Shader.TileMode有3種引數可供選擇，分別為CLAMP、REPEAT和MIRROR：

CLAMP的作用：是如果渲染器超出原始邊界範圍，則會複製邊緣顏色對超出範圍的區域進行著色

REPEAT的作用是：在橫向和縱向上以平鋪的形式重複渲染點陣圖

MIRROR的作用是：在橫向和縱向上以映象的方式重複渲染點陣圖

注意：通常，引數positions設為null，表示顏色陣列以斜坡線的形式均勻分佈。

public class GradientTextView extends TextView
{

	private LinearGradient mLinearGradient;
	private Matrix mGradientMatrix;
	private Paint mPaint;
	private int mViewWidth = 0;
	private int mTranslate = 0;

	private boolean mAnimating = true;

	public GradientTextView(Context context, AttributeSet attrs)
	{
		super(context, attrs);
	}

	@Override
	protected void onSizeChanged(int w, int h, int oldw, int oldh)
	{
		super.onSizeChanged(w, h, oldw, oldh);
		if (mViewWidth == 0)
		{
			//getWidth得到是某個view的實際尺寸.
			//getMeasuredWidth是得到某view想要在parent view裡面佔的大小.
			mViewWidth = getMeasuredWidth();
			if (mViewWidth > 0)
			{
				mPaint = getPaint();
				//線性漸變
				mLinearGradient = new LinearGradient(-mViewWidth, 0, 0, 0, new int[]
				{ 0x33ffffff, 0xffffffff, 0x33ffffff }, new float[]
				{ 0, 0.5f, 1 }, Shader.TileMode.CLAMP);
				mPaint.setShader(mLinearGradient);
				mGradientMatrix = new Matrix();
			}
		}
	}

	@Override
	protected void onDraw(Canvas canvas)
	{
		super.onDraw(canvas);
		if (mAnimating && mGradientMatrix != null)
		{
			mTranslate += mViewWidth / 10;
			if (mTranslate > 2 * mViewWidth)
			{
				mTranslate = -mViewWidth;
			}
			mGradientMatrix.setTranslate(mTranslate, 0);
			mLinearGradient.setLocalMatrix(mGradientMatrix);
			//50ms重新整理一次
			postInvalidateDelayed(50);
		}
	}

}