一、先来看下效果图

二、实现思路与原理

1、字体渐变色，只需要给TextView的Paint添加渐变色shader即可

 @Override
 protected void onDraw(Canvas canvas) {
      LinearGradient linearGradient = new LinearGradient(0, 0, getWidth(), 0,  gradientColors, gradientPositions, Shader.TileMode.CLAMP);

      getPaint().setShader(linearGradient);
      super.onDraw(canvas);

 }

2、字体加粗边在绘制TextView之前，先给TextView的画笔设置画笔宽度，然后先绘制粗边再把画笔宽度设置回去，然后再绘制原本的内容

@Override
protected void onDraw(Canvas canvas) {
    TextPaint textPaint = getPaint();
    Paint.Style oldStyle = textPaint.getStyle();
    //首先设置画笔宽度就出现粗边
    textPaint.setStrokeWidth(strokeWidth);
    textPaint.setStyle(Paint.Style.FILL_AND_STROKE);
    //如需渐变色加上shader
    LinearGradient linearGradient = new LinearGradient(0, 0, getWidth(), 0,  gradientColors, gradientPositions, Shader.TileMode.CLAMP);
    textPaint.setShader(linearGradient);
    //然后调用 super.onDraw(canvas) 就绘制出来了
    super.onDraw(canvas);

    //绘制完粗边接着把画笔宽度设置回去
    textPaint.setStrokeWidth(0);
    textPaint.setStyle(oldStyle);
    //如需渐变色加上shader
    LinearGradient linearGradient = new LinearGradient(0, 0, getWidth(), 0,  gradientColors, gradientPositions, Shader.TileMode.CLAMP);
    textPaint.setShader(linearGradient);
    //然后再绘制原本内容
    super.onDraw(canvas);
}

三、我已经将项目开源，可以直接使用，Github开源地址：

https://github.com/FlyJingFish/GradientTextView

使用起来非常简单，例如：

<com.flyjingfish.gradienttextviewlib.GradientTextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="10dp"
    android:text=" Hello World! "
    android:textColor="@color/white"
    android:textSize="30sp"
    app:gradient_angle="0"
    app:gradient_endColor="@color/white"
    app:gradient_startColor="@color/teal_200"
    app:gradient_stroke_angle="0"
    app:gradient_stroke_strokeWidth="6dp"
    app:gradient_stroke_textColor="@color/purple_700" />