How to use android canvas to draw a Rectangle with only topleft and topright corners round?

For API 21 and above the Path class added a new method addRoundRect() which you can use it like this.

corners = new float[]{
    80, 80,        // Top left radius in px
    80, 80,        // Top right radius in px
    0, 0,          // Bottom right radius in px
    0, 0           // Bottom left radius in px
};

final Path path = new Path();
path.addRoundRect(rect, corners, Path.Direction.CW);
canvas.drawPath(path, mPaint);

in Kotlin

val corners = floatArrayOf(
    80f, 80f,   // Top left radius in px
    80f, 80f,   // Top right radius in px
    0f, 0f,     // Bottom right radius in px
    0f, 0f      // Bottom left radius in px
)

val path = Path()
path.addRoundRect(rect, corners, Path.Direction.CW)
canvas.drawPath(path, mPaint)