iTunes歌曲标题在可可中滚动

Question

我已经进行了广泛的搜索,并且在我的生活中找不到任何关于如果在Cocoa中文本太大而如何实现与iTunes歌曲标题滚动类似效果的信息.我试过在NST​​extField上设置界限无济于事.我尝试过使用NSTextView以及使用NSScrollView的各种尝试.我相信我错过了一些简单的东西,但任何帮助都会非常感激.我也希望如果可能的话不必使用CoreGraphics.

例如,请注意"Base.FM http:// www." 文本已滚动.如果您需要一个更好的示例,请打开带有相当大标题的歌曲的iTunes,并观看它来回滚动.

我想肯定有一个简单的办法只有创建具有的NSTextField和一个NSTimer,但可惜选取框型的效果.

Answer 1

如果你试图将功能强加到一个存在的控件中,我可以看到这将是多么困难.但是,如果你只是从一个简单的NSView开始,它就不那么糟糕了.我在大约10分钟内掀起了这个......

//ScrollingTextView.h:
#import <Cocoa/Cocoa.h>
@interface ScrollingTextView : NSView {
    NSTimer * scroller;
    NSPoint point;
    NSString * text;
    NSTimeInterval speed;
    CGFloat stringWidth;
}

@property (nonatomic, copy) NSString * text;
@property (nonatomic) NSTimeInterval speed;

@end


//ScrollingTextView.m

#import "ScrollingTextView.h"

@implementation ScrollingTextView

@synthesize text;
@synthesize speed;

- (void) dealloc {
    [text release];
    [scroller invalidate];
    [super dealloc];
}

- (void) setText:(NSString *)newText {
    [text release];
    text = [newText copy];
    point = NSZeroPoint;

    stringWidth = [newText sizeWithAttributes:nil].width;

    if (scroller == nil && speed > 0 && text != nil) {
        scroller = [NSTimer scheduledTimerWithTimeInterval:speed target:self selector:@selector(moveText:) userInfo:nil repeats:YES];
    }
}

- (void) setSpeed:(NSTimeInterval)newSpeed {
    if (newSpeed != speed) {
        speed = newSpeed;

        [scroller invalidate];
        scroller == nil;
        if (speed > 0 && text != nil) {
            scroller = [NSTimer scheduledTimerWithTimeInterval:speed target:self selector:@selector(moveText:) userInfo:nil repeats:YES];
        }
    }
}

- (void) moveText:(NSTimer *)timer {
    point.x = point.x - 1.0f;
    [self setNeedsDisplay:YES];
}

- (void)drawRect:(NSRect)dirtyRect {
    // Drawing code here.

    if (point.x + stringWidth < 0) {
        point.x += dirtyRect.size.width;
    }

    [text drawAtPoint:point withAttributes:nil];

    if (point.x < 0) {
        NSPoint otherPoint = point;
        otherPoint.x += dirtyRect.size.width;
        [text drawAtPoint:otherPoint withAttributes:nil];
    }
}

@end

只需在Interface Builder中将NSView拖到窗口上,然后将其类更改为"ScrollingTextView".然后(在代码中),你做:

[myScrollingTextView setText:@"This is the text I want to scroll"];
[myScrollingTextView setSpeed:0.01]; //redraws every 1/100th of a second

这显然是非常简陋的,但它确实包含了你正在寻找的东西,并且是一个体面的起点.