我为学校创建了一个表格视图,作为应用程序的一部分,该视图允许学生输入作业,然后将其选中并消失,就像提醒应用程序一样。我遇到的问题是,当我检查一行以使其消失时,我从表中删除了该行,并从保存所有HomeworkItem
的数组中删除了HomeworkItem
及其数据。但是,下次我尝试添加一行(通过单击末尾的缓冲区行)时,添加的新行是我刚刚删除的同一行,具有相同的HomeworkItem
信息,即使该HomeworkItem
具有已从阵列中删除。我记得读过NSableViews试图重用行以提高内存效率,但是我不明白为什么行会挂在旧信息上。有人可以解释为什么会发生这种情况,或者我该如何解决?
这是自定义TableViewCell的代码:
HomeworkTableViewCell.h:
#import <Cocoa/Cocoa.h>
#import "AppDelegate.h"
#import "ClassViewController.h"
@class ClassViewController;
@class AppDelegate;
@interface HomeworkTableCellView : NSTableCellView
@property (weak) IBOutlet NSTextField *assignmentName;
@property (weak) IBOutlet NSDatePicker *dueDatePicker;
@property BOOL isCompleted;
@property NSInteger rowNumber;
@property (weak) AppDelegate *ad;
@property NSTableView *superTable;
@property ClassViewController *superCVC;
- (void)setSuperRow:(id)sender;
- (IBAction)completed:(id)sender;
- (IBAction)dateChanged:(id)sender;
@end
家庭作业TableViewCell.m:
#import "HomeworkTableCellView.h"
@implementation HomeworkTableCellView
- (id)initWithCoder:(NSCoder *)aDecoder{
// NSLog(@"I");//TEST
self = [super initWithCoder:aDecoder];
if (self) {
self.ad = [[NSApplication sharedApplication]delegate];
self.superTable = self.ad.classViewController.homeworkTable;
self.superCVC = self.ad.classViewController;
self.isCompleted = NO;
}
return self;
}
- (void)setSuperRow:(id)sender{
[self.superCVC updateRow:sender];
}
- (IBAction)completed:(id)sender{
self.isCompleted = !self.isCompleted;
[self.superCVC changeStateOfHomeworkItem:self];
[self.superCVC updateRow:sender];
}
- (IBAction)dateChanged:(id)sender{
[self.superCVC updateRow:sender];
[self.superCVC editDateOfHomeworkItem];
}
@end
以下是出现问题的视频的链接:http://youtu.be/Ot8w5oz8L-E
控制台中的文本表示删除对象后家庭作业数组中的内容,因此很明显,已删除的对象不再存在。
编辑:
这是我根据uasi的建议想到的:
- (NSView *)tableView:(NSTableView *)tableView viewForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row
{
HomeworkTableCellView *HTCV = [self.homeworkTable makeViewWithIdentifier:tableColumn.identifier owner:self];//maybe owner:nil
[HTCV.assignmentName setStringValue: @""];
[HTCV.dueDatePicker setDateValue: [[NSDate alloc]initWithString:@"1-1-1 0:0:0 +0000"]];//false date for testing
HTCV.isCompleted = NO;
[HTCV.checkBox setState:NSOffState];
[self updateTableView];
return HTCV;
}
- (void)updateTableView{
for (int i = 0; i < self.ad.currentSubject.homework.count; i++) {
HomeworkTableCellView *HTCV = [self.homeworkTable viewAtColumn:0 row:i makeIfNecessary:NO];
HomeworkItem *HI = [self.ad.currentSubject.homework objectAtIndex:i];
[HTCV.dueDatePicker setDateValue: HI.dueDate];
[HTCV.assignmentName setStringValue: HI.details];
}
}
最佳答案
您可能不使用-tableView:objectValueForTableColumn:row:
进行表格单元格视图。虽然文档声称“此方法是强制性的”,但对<AppKit/NSTableView.h>
中找到的方法的注释说:“此方法对于“基于单元的” TableView是必需的,而对于“基于视图的” TableView是可选的。
相反,您可以使用NSTableViewDelegate
的-tableView:viewForTableColumn:row:
方法:
- (NSView *)tableView:(NSTableView *)tableView
viewForTableColumn:(NSTableColumn *)tableColumn
row:(NSInteger)row
{
// Instantiate a view object from XIB or reuse one in the cache.
NSString *identifier = @"YOUR_CELL_VIEW_IDENTIFIER";
HomeworkTableCellView *HTCV = [tableView makeViewWithIdentifier:identifier owner:nil];
#if 0
// If you have not put a HomeworkTableCellView object in a XIB with identifier,
// you'll need to create an instance programatically like this;
// It seems not to be the case, though.
if (HTCV == nil) {
HTCV = [[HomeworkTableCellView alloc] initWithFrame:NSZeroRect];
HTCV.identifier = identifier;
}
#endif
// Do initialization anything specific to a row here,
// because the view's -init{WithCoder:,WithFrame:} method
// is not always called for each row due to the cache mechanism.
HomeworkItem *HI = [self.homeworkArray objectAtIndex:row];
[HTCV.dueDatePicker setDateValue: HI.dueDate];
// ...
return HTCV;
}