在運行時設置JLabel文本

Question

我對Java很新（約2周），並且試圖設置JLabel的文本。唯一的問題是我在另一個課程中進行計算，我不知道如何引用我已經創建的Jlabel。這是兩個有問題的課程。

package fightsim; 

import javax.swing.JPanel; 
import net.miginfocom.swing.MigLayout; 
import javax.swing.JLabel; 
import javax.swing.JButton; 
import java.awt.event.ActionListener; 
import java.awt.event.ActionEvent; 

public class FightSimPane extends JPanel { 
FightManager FightManager = new FightManager(); 
/** 
* Create the panel. 
*/ 
public FightSimPane() { 
    setLayout(new MigLayout("", "[][][][][][][][][][]", "[][][][]")); 

    JLabel lblChampionleft = new JLabel("ChampionLeft"); 
    add(lblChampionleft, "cell 1 3"); 

    JButton btnGo = new JButton("Go"); 
    btnGo.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent arg0) { 

      FightManager.startFight(); 
      FightManager.runTheFight(); 

     } 
    }); 
    add(btnGo, "cell 5 3"); 

    JLabel lblChampionright = new JLabel("ChampionRight"); 
    add(lblChampionright, "cell 9 3"); 

} 


public void setLeftChampionLabel(String s){ 
    //not able to reference Jlabel lblChampionLeft here??? 
    System.out.println("Setting Left Champion text to"+s); 

} 

public void setRightChampionLabel(String s){ 
    //not able to reference Jlabel lblChampionRight here??? 
    System.out.println("Setting Right Champion text to"+s); 
} 


} 

而試圖設置標籤的類。

package fightsim; 

public class FightManager { 

Champion LeftChamp = new Champion(); 
Champion RightChamp = new Champion(); 

public FightManager() { 

} 

Thread LeftChampThread = new Thread(LeftChamp); 
Thread RightChampThread = new Thread(RightChamp); 

; 

public void startFight() { 

    LeftChamp.setHealth(200); 
    RightChamp.setHealth(300); 
    LeftChamp.setATKsp(1000); 
    RightChamp.setATKsp(1000); 
    LeftChamp.setAD(20); 
    RightChamp.setAD(20); 

} 

public void runTheFight() { 
    System.out.println("Starting Threads"); 
    LeftChampThread.start(); 
    RightChampThread.start(); 

    while ((LeftChamp.getHealth() > 0) && (RightChamp.getHealth() > 0)) { 

     if (RightChamp.isReadyToAttack()) { 
      LeftChamp.setHealth(LeftChamp.getHealth() -  RightChamp.getAD()); 
      RightChamp.setNotReady(); 
      System.out.println("Setting Left Champion test to" 
        + Integer.toString(LeftChamp.getHealth())); 

      // This is where I'd like to update the left Jlabel in 
      // FightSimPane 

     } 
     if (LeftChamp.isReadyToAttack()) { 
      RightChamp 
        .setHealth(RightChamp.getHealth() - LeftChamp.getAD()); 
      LeftChamp.setNotReady(); 
      System.out.println("Setting Right Champion test to" 
        + Integer.toString(RightChamp.getHealth())); 

      // This is where I'd like to update the right Jlabel in 
      // FightSimPane 
     } 

    } 

} 
} 

所以，問題...我如何讓我的FightManager類訪問和更改了的JLabel我FightSimPane類/ GUI。在此先感謝，如果這是一個愚蠢的問題，很抱歉。我對編程非常陌生，我仍然試圖將其全部納入其中。有了這些說法，其他任何建議都會很棒。謝謝！

Answer 1

傳遞引用使得類可以相互通信，不僅如此，而且還有另一類類的正確活動實例。舉例來說，你可以給一個FlightManager場FlightSimPane：

class FightManager { 

    private FightSimPane fightSimPane; 

    // and fill it in the constructor: 
    public FightManager(FightSimPane fightSimPane) { 
     this.fightSimPane = fightSimPane; 
    } 

然後你會被處理的實際可視化FightSimPane GUI對象。

請注意，你必須照顧到傳遞正確的實例：

public class FightSimPane extends JPanel { 
    FightManager FightManager = new FightManager(this); 

然後就可以調用FightSimPane的公共方法在FightManager類：

public void runTheFight() { 
    System.out.println("Starting Threads"); 
    LeftChampThread.start(); 
    RightChampThread.start(); 

    while ((LeftChamp.getHealth() > 0) && (RightChamp.getHealth() > 0)) { 

    if (RightChamp.isReadyToAttack()) { 
     LeftChamp.setHealth(LeftChamp.getHealth() - RightChamp.getAD()); 
     RightChamp.setNotReady(); 
     System.out.println("Setting Left Champion test to" 
       + Integer.toString(LeftChamp.getHealth())); 

     // !!! **** added this ************* 
     fightSimPane.setRightChampionLabel("Setting Left Champion test to" 
       + Integer.toString(LeftChamp.getHealth())); 

    } 

編輯1
我看到另一個潛在的嚴重和不相關的問題在這裏：

while ((LeftChamp.getHealth() > 0) && (RightChamp.getHealth() > 0)) { 

    //......... 

    } 

此代碼似乎在主Swing線程中調用，EDT和它的本質（while（true））表明它有很好的機會鎖定EDT，使您的Swing GUI的圖形處理和更新和所有的用戶交互到尖銳的停頓。您可能需要爲此或後臺線程使用Swing Timer，以使EDT免費進行必要的工作。

Answer 2

在FightManager類中聲明參考變量FightSimPane類，並通過FightManager的構造函數傳遞參考FightSimPane對象。

在FightManager類，

public class FightManager { 

Champion LeftChamp = new Champion(); 
Champion RightChamp = new Champion(); 
private FightSimPane pane; 

public FightManager(FightSimPane pane) { this.pane=pane;} 
public FightManager() { 
} 
.... 

使用 「窗格中」 引用變量可以訪問FightSimPane類的可訪問的元素。

修改FightSimPane代碼，

public class FightSimPane extends JPanel { 
FightManager fightManager; 

public FightSimPane() { 
    fightManager= new FightManager(this); 
    ... 
}