设置NSTextView的占位符字符串 [英] Set the placeholder string for NSTextView

问题描述

有没有办法像 NSTextField 中那样设置 NSTextView 的占位符字符串？我已经检查的属性，但找不到它。我已搜索了一些问题，但没有正确的解释。

Is there any way to set the placeholder string for NSTextView like that in NSTextField? I have checked the property but couldn't find it. I have searched some questions but there isn't a proper explanation.

推荐答案

Philippe Mougin 这样做了。

static NSAttributedString *placeHolderString;

@implementation TextViewWithPlaceHolder

+(void)initialize
{
  static BOOL initialized = NO;
  if (!initialized)
{
     NSColor *txtColor = [NSColor grayColor];
     NSDictionary *txtDict = [NSDictionary dictionaryWithObjectsAndKeys:txtColor, NSForegroundColorAttributeName, nil];
     placeHolderString = [[NSAttributedString alloc] initWithString:@"This is my placeholder text" attributes:txtDict];
 }
}

- (BOOL)becomeFirstResponder
{
  [self setNeedsDisplay:YES];
  return [super becomeFirstResponder];
}

- (void)drawRect:(NSRect)rect
{
  [super drawRect:rect];
 if ([[self string] isEqualToString:@""] && self != [[self window] firstResponder])
 [placeHolderString drawAtPoint:NSMakePoint(0,0)];
}

- (BOOL)resignFirstResponder
{
   [self setNeedsDisplay:YES];
   return [super resignFirstResponder];
}

@end

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