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Building Android UIs with Custom Views by Raimon Ràfols Montané

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Creating the basic circular activity indicator

The Canvas class provides us with many drawing functions; for example:

  • drawArc()
  • drawBitmap()
  • drawOval()
  • drawPath()

To draw a circular activity indicator, we can use the drawArc() method. Let's create the basic class and draw an arc:

public class CircularActivityIndicator extends View { 
    private static final int DEFAULT_FG_COLOR = 0xffff0000; 
    private static final int DEFAULT_BG_COLOR = 0xffa0a0a0; 
    private Paint foregroundPaint; 
    private int selectedAngle; 
 
    public CircularActivityIndicator(Context context, AttributeSet attributeSet) { super(context, attributeSet); foregroundPaint = new Paint(); foregroundPaint.setColor(DEFAULT_FG_COLOR); foregroundPaint.setStyle(Paint.Style.FILL); selectedAngle ...

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