java - 我有两个类，想要从一个类到另一个类获取一个变量

Question

我有两个类。绘制和绘制GUI。在 DrawGUI 中我有一个 JPanel。对于我的 JUnit 测试，我需要向 Draw 类询问 getWidth() 和 getHeight()。所以我的代码如下:

public class Draw {
public static void main(String[] args) throws ColorException {new Draw();}

/** Application constructor:  create an instance of our GUI class */
  public Draw() throws ColorException { window = new DrawGUI(this); }

  protected JFrame window;

  public void getWidth(){
  }


}

class DrawGUI extends JFrame {
  JPanel drawPanel;

  public DrawGUI(Draw application) throws ColorException {
    super("Draw");        // Create the window
    app = application;

    drawPanel = new JPanel();
  }
}

那么如何实现 getWidth 呢？ getWidth 应该返回 JPanel drawPanel 的宽度

Answer 1

一种选择是更改您保存窗口的弱类型:

public class Draw {
    public static void main(String[] args) throws ColorException {new Draw();}

    /** Application constructor:  create an instance of our GUI class */
    public Draw() throws ColorException { window = new DrawGUI(this); }

    protected DrawGUI window;  // <- is now a DrawGUI

    public int getWidth(){
        return window.getPanelWidth();
    }

}

class DrawGUI extends JFrame {
    JPanel drawPanel;
    ...

    public DrawGUI(Draw application) throws ColorException {
        super("Draw");        // Create the window
        app = application;

        drawPanel = new JPanel();
    }

    public int getPanelWidth() {  // <- added method to get panel width
        return drawPanel.getWidth();
    }
}

还有其他选择。您也可以只为整个面板制作一个 setter/getter ，但这样您的封装就会减少。

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