Android自定义评分控件：RatingStarView

private static final float[] starVertexes = new float[]{
        -0.9511f, 0.3090f,         // E (left)
        0.0000f, 1.0000f,         // A (top vertex)
        0.9511f, 0.3090f,         // B (right)
        0.5878f, -0.8090f,        // C (bottom right)
        -0.5878f, -0.8090f,        // D (bottom left)
};

class VertexF {
    public VertexF() {
    }

    public VertexF(float x, float y) {
        this.x = x;
        this.y = y;
    }

    public float x;
    public float y;

    public VertexF next;
}

public class RatingStarView extends View;

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);
    int widthSize = MeasureSpec.getSize(widthMeasureSpec);
    int heightSize = MeasureSpec.getSize(heightMeasureSpec);

    float width;
    int height; // must have height

    if (heightMode == MeasureSpec.EXACTLY) {
        height = heightSize;
    } else {
        height = DEFAULT_STAR_HEIGHT;
        if (heightMode == MeasureSpec.AT_MOST) {
            height = Math.min(height, heightSize);
        }
    }

    float starHeight = height - getPaddingBottom() - getPaddingTop();

    if (widthMode == MeasureSpec.EXACTLY) {
        // Parent has told us how big to be. So be it.
        width = widthSize;
    } else {
        // get the perfect width
        width = getPaddingLeft() + getPaddingRight();
        if (starNum > 0) {
            if (starHeight > 0) {
                width += starMargin * (starNum - 1);
                width += StarModel.getStarWidth(starHeight) * starNum;
            }
        }

        if (widthMode == MeasureSpec.AT_MOST) {
            width = Math.min(widthSize, width);
        }
    }  

    int widthInt = (int) (width);
    if (widthInt < width) {
        widthInt++;
    }

    setMeasuredDimension(widthInt, height);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    if (h != oldh) {
        calcStars();
    }
}

/**
 * Create all stars data, according to the contentWidth/contentHeight.
 */
private void calcStars() {
    int paddingLeft = getPaddingLeft();
    int paddingTop = getPaddingTop();
    int paddingRight = getPaddingRight();
    int paddingBottom = getPaddingBottom();
    int contentWidth = getWidth() - paddingLeft - paddingRight;
    int contentHeight = getHeight() - paddingTop - paddingBottom;

    int left = paddingLeft;
    int top = paddingTop;

    // according to the View's height , make star height.
    int starHeight = contentHeight;
    if (contentHeight > contentWidth) {
        starHeight = contentWidth;
    }

    if (starHeight <= 0) return;
    float startWidth = StarModel.getStarWidth(starHeight);

    // starCount * startWidth + (starCount - 1) * starMargin = contentWidth
    int starCount = (int) ((contentWidth + starMargin) / (startWidth + starMargin));
    if (starCount > starNum) {
        starCount = starNum;
    }

    starList = new ArrayList<>(starCount);

    for (int i = 0; i < starCount; i++) {
        StarModel star = new StarModel(starThicknessFactor);
        starList.add(star);
        star.setDrawingOuterRect(left, top, starHeight);
        left += startWidth + 0.5f + starMargin;
    }
    ...
}

/**
 * Draw the specified path using the specified paint. The path will be
 * filled or framed based on the Style in the paint.
 *
 * @param path  The path to be drawn
 * @param paint The paint used to draw the path
 */
public void drawPath(@NonNull Path path, @NonNull Paint paint)

/**
 * Set or clear the patheffect object.
 * <p />
 * Pass null to clear any previous patheffect.
 * As a convenience, the parameter passed is also returned.
 *
 * @param effect May be null. The patheffect to be installed in the paint
 * @return       effect
 */
public PathEffect setPathEffect(PathEffect effect)

@Override
public boolean onTouchEvent(MotionEvent event) {
   if (event.getAction() == MotionEvent.ACTION_DOWN) {
       clickedX = event.getX();
       clickedY = event.getY();
   }
   return super.onTouchEvent(event);
}

allprojects {
    repositories {
        ...
        maven { url 'https://jitpack.io' }
    }
}

dependencies {
    compile 'com.github.everhad:AndroidRatingStar:v1.0.1'
}

<com.idlestar.ratingstar.RatingStarView
     app:cornerRadius="4dp"
     app:starMargin="12dp"
     app:strokeWidth="2px"
     app:strokeColor="#457DD7"
     app:starForegroundColor="#DB6958"
     app:starBackgroundColor="#E8E8E8"
     app:starNum="5"
     app:rating="1"
     app:enableSelectRating="true"
     app:starThickness="0.7"
     android:layout_marginTop="8dp"
     app:drawStrokeForEmptyStar="false"
     app:drawStrokeForHalfStar="true"
     android:paddingTop="2dp"
     android:paddingLeft="0dp"
     android:paddingRight="0dp"
     android:background="#fff"
     android:layout_width="wrap_content"
     android:layout_height="40dp" />

@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  RatingStarView rsv_rating = (RatingStarView) findViewById(R.id.rsv_rating);
  rsv_rating.setRating(1.5f);
}