- (UIButton *)panButton {
 if (!_panButton) {
  UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panAction:)];
  _panButton = [[UIButton alloc] init];
  _panButton.backgroundColor = [UIColor blueColor];
  _panButton.layer.borderWidth = 1.f;
  _panButton.layer.borderColor = [UIColor greenColor].CGColor;
  [_panButton setTitle:@"清除緩存" forState:UIControlStateNormal];
  _panButton.titleLabel.font = [UIFont systemFontOfSize:9];
  [_panButton addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
  [_panButton addGestureRecognizer:panGesture];
 }
 return _panButton;
}
- (void)panAction:(UIPanGestureRecognizer *)recognizer {
 CGPoint translationPoint = [recognizer translationInView:self.view];
 CGPoint center = recognizer.view.center;
 recognizer.view.center = CGPointMake(center.x + translationPoint.x, center.y + translationPoint.y);
 [recognizer setTranslation:CGPointZero inView:self.view];
}
-(void)buttonAction:(UIButton *)sender
{
 NSLog(@"煩人，點我干啥~");
}