如何更改默认的擦除颜色在涂料中的应用在Android中？ [英] How to change default erase color in paint application in Android?

问题描述

我做的，我要删除与事件画线的应用。为此，我使用

I make an Application in which I want to erase drawing lines with event. For this I used

mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

但删除一行时，该行成为黑先擦除。我希望有一个透明的颜色擦除绘制路径。

but at the time of erasing a line, that line becomes black first then erased. I want a transparent color for erasing a drawing a path.

推荐答案

以下适用于消除在一个透明的背景...

The below works for erasing on a transparent background...

呼叫SetErase（真）开始擦除。

Call SetErase(true) to start erasing.

在OnDraw的方法再画一个白色的路径（而不是黑色），这将随后得到清除，以透明色，你把所有的路撤销信息。

The OnDraw method will then draw a white path (instead of black)which will then get cleared to the transparent color and you keep all your path undo info.

呼叫SetErase（）来切换消除开/关

Call SetErase() to toggle erasing on/off

    public void SetErase(bool On)
    {
        if (On)
        {
            if (!_erasing)
            {
                _delpaint = new Paint(_paint);
                _delpaint.Color = Color.White; 
                _paint.SetXfermode(new PorterDuffXfermode(PorterDuff.Mode.Clear));
                _erasing = true;
            }
        }
        else if (_erasing)
        {
            _erasing = false;
            _paint.SetXfermode(null);
        }
    }

    protected override void OnDraw(Canvas canvas)
    {
        canvas.DrawColor(BackgroundColor);
        canvas.DrawBitmap(CanvasBitmap, 0, 0, _bitmapPaint);
        if (_erasing)
        {
            canvas.DrawPath(_path, _delpaint); // draw white path
        }
        else
        {
            canvas.DrawPath(_path, _paint);
        }
    }

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