如何让 class 添加到我的绘画功能中？

Question

我知道这句话措辞不好，但我不知道怎么说才好。本质上我有自己的 JComponent MyComponent 并且它在其图形上绘制了一些东西。我想让它绘制它的东西，然后调用一个方法来完成绘制，这里是一个例子：

public class MyComponent extends JComponent{
    // etc
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g2 = (Graphics2D)g;
        g2.drawSomething(); // etc

        // Once it is done, check if that function is exists, and call it.
        if(secondaryPaint != null){
            secondaryPaint(g2);
        }
    }
}

然后，在另一个 class 中：

// etc
MyComponent mc = new MyComponent()
mc.setSecondaryDrawFunction(paint);

// etc

private void paint(Graphics2D g2){
    g2.drawSomething();
}

我不确定 lambda 是如何工作的，或者它们是否适用于这种情况，但也许吧？

Answer 1

没有 lambda，但 Function 接口可以工作

你可以做到：

public class MyComponent extends JComponent{
    // etc
    Function<Graphics2D, Void> secondaryPaint;
    public MyComponent(Function<Graphics2D, Void> myfc){
        secondaryPaint = myfc;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        //g2.drawSomething(); // etc

        // Once it is done, check if that function is exists, and call it.
        if(secondaryPaint != null){
            secondaryPaint.apply(g2);
        }
    }

    static class Something {
        public static Void compute(Graphics2D g){
            return null;
        }

        public Void computeNotStatic(Graphics2D g){
            return null;
        }
    }

    public static void main(String[] args) {
        Something smth = new Something();
        new MyComponent(Something::compute); // with static
        new MyComponent(smth::computeNotStatic); // with non-static
    }
}

如何让 class 添加到我的绘画功能中？

How can I let a class add onto my paint function?

java

jcomponent