IPhone中的使用时注意雷区：
1. 必须实现以下代理，否则无法使用：
```
#pragma mark - <UIPopoverPresentationControllerDelegate>
- (UIModalPresentationStyle)adaptivePresentationStyleForPresentationController:(UIPresentationController *)controller {
return UIModalPresentationNone;
}
```
2. 必须使用`UIViewController`的`子类`中使用，简单使用例子如下：
```
TestViewController *testVC = [[TestViewController alloc] init];
testVC.preferredContentSize = CGSizeMake(150, 150);
testVC.modalPresentationStyle = UIModalPresentationPopover;
testVC.popoverPresentationController.delegate = self;
testVC.popoverPresentationController.sourceView = _button;
testVC.popoverPresentationController.sourceRect = CGRectMake(0, 0, _button.bounds.size.width / 2.0, _button.bounds.size.height / 2.0);
testVC.popoverPresentationController.permittedArrowDirections = UIPopoverArrowDirectionLeft;
testVC.popoverPresentationController.backgroundColor = [UIColor redColor];
testVC.popoverPresentationController.canOverlapSourceViewRect = NO;
[self presentViewController:testVC animated:YES completion:^{
}];
```
3. 调整建议，如需去掉背景蒙版，可通过重写`UIPopoverBackgroundView`，如下：
```
@interface LYIMOrderTipBackgroundView : UIPopoverBackgroundView
@end
@implementation LYIMOrderTipBackgroundView
- (instancetype)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
self.arrowDirection = UIMenuControllerArrowUp;
[self setHidden:YES];
}
return self;
}
//是否使用默认的内置阴影和圆角
+ (BOOL)wantsDefaultContentAppearance {
return NO;
}
- (void)layoutSubviews {
[super layoutSubviews];
self.backgroundColor = [UIColor clearColor];
}
//这个方法返回箭头宽度
+ (CGFloat)arrowBase {
return 0;
}
//这个方法中返回内容视图的偏移
+ (UIEdgeInsets)contentViewInsets {
return UIEdgeInsetsMake(0, 0, 0, 0);
}
//这个方法返回箭头高度
+ (CGFloat)arrowHeight {
return 0;
}
//这个方法返回箭头的方向
- (UIPopoverArrowDirection)arrowDirection {
return UIPopoverArrowDirectionUp;
}
//这个在设置箭头方向时被调用 可以监听做处理
- (void)setArrowDirection:(UIPopoverArrowDirection)arrowDirection {
}
//这个方法在设置箭头偏移量时被调用 可以监听做处理
- (void)setArrowOffset:(CGFloat)arrowOffset {
}
@end
```
* 以下为绘制箭头图片
```
- (UIImage *)drawArrowImage:(CGSize)size {
UIGraphicsBeginImageContextWithOptions(size, NO, 0);
CGContextRef ctx = UIGraphicsGetCurrentContext();
[[UIColor clearColor] setFill];
CGContextFillRect(ctx, CGRectMake(0.0f, 0.0f, size.width, size.height));
CGPoint point1;
CGPoint point2;
CGPoint point3;
point1 = CGPointMake(size.width/2.0, 0);
point2 = CGPointMake(size.width, size.height);
point3 = CGPointMake(0, size.height);
CGMutablePathRef arrowPath = CGPathCreateMutable();
CGPathMoveToPoint(arrowPath, NULL, point1.x, point1.y);
CGPathAddLineToPoint(arrowPath, NULL, point2.x, point2.y);
CGPathAddLineToPoint(arrowPath, NULL, point3.x, point3.y);
CGPathCloseSubpath(arrowPath);
CGContextAddPath(ctx, arrowPath);
CGPathRelease(arrowPath);
CGContextSetFillColorWithColor(ctx, self.bgColor.CGColor);
CGContextDrawPath(ctx, kCGPathFill);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
```
