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Android - Basic Steps (Graphics)

Graphics


2D Graphics, it can be draw in two ways
  • Views
    • Simple graphics, little or no update
    • Shapes can be defined in xml files in res/drawable folder
  • Canvas
    • Complex graphics with regular updates
    • It allow to use methods like
      • drawText()
      • drawPoints()
      • drawColors()
    • Also the canvas use the class Paint for parameters
      • setStrokeWidth()
      • setTextSize()

Drawable class

It can draw using 
  • ShapeDrawable
    • Draw primitive shapes represented by classes as
      • PathShape - Lines
      • RectShape
      • OvalShape
  • BitmapDrawable
  • ColorDrawale
You can draw programmatically or using an xml file

SurfaceView

  • Manages a Low-level drawing area called a surface
  • The surface represents a drawing area within the view hierarchy
Use of SurfaceView
  • Call method getHolder() to acquire its SurfaceHolder
  • Register for callbacks with addCallack()
    • surfaceCreated() - Until this method is call you can't draw
    • surfaceChanged()
    • surfaceDestroyed()
  • Create thread on which drawing operation will execute
  • Lock on canvas using SurfaceHolder.lockCanvas()
  • Draw with Canvas.drawBitmap()
  • Unlock canvas with SurfaceHolder.unlockCanvasAndPost()

Animation

For animate the View are the following classes:

  • TransitionDrawable
  • AnimationDrawable
  • Animation
    • Properties
      • ValueAnimator - Time engine
      • TimeInterpolator - Defines how values changes as a function of time
      • AnimatorUpdateListener - called back at every animation frame change
      • TypeEvaluator - Calculates a property's value at a given point in time




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