需要恢复图形原始状态当被覆盖的油漆或的paintComponent [英] The Need To Restore Graphics Original State When Overwritten paint or paintComponent

问题描述

我知道大多数的Java code，以覆盖油漆或paintComponent方法，大多没有恢复旧态图形对象后，他们不得不改变状态的图形对象。例如，setStroke，setRenderingHint ...

I realize most of the Java code to overwritten paint or paintComponent, most of them doesn't restore the old state of graphics object, after they had change the state of graphics object. For example, setStroke, setRenderingHint...

我不知道它是否是我们恢复回来显卡的老态对象，从方法返回前一个很好的做法。例如：

I was wondering whether it is a good practice that we restore back the old state of graphics object, before returning from the method. For example

public void paintComponent(Graphics g) {
    super.paintComponet(g);
    Stroke oldStroke = g.getStroke();
    g.setStroke(newStroke);
    // Do drawing operation.
    g.setStroke(oldStroke);
}

这是一个好的做法呢？或者是在做什么？

Is this a good practice? Or it is over done?

推荐答案

您不应改变图形在所有传入的对象，而在它的一个副本，然后您再进行处置执行所有图形操作。再也没有必要在所有然后复位状态。

You should not alter the Graphics object passed in at all, rather perform all your graphics operations on a copy of it which you then dispose. There'll be no need to reset the state at all then.

public void paintComponent(Graphics g1) {
    super.paintComponent(g1);
    final Graphics2D g = (Graphics2D)g1.create();
    try {
         // ...Whole lotta drawing code...
    } finally {
         g.dispose();
    }
}

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