UITextFiled不能多行，UITextView没有plac

UITextFiled不能多行，UITextView没有placeholder属性，我们UITextView改成类似有placeholder效果,遵守UITextView的代理方法<UITextViewDelegate>

 UITextView.text = @"placeholder";

- (void)textViewDidBeginEditing:(UITextView*)textView {

if([textView.textisEqualToString:@"placeholder"]) {

textView.text=@"";

textView.textColor= [UIColor blackColor];

}

}

- (void)textViewDidEndEditing:(UITextView*)textView {

if(textView.text.length<1) {

textView.text=@"placeholder";

textView.textColor= [UIColor GrayColor];

}

}