NSOutlineView中的拖放问题

Question

NSOutlineView中的拖放问题

4

我遇到的问题是：我有一个带有拖放功能的NSOutlineView（拖放工作的代码请参见本文末尾），它能够正常工作，但当我将一行拖入另一行时，被拖动的行会变成子项，但也会保留原来位置上的父项，且当我删除任意一行时，两个都会被删除。

为了更清楚地展示我的意思，我录制了这个问题的视频，链接在此http://dvlp.me/6kya9 下面是使大纲视图中的拖放功能生效的代码： 头文件。

@interface _NSControllerTreeProxy : NSObject 
{
    // opaque
}
//
// Number of objects at the root level.
//
- (unsigned int)count;

- (id)nodeAtIndexPath:(id)fp8;
- (id)objectAtIndexPath:(id)fp8;
@end

@interface _NSArrayControllerTreeNode : NSObject
{
    // opaque
}
- (unsigned int)count;
- (id)observedObject;
- (id)parentNode;
- (id)nodeAtIndexPath:(id)fp8;
- (id)subnodeAtIndex:(unsigned int)fp8;
- (BOOL)isLeaf;
- (id)indexPath;
- (id)objectAtIndexPath:(id)fp8;
@end

// some more detailed reverse engineering is available here
// http://www.blueboxmoon.com/wiki/?page=Binding%20Tree


@interface DragController : NSObject
{
    IBOutlet NSTreeController *groupTreeControl;
    IBOutlet NSOutlineView *treeTable;

    NSArray* dragType;

    _NSArrayControllerTreeNode* draggedNode;


}

- (void) resortGroups:(NSManagedObjectContext*)objectContext forParent:(NSManagedObject*)parent;
- (NSArray* ) getSubGroups:(NSManagedObjectContext*)objectContext forParent:(NSManagedObject*)parent;
- (BOOL) category:(NSManagedObject* )cat isSubCategoryOf:(NSManagedObject* ) possibleSub;

@end

#define INTERVAL 10

实现文件。

@implementation DragController
- (void)awakeFromNib {  

    dragType = [NSArray arrayWithObjects:   @"factorialDragType", nil];

    [ dragType retain ]; 

    [ treeTable registerForDraggedTypes:dragType ];
    NSSortDescriptor* sortDesc = [[NSSortDescriptor alloc] initWithKey:@"position" ascending:YES];
    [groupTreeControl setSortDescriptors:[NSArray arrayWithObject: sortDesc]];
    [ sortDesc release ];
}   


//------------------------------------
#pragma mark NSOutlineView datasource methods -- see NSOutlineViewDataSource
//---------------------------------------------------------------------------   
- (BOOL) outlineView : (NSOutlineView *) outlineView 
          writeItems : (NSArray*) items 
        toPasteboard : (NSPasteboard*) pboard {

    [ pboard declareTypes:dragType owner:self ];        
    // items is an array of _NSArrayControllerTreeNode see http://theocacao.com/document.page/130 for more info
    draggedNode = [ items objectAtIndex:0 ];

    return YES; 
}




- (BOOL)outlineView:(NSOutlineView *)outlineView acceptDrop:(id <NSDraggingInfo>)info item:(id)item childIndex:(int)index {

    _NSArrayControllerTreeNode* parentNode = item;
    _NSArrayControllerTreeNode* siblingNode;
    _NSControllerTreeProxy* proxy = [ groupTreeControl arrangedObjects ];

    NSManagedObject* draggedGroup = [ draggedNode observedObject ];

    BOOL draggingDown = NO;
    BOOL isRootLevelDrag = NO;

    // ----------------------
    // Setup comparison paths
    // -------------------------
    NSIndexPath* draggedPath = [ draggedNode indexPath ];
    NSIndexPath* siblingPath =  [ NSIndexPath indexPathWithIndex:  index  ];
    if ( parentNode == NULL ) {     
        isRootLevelDrag = YES;
    } else {
        // A non-root drag - the index value is relative to this parent's children
        siblingPath = [ [ parentNode indexPath ] indexPathByAddingIndex: index ];
    }

    // ----------------------
    // Compare paths - modify sibling path for down drags, exit for redundant drags
    // -----------------------------------------------------------------------------    
    switch ( [ draggedPath compare:siblingPath] ) {
        case NSOrderedAscending:  // reset path for down dragging
            if ( isRootLevelDrag ) {
                siblingPath = [ NSIndexPath indexPathWithIndex: index  - 1];                             
            } else {
                siblingPath = [ [ parentNode indexPath ] indexPathByAddingIndex: index - 1 ]; 
            }
            draggingDown = YES;
            break;

        case NSOrderedSame:
            return NO;
            break;               
    }

    siblingNode = [ proxy nodeAtIndexPath:siblingPath ];    

    //  NSLog(@"returning early");
    //  return NO;  // TODO robustify


    // ------------------------------------------------------------ 
    // SPECIAL CASE: Dragging to the bottom
    // ------------------------------------------------------------
    // - K                               - K                            - C                              - C
    // - - U                             - - C     OR     - U                                - F
    // - - C     ====>     - - F                    - F                              - K
    // - - F               - U              - K                              - U
    // ------------------------------------------------------------ 
    if ( isRootLevelDrag  && siblingNode == NULL ) {        
        draggingDown = YES;
        siblingPath = [ NSIndexPath indexPathWithIndex: [ proxy count ] - 1 ];          
        siblingNode = [ proxy nodeAtIndexPath:siblingPath ] ;
    }

    // ------------------------------------------------------------ 
    // Give the dragged item a position relative to it's new sibling
    // ------------------------------------------------------------ 
    NSManagedObject* sibling = [ siblingNode observedObject ];   
    NSNumber* bystanderPosition = [ sibling valueForKey:@"position"];
    int newPos =   ( draggingDown ? [ bystanderPosition intValue ]  + 1 : [ bystanderPosition intValue ]  - 1 );
    [draggedGroup setValue:[ NSNumber numberWithInt:newPos ] forKey:@"position"];   

    // ----------------------------------------------------------------------------------------------
    // Set the new parent for the dragged item, resort the position attributes and refresh the tree
    // ----------------------------------------------------------------------------------------------    
    [ draggedGroup setValue:[ parentNode observedObject ] forKey:@"parent" ];
    [ self resortGroups:[draggedGroup managedObjectContext] forParent:[ parentNode observedObject ] ];          
    [ groupTreeControl rearrangeObjects ];  
    return YES;             
}






- (NSArray* ) getSubGroups:(NSManagedObjectContext*)objectContext forParent:(NSManagedObject*)parent {
    NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"projects" inManagedObjectContext:objectContext];

    [request setEntity:entity];
    NSSortDescriptor* aSortDesc = [[NSSortDescriptor alloc] initWithKey:@"position" ascending:YES];
    [request setSortDescriptors:[NSArray arrayWithObject: aSortDesc] ];
    [aSortDesc release];

    NSPredicate* validationPredicate = [NSPredicate predicateWithFormat:@"parent == %@", parent ];

    [ request setPredicate:validationPredicate ];

    NSError *error = nil;  // TODO - check the error bozo
    return [objectContext executeFetchRequest:request error:&error];    
}




- (void) resortGroups:(NSManagedObjectContext*)objectContext forParent:(NSManagedObject*)parent {

    NSArray *array = [ self getSubGroups:objectContext forParent:parent ];

    // Reset the indexes...
    NSEnumerator *enumerator = [array objectEnumerator];
    NSManagedObject* anObject;
    int index = 0;
    while (anObject = [enumerator nextObject]) {
        // Multiply index by 10 to make dragging code easier to implement ;) ....
        [anObject setValue:[ NSNumber numberWithInt:(index * INTERVAL ) ] forKey:@"position"];    
        index++;
    }   


}

- (NSDragOperation)outlineView:(NSOutlineView *)outlineView validateDrop:(id <NSDraggingInfo>)info proposedItem:(id)item proposedChildIndex:(int)index {

    _NSArrayControllerTreeNode* newParent = item;

    // drags to the root are always acceptable
    if ( newParent == NULL ) {  
        return  NSDragOperationGeneric; 
    }

    // Verify that we are not dragging a parent to one of it's ancestors
    // causes a parent loop where a group of nodes point to each other and disappear
    // from the control 
    NSManagedObject* dragged = [ draggedNode observedObject ];      
    NSManagedObject* newP = [ newParent observedObject ];

    if ( [ self category:dragged isSubCategoryOf:newP ] ) {
        return NO;
    }       

    return NSDragOperationGeneric;
}

- (BOOL) category:(NSManagedObject* )cat isSubCategoryOf:(NSManagedObject* ) possibleSub {

    // Depends on your interpretation of subCategory ....
    if ( cat == possibleSub ) { return YES; }

    NSManagedObject* possSubParent = [possibleSub valueForKey:@"parent"];   

    if ( possSubParent == NULL ) {  return NO; }

    while ( possSubParent != NULL ) {       
        if ( possSubParent == cat ) { return YES;   }

        // move up the tree
        possSubParent = [possSubParent valueForKey:@"parent"];          
    }   

    return NO;
}




// This method gets called by the framework but the values from bindings are used instead
- (id)outlineView:(NSOutlineView *)outlineView objectValueForTableColumn:(NSTableColumn *)tableColumn byItem:(id)item { 
    return NULL;
}

/* 
 The following are implemented as stubs because they are required when 
 implementing an NSOutlineViewDataSource. Because we use bindings on the
 table column these methods are never called. The NSLog statements have been
 included to prove that these methods are not called.
 */
- (int)outlineView:(NSOutlineView *)outlineView numberOfChildrenOfItem:(id)item {
    NSLog(@"numberOfChildrenOfItem");
    return 1;
}

- (BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(id)item {
    NSLog(@"isItemExpandable");
    return NO;
}

- (id)outlineView:(NSOutlineView *)outlineView child:(int)index ofItem:(id)item {
    NSLog(@"child of Item");
    return NULL;
}



@end

- Joshua

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Joshua · Accepted Answer

我刚刚进行了一些搜索，找到了如何解决它。在NSTreeController的属性中，将获取谓词设置为parent == nil。