PieChart 笔记

1. 一个接口 Listener

OnCurrentItemChangedListener ：监听 item 变化

看一下定义：

public interface OnCurrentItemChangedListener {
  void OnCurrentItemChanged(PieChart source, int currentItem);
}

2. 四个内部类

Item ：存储 Item 的信息
PieView : 饼图
PointerView : 小黑点
GestureListener ：继承自 extends GestureDetector.SimpleOnGestureListener，自定义手势监听器

1. Item

/* 保存 item 状态信息 */
private class Item {
    public String mLabel;  //标签
    public float mValue;  // 值
    public int mColor;  // 颜色

    // computed values
    public int mStartAngle;  // 开始角度
    public int mEndAngle;  // 结束角度

    public int mHighlight;  // 高亮
    public Shader mShader;  // 着色器
}

2. PieView

• 首先定义3个参数

private class PieView extends View {
    // Used for SDK < 11  why? SDK < 11 不支持属性动画 Animator 
    private float mRotation = 0; //旋转
    private Matrix mTransform = new Matrix(); //3x3的矩阵
    private PointF mPivot = new PointF();  //中心点
    RectF mBounds; //矩形左上，右下角两点坐标

1. Matrix：Android提供的一个矩阵工具类，它本身不能对图像或View进行变换，但它可与其他API结合来控制图形、 View的变换，如Canvas。
2. RectF ：矩形左上，右下角两点坐标
3. PointF：圆点圆心坐标

• 重写的方法

@Override  //在onLayout 内调用
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    mBounds = new RectF(0, 0, w, h);
}

@Override  
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas); //单纯继承 View，此方法为空，do nothing

    if (Build.VERSION.SDK_INT < 11) {
      mTransform.set(canvas.getMatrix());
      mTransform.preRotate(mRotation, mPivot.x, mPivot.y);
      canvas.setMatrix(mTransform);
    }

    for (Item it : mData) {
      mPiePaint.setShader(it.mShader);
      canvas.drawArc(mBounds,   //绘制圆弧，椭圆或圆的边界
                     360 - it.mEndAngle,  //起始角度
                     it.mEndAngle - it.mStartAngle,  //顺时旋转角度
                     true,   //如果为True时，在绘制圆弧时将圆心包括在内，通常用来绘制扇形
                     mPiePaint);  //绘制圆弧的画板属性，如颜色，是否填充等
    }
}

• 开启硬件加速

private void setLayerToHW(View v) {
    if (!v.isInEditMode() && Build.VERSION.SDK_INT >= 11) {
        setLayerType(View.LAYER_TYPE_HARDWARE, null);
    }
}

3. PointerView

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawLine(mTextX, mPointerY, mPointerX, mPointerY, mTextPaint);
    canvas.drawCircle(mPointerX, mPointerY, mPointerRadius, mTextPaint);
}

4. GestureListener

private class GestureListener extends GestureDetector.SimpleOnGestureListener {
    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        // Set the pie rotation directly.
        float scrollTheta = vectorToScalarScroll(
                distanceX,
                distanceY,
                e2.getX() - mPieBounds.centerX(),  //e1 是down事件，e2 是move事件
                e2.getY() - mPieBounds.centerY());  
        setPieRotation(getPieRotation() - (int) scrollTheta / FLING_VELOCITY_DOWNSCALE);
        return true;
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        // Set up the Scroller for a fling
        float scrollTheta = vectorToScalarScroll(
                velocityX,
                velocityY,
                e2.getX() - mPieBounds.centerX(),
                e2.getY() - mPieBounds.centerY());
        mScroller.fling(
                0,
                (int) getPieRotation(),
                0,
                (int) scrollTheta / FLING_VELOCITY_DOWNSCALE,
                0,
                0,
                Integer.MIN_VALUE,
                Integer.MAX_VALUE);

        // Start the animator and tell it to animate for the expected duration of the fling.
        if (Build.VERSION.SDK_INT >= 11) {
            mScrollAnimator.setDuration(mScroller.getDuration());
            mScrollAnimator.start();
        }
        return true;
    }

    @Override
    public boolean onDown(MotionEvent e) {
        // The user is interacting with the pie, so we want to turn on acceleration
        // so that the interaction is smooth.
        mPieView.accelerate();
        if (isAnimationRunning()) {
            stopScrolling();
        }
        return true;
    }
}

3. PieChart 实现

• 构造方法

  public PieChart(Context context, AttributeSet attrs) {
      super(context, attrs);
  
      // attrs contains the raw values for the XML attributes
      // that were specified in the layout, which don't include
      // attributes set by styles or themes, and which may have
      // unresolved references. Call obtainStyledAttributes()
      // to get the final values for each attribute.
      //
      // This call uses R.styleable.PieChart, which is an array of
      // the custom attributes that were declared in attrs.xml.
      TypedArray a = context.getTheme().obtainStyledAttributes(
        attrs,
        R.styleable.PieChart,
        0, 0
      );
  
      try {
        // Retrieve the values from the TypedArray and store into
        // fields of this class.
        //
        // The R.styleable.PieChart_* constants represent the index for
        // each custom attribute in the R.styleable.PieChart array.
        mShowText = a.getBoolean(R.styleable.PieChart_showText, false);
        mTextY = a.getDimension(R.styleable.PieChart_labelY, 0.0f);
        mTextWidth = a.getDimension(R.styleable.PieChart_labelWidth, 0.0f);
        mTextHeight = a.getDimension(R.styleable.PieChart_labelHeight, 0.0f);
        mTextPos = a.getInteger(R.styleable.PieChart_labelPosition, 0);
        mTextColor = a.getColor(R.styleable.PieChart_labelColor, 0xff000000);
        mHighlightStrength = a.getFloat(R.styleable.PieChart_highlightStrength, 1.0f);
        mPieRotation = a.getInt(R.styleable.PieChart_pieRotation, 0);
        mPointerRadius = a.getDimension(R.styleable.PieChart_pointerRadius, 2.0f);
        mAutoCenterInSlice = a.getBoolean(R.styleable.PieChart_autoCenterPointerInSlice, false);
      } finally {
        // release the TypedArray so that it can be reused.
        a.recycle();
      }
    // 初始化 Paint、Scroller, addView
      init();
  }
  

  • isInEditMode

    // In edit mode it's nice to have some demo data, so add that here.
    if (this.isInEditMode()) {
        Resources res = getResources();
        addItem("Annabelle", 3, res.getColor(R.color.bluegrass));
        addItem("Brunhilde", 4, res.getColor(R.color.chartreuse));
        addItem("Carolina", 2, res.getColor(R.color.emerald));
        addItem("Dahlia", 3, res.getColor(R.color.seafoam));
        addItem("Ekaterina", 1, res.getColor(R.color.slate));
    }
    

    ​