问题
I am trying to write a category for NSTextField which will add a new method setAnimatedStringValue. This method is supposed to nicely fade-out the current text, then set the new text and then fade that in.
Below is my implementation:-
- (void) setAnimatedStringValue:(NSString *)aString {
if ([[self stringValue] isEqualToString:aString]) {
return;
}
NSMutableDictionary *dict = Nil;
NSViewAnimation *fadeOutAnim;
dict = [NSDictionary dictionaryWithObjectsAndKeys:self, NSViewAnimationTargetKey,
NSViewAnimationFadeOutEffect, NSViewAnimationEffectKey, nil];
fadeOutAnim = [[NSViewAnimation alloc] initWithViewAnimations:[NSArray arrayWithObjects:
dict, nil]];
[fadeOutAnim setDuration:2];
[fadeOutAnim setAnimationCurve:NSAnimationEaseOut];
[fadeOutAnim setAnimationBlockingMode:NSAnimationBlocking];
NSViewAnimation *fadeInAnim;
dict = [NSDictionary dictionaryWithObjectsAndKeys:self, NSViewAnimationTargetKey,
NSViewAnimationFadeInEffect, NSViewAnimationEffectKey, nil];
fadeInAnim = [[NSViewAnimation alloc] initWithViewAnimations:[NSArray arrayWithObjects:
dict, nil]];
[fadeInAnim setDuration:3];
[fadeInAnim setAnimationCurve:NSAnimationEaseIn];
[fadeInAnim setAnimationBlockingMode:NSAnimationBlocking];
[fadeOutAnim startAnimation];
[self setStringValue:aString];
[fadeInAnim startAnimation];
}
Needless to say, but the above code does not work at all. The only effect I see is the flickering of a progress bar on the same window. That is possibly because I am blocking the main runloop while trying to "animate" it.
Please suggest what is wrong with the above code.
Additional note:
setAnimatedStringValue is always invoked by a NSTimer, which is added to the main NSRunLoop.
回答1:
I'll take a stab:
I found a couple problems here. First off, this whole thing is set up to be blocking, so it's going to block the main thread for 5 seconds. This will translate to the user as a SPOD/hang. You probably want this to be non-blocking, but it'll require a little bit of extra machinery to make that happen.
Also, you're using NSAnimationEaseOut for the fade out effect, which is effected by a known bug where it causes the animation to run backwards. (Google for "NSAnimationEaseOut backwards" and you can see that many have hit this problem.) I used NSAnimationEaseIn for both curves for this example.
I got this working for a trivial example with non-blocking animations. I'm not going to say that this is the ideal approach (I posted a second answer that arguably better), but it works, and can hopefully serve as a jumping off point for you. Here's the crux of it:
@interface NSTextField (AnimatedSetString)
- (void) setAnimatedStringValue:(NSString *)aString;
@end
@interface SOTextFieldAnimationDelegate : NSObject <NSAnimationDelegate>
- (id)initForSettingString: (NSString*)newString onTextField: (NSTextField*)tf;
@end
@implementation NSTextField (AnimatedSetString)
- (void) setAnimatedStringValue:(NSString *)aString
{
if ([[self stringValue] isEqual: aString])
{
return;
}
[[[SOTextFieldAnimationDelegate alloc] initForSettingString: aString onTextField: self] autorelease];
}
@end
@implementation SOTextFieldAnimationDelegate
{
NSString* _newString;
NSAnimation* _fadeIn;
NSAnimation* _fadeOut;
NSTextField* _tf;
}
- (id)initForSettingString: (NSString*)newString onTextField: (NSTextField*)tf
{
if (self = [super init])
{
_newString = [newString copy];
_tf = [tf retain];
[self retain]; // we'll autorelease ourselves when the animations are done.
_fadeOut = [[NSViewAnimation alloc] initWithViewAnimations: @[ (@{
NSViewAnimationTargetKey : tf ,
NSViewAnimationEffectKey : NSViewAnimationFadeOutEffect})] ];
[_fadeOut setDuration:2];
[_fadeOut setAnimationCurve: NSAnimationEaseIn];
[_fadeOut setAnimationBlockingMode:NSAnimationNonblocking];
_fadeOut.delegate = self;
_fadeIn = [[NSViewAnimation alloc] initWithViewAnimations: @[ (@{
NSViewAnimationTargetKey : tf ,
NSViewAnimationEffectKey : NSViewAnimationFadeInEffect})] ];
[_fadeIn setDuration:3];
[_fadeIn setAnimationCurve:NSAnimationEaseIn];
[_fadeIn setAnimationBlockingMode:NSAnimationNonblocking];
[_fadeOut startAnimation];
}
return self;
}
- (void)dealloc
{
[_newString release];
[_tf release];
[_fadeOut release];
[_fadeIn release];
[super dealloc];
}
- (void)animationDidEnd:(NSAnimation*)animation
{
if (_fadeOut == animation)
{
_fadeOut.delegate = nil;
[_fadeOut release];
_fadeOut = nil;
_tf.hidden = YES;
[_tf setStringValue: _newString];
_fadeIn.delegate = self;
[_fadeIn startAnimation];
}
else
{
_fadeIn.delegate = nil;
[_fadeIn release];
_fadeIn = nil;
[self autorelease];
}
}
@end
It would be really nice if there were block-based API for this... it'd save having to implement this delegate object.
I put the whole project up on GitHub.
回答2:
I was poking around a bit after posting the previous answer. I'm leaving that answer because it corresponds closely to the code you posted, and uses NSViewAnimation. I did, however, come up with a considerably more concise, albeit slightly harder to read (owing to block parameter indentation) version that uses NSAnimationContext instead. Here 'tis:
#import <QuartzCore/QuartzCore.h>
@interface NSTextField (AnimatedSetString)
- (void) setAnimatedStringValue:(NSString *)aString;
@end
@implementation NSTextField (AnimatedSetString)
- (void) setAnimatedStringValue:(NSString *)aString
{
if ([[self stringValue] isEqual: aString])
{
return;
}
[NSAnimationContext runAnimationGroup:^(NSAnimationContext *context) {
[context setDuration: 1.0];
[context setTimingFunction: [CAMediaTimingFunction functionWithName: kCAMediaTimingFunctionEaseOut]];
[self.animator setAlphaValue: 0.0];
}
completionHandler:^{
[self setStringValue: aString];
[NSAnimationContext runAnimationGroup:^(NSAnimationContext *context) {
[context setDuration: 1.0];
[context setTimingFunction: [CAMediaTimingFunction functionWithName: kCAMediaTimingFunctionEaseIn]];
[self.animator setAlphaValue: 1.0];
} completionHandler: ^{}];
}];
}
@end
Note: To get access to the CAMediaTimingFunction class used here for specifying non-default timing functions using this API, you'll need to include QuartzCore.framework in your project.
Also on GitHub.
回答3:
For Swift 3, here are two convenient setText() and setAttributedText() extension methods that fade over from one text to another:
import Cocoa
extension NSTextField {
func setStringValue(_ newValue: String, animated: Bool = true, interval: TimeInterval = 0.7) {
guard stringValue != newValue else { return }
if animated {
animate(change: { self.stringValue = newValue }, interval: interval)
} else {
stringValue = newValue
}
}
func setAttributedStringValue(_ newValue: NSAttributedString, animated: Bool = true, interval: TimeInterval = 0.7) {
guard attributedStringValue != newValue else { return }
if animated {
animate(change: { self.attributedStringValue = newValue }, interval: interval)
}
else {
attributedStringValue = newValue
}
}
private func animate(change: @escaping () -> Void, interval: TimeInterval) {
NSAnimationContext.runAnimationGroup({ context in
context.duration = interval / 2.0
context.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
animator().alphaValue = 0.0
}, completionHandler: {
change()
NSAnimationContext.runAnimationGroup({ context in
context.duration = interval / 2.0
context.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
self.animator().alphaValue = 1.0
}, completionHandler: {})
})
}
}
Call them as following:
var stringTextField: NSTextField
var attributedStringTextField: NSTextField
...
stringTextField.setStringValue("New Text", animated: true)
...
let attributedString = NSMutableAttributedString(string: "New Attributed Text")
attributedString.addAttribute(...)
attributedStringTextField.setAttributedStringValue(attributedString, animated: true)
来源：https://stackoverflow.com/questions/14174911/how-do-i-animate-fadein-fadeout-effect-in-nstextfield-when-changing-its-text