ProgressView

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <declare-styleable name="ProgressView">
    <attr name="max" format="integer"/>
    <attr name="progress" format="integer"/>
    <attr name="progressColor" format="color"/>
    <attr name="backgroundColor" format="color"/>
  </declare-styleable>
</resources>

ProgressView.java

public class ProgressView extends View {
  private static final int DEFAULT_PROGRESS = 0;
  private static final int DEFAULT_PROGRESS_MAX = 100;
  private static final int DEFAULT_COLOR_BACKGROUND = Color.GRAY;
  private static final int DEFAULT_COLOR_PROGRESS = Color.BLUE;

  private Paint paintProgress;
  private Paint paintProgressBackground;

  private int height;
  private int width;
  private int max;
  private int progress;

  public ProgressView(Context context) {
    this(context, null);
  }

  public ProgressView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }

  public ProgressView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init(context, attrs);
  }

  @TargetApi(Build.VERSION_CODES.LOLLIPOP)
  public ProgressView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    super(context, attrs, defStyleAttr, defStyleRes);
    init(context, attrs);
  }

  @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    width = MeasureSpec.getSize(widthMeasureSpec);
    height = MeasureSpec.getSize(heightMeasureSpec);
  }

  @Override protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawRect(0, 0, width, height, paintProgressBackground);
    canvas.drawRect(0, 0, calculateProgressPosition(progress), height, paintProgress); // TODO
  }

  private void init(Context context, AttributeSet attrs) {

    final TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ProgressView);
    setMax(typedArray.getInt(R.styleable.ProgressView_max, DEFAULT_PROGRESS_MAX));
    setProgress(typedArray.getInt(R.styleable.ProgressView_progress, DEFAULT_PROGRESS));
    int progressColor =
        typedArray.getColor(R.styleable.ProgressView_progressColor, DEFAULT_COLOR_PROGRESS);
    int backgroundColor =
        typedArray.getColor(R.styleable.ProgressView_backgroundColor, DEFAULT_COLOR_BACKGROUND);
    typedArray.recycle();

    paintProgressBackground = new Paint();
    paintProgressBackground.setColor(backgroundColor);
    paintProgressBackground.setStyle(Paint.Style.FILL);
    paintProgressBackground.setAntiAlias(true);

    paintProgress = new Paint();
    paintProgress.setColor(progressColor);
    paintProgress.setStyle(Paint.Style.FILL);
    paintProgress.setAntiAlias(true);
  }

  private int calculateProgressPosition(int currentProgress) {
    if (max == 0) {
      return 0;
    }
    return (currentProgress * width) / max;
  }

  public void reset() {
    progress = 0;
    invalidate();
  }

  public int getMax() {
    return max;
  }

  public void setMax(int max) {
    if (max < 0) {
      max = 0;
    }
    if (max < progress) {
      max = progress;
    }
    this.max = max;
    invalidate();
  }

  public int getProgress() {
    return progress;
  }

  public void setProgress(int progress) {
    if (progress < 0) {
      progress = 0;
    }
    if (progress > max) {
      progress = max;
    }
    this.progress = progress;
    invalidate();
  }
}