在 OSX 10.8 SDK/objective-c 中拖动一个按钮

Question

我今天开始使用objective-c ，以便为OSX（山狮）开发一个应用程序。 我有一堆按钮，我想将它们拖到其他对象中，例如文本字段。我按照苹果开发网站上的教程进行操作，但我无法让拖动部分正常工作（例如，拖放部分工作，我可以将文件从 finder 拖动到文本文件中并显示其路径）。

我首先创建了一个 NSButton 子类： @interface mp3OCDDraggableButton : NSButton

并实现了如下所述的方法： https://developer.apple.com/library/mac/#samplecode/CocoaDragAndDrop/Introduction/Intro.html

但那东西不动！

我在 mouseDown: 中放置了一些日志消息，我可以在其中看到，但如果我将其替换为 mouseDragged: 则不会： - 这能告诉我什么吗？

任何人都可以发布一个具有此功能的简单示例吗？我找不到任何有用的东西：\

非常感谢！

这是迄今为止我为可拖动按钮编写的代码。与教程中的几乎相同。

//myDraggableButton.h

@interface myDraggableButton : NSButton <NSDraggingSource, NSPasteboardItemDataProvider>
@end

和

//myDraggableButton.m

#import "myDraggableButton.h"

@implementation myDraggableButton

- (void)mouseDown:(NSEvent *)theEvent:(NSEvent*)event
{

    NSLog(@"mouseDown");

    NSPasteboardItem *pbItem = [NSPasteboardItem new];
    [pbItem setDataProvider:self forTypes:[NSArray arrayWithObjects:NSPasteboardTypeString, nil]];
    NSDraggingItem *dragItem = [[NSDraggingItem alloc] initWithPasteboardWriter:pbItem];
    NSRect draggingRect = self.bounds;
    [dragItem setDraggingFrame:draggingRect contents:[self image]];
    NSDraggingSession *draggingSession = [self beginDraggingSessionWithItems:[NSArray arrayWithObject:dragItem] event:event source:self];
    draggingSession.animatesToStartingPositionsOnCancelOrFail = YES;
    draggingSession.draggingFormation = NSDraggingFormationNone;
}

- (NSDragOperation)draggingSession:(NSDraggingSession *)session sourceOperationMaskForDraggingContext:(NSDraggingContext)context
{
    switch (context) {
        case NSDraggingContextOutsideApplication:
            return NSDragOperationCopy;
        case NSDraggingContextWithinApplication:
        default:
            return NSDragOperationCopy;
            break;
    }
}

- (BOOL)acceptsFirstMouse:(NSEvent *)event
{
    return YES;
}

- (void)pasteboard:(NSPasteboard *)sender item:(NSPasteboardItem *)item provideDataForType:(NSString *)type
{
    if ( [type compare: NSPasteboardTypeTIFF] == NSOrderedSame ) {
        [sender setData:[[self image] TIFFRepresentation] forType:NSPasteboardTypeTIFF];
    } else if ( [type compare: NSPasteboardTypePDF] == NSOrderedSame ) {
        [sender setData:[self dataWithPDFInsideRect:[self bounds]] forType:NSPasteboardTypePDF];
    }

}

@end

Answer 1

我为死灵法致歉，但我在尝试自己实现这个问题时偶然发现了这个问题，并想分享答案，因为它可能对其他人有用。

此解决方案使用NSActionCell 和NSControl 上的类别，因为我需要能够拖动多种控件类型，而不仅仅是按钮。您可以根据自己的需要/课程进行调整。

我已注释掉与隐藏/取消隐藏控件时不希望出现的淡入淡出动画的变通办法hack 相关的代码。我摆弄了隐式动画等，但想不出更好的方法。 hack 确实很好用，但我把窗口实现代码留了下来。

@implementation NSControl (DragControl)

- (NSDraggingSession*)beginDraggingSessionWithDraggingCell:(NSActionCell <NSDraggingSource> *)cell event:(NSEvent*) theEvent
{
    NSImage* image = [self imageForCell:cell];
    NSDraggingItem* di = [[NSDraggingItem alloc] initWithPasteboardWriter:image];
    NSRect dragFrame = [self frameForCell:cell];
    dragFrame.size = image.size;
    [di setDraggingFrame:dragFrame contents:image];

    NSArray* items = [NSArray arrayWithObject:di];

    [self setHidden:YES];
    return [self beginDraggingSessionWithItems:items event:theEvent source:cell];
}

- (NSRect)frameForCell:(NSCell*)cell
{
    // override in multi-cell cubclasses!
    return self.bounds;
}

- (NSImage*)imageForCell:(NSCell*)cell
{
    return [self imageForCell:cell highlighted:[cell isHighlighted]];
}

- (NSImage*)imageForCell:(NSCell*)cell highlighted:(BOOL) highlight
{
    // override in multicell cubclasses to just get an image of the dragged cell.
    // for any single cell control we can just make sure that cell is the controls cell

    if (cell == self.cell || cell == nil) { // nil signifies entire control
                                            // basically a bitmap of the control
                                            // NOTE: the cell is irrelevant when dealing with a single cell control
        BOOL isHighlighted = [cell isHighlighted];
        [cell setHighlighted:highlight];

        NSRect cellFrame = [self frameForCell:cell];

        // We COULD just draw the cell, to an NSImage, but button cells draw their content
        // in a special way that would complicate that implementation (ex text alignment).
        // subclasses that have multiple cells may wish to override this to only draw the cell
        NSBitmapImageRep* rep = [self bitmapImageRepForCachingDisplayInRect:cellFrame];
        NSImage* image = [[NSImage alloc] initWithSize:rep.size];

        [self cacheDisplayInRect:cellFrame toBitmapImageRep:rep];
        [image addRepresentation:rep];
        // reset the original cell state
        [cell setHighlighted:isHighlighted];
        return image;
    }
    // cell doesnt belong to this control!
    return nil;
}

#pragma mark NSDraggingDestination
// message forwarding doesnt work for NSDraggingDestination methods
// because NSView implements empty methods for the protocol
/*
- (NSDragOperation)draggingEntered:(id < NSDraggingInfo >)sender
{
    return [self.cell draggingEntered:sender];
}

- (void)draggingExited:(id < NSDraggingInfo >)sender
{
    [self.cell draggingExited:sender];
}

- (BOOL)prepareForDragOperation:(id < NSDraggingInfo >)sender
{
    return [self.cell prepareForDragOperation:sender];
}

- (BOOL)performDragOperation:(id < NSDraggingInfo >)sender
{
    return [self.cell performDragOperation:sender];
}

- (void)concludeDragOperation:(id < NSDraggingInfo >)sender
{
    return [self.cell concludeDragOperation:sender];
}
*/
- (void)draggingEnded:(id < NSDraggingInfo >)sender
{
    // implement whatever you want to do here.
    [self setHidden:NO];
}

@end


static NSPoint _dragImageOffset;
@implementation NSActionCell (DragCell)

- (void)setControlView:(NSView *)view
{
    // this is a bit of a hack, but the easiest way to make the control dragging work.
    // force the control to accept image drags.
    // the control will forward us the drag destination events via our DragControl category

    [view registerForDraggedTypes:[NSImage imagePasteboardTypes]];
    [super setControlView:view];
}

- (BOOL)trackMouse:(NSEvent *)theEvent inRect:(NSRect)cellFrame ofView:(NSView *)controlView untilMouseUp:(BOOL)untilMouseUp
{
    BOOL result = NO;
    NSPoint currentPoint = theEvent.locationInWindow;
    BOOL done = NO;
    BOOL trackContinously = [self startTrackingAt:currentPoint inView:controlView];

    BOOL mouseIsUp = NO;
    NSEvent *event = nil;
    while (!done)
    {
        NSPoint lastPoint = currentPoint;

        event = [NSApp nextEventMatchingMask:(NSLeftMouseUpMask|NSLeftMouseDraggedMask)
                                   untilDate:[NSDate distantFuture]
                                      inMode:NSEventTrackingRunLoopMode
                                     dequeue:YES];

        if (event)
        {
            currentPoint = event.locationInWindow;

            // Send continueTracking.../stopTracking...
            if (trackContinously)
            {
                if (![self continueTracking:lastPoint
                                         at:currentPoint
                                     inView:controlView])
                {
                    done = YES;
                    [self stopTracking:lastPoint
                                    at:currentPoint
                                inView:controlView
                             mouseIsUp:mouseIsUp];
                }
                if (self.isContinuous)
                {
                    [NSApp sendAction:self.action
                                   to:self.target
                                 from:controlView];
                }
            }

            mouseIsUp = (event.type == NSLeftMouseUp);
            done = done || mouseIsUp;

            if (untilMouseUp)
            {
                result = mouseIsUp;
            } else {
                // Check if the mouse left our cell rect
                result = NSPointInRect([controlView
                                        convertPoint:currentPoint
                                        fromView:nil], cellFrame);
                if (!result)
                    done = YES;
            }

            if (done && result && ![self isContinuous])
                [NSApp sendAction:self.action
                               to:self.target
                             from:controlView];
            else {
                done = YES;
                result = YES;

                // this initiates the control drag event using NSDragging protocols
                NSControl* cv = (NSControl*)self.controlView;
                NSDraggingSession* session = [cv beginDraggingSessionWithDraggingCell:self
                                                                                event:theEvent];
                // _dragImageOffset = [cv convertPoint:[theEvent locationInWindow] fromView:nil];
                // Note that you will get an ugly flash effect when the image returns if this is set to yes
                // you can work around it by setting NO and faking the release by animating an NSWindowSubclass with the image as the content
                // create the window in the drag ended method for NSDragOperationNone
                // there is [probably a better and easier way around this behavior by playing with view animation properties.
                session.animatesToStartingPositionsOnCancelOrFail = YES;
            }

        }
    }
    return result;
}

#pragma mark - NSDraggingSource Methods
- (NSDragOperation)draggingSession:(NSDraggingSession *)session sourceOperationMaskForDraggingContext:(NSDraggingContext)context
{
    switch(context) {
        case NSDraggingContextOutsideApplication:
            return NSDragOperationNone;
            break;

        case NSDraggingContextWithinApplication:
        default:
            return NSDragOperationPrivate;
            break;
    }
}
/*
- (void)draggingSession:(NSDraggingSession *)session willBeginAtPoint:(NSPoint)screenPoint
{
    DragAnimationWindow* dw = [DragAnimationWindow sharedAnimationWindow];
    NSControl* cv = (NSControl*)self.controlView;

    NSImage* image = [[NSImage alloc] initWithPasteboard:session.draggingPasteboard];
    [dw setupDragAnimationWith:cv usingDragImage:image];
    [image release];
    NSRect frame = [cv frameForCell:self];
    frame = [cv convertRect:frame toView:nil];
    [dw setFrame:[cv.window convertRectToScreen:frame] display:NO];
}
*/
- (void)draggingSession:(NSDraggingSession *)session endedAtPoint:(NSPoint)screenPoint operation:(NSDragOperation)operation
{
    /*
    if (operation == NSDragOperationNone) {
        DragAnimationWindow* dw = [DragAnimationWindow sharedAnimationWindow];
        NSRect frame = dw.frame;

        NSPoint start = screenPoint;
        start.y += _dragImageOffset.y;
        start.x -= _dragImageOffset.x;

        [dw setFrameTopLeftPoint:start];
        [dw animateToFrame:frame];
    }*/
    // now tell the control view the drag ended so it can do any cleanup it needs
    // this is somewhat hackish
    [self.controlView draggingEnded:nil];
}

@end

Answer 2

问题可能是您使用NSPasteboardTypeString 调用-setDataProvider:forTypes:，但您的-pasteboard:item:provideDataForType: 在传递该类型时没有执行任何操作？