滚动离开屏幕时 UITableViewCell 附件消失

Question

我有一个装满对象的 UITableView。在 didSelectRowAtIndexPath 方法中，我有一个 UITableViewCellAccessoryCheckmark 在选中行时出现，在未选中时消失。

didSelectRowAtIndexPath 方法的代码如下：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
[tableView deselectRowAtIndexPath:indexPath animated:NO];
 UITableViewCell *curCell = [beerTable cellForRowAtIndexPath:indexPath];

if (curCell.accessoryType == UITableViewCellAccessoryCheckmark) {
    [curCell setAccessoryType:UITableViewCellAccessoryNone];
    compareCount = (compareCount - 1);

    if (tableView == [[self searchDisplayController] searchResultsTableView]) {
        NSString *objBeer = [searchResults objectAtIndex:indexPath.row];
        [compareBeers removeObject:[searchResults objectAtIndex:indexPath.row]];
        [compareCarbs removeObject:[carbAmount objectAtIndex:[beerNames indexOfObject:objBeer]]];
    }
    else {
        [compareBeers removeObject:[beerNames objectAtIndex:indexPath.row]];
        [compareCarbs removeObject:[carbAmount objectAtIndex:indexPath.row]];
    }

}
else {
    [curCell setAccessoryType:UITableViewCellAccessoryCheckmark];
    compareCount = (compareCount + 1);

    if (tableView == [[self searchDisplayController] searchResultsTableView]) {
        NSString *objBeer = [searchResults objectAtIndex:indexPath.row];
        [compareBeers addObject:[searchResults objectAtIndex:indexPath.row]];
        [compareCarbs addObject:[carbAmount objectAtIndex:[beerNames indexOfObject:objBeer]]];
    }
    else {
        [compareBeers addObject:[beerNames objectAtIndex:indexPath.row]];
        [compareCarbs addObject:[carbAmount objectAtIndex:indexPath.row]];
    }

}

if (compareCount > 0) {
    if (compareOn == YES){
    }
    else {
    compareButton.enabled = YES;
    UIImage *image = [UIImage imageNamed:@"redbutton.png"];
    [compareButton setImage:image];
    }
}

else {
    compareButton.enabled = NO;
    [compareButton setImage:nil];
    [compareButton setCustomView:nil];
}

}

我也有这个作为我的cellForIndexPath：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {


static NSString *CellIdentifier = @"CustomCell";

CustomCell *cell = (CustomCell *) [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {

    NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"CustomCell" owner:self options:nil];

    for (id currentObject in topLevelObjects){
        if ([currentObject isKindOfClass:[UITableViewCell class]]){
            cell =  (CustomCell *) currentObject;
            break;
        }
    }
}

// Setting separate tables correctly....


return cell;
}

My problem is that when the cell that is selected is scrolled out of view the checkmark associated with that value is now gone when back into view.

我应该怎么做才能使复选标记不消失？

谢谢

Answer 1

当您滚动浏览数据时，您的单元格会被重新使用（这就是 dequeueReusableCellWithIdentifier 所做的）。在 didSelectRowAtIndexPath 中获得复选标记的单元格将被回收用于不同的行，并且不再与选中的行有任何连接。

您需要在CellForrowatIndExpath中设置/解开附件视图，因此当签到的行滚动回到视图中时，它们会得到适当检查。

Answer 2

对于任何想要更通用方法和多个选定单元格的人

首先创建一个 (NSMutableArray *)selectedCells 来跟踪选定的单元格。 接下来实现2个委托方法

-(void)tableView:(UITableView *)tableView 
    didSelectRowAtIndexPath:(NSIndexPath *)indexPath{

//add the checkmark to cell when selected
if ([tableView cellForRowAtIndexPath:indexPath].accessoryType == UITableViewCellAccessoryNone){
[tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryCheckmark;

}

//once selected add that selected cell to the selectedCells array 

[self.selectedCells addObject:@(indexPath.row) ];

}

与

-(void)tableView:(UITableView *)tableView 
                 didDeselectRowAtIndexPath:(NSIndexPath *)indexPath{ 

//set the accessory type back to none 
if([tableView cellForRowAtIndexPath:indexPath].accessoryType == UITableViewCellAccessoryCheckmark){
[tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryNone;
}

//remove the selected cells index from the selectedCells array
[self.selectedCells removeObject:@(indexPath.row) ];

}

现在，当您选择一个单元格时，会添加一个复选标记，并将 indexPath.row 存储到 NSMutableArray 中。当您取消选择该单元格时，它会删除复选标记并将其从数组中删除。这意味着该数组将仅保存已检查的单元格。

然后我们使用该数组在 cellForRowAtIndexPath 方法中为单元格提供正确的附件类型。每次 tableView 需要一个单元格时调用此方法，我们告诉它是否在创建时需要有一个复选标记。

-(UITableViewCell *)tableView:(UITableView *)tableView 
                cellForRowAtIndexPath:(NSIndexPath *)indexPath{

 static NSString *CellIdentifier = @"Cell";
 UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (cell == nil) {
  cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];

//Create an NSNumber to hold the row of the cell to be created   
   NSNumber *rowNsNum = [NSNumber numberWithUnsignedInt:indexPath.row];

//then ask the array if the selectedCells array has that object.
//if it does then that cell needs a checkmark when created.

if ([self.selectedCells containsObject:rowNsNum]){
   cell.accessoryType = UITableViewCellAccessoryCheckmark;
     }
else { cell.accessoryType = UITableViewCellAccessoryNone;
     }

    [cell.textLabel setText:@"your contents"];
 }

 return cell;
 }

Answer 3

UITableViewCell 在滚动时被回收。因此，当您再次上下滚动 tableView 时，您看到的单元格可能与之前可见的单元格不同。

您需要每次在 cellForRowAtIndexPath 中重置单元格的状态。你的代码有这个评论区 // 正确设置单独的表......

这是您进行设置的地方。当它被调用时，检查单元格是否应该显示一个复选标记，并相应地设置它

Answer 4

尝试在 didSelectRow 方法中将选定单元格的选定索引存储在数组或字典中，并在 cellForRowAtIndexPath 中检查该索引是否在数组中可用，然后通过设置 accesoryType 选中该单元格。希望你能理解

Answer 5

这是我认为效果最好的：

（只是“添加这个”和“结束添加这个”之间的任何代码）

另外，请确保将“(Your Number ofRows)”更改为返回 int 或本身为 int 的对象。比如myCustomArray.count，或者24。

//In .h file add this
NSMutableArray *indexArray;

//in .m file 

- (void)viewDidLoad {
    //Add this
    indexArray = [[NSMutableArray alloc] init];
    int i;
    for (i = 0; i <= (Your Number ofRows); i++) {
        [indexArray addObject:[NSNumber numberWithDouble:0]];
    }
NSLog(@"indexArray = %@",indexArray);//You can check the console now to see if you have an array of "zeros" 
    //End Add this
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
[tableView deselectRowAtIndexPath:indexPath animated:NO];
UITableViewCell *curCell = [beerTable cellForRowAtIndexPath:indexPath];


if (curCell.accessoryType == UITableViewCellAccessoryCheckmark) {
    [curCell setAccessoryType:UITableViewCellAccessoryNone];
    compareCount = (compareCount - 1);

    //Add this
    [indexArray replaceObjectAtIndex:indexPath.row withObject:[NSNumber numberWithDouble:0]]; 
    //End Add this


    if (tableView == [[self searchDisplayController] searchResultsTableView]) {
        NSString *objBeer = [searchResults objectAtIndex:indexPath.row];
        [compareBeers removeObject:[searchResults objectAtIndex:indexPath.row]];
        [compareCarbs removeObject:[carbAmount objectAtIndex:[beerNames indexOfObject:objBeer]]];
    }
    else {
        [compareBeers removeObject:[beerNames objectAtIndex:indexPath.row]];
        [compareCarbs removeObject:[carbAmount objectAtIndex:indexPath.row]];
    }

}
else {
    [curCell setAccessoryType:UITableViewCellAccessoryCheckmark];
    compareCount = (compareCount + 1);

    //Add this
    [indexArray replaceObjectAtIndex:indexPath.row withObject:[NSNumber numberWithDouble:1]]; 
    //End Add this

    if (tableView == [[self searchDisplayController] searchResultsTableView]) {
        NSString *objBeer = [searchResults objectAtIndex:indexPath.row];
        [compareBeers addObject:[searchResults objectAtIndex:indexPath.row]];
        [compareCarbs addObject:[carbAmount objectAtIndex:[beerNames indexOfObject:objBeer]]];
    }
    else {
        [compareBeers addObject:[beerNames objectAtIndex:indexPath.row]];
        [compareCarbs addObject:[carbAmount objectAtIndex:indexPath.row]];
    }

}

if (compareCount > 0) {
    if (compareOn == YES){
    }
    else {
        compareButton.enabled = YES;
        UIImage *image = [UIImage imageNamed:@"redbutton.png"];
        [compareButton setImage:image];
    }
}

else {
    compareButton.enabled = NO;
    [compareButton setImage:nil];
    [compareButton setCustomView:nil];
}

}    



- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {


static NSString *CellIdentifier = @"CustomCell";

CustomCell *cell = (CustomCell *) [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {

    NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"CustomCell" owner:self options:nil];

    for (id currentObject in topLevelObjects){
        if ([currentObject isKindOfClass:[UITableViewCell class]]){
            cell =  (CustomCell *) currentObject;
            break;
        }
    }
}

// Setting separate tables correctly....

//Add this
if ([[indexArray objectAtIndex:indexPath.row] doubleValue] == 1) {
    cell.accesoryType = UITableViewCellAccesoryTypeCheckmark;
} else {
    cell.accesoryType = UITableViewCellAccesoryTypeNone; 
}
//End Add this 

return cell;
}