Question

我有一个带有自定义tablecells的UITableView。首先，我有一个版本，它实现了一个单独的NIB文件来创建自定义单元格视图，但这使得滚动非常慢。官方的答案是做自己的绘图，所以我实现了一个绘图变体（ABTableViewCell）。

现在一切正常，除了绘制视图外的单元格。前8个单元格被正确绘制 - 它们获得正确的标题，图像等 - 但除此之外的所有内容都会随机重复已绘制的单元格。只有在单击/触摸单元格时，才会使用正确的数据更新单元格的标签和图像。

我的RootViewController实现了UITableViewDataSource，并在那里初始化了CustomCell。

我已经验证所有数据都正确传递给CustomCell，因此它必须与绘图有关。我想我已经跟踪了这样一个事实：drawContentView方法仅针对视图中的单元格而不是滚动到视图中的单元格。

如何再次触发drawContentView来更新进入视图的单元格？这是我必须从我的RootViewController做的事情，使用的不是：(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath？

CustomCell.h：

#import "ABTableViewCell.h"

@interface CustomCell : ABTableViewCell {
  NSString * cellSubText;
  NSString * cellText;
  NSString * cellImage;
  NSString * cellIcon;
  NSString * cellId;
}

@property (nonatomic, copy) NSString *cellSubText;
@property (nonatomic, copy) NSString *cellText;
@property (nonatomic, copy) NSString *cellImage;
@property (nonatomic, copy) NSString *cellIcon;
@property (nonatomic, copy) NSString *cellId;

@end

CustomCell.m：

#import "CustomCell.h"

@implementation CustomCell

@synthesize cellSubText, cellText, cellImage, cellIcon, cellId;

static UIFont *celSubFont = nil;
static UIFont *cellFont = nil;

+ (void)initialize {
    if(self == [CustomCell class]) {
        cellSubFont = [[UIFont systemFontOfSize:13] retain];
        cellFont = [[UIFont boldSystemFontOfSize:17] retain];
    }
}

- (void)setFirstText:(NSString *)s {
    [cellSubText release];
    cellSubText = [s copy];
    [self setNeedsDisplay]; 
}

- (void)setLastText:(NSString *)s {
    [cellText release];
    cellText = [s copy];
    [self setNeedsDisplay]; 
}

- (void)drawContentView:(CGRect)r {
    CGContextRef context = UIGraphicsGetCurrentContext();

    UIColor *backgroundColour = [UIColor whiteColor];
    UIColor *categoryColour = [UIColor grayColor];
    UIColor *titleColour = [UIColor blackColor];
  if(self.highlighted || self.selected) {
    backgroundColour = [UIColor clearColor];
        categoryColour = [UIColor whiteColor];
    titleColour = [UIColor whiteColor];
    }

    [backgroundColour set];
    CGContextFillRect(context, r);

    CGPoint pCategory;
    pCategory.x = 60;
    pCategory.y = 3;

    [categoryColour set];
  [cellSubText drawAtPoint:pCategory forWidth:235 withFont:categoryFont minFontSize:13 actualFontSize:NULL lineBreakMode:UILineBreakModeTailTruncation baselineAdjustment:UIBaselineAdjustmentNone];  

  CGPoint pTitle;
    pTitle.x = 60;
    pTitle.y = 17;

  [titleColour set];
  [cellText drawAtPoint:pTitle forWidth:235 withFont:titleFont minFontSize:17 actualFontSize:NULL lineBreakMode:UILineBreakModeTailTruncation baselineAdjustment:UIBaselineAdjustmentNone];  

  //Display the image
  CGPoint pImage;
    pImage.x = 5;
    pImage.y = 5;

  NSData *imageData = [[NSData dataWithContentsOfURL:[NSURL URLWithString:cellImage]] retain];
  UIImage *image = [UIImage imageWithData:imageData];
  [image drawAtPoint:pImage];
}

- (void)dealloc {
  [cellSubText release];
  [cellText release];
  [cellIcon release];
  [cellImage release];
  [super dealloc];
}
@end

RootViewController.m

#import "CustomCell.h"
#import "MyAppDelegate.h"
#import "RootViewController.h"
#import "DetailViewController.h"

@implementation RootViewController
@synthesize tableDataArray;

- (void)viewDidLoad {
  [super viewDidLoad];
}

//Override the default initWithNibName method
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil tableDataSource:(NSArray*)tableData {
  if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
    // Custom initialization
    tableDataArray = [tableData retain];   
  }
  return self;
}

-(void)viewWillAppear:(BOOL)animated {
  appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];    
  [super viewWillAppear:animated];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
  return [self.tableDataArray count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CustomCellIdentifier = @"CustomCellIdentifier";

    CustomCell *cell = (CustomCell *)[tableView dequeueReusableCellWithIdentifier:CustomCellIdentifier];
    if(cell == nil) {
        cell = [[[CustomCell alloc] initWithFrame:CGRectZero reuseIdentifier:CustomCellIdentifier] retain];
    }
  cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
  NSUInteger row = [indexPath row];
  NSDictionary *rowData = [self.tableDataArray objectAtIndex:row];
    cell.cellSubText = [rowData objectForKey:@"Date"];
    cell.cellText = [rowData objectForKey:@"Name"];
  cell.cellImage = [rowData objectForKey:@"Image"];
  cell.cellId = [rowData objectForKey:@"Id"];

    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { 
  NSString *selectedCell = [tableDataArray objectAtIndex:indexPath.row];

  DetailViewController *detailViewController = [[DetailViewController alloc] initWithNibName:@"DetailView" bundle:[NSBundle mainBundle]];
  detailViewController.selectedCell = selectedCell;
  [self.navigationController pushViewController:detailViewController animated:YES];
  [detailViewController release];
  detailViewController = nil;
}

- (void)dealloc { 
    [super dealloc];
}

@end

Answer 1

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CustomCellIdentifier = @"CustomCellIdentifier";

    CustomCell *cell = (CustomCell *)[tableView dequeueReusableCellWithIdentifier:CustomCellIdentifier];
    if(cell == nil) {
        cell = [[[CustomCell alloc] initWithFrame:CGRectZero reuseIdentifier:CustomCellIdentifier] retain];
    }

静态NSString * CustomCellIdentifier = @“CustomCellIdentifier”;

以上粗体代码正在为您做出这样的行为。

在iphone中，tableview重用已经创建的单元格。这是不可见的。例如：前8个单元格将单独创建。当你向下滚动时，前几行将被隐藏。现在隐藏的细胞将被现在要显示的细胞重复使用。这就是为什么你会得到这种行为:)如果表视图内容较少，请尝试给出唯一标识符。

或

如果您的单元格是UITableViewCell的子类，则可以覆盖

- （void）prepareForReuse

在从

返回单元格之前调用

- （UITableViewCell *）dequeueReusableCellWithIdentifier：（NSString *）标识符

Answer 2

表格视图可能会重复使用您的单元格，并通过重复使用当前设置的单元格为您提供随机结果;你看过- (void)prepareForReuse班的UITableViewCell吗？

Answer 3

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    int myButtonTag = 1000+(10*indexPath.section)+indexPath.row;
    NSString *kCellID = [NSString stringWithFormat:@"cellId_%i",myButtonTag];

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellID];
    if (cell == nil)
    {
       //[[cell viewWithTag:myButtonTag] removeFromSuperview];
       cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:kCellID];
    }

    cell.accessoryType = UITableViewCellAccessoryNone;
}

为了在UITableView中快速滚动（特别是在ARC控制的环境中）时从单元格中删除数据，请记住在cellId字符串中设置唯一的CellIdentifier，这会使旧单元格出列。这样它就可以免于填充重复的细胞。希望您觉得合适并符合您的喜好。干杯！

使用正确的数据绘制自定义UITableCells

3 个答案: