Android Custom View Knowledge points

Learn and summarize according to the knowledge points provided by Hencoder.

Three points:

1. Layout
2. Draw
3. Touch Feedback

Draw

• Custom Draw: Implement the drawing process by yourself
• Common drawing methods OnDraw (canvas canvas)
• Draw key:
  1. Canvas: Drawing Tools
     • Drawing class methods
     • Drawcircle (): Draw a circle
     • DrawRect (): Draw Square
     • DrawPath (): Draw route
     • DrawText (): Drawing text
     • Drawbitmap (): Painting bitmap
     • Drawing Accessibility Tools
     • Crop the drawing range
     • Geometric transformations for drawing content
       
  2. Paint: Original paint, Android middle finger to strengthen the pigment, can be set in various styles, such as hollow or solid or thickness, etc.
  3. Drawing order: Android is drawn in order. Drawing foreground (forground) and background (BackGround) In addition to the OnDraw () Drawing body part

Example: Paint Common settings:

• Mpaint.setcolor (color.red): Set color
• Mpaint.setstyle (Style.stroke): Set drawing mode
• Mpaint.setstrokewidth (20): Set line switch
• Mpaint.setantialias (TRUE): Set anti-aliasing

Cancan drawing a class method drawing color

* canvas.drawColor(Color.RED);* canvas.drawColor(Color.parseColor("#00ff00"));* canvas.drawColor(Color.parseColor("#8800ff00"));* canvas.drawRGB(255, 0, 0);* canvas.drawARGB(100, 255, 0, 0);

Draw a Circle

1. 实心圆：         mPaint = new Paint();        canvas.drawCircle(100, 100, 50, mPaint);2. 空心圆          mPaint.setStyle(Style.STROKE);        canvas.drawCircle(200, 200, 50, mPaint);3. 蓝色实心圆        mPaint.setStyle(Style.FILL);        mPaint.setColor(Color.BLUE);        canvas.drawCircle(200, 400, 50, mPaint);4. 线宽为20的空心圆        mPaint.setStyle(Style.STROKE);        mPaint.setStrokeWidth(20);        canvas.drawCircle(400, 200, 50, mPaint);

Draw Ellipse

    canvas.drawOval(300, 100, 700, 300, mPaint);

Draw a rectangle

    canvas.drawRect(250, 500, 700, 800, mPaint);    //    Rect tem1 = new Rect(250, 500, 700, 800);    canvas.drawRect(tem1, mPaint);    //    RectF tem2 = new RectF(250, 500, 700, 800);    canvas.drawRect(tem2, mPaint);

Draw rounded rectangles

    RectF t = new RectF(150, 200, 500, 350);    canvas.drawRoundRect(t, 50, 50, mPaint);    //    canvas.drawRoundRect(150, 200, 500, 350, 50, 50, mPaint);

Draw arcs or fans

• DrawArc (float left, float top, float right, float bottom, float startangle,float sweepAngle, Boolean usecenter, Paint pain T
  * Left,top,right,bottom: Ellipse where arc is located
  * StartAngle: The starting angle of the arc (the positive direction of the x-axis, that is, the position of the right, 0 degrees). Clockwise is positive angle, counterclockwise is negative angle)
  * SweepAngle: Arc across the angle
  * Usecenter: Indicates a very connected center, 连接圆心是扇形不连接圆心是弧形

• Drawing arcs

  canvas.drawArc(200, 600, 800, 1000, 0, 47, false, mPaint);

• Draw sector

  canvas.drawArc(200, 600, 800, 1000, 0, 135, true, mPaint);

• Example:

  mPaint.setAntiAlias(true);mPaint.setStyle(Style.FILL);canvas.drawArc(200, 100, 800, 500, -110, 100, true, mPaint); // 绘制扇形canvas.drawArc(200, 100, 800, 500, 20, 140, false, mPaint); // 绘制弧形mPaint.setStyle(Paint.Style.STROKE); // 画线模式canvas.drawArc(200, 100, 800, 500, 180, 60, false, mPaint); // 绘制不封口的弧形

Draw a custom graphic

• DrawPath (path path, paint paint): Drawing graphics by describing paths
• Path: The object that describes the path

• Paint

• Path
• Direct Path Description
  1. addxxx ()--Add a child shape
  • addcircle (float x, float y, float radius, Direction dir), This method, like the Canvas's drawcircle (), draws a circular
    • description: Add circle
    • parameter x and parameter y: OK center
    • parameter radius: Determines the radius of the circle
    • dir: Draw the direction of the circular path, enum type, CW (clockwise) clockwise/CCW (counter-clockwise) counterclockwise
  • addarc (): Drawa with Canvas RC (), draw an arc or sector
  • addoval (): Like the canvas's DrawOval (), draw the ellipse
  • addrect (): Like the canvas's DrawRect (), Draw the rectangle
  • Addroundrect (): Draw rounded rectangles
  1. xxxto () As with Canvas's Drawroundrect ()--Draw lines (lines or curves)
  • LineTo (): Draw a line, draw a line from the current position to the target, X, y
  • Rlineto (): As with the LineTo () method, the parameter is relative to the current position
  • MoveTo (): Move to the target location
  • Rmoveto ()
  • Cubicto (): Draw three Bezier curves
  • Rcubicto ()
  • quadto (): Draw two Bezier curves
  • rquadto ()
  • ArcTo: Drawing arcs
  1. Close (): Encloses the current sub-shape, as with lineTo (starting coordinates)
• Auxiliary settings or calculations
  • Setfilltype (): Set fill mode
  • Even_odd: Odd-even principle, cross-fill mode, for any point in the plane, a ray in any direction, the number of times the ray and the graph intersect (intersection is calculated, tangent does not count) if it is odd, then this point is considered inside the graph, is to be painted area; This point is considered to be outside of the graph and is not a painted area.
  • Winding (default): Non-0 surround number principle, full fill mode
  • Inverse_even_odd
  • Inverse_winding

Draw Bitmap

• Drawbitmap ()

Draw text

• DrawText ()

Android Custom View Knowledge points