这必须是一个简单的人，但我真的很茫然......下面code绘制一个矩形，由左到右，从白到黑的线性渐变去，

This must be an easy one but I'm really at a loss... The following code draws a rectangle with a linear gradient going from left to right, from white to black,

int x1 = 0, y1 = 0, x2 = 100,  y2 = 40;
Shader shader = new LinearGradient(x1, y1, x2, y2, Color.WHITE, Color.BLACK, TileMode.CLAMP);
Paint paint = new Paint();
paint.setShader(shader);
canvas.drawRect(new RectF(x1, y1, x2, y2), paint);

好了，挺好的。现在我想要做的就是要改变这种渐变成水平一体，使颜色变从白到黑，从上到下。我试图做的是增加：

Ok, fine. Now what I'd like to do is to change this gradient into a horizontal one, so that the color goes from white to black, from top to bottom. What I tried to do is to add:

Matrix trans = new Matrix();
trans.setRotate(90);
shader.setLocalMatrix(trans);

而是梯度推移在一个有趣的天使，或有只是一个单一的颜色......我也试过用各种方式渐变的坐标打（想，也许他们应该转变）无无济于事。我在想什么？

but instead the gradient goes at a funny angel, or there is just a single color... I also tried to play with the coordinates of the gradient in all sorts of way (thinking that maybe they should be transformed) to no avail. What am I missing?

推荐答案

这并不是说我已经做了很多的Andr​​oid代码，但肯定所有你需要做的是：

Not that I've done much android coding, but surely all you need to do is:

int x1 = 0, y1 = 0, x2 = 0,  y2 = 40;

把X永远不会改变渐变只在y一样。

So the x never changes in the gradient only the y does.

所以基本上：

Shader shader = new LinearGradient(0, 0, 0, 40, Color.WHITE, Color.BLACK, TileMode.CLAMP);
Paint paint = new Paint(); 
paint.setShader(shader); 
canvas.drawRect(new RectF(0, 0, 100, 40), paint);