<?xml version="1.0" encoding="utf-8"?>
<resources>
  <declare-styleable name="RatingStar">
    <attr name="starNormal" format="reference"/>
    <attr name="starFocus" format="reference"/>
    <attr name="starNumber" format="integer"/>
  </declare-styleable>
</resources>

/**
 * Created by Michael on 2019/11/1.
 */
 
public class RatingStar extends View {
 
  private int normalId;
  private int focusId;
  private Bitmap normalImg;
  private Bitmap focusImg;
  private int number;
  private int w1;
  private int h1;
  private int marginLeft;
  private int marginTop;
  private int marginBottom;
  private int marginRight;
  private int height;
  private int width;
  private int p;
  private float w0;
  private int i0;
  private int mGrade;
 
  public RatingStar(Context context) {
    this(context,null);
  }
 
  public RatingStar(Context context, @Nullable AttributeSet attrs) {
    this(context, attrs,0);
  }
 
  public RatingStar(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    TypedArray array = context.obtainStyledAttributes(attrs,R.styleable.RatingStar);
    normalId = array.getResourceId(R.styleable.RatingStar_starNormal,0);
    focusId = array.getResourceId(R.styleable.RatingStar_starFocus,0);
    normalImg = BitmapFactory.decodeResource(getResources(), normalId);
    focusImg = BitmapFactory.decodeResource(getResources(), focusId);
    number = array.getInteger(R.styleable.RatingStar_starNumber,5);
    array.recycle();
    i0 = -1;
 
  }
 
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    w1 = normalImg.getWidth();
    h1 = normalImg.getHeight();
    //中間間隔
    p = 30;
    marginTop = 20;
    marginBottom = 20;
    marginLeft = 20;
    marginRight = 20;
    height = h1 + marginTop + marginBottom;
    width = w1 *number+(number-1)*p +marginLeft+marginRight;
    setMeasuredDimension(width, height);
  }
 
  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    for (int i = 0; i < number; i++) {
      if (i <= i0){
        canvas.drawBitmap(focusImg,i*w1+marginLeft+i*p,marginTop,null);
        mGrade = i+1;
      }else{
        canvas.drawBitmap(normalImg,i*w1+marginLeft+i*p,marginTop,null);
      }
    }
    Log.e("msg","我被調用了！");
 
  }
 
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    float x = event.getX();//相對于控件自身的距離
    //event.getRawX() 相對于屏幕的距離
    switch (event.getAction()){
      case MotionEvent.ACTION_DOWN:
      case MotionEvent.ACTION_MOVE:
      //case MotionEvent.ACTION_UP:
        w0 = getWidth()/5;
        i0 = (int) (x/w0);
        //性能優(yōu)化，減少onDraw()調用
        if (mGrade == i0+1){
          return true;
        }
        invalidate();
        break;
    }
    return true;
  }
}

 <com.example.star.RatingStar
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:starNormal="@mipmap/star_normal"
    app:starFocus="@mipmap/star_selected"
    app:starNumber="5"
    />