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重写Java中的构造函数

override constructor inheritance java

0

cutsoy · 技术社区 · 16 年前

我创建了一个超类(也可以用作基类):

public class CellView {
    public CellViewHelper helper; // CellViewHelper is just an example

    public CellView() {
        this.helper = new CellViewHelper();
        this.helper.someVariable = <anything>;

        System.out.println("CellView_constructor");
    }
    
    public void draw() {
        System.out.println("CellView_draw");
    }

    public void needsRedraw() {
        this.draw();
    }

}

public class ImageCellView extends CellView {

    public Image someImage;

    public ImageCellView() {
        super();
        this.someImage = new Image();
        System.out.println("ImageCellView_constructor");
    }

    public void setSomeParam() {
        this.needsRedraw(); // cannot be replaced by this.draw(); since it's some more complicated.
    }

    @Override public void draw() {
        super.draw();
        System.out.println("ImageCellView_draw");
    }

}

现在,当我这样称呼它:

ImageCellView imageCellView = new ImageCellView();
imageCellView.setSomeParam();

我明白了:

CellView\u构造函数

但是,我希望它是:

ImageCellView\u构造函数

ImageCellView\u绘图

提前谢谢,

提姆

我还在CellView中实现了这个方法:

public void needsRedraw() {
    this.draw();
}

以下是ImageCellView:

public void setSomeParam() {
    this.needsRedraw(); // cannot be replaced by this.draw(); since it's some more complicated.
}

我一直在说:

ImageCellView ImageCellView=新建ImageCellView();

这是否会导致问题(当我从super调用函数时,它会调用super

2 回复 | 直到 6 年前

1

2

YoK 16 年前

你应该得到适当的输出。

我试过你的例子只是评论了一些不相关的东西:

import java.awt.Image;

public class CellView {
    //public CellViewHelper helper; // CellViewHelper is just an example

    public CellView() {
        //this.helper = new CellViewHelper();
        //this.helper.someVariable = <anything>;

        System.out.println("CellView_constructor");
    }

    public void draw() {
        System.out.println("CellView_draw");
    }

    public static void main(String[] args) {
        ImageCellView imageCellView = new ImageCellView();
        imageCellView.draw();
    }
}

class ImageCellView extends CellView {

    public Image someImage;

    public ImageCellView() {
        super();
        //this.someImage = new Image();
        System.out.println("ImageCellView_constructor");
    }

    @Override public void draw() {
        super.draw();
        System.out.println("ImageCellView_draw");
    }

}

我得到以下结果:

CellView\u构造函数

ImageCellView\u绘图

这正是你想要的,这就是你的代码打印。

2

1

akf 16 年前

简单的回答是“你不能”

对象是自下而上构造的,在子类初始化器之前调用基类初始化器,在子类构造函数之前调用基类构造函数。

编辑:

根据你的编辑,你的代码看起来不错。我会完成一些平凡的任务,比如确保在添加代码之后编译代码 System.out.println 调用子类