在画布绘制的形状周围创建阴影？

Question

创建一个形状需要哪些步骤,例如使用Canvas从头开始带阴影的矩形？

在用于绘制矩形的绘制中添加阴影图层不会成功.

Answer 1

不需要Bitmap,只需将图层类型设置LAYER_TYPE_SOFTWARE为原始方法即可.

public class TestShapeShadow extends View
{
    Paint paint;

    public TestShapeShadow(Context context)
    {
       super(context);  

        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setShadowLayer(12, 0, 0, Color.YELLOW);

        // Important for certain APIs 
        setLayerType(LAYER_TYPE_SOFTWARE, paint);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {   
        canvas.drawRect(20, 20, 100, 100, paint);
    }
}

Answer 2

1. 创建.一个路径,添加一些元素

2. 将BlurMaskFilter设置为Paint

3. 用dx,dy阴影偏移绘制路径

4. 未设置掩码过滤器

5. 再画一条路,没有.抵消

Answer 3

我按照上面@pskink的想法找到了解决方案。我把代码片段放在这里给有需要的人。

如果你想知道影子属性是什么，你可以参考这个测试器：https : //okawa-h.github.io/box-shadow_tester/

public class MyViewWithShadow extends View {

    Paint paint;
    int mainColor;
    int shadowColor;

    // shadow properties
    int offsetX = -25;
    int offsetY = 30;
    int blurRadius = 5;

    public MyViewWithShadow(Context context)
    {
        super(context);

        mainColor = Color.RED;
        shadowColor = Color.BLACK; // this color can also have alpha

        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setStyle(Paint.Style.FILL);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {   
        // Create paint for shadow
        paint.setColor(shadowColor);
        paint.setMaskFilter(new BlurMaskFilter(
            blurRadius /* shadowRadius */,
            BlurMaskFilter.Blur.NORMAL));

        // Draw shadow before drawing object
        canvas.drawRect(20 + offsetX, 20 + offsetY, 100 + offsetX, 100 + offsetY, paint);

        // Create paint for main object
        paint.setColor(mainColor);
        paint.setMaskFilter(null);

        // Draw main object 
        canvas.drawRect(20, 20, 100, 100, paint);
    }
}