从 java 中的另一个 class 接收 textArea 的内容（附代码）

Question

我正在开发一个有两个 classes MainGUI 和 MainTest 的项目。所以我的问题是我想在 MainGUI 的 testArea 上打印在 MainTest class 中完成的计算结果。我所做的是，

MainGUI obj=new MainGUI(); \declared in MainTest class obj.myTextField.setTest("Result"); \Result from the function

我还尝试了 append() 函数 too.But 它在我执行代码时显示了我的代码中的一堆错误。请帮忙..

节目具体如下

1.Class MainGUI

public class MainGUI {

  private JFrame frame;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    MainGUI window = new MainGUI();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public MainGUI() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        JTextArea myTextArea = new JTextArea();
        myTextArea.setBounds(124, 71, 192, 116);
        frame.getContentPane().add(myTextArea);

        JLabel lblTheResultWill = new JLabel("The Result Will Be Displyed Below.");
        lblTheResultWill.setBounds(118, 46, 274, 14);
        frame.getContentPane().add(lblTheResultWill);
    }
}

2.Class 主测试

public class SquareRootDemo2 
{

    public static void main(String[] args)
    {
        //Number for which square root is to be found
        double number = -12;

        //This method finds out the square root 
        findSquareRoot(number);

    }

    /*This method finds out the square root without using
    any built-in functions and displays it */
    public static void findSquareRoot(double number)
    {
        MainGUI obj = new MainGUI();
        boolean isPositiveNumber = true;
        double g1;

        //if the number given is a 0
        if(number==0)
        {
            obj.myTextField.setTest("Square root of "+number+" = "+0);
        }

        //If the number given is a -ve number
        else if(number<0)
        {   
            number=-number;
            isPositiveNumber = false;
        }

        //Proceeding to find out square root of the number
        double squareRoot = number/2;
        do
        {
            g1=squareRoot;
            squareRoot = (g1 + (number/g1))/2;
        }
        while((g1-squareRoot)!=0);

        //Displays square root in the case of a positive number
        if(isPositiveNumber)
        {
            obj.myTextField.setTest("Square roots of "+number+" are ");
            obj.myTextField.setTest("+"+squareRoot);
            obj.myTextField.setTest("-"+squareRoot);
        }
        //Displays square root in the case of a -ve number
        else
        {
            obj.myTextField.setTest("Square roots of -"+number+" are ");
            obj.myTextField.setTest("+"+squareRoot+" i");
            obj.myTextField.setTest("-"+squareRoot+" i");
        }

    }
}

Answer 1

您必须将代码放在按钮中 method.so 当按下按钮时您的代码 implements.that 这就是您得不到结果的原因。

private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        MainGUI obj=new MainGUI();//declared in MainTest class' 

        obj.myTextField.setText("Result");//Result from the function'
        obj.setVisible(true);
    }

Answer 2

What I need is that I want to print the result of Squre root of a number in the textArea of MainGUI class

问题 #1...

无法从 initialize 方法外部访问 JTextArea...

private void initialize() {
    //...
    JTextArea myTextArea = new JTextArea();

您需要将其设为实例字段

public class MainGUI {

  private JFrame frame;
  private JTextArea myTextArea;
  //...

  private void initialize() {
      //...
      myTextArea = new JTextArea();

接下来，您需要提供一些方法来修改 JTextArea...

public class MainGUI {
    //...
    public void seText(String text) {
        myTextArea.append(text);
    }

    public void append(String text) {
        myTextArea.seText(text);
    }

问题 #2...

您违反了 Swing 的单线程规则，您不应该在事件调度线程之外创建或修改任何 UI 组件...

类似...

public static void findSquareRoot(double number) {
    MainGUI obj = null;
    SwingUtilities.invokeAndWait(new Runnable() {
        @Override
        public void run() {
            obj = new MainGUI();
        }
    });

    boolean isPositiveNumber = true;
    double g1;

    //if the number given is a 0
    if (number == 0) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                obj.myTextField.setTest("Square root of " + number + " = " + 0);
            }
        });
    } //If the number given is a -ve number
    else if (number < 0) {
        number = -number;
        isPositiveNumber = false;
    }

    //Proceeding to find out square root of the number
    double squareRoot = number / 2;
    do {
        g1 = squareRoot;
        squareRoot = (g1 + (number / g1)) / 2;
    } while ((g1 - squareRoot) != 0);

    //Displays square root in the case of a positive number
    if (isPositiveNumber) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                obj.append("Square roots of " + number + " are ");
                obj.append("+" + squareRoot);
                obj.append("-" + squareRoot);
            }
        });
    } //Displays square root in the case of a -ve number
    else {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                obj.append("Square roots of -" + number + " are ");
                obj.append("+" + squareRoot + " i");
                obj.append("-" + squareRoot + " i");
            }
        });
    }

}

例如...

关于这里，我认为 SwingWorker 会更有用

看看：

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