Android Custom Views Masterclass

Explore the scaffold of a custom view by extending the base view class, overriding constructors, and implementing onSizeChanged and onDraw to initialize size-dependent values and render on the canvas.

Explore how Android views use a screen-aligned coordinate system with x and y axes, where each view’s getX and getY are relative to its parent’s origin, not the screen.

Draw a circle in Android Studio with canvas draw circle and a center. Fetch color from colors.xml via context compat and compute center coordinates and radius in size change.

Master the concepts of view positioning in Android custom views, including left, translationX, and x properties, and learn how the layout system and UI post calls affect post-layout updates.

Explore the basics of animations, defined as gradual changes of properties over time, and learn how motion provides visual feedback, ripple effects, progress indicators, and data visualization in Android apps.

Learn to use the Path class to draw custom shapes, such as an equilateral triangle, via moveTo, lineTo, and close, with padding and anti-aliasing for smooth edges.

Practice drawing a green check mark in an Android custom view, then animate it, scaling to fit width or height, calculating vertices from a right triangle, and animating the path.

Build a states progression indicator in a custom view that auto sizes to content, draws bullet points and names with active and inactive colors, and uses invalidate and requestLayout appropriately.

Master rotating elements in Android custom views with matrices by translating to a pivot and applying rotation. Learn that the operation order matters for rotation around the pivot.

Concatenate matrices to perform multiple transformations in one operation with the standard matrices api, and learn to order post scale, post rotate, and post translate.

Explore a solution to exercise nine, implementing a draggable crosshair with fractional positions for save state and restore, and canvas transformations that draw four rotated hairs.

Learn to implement a custom two-finger rotation gesture detector in Android, handling multi-touch pointers, angle calculation, and rotation begin/end callbacks, since Android lacks a built‑in rotation detector.

Design an interactive smiley with matrix transformations enabling drag, scale, and rotate gestures, using scale and rotation gesture detectors, and preserve state across configuration changes and process death.

Master matrix transformations, combining translation, scaling, and rotation into a single matrix with inverse options, and learn gesture detection for taps, long presses, and two-finger scales, rotation requires custom code.