textField 左侧的小图标

imageView.image = [UIImage imageNamed:@"HomeView_magnifier_white"];

        

        self.mainTextField.leftView = imageView;

        

        self.mainTextField.leftViewMode = UITextFieldViewModeAlways;

        ／／竖直对齐方式

        self.mainTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;