton start, exit1, exit2, nxt1, bck1, nxt2, bck2, done, bck3, tips, calc; 

JTextField numRam, numSSD, numHDD, numFan, numGpu, hoursUse, 
     outagePC, perYear, cost; 

JComboBox mboardBox, ramBox, oddBox, cpuBox, gpuBox, 
     monitorBox; 

public MainProject() { 
    initComponents(); 
} 

public void initComponents() { 

    setTitle("Power Consumption Calculator"); 
    setDefaultCloseOperation(EXIT_ON_CLOSE); 
    setSize(500, 400); 

    Container contentPane = getContentPane(); 

    contentPane.setLayout(cl); 

    /* 
    panelCont = new JPanel(); 
    cl = new CardLayout(); 
    */ 

    //contentPane.add(panelCont); 

    /* 
    panelCont.setLayout(cl); 
    panelCont.add(mainPage,"1"); 
    panelCont.add(secondPage,"2"); 
    panelCont.add(thirdPage,"3"); 
    panelCont.add(results,"4"); 
    cl.show(panelCont,"1"); 
    */ 

    mainPage = new JPanel(); 

    secondPage = new JPanel(); 

    thirdPage = new JPanel(); 

    results = new JPanel(); 

    cl.show(contentPane,"1"); 

    contentPane.add("1", mainPage); 
    contentPane.add("2", secondPage); 
    contentPane.add("3", thirdPage); 
    contentPane.add("4", results); 

    title.setFont(new Font("Tahoma", Font.BOLD, 18)); 
    title.setText("Computer Power Consumption Calculator"); 
    motherboard.setText("Motherboard:"); 
    ram.setText("RAM:"); 
    numram.setText("No. of RAM Sticks:"); 
    numssd.setText("Num. of SSD:"); 
    numhdd.setText("Num. of HDD:"); 
    odd.setText("Optical Disk Drive:"); 
    numfan.setText("Num. of Fans:"); 
    cpu.setText("CPU:"); 
    gpu.setText("GPU:"); 
    numgpu.setText("Num. of GPU:"); 
    monitor.setText("Monitor:"); 
    hours.setText("Hours of usage/day:"); 
    outage.setText("PC Power Outage:"); 
    peryear.setText("Per year:"); 
    costyear.setText("Cost/year"); 
    watt.setText("Watts (W)"); 
    kwatt.setText("kiloWatts(kW)"); 
    rm.setText("RM"); 

    icon.setIcon(new javax.swing.ImageIcon(getClass().getResource("/my/Project/pclogo.png"))); 

    BorderLayout mainL = new BorderLayout(); 
    mainPage.setLayout(mainL); 
    mainPage.add(title, BorderLayout.PAGE_START); 
    mainPage.add(icon, BorderLayout.CENTER); 
    mainPage.add(start, BorderLayout.SOUTH); 
    mainPage.add(exit1,BorderLayout.SOUTH); 

    GridLayout secondL = new GridLayout(0,2); 
    secondPage.setLayout(secondL); 
    secondPage.add(motherboard); 
    secondPage.add(mboardBox); 
    secondPage.add(ram); 
    secondPage.add(ramBox); 
    secondPage.add(numram); 
    secondPage.add(numRam); 
    secondPage.add(numssd); 
    secondPage.add(numSSD); 
    secondPage.add(numhdd); 
    secondPage.add(numHDD); 
    secondPage.add(odd); 
    secondPage.add(oddBox); 
    secondPage.add(numfan); 
    secondPage.add(numFan); 
    secondPage.add(nxt1); 
    secondPage.add(bck1); 

    GridLayout thirdL = new GridLayout(0,2); 
    thirdPage.setLayout(thirdL); 
    thirdPage.add(cpu); 
    thirdPage.add(cpuBox); 
    thirdPage.add(gpu); 
    thirdPage.add(gpuBox); 
    thirdPage.add(numGpu); 
    thirdPage.add(monitor); 
    thirdPage.add(monitorBox); 
    thirdPage.add(hours); 
    thirdPage.add(hoursUse); 
    thirdPage.add(nxt2); 
    thirdPage.add(bck2); 

    GridLayout resultL = new GridLayout(0,3); 
    results.setLayout(resultL); 
    results.add(outage); 
    results.add(outagePC); 
    results.add(watt); 
    results.add(peryear); 
    results.add(perYear); 
    results.add(kwatt); 
    results.add(costyear); 
    results.add(cost); 
    results.add(rm); 
    results.add(calc); 
    results.add(bck3); 
    results.add(exit2); 
    results.add(tips); 

    start.setText("Start"); 
    start.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      //startActionPerformed(evt); 
      cl.show(contentPane,"2"); 
     } 
    }); 

    exit1.setText("Exit"); 
    exit1.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // exit1ActionPerformed(evt); 
      System.exit(0); 
     } 
    }); 

    exit2.setText("Exit"); 
    exit2.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // exit2ActionPerformed(evt); 
      System.exit(0); 
     } 
    }); 

    nxt1.setText("Next >>"); 
    nxt1.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // nxt1ActionPerformed(evt); 
      cl.show(contentPane,"3"); 
      ramNum = Integer.parseInt(numRam.getText()); 
      ssdNum = Integer.parseInt(numSSD.getText()); 
      hddNum = Integer.parseInt(numHDD.getText()); 
      fanNum = Integer.parseInt(numFan.getText()); 

      JComboBox cb1 = (JComboBox)evt.getSource(); 
      String mboard = (String)cb1.getSelectedItem(); 
      if("Average".equals(mboard)) { 
       motherboardP = 32; 
      } 
      if("High End".equals(mboard)) { 
       motherboardP = 60; 
      } 

      JComboBox cb2 = (JComboBox)evt.getSource(); 
      String ramType = (String)cb2.getSelectedItem(); 
      if("DDDR1".equals(ramType)) { 
       ramP = 5; 
      } 
      if("DDR2".equals(ramType)) { 
       ramP = 4; 
      } 
      if("DDR3".equals(ramType)) { 
       ramP = 2.5; 
      } 

      JComboBox cb3 = (JComboBox)evt.getSource(); 
      String typeODD = (String)cb3.getSelectedItem(); 
      if("DVD".equals(typeODD)) { 
       oddP = 22; 
      } 
      if("BluRay".equals(typeODD)) { 
       oddP = 27; 
      } 


     } 
    }); 

    nxt2.setText("Next >>"); 
    nxt2.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // nxt2ActionPerformed(evt); 
      cl.show(contentPane,"4"); 

      gpuNum = Integer.parseInt(numGpu.getText()); 
      hoursint = Integer.parseInt(hoursUse.getText()); 

      JComboBox cb4 = (JComboBox)evt.getSource(); 
      int inCPU = (Integer)cb4.getSelectedIndex(); 
      switch(inCPU) { 
       case 0: 
        cpuP = 89; 
        break; 
       case 1: 
        cpuP = 119; 
        break; 
       case 2: 
        cpuP = 127; 
        break; 
       case 3: 
        cpuP = 125; 
        break; 
       case 4: 
        cpuP = 33; 
        break; 
       case 5: 
        cpuP = 98; 
        break; 

      } 

      JComboBox cb5 = (JComboBox)evt.getSource(); 
      int nvGPU = (Integer)cb5.getSelectedIndex(); 

      switch(nvGPU) { 
       case 0: 
        gpuP = 295; 
        break; 
       case 1: 
        gpuP = 100; 
        break; 
       case 2: 
        gpuP = 250; 
        break; 
       case 3: 
        gpuP = 150; 
        break; 
       case 4: 
        gpuP = 105; 
        break; 
       case 5: 
        gpuP = 275; 
        break; 
      } 

      JComboBox cb6 = (JComboBox)evt.getSource(); 
      int mSize = (Integer)cb6.getSelectedIndex(); 
      if(mSize == 0) { 
       monitorP = 20; 
      } 
      if(mSize == 1) { 
       monitorP = 28; 
      } 
      if(mSize == 2) { 
       monitorP = 50; 
      } 

     } 
    }); 

    bck1.setText("<< Back"); 
    bck1.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // bck1ActionPerformed(evt); 
      cl.show(contentPane,"1"); 
     } 
    }); 

    bck2.setText("<< Back"); 
    bck2.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // bck2ActionPerformed(evt); 
      cl.show(contentPane,"2"); 
     } 
    }); 

    bck3.setText("<< Back"); 
    bck3.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // bck3ActionPerformed(evt); 
      cl.show(contentPane,"3"); 
     } 
    }); 

    tips.setText("Tips on saving energy"); 
    tips.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      //tipsActionPerformed(evt); 
      try { 

     String url ="http://www.toptenreviews.com/computers/articles/10-computer-energy-saving-tips-go-green/"; 

     Desktop dt = Desktop.getDesktop(); 
     URI uri = new URI(url); 
     dt.browse(uri.resolve(uri)); 
    }  

    catch (URISyntaxException | IOException e) { 
     JOptionPane.showMessageDialog(null, e.getMessage()); 
    } 
     } 
    }); 

    calc.setText("Calculate"); 
    calc.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // calcActionPerformed(evt); 

      gpuP *= gpuNum; 
      ramP *= ramNum; 
      hddP = hddNum * 5; 
      ssdP = ssdNum * 3; 
      fanP = fanNum * 4; 

      totalP = motherboardP + cpuP + gpuP + ramP + 
      hddP + ssdP + monitorP + fanP; 
      powerPerYear = totalP * hoursint * 365; 

      costRM = (float) ((powerPerYear/1000) * tariff); 

      DecimalFormat df = new DecimalFormat("#.##"); 
      df.format(costRM); 

      String outage = Double.toString(totalP); 
      String ppy = Double.toString(powerPerYear); 
      String price = Float.toString(costRM); 

      outagePC.setText(outage); 
      perYear.setText(ppy); 
      cost.setText(price); 
     } 
    }); 

    mboardBox.setModel(new DefaultComboBoxModel(new String[] { "Average", "High End" })); 
    mboardBox.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      // mboardBoxActionPerformed(evt); 
      JComboBox cb = (JComboBox)evt.getSource(); 
      String mboard = (String)cb.getSelectedItem(); 
      if("Average".equals(mboard)) { 
       motherboardP = 32; 
      } 
      if("High End".equals(mboard)) { 
       motherboardP = 60; 
      } 
     } 
    }); 

    ramBox.setModel(new DefaultComboBoxModel(new String[] { "DDR1", "DDR2", "DDR3" })); 
    ramBox.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      //ramBoxActionPerformed(evt); 
      JComboBox cb = (JComboBox)evt.getSource(); 
      String ramType = (String)cb.getSelectedItem(); 
      if("DDDR1".equals(ramType)) { 
       ramP = 5; 
      } 
      if("DDR2".equals(ramType)) { 
       ramP = 4; 
      } 
      if("DDR3".equals(ramType)) { 
       ramP = 2.5; 
      } 
     } 
    }); 

    oddBox.setModel(new DefaultComboBoxModel(new String[] { "DVD", "BluRay" })); 
    oddBox.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      //oddBoxActionPerformed(evt); 
      JComboBox cb = (JComboBox)evt.getSource(); 
      String typeODD = (String)cb.getSelectedItem(); 
      if("DVD".equals(typeODD)) { 
       oddP = 22; 
      } 
      if("BluRay".equals(typeODD)) { 
       oddP = 27; 
      } 
     } 
    }); 

    cpuBox.setModel(new DefaultComboBoxModel(new String[] { "intel Core i3", "intel Core i5", "intel Core i7", "AMD FX 4350", "AMD Sempron 64 3500", "AMD Athlon 64 FX-62" })); 
    cpuBox.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      //cpuBoxActionPerformed(evt); 
      JComboBox cb = (JComboBox)evt.getSource(); 
      int inCPU = (Integer)cb.getSelectedIndex(); 
      switch(inCPU) { 
       case 0: 
        cpuP = 89; 
        break; 
       case 1: 
        cpuP = 119; 
        break; 
       case 2: 
        cpuP = 127; 
        break; 
       case 3: 
        cpuP = 125; 
        break; 
       case 4: 
        cpuP = 33; 
        break; 
       case 5: 
        cpuP = 98; 
        break; 

      } 

     } 
    }); 

    gpuBox.setModel(new DefaultComboBoxModel(new String[] { "NVidia GTX 500", "NVidia GTX 700", "NVidia GTX Titan", "AMD Radeon HD 2900", "AMD Radeon HD 3870", "AMD Radeon R9 Fury X" })); 
    gpuBox.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      //gpuBoxActionPerformed(evt); 
      JComboBox cb = (JComboBox)evt.getSource(); 
      int nvGPU = (Integer)cb.getSelectedIndex(); 

      switch(nvGPU) { 
       case 0: 
        gpuP = 295; 
        break; 
       case 1: 
        gpuP = 100; 
        break; 
       case 2: 
        gpuP = 250; 
        break; 
       case 3: 
        gpuP = 150; 
        break; 
       case 4: 
        gpuP = 105; 
        break; 
       case 5: 
        gpuP = 275; 
        break; 
      } 
     } 

    }); 

    monitorBox.setModel(new DefaultComboBoxModel(new String[] { "17\"-19\"", "20\"-22\"", "24\"-30\"" })); 
    monitorBox.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent evt) { 
      //monitorBoxActionPerformed(evt); 
      JComboBox cb = (JComboBox)evt.getSource(); 
      int mSize = (Integer)cb.getSelectedIndex(); 
      if(mSize == 0) { 
       monitorP = 20; 
      } 
      if(mSize == 1) { 
       monitorP = 28; 
      } 
      if(mSize == 2) { 
       monitorP = 50; 
      } 
     } 

    }); 


} 

public static void go() { 

    JFrame frame = new JFrame(); 
    frame.setVisible(true); 
} 

public static void main(String[] args) { 

    MainProject.go(); 

} 

} 

ここでコードを修正し、悪いJavaプログラミングのプラクティスをコード内でいくつ実装しましたか？まず

Answer 1

...あなたはコンテナにそれを適用する前にCardLayoutのインスタンスを作成し、前の任意のコンポーネントを追加する必要が

...第二

cl = new CardLayout(); 
    contentPane.setLayout(cl); 

...

add(Component, Object)メソッドを使用する必要があります。

contentPane.add(mainPage, "1"); 

Thrid

public static void go() { 

    JFrame frame = new JFrame(); 
    frame.setVisible(true); 
} 

空のフレームは何も作成せず、何もしません。それはJFrame

四...

はあなたがクラスに新しい機能を追加していない、JFrameから直接延長しないでください、それはにあなたをロックから延びているので、それは、実際にMainProjectを使用すると便利かもしれません1つのユースケースとそれはあなたが持っているもののような問題を引き起こす。代わりに

、JPanel代わりに...

public class MainProject extends JPanel { 

で始まる考える（この変更は、私がしようとすると、ここで修正するつもりはないされ、他のコンパイルエラーが発生することがありPS-）

フィフス

public static void go() { 
    EventQueue.invokeLater(new Runnable() { 
     @Override 
     public void run() { 
      try { 
       UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
      } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { 
       ex.printStackTrace(); 
      } 

      JFrame frame = new JFrame("Testing"); 
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      frame.add(new MainProject()); 
      frame.pack(); 
      frame.setLocationRelativeTo(null); 
      frame.setVisible(true); 
     } 
    }); 
} 

... JFrameの新しいインスタンスを作成して、あなたのコンポーネントを追加し、簡単なあなたが詳しく見てみたいことがあります

...

• Creating a GUI With JFC/Swing
• How to Use CardLayout

と...いくつかのより多くのアイデアのための

• Why is my JLabel not showing up
• Listener Placement Adhering to the Traditional (non-mediator) MVC Pattern

とどのようにあなたがより良いあなたは、代替