清除画布Canvas.drawColor（） [英] Clearing canvas with Canvas.drawColor()

问题描述

我试图更改自定义视图取得了一些成功的背景图像。图像将改变，但问题是，我仍然看到旧形象的痕迹。当我试图清除画布上绘制新的图像之前，它不会出现工作。我创建了一个位图来存储图像。改变图像的时候，我打电话Canvas.drawColor（）绘制新的形象出现，但旧的图像仍然存在。我试过drawColor（0），drawColor（Color.BLACK），c.drawColor（0，PorterDuff.Mode.CLEAR），并没有上述作品。因此，我不得不发布此审查从有经验的头脑比我的。

实际code是如下：

 私人诠释BGND;
私人布尔切换;

公共无效setBgnd（INT进入）{
    开关= TRUE;
    开关（进入）{

    案例R.drawable.image1：
        BGND =传入;
        this.invalidate（）;
        打破;

    案例R.drawable.image2：
        BGND =传入;
        this.invalidate（）;
        打破;

    }
}



保护无效的OnDraw（帆布C）{
    如果（切换==真）{
        位图B = BitmapFactory.de codeResource（getResources（），BGND）;
        c.drawColor（0，PorterDuff.Mode.CLEAR）;
        c.drawBitmap（二，0，0，NULL）;
        开关= FALSE;

    }其他{
        位图B = BitmapFactory.de codeResource（getResources（），BGND）;
        c.drawBitmap（二，0，0，NULL）;
    }
}
 

解决方案

和你一样，我挣扎着如何清除顶层/ surfaceview在我的多层/ surfaceview应用程序。经过2天的搜索和编码，我发现我自己的路，这是我清除了绘图画布，可以具有多层/ surfaceviews时使用它。背景层不会被覆盖着黑色的，那就是绝招。

 油漆涂料=新的油漆（）;
paint.setXfermode（新PorterDuffXfermode（Mode.CLEAR））;
canvas.drawPaint（油漆）;
paint.setXfermode（新PorterDuffXfermode（Mode.SRC））;
//开始自己的绘图
 

i'm attempting to change the background image of a custom View with some success. the image will change but the problem is that i still see traces of the old image. when i attempt to clear the canvas before drawing the new image, it doesn't appear to work. i create a bitmap to store the image. when changing the image, i call Canvas.drawColor() before drawing the new image but the old image persists. i've tried drawColor(0), drawColor(Color.BLACK), c.drawColor(0, PorterDuff.Mode.CLEAR), and none of the above works. as such, i had to post this for review from more experienced minds than mine.

the actual code is as follows:

private int bgnd;
private boolean switching;

public void setBgnd(int incoming){
    switching = true;
    switch (incoming){

    case R.drawable.image1:
        bgnd = incoming;
        this.invalidate();
        break;

    case R.drawable.image2:
        bgnd = incoming;
        this.invalidate();
        break;

    }
}



protected void onDraw(Canvas c){
    if(switching == true){
        Bitmap b = BitmapFactory.decodeResource(getResources(), bgnd);
        c.drawColor(0, PorterDuff.Mode.CLEAR);
        c.drawBitmap(b, 0, 0, null);
        switching = false;

    }else{
        Bitmap b = BitmapFactory.decodeResource(getResources(), bgnd);
        c.drawBitmap(b, 0, 0, null);
    }
}

解决方案

Just like you, I struggled how to clear a top layer/surfaceview in my multiple layer/surfaceview app. After 2 days searching and coding, I found out my own way and this is how I cleared a canvas before drawing, you can use it when having multiple layers/surfaceviews. The background layer will not be covered with black, that is the trick.

Paint paint = new Paint();
paint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));
canvas.drawPaint(paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC));
// start your own drawing

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