cocoa - 基于 View 的 NSOutlineView 中的子项未调用 viewForTableColumn

Question

我有一个问题，该方法

-(NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item;

当项目不是组项目时，不会调用

。方法

-(BOOL)outlineView:(NSOutlineView *)outlineView isGroupItem:(id)item;
-(BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(id)item;

的实现是为(相同且)正确的标题/组项集返回 YES。方法如下

-(NSInteger)outlineView:(NSOutlineView *)outlineView numberOfChildrenOfItem:(id)item;
-(id)outlineView:(NSOutlineView *)outlineView child:(NSInteger)childIndex ofItem:(id)item;

还分别返回子项的合理计数和有效的子项。但上面的 outlineView:viewForTableColumn:item: 方法永远不会为子项调用。这些行是为子项布局的，但是是空白的(如下面的屏幕截图所示)，因为 View 生成方法 outlineView:viewForTableColumn:item: 永远不会为子项调用。

请注意，我没有任何 XIB，所有 View 都是以编程方式布局的。特别是，这意味着我无法通过 XIB 在大纲 View 的基础 TableView 上设置内容模式的“基于 View ”值，如 Apple 示例代码 https://developer.apple.com/library/mac/samplecode/SidebarDemo/Introduction/Intro.html#//apple_ref/doc/uid/DTS40010893 中所做的那样。 .

如果有一种方法可以以编程方式执行此操作，那将是一个很大的帮助。尽管由于父项调用了 View 方法，但不确定这是否是真正的问题。

对我来说另一个谜团是以下两种方法返回的 View 如何协同工作:

- (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item;
- (NSTableRowView *)outlineView:(NSOutlineView *)outlineView rowViewForItem:(id)item;

有关解决此问题的任何线索都会有很大帮助吗？

Answer 1

这是我整理的一些代码，以显示 -(NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item;
确实被调用了。也许通过查看它，您可以看到您在某处犯的错误:

// AppDelegate.m

#import "AppDelegate.h"
#import "Item.h"

@interface AppDelegate ()

@property (strong) NSMutableArray *items;
@property (weak) IBOutlet NSWindow *window;

@end

@implementation AppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    // Insert code here to initialize your application
    self.items = [NSMutableArray array];

    Item *group1 = [Item itemWithName:@"GROUP 1"];
    [group1 addChild:[Item itemWithName:@"0,0"]];
    [group1 addChild:[Item itemWithName:@"1,0"]];
    [group1 addChild:[Item itemWithName:@"2,0"]];

    Item *group2 = [Item itemWithName:@"GROUP 2"];
    [group2 addChild:[Item itemWithName:@"0,1"]];
    [group2 addChild:[Item itemWithName:@"1,1"]];
    [group2 addChild:[Item itemWithName:@"2,1"]];

    Item *group3 = [Item itemWithName:@"GROUP 3"];
    [group3 addChild:[Item itemWithName:@"0,2"]];
    [group3 addChild:[Item itemWithName:@"1,2"]];
    [group3 addChild:[Item itemWithName:@"2,2"]];

    [self.items addObject: group1];
    [self.items addObject: group2];
    [self.items addObject: group3];

    [self.souceList reloadData];
}

- (BOOL)outlineView:(NSOutlineView *)outlineView isGroupItem:(Item *)item {
    return !item.parent;
}

- (BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(Item *)item {
    return item.children.count;
}

- (id)outlineView:(NSOutlineView *)outlineView child:(NSInteger)index ofItem:(Item *)item {
    if (!item) {
        return self.items[index];
    }

    if (item.children.count > index)
        return item.children[index];
    return nil;
}

- (NSInteger)outlineView:(NSOutlineView *)outlineView numberOfChildrenOfItem:(Item *)item {
    if (!item) {
        return self.items.count;
    }
    return item.children.count;
}

- (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(Item *)item {
    // Breakpoint set here to test
    return [[NSView alloc] init];
}

@end

// Item.h
@interface Item : NSObject
@property (weak) Item *parent;
@property (copy) NSString *name;

+ (instancetype)itemWithName:(NSString *)name;
- (instancetype)initWithName:(NSString *)name;

- (void)addChild:(Item *)child;
- (void)removeChild:(Item *)child;

@end

@interface Item (Property)
@property (readonly, strong) NSArray *children;
@end

// Item.m

#import "Item.h"

@interface Item ()
@property (readwrite, strong) NSMutableArray *children;
@end

@implementation Item

+ (instancetype)itemWithName:(NSString *)name {
    return [[self alloc] initWithName:name];
}

- (instancetype)initWithName:(NSString *)name {
    if ((self = [self init])) {
        self.name = name;
    }
    return self;
}

- (id)init {
    if ((self = [super init])) {
        self.name = @"No Name";
        self.children = [NSMutableArray array];
    }
    return self;
}

- (void)addChild:(Item *)child {
    child.parent = self;
    [self.children addObject: child];
}
- (void)removeChild:(Item *)child {
    if (child.parent == self)
        child.parent = nil;
    [self.children removeObject:child];
}

@end

关于关于 NSTableView/NSOutlineView 的基于 View 状态的第二个问题:该值是根据实现的委托(delegate)/数据源方法自动设置的。如果您正在实现 -(NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item;，则 View 将被视为基于 View 。

至于你关于这两个的最后一个问题:

- (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item;
- (NSTableRowView *)outlineView:(NSOutlineView *)outlineView rowViewForItem:(id)item;

第二种方法涉及跨越表格宽度的 View ，包含每个表格列的单元格 View 。这意味着您有多个单元格 View - 每列一个 - 由第一个方法返回，它们是第二个方法为每行返回的一个 View 的 subview 。