为 NSTextView 设置占位符字符串

Question

有没有办法像 NSTextField 那样为 NSTextView 设置占位符字符串？我检查了属性但没找到。我搜索了一些问题，但没有合适的解释。

Answer 1

我在网上找到了这个答案。 Philippe Mougin 做了这个。

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

Answer 2

Swift 2.0

var placeHolderTitleString: NSAttributedString = NSAttributedString(string: "Place Holder Value", attributes: [NSForegroundColorAttributeName : NSColor.grayColor()])

override func becomeFirstResponder() -> Bool {
    self.needsDisplay = true
    return super.becomeFirstResponder()
}

override func drawRect(rect: NSRect) {
    super.drawRect(rect)

    if (self.string! == "") {
        placeHolderString.drawAtPoint(NSMakePoint(0, 0))
    }
}

Answer 3

Swift 4

事实证明，NSTextView 中似乎已经有一个 placeholderAttributedString 属性没有公开。因此，您可以简单地在自己的子类中实现它并获得默认的占位符行为（类似于 NSTextField）。

class PlaceholderTextView: NSTextView {
     @objc var placeholderAttributedString: NSAttributedString?
}

而且如果这个属性将来可以使用，你只需要使用NSTextView而不是这个子类。

Answer 4

找这个。这可能是更好的方法！

final class CustomTextView: NSTextView {

    private var placeholderAttributedString: NSAttributedString? = NSAttributedString(string: "Your placeholder string here")
    private var placeholderInsets = NSEdgeInsets(top: 0.0, left: 4.0, bottom: 0.0, right: 4.0)

    override func becomeFirstResponder() -> Bool {
        self.needsDisplay = true
        return super.becomeFirstResponder()
    }

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)

        guard string.isEmpty else { return }
        placeholderAttributedString?.draw(in: dirtyRect.insetBy(placeholderInsets))
    }
}

extension NSRect {
    func insetBy(_ insets: NSEdgeInsets) -> NSRect {
        return insetBy(dx: insets.left + insets.right, dy: insets.top + insets.bottom)
        .applying(CGAffineTransform(translationX: insets.left - insets.right, y: insets.top - insets.bottom))
    }
}

Answer 5

如果您使用故事板，最好的方法是放置一个 NSTextView 并将其值绑定到一个

@objc dynamic var myString: String?

属性在你的控制器中。然后，在绑定检查器中，您可以设置一个 Null Placeholder 值，文本视图将使用该值，而您根本不必使用任何显式私有 API。

为 NSTextView 设置占位符字符串

Set the placeholder string for NSTextView

macos

cocoa

nstextview