關于UITextField和UITextView的placeholder

1. 大家都知道UITextField支援設定placeholder, 并且可以改變placeholder字型大小和顔色, 參照代碼:

/* 設定placeholder*/
[textField setPlaceholder:@"placeholder in textField"];

/* 改變placeholder的顔色 */
[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];  

/* 改變placeholder的字型大小 */
[textField setValue:[UIFont systemFontOfSize:20.f] forKeyPath:@"_placeholderLabel.font"];
           

2. UITextView是不支援placeholder, 不過沒事, 我們可以手動添加一個label, 設定字型大小顔色就隻需要操作label即可:

/* 添加UITextView */
UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0, 0, 320.f, 47.f)];
textView.delegate = self;        // 
textView.backgroundColor = [UIColor clearColor];
[self addSubView:textView];
    
/* 添加placeholder Label */
UILabel *placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectZero];
placeHolderLabel.textColor = [UIColor lightGrayColor];
placeHolderLabel.text = @"placeholder in textView";
[placeHolderLabel sizeToFit];
placeHolderLabel.frame = CGRectMake(0, 5.f, placeHolderLabel.frame.size.width, placeHolderLabel.frame.size.height);
[self addSubView:placeHolderLabel];

/* 監聽textView發生變化, 無内容則顯示placeholder */
- (void)textViewDidChange:(UITextView *)textView{
    if ([[textView.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] isEqualToString:@""]) {
        placeHolderLabel.text = @"placeholder in textView";
    }else{
        placeHolderLabel.text = @"";
    }
}