Android自定义ViewGroup实现带箭头的圆角矩形菜单

 <resources>
 <declare-styleable name="ArrowRectangleView">
 <attr name="arrow_width" format="dimension" />
 <attr name="arrow_height" format="dimension" />
 <attr name="arrow_offset" format="dimension" />
 <attr name="radius" format="dimension" />
 <attr name="background_color" format="color" />
 <attr name="shadow_color" format="color" />
 <attr name="shadow_thickness" format="dimension" />
 </declare-styleable>
</resources> 

 public class ArrowRectangleView extends ViewGroup {
 ... ...
 public ArrowRectangleView(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);

 TypedArray a = context.getTheme().obtainStyledAttributes(attrs,
 R.styleable.ArrowRectangleView, defStyleAttr, 0);
 for (int i = 0; i < a.getIndexCount(); i++) {
 int attr = a.getIndex(i);
 switch (attr) {
 case R.styleable.ArrowRectangleView_arrow_width:
  mArrowWidth = a.getDimensionPixelSize(attr, mArrowWidth);
  break;
 case R.styleable.ArrowRectangleView_arrow_height:
  mArrowHeight = a.getDimensionPixelSize(attr, mArrowHeight);
  break;
 case R.styleable.ArrowRectangleView_radius:
  mRadius = a.getDimensionPixelSize(attr, mRadius);
  break;
 case R.styleable.ArrowRectangleView_background_color:
  mBackgroundColor = a.getColor(attr, mBackgroundColor);
  break;
 case R.styleable.ArrowRectangleView_arrow_offset:
  mArrowOffset = a.getDimensionPixelSize(attr, mArrowOffset);
  break;
 case R.styleable.ArrowRectangleView_shadow_color:
  mShadowColor = a.getColor(attr, mShadowColor);
  break;
 case R.styleable.ArrowRectangleView_shadow_thickness:
  mShadowThickness = a.getDimensionPixelSize(attr, mShadowThickness);
  break;
 }
 }
 a.recycle();
 } 

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 int count = getChildCount();
 int maxWidth = 0;
 // reserve space for the arrow and round corners
 int maxHeight = mArrowHeight + mRadius;
 for (int i = 0; i < count; i++) {
 final View child = getChildAt(i);
 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
 if (child.getVisibility() != GONE) {
 measureChild(child, widthMeasureSpec, heightMeasureSpec);
 maxWidth = Math.max(maxWidth, child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin);
 maxHeight = maxHeight + child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
 }
 }

 maxWidth = maxWidth + getPaddingLeft() + getPaddingRight() + mShadowThickness;
 maxHeight = maxHeight + getPaddingTop() + getPaddingBottom() + mShadowThickness;

 setMeasuredDimension(maxWidth, maxHeight);
 } 

 @Override
 public ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs) {
 return new MarginLayoutParams(getContext(), attrs);
 } 

 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
 int count = getChildCount();
 int topOffset = t + mArrowHeight + mRadius/2;
 int top = 0;
 int bottom = 0;
 for (int i = 0; i < count; i++) {
 final View child = getChildAt(i);
 top = topOffset + i * child.getMeasuredHeight();
 bottom = top + child.getMeasuredHeight();
 child.layout(l, top, r - mRadius/2 - mShadowThickness, bottom);
 }
 } 

 @Override
 protected void dispatchDraw(Canvas canvas) {
 // disable h/w acceleration for blur mask filter
 setLayerType(View.LAYER_TYPE_SOFTWARE, null);

 Paint paint = new Paint();
 paint.setAntiAlias(true);
 paint.setColor(mBackgroundColor);
 paint.setStyle(Paint.Style.FILL);

 // set Xfermode for source and shadow overlap
 paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OVER));

 // draw round corner rectangle
 paint.setColor(mBackgroundColor);
 canvas.drawRoundRect(new RectF(0, mArrowHeight, getMeasuredWidth() - mShadowThickness, getMeasuredHeight() - mShadowThickness), mRadius, mRadius, paint);

 // draw arrow
 Path path = new Path();
 int startPoint = getMeasuredWidth() - mArrowOffset;
 path.moveTo(startPoint, mArrowHeight);
 path.lineTo(startPoint + mArrowWidth, mArrowHeight);
 path.lineTo(startPoint + mArrowWidth / 2, 0);
 path.close();
 canvas.drawPath(path, paint);

 // draw shadow
 if (mShadowThickness > 0) {
 paint.setMaskFilter(new BlurMaskFilter(mShadowThickness, BlurMaskFilter.Blur.OUTER));
 paint.setColor(mShadowColor);
 canvas.drawRoundRect(new RectF(mShadowThickness, mArrowHeight + mShadowThickness, getMeasuredWidth() - mShadowThickness, getMeasuredHeight() - mShadowThickness), mRadius, mRadius, paint);
 }

 super.dispatchDraw(canvas);
 } 

 <?xml version="1.0" encoding="utf-8"?>
<com.xinxin.arrowrectanglemenu.widget.ArrowRectangleView
 xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:orientation="vertical"
 android:background="@android:color/transparent"
 android:paddingLeft="3dp"
 android:paddingRight="3dp"
 android:splitMotionEvents="false"
 app:arrow_offset="31dp"
 app:arrow_width="16dp"
 app:arrow_height="8dp"
 app:radius="5dp"
 app:background_color="#ffb1df83"
 app:shadow_color="#66000000"
 app:shadow_thickness="5dp">
 <LinearLayout
 android:id="@+id/cmx_toolbar_menu_turn_off"
 android:layout_width="wrap_content"
 android:layout_height="42dp">
 <TextView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_gravity="center_vertical"
 android:textSize="16sp"
 android:textColor="#FF393F4A"
 android:paddingLeft="16dp"
 android:paddingRight="32dp"
 android:clickable="false"
 android:text="Menu Item #1"/>
 </LinearLayout>
 <LinearLayout
 android:id="@+id/cmx_toolbar_menu_feedback"
 android:layout_width="wrap_content"
 android:layout_height="42dp">
 <TextView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_gravity="center_vertical"
 android:textSize="16sp"
 android:textColor="#FF393F4A"
 android:paddingLeft="16dp"
 android:paddingRight="32dp"
 android:clickable="false"
 android:text="Menu Item #2"/>
 </LinearLayout>
</com.xinxin.arrowrectanglemenu.widget.ArrowRectangleView>