public class PlayText extends android.support.v7.widget.AppCompatTextView {

private Paint mPaint;
private int mWidth;
private LinearGradient mLinearGradient;
private Matrix mMatrix;
private int mTranslate;

public PlayText(Context context) {
    this(context,null);
}

public PlayText(Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
}


@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    mWidth = getMeasuredWidth();
    if (mWidth == 0 ){
        mWidth = getMeasuredWidth();
    }
    if (mWidth > 0 ){
        mPaint = getPaint();
        //参数一为渐变起初点坐标x位置，参数二为y轴位置，参数三和四分辨对应渐变终点，参数五是参与渐变效果的颜色集合,参数六是是定义每个颜色处于的渐变相对位置,最后参数为平铺方式，这里设置为镜像
        mLinearGradient = new LinearGradient(0,0,mWidth,0,new int[]{
                Color.BLUE,0xffffffff,Color.RED,Color.GREEN
        },null, Shader.TileMode.CLAMP);
        mPaint.setShader(mLinearGradient);
        mMatrix = new Matrix();
    }

}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if (mMatrix != null) {
        mTranslate += mWidth/5;
        if (mTranslate > 2*mWidth){
            mTranslate = -mWidth;
        }
        mMatrix.setTranslate(mTranslate,0);
        mLinearGradient.setLocalMatrix(mMatrix);
        postInvalidateDelayed(100);
    }
}

}