为什么我们在UITableViewController中检查if(cell == nil)? [英] Why we are checking if (cell == nil) in UITableViewController?
问题描述
我正在尝试实现基于UITableView的Application.For我选择UITableViewStyle是Group。在我的TableView中,它们是 15 部分,每个部分有1行。
I am trying to implement UITableView based Application.For that I select UITableViewStyle is Group.In my TableView their is 15 section each section having 1 row.
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 15;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 1;
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.section==12)
{
return 120;
}
else
{
return 60;
}
}
我想在Section上添加一个UITextView 12
I want add a UITextView on Section 12
为此我做了以下代码
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
if ([indexPath section] == 12)
{
if([indexPath row]==0)
{
descriptionTextField=[[UITextView alloc] initWithFrame:CGRectMake(5, 8, 290, 106)];
descriptionTextField.font = [UIFont systemFontOfSize:15.0];
descriptionTextField.backgroundColor=[UIColor scrollViewTexturedBackgroundColor];
[descriptionTextField setDelegate:self];
[descriptionTextField setTag:2];
[descriptionTextField setText:@"Enter Location Description."];
descriptionTextField.keyboardType=UIKeyboardTypeDefault;
descriptionTextField.returnKeyType=UIReturnKeyNext;
descriptionTextField.textColor=[UIColor blackColor];
descriptionTextField.editable=YES;
descriptionTextField.autocapitalizationType=UITextAutocapitalizationTypeWords;
descriptionTextField.autocorrectionType=UITextAutocorrectionTypeDefault;
descriptionTextField.textAlignment=UITextAlignmentLeft;
UIToolbar* keboardToolBar=[[UIToolbar alloc]initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, 32)];
UIBarButtonItem *extra=[[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];
UIBarButtonItem *Done=[[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(keyboardDoneButtonActin:)];
[Done setWidth:65.0f];
[keboardToolBar setItems:[[[NSArray alloc]initWithObjects:extra,Done, nil]autorelease] ];
[extra release];
[Done release];
[keboardToolBar setTintColor:[UIColor blackColor]];
[keboardToolBar setAlpha:.70];
[descriptionTextField setInputAccessoryView:keboardToolBar];
[descriptionTextField setTag:101];
[cell.contentView addSubview:descriptionTextField];
[descriptionTextField release];
}
}
return cell;
}
在initil阶段,这样的表视图
In the initil stage the table view like this
如果我上下滚动tableview,则更改uitextView部分,它将显示多个位置。
if i am scrolling tableview up and down , then the uitextView section changed and it will display multiple location.
我无法理解我的错,为什么会这样?
I can't understand my fault, why this happend?
如果在if(cell == nil)一边实现上述代码
if am implementing the above code in side the if(cell==nil)
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
if ([indexPath section] == 12)
{
if([indexPath row]==0)
{
**/* implemention all code here*/**
[cell.contentView addSubview:descriptionTextField];
[descriptionTextField release];
}
}
return cell;
}
UITextView不显示,i认为它不是分配。
UITextView not disply, i think it is not allocating.
那么在
中实现的代码之间有什么区别if(cell == nil)
{
在
}里面
so what is the difference between code implementing in if (cell == nil) { inside }
if(cell == nil)
{
}
out side
if (cell == nil) { } out side
推荐答案
NSString *CellIdentifier = [NSString stringWithFormat:@"%i",indexPath.row];
// Dequeue or create a cell of the appropriate type.
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
这可以用来代替
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
这是在单元格内写入的简单示例== nill
this is the simple example to write inside the cell ==nill
- (UITableViewCell *)tableView:(UITableView *)tableView1 cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = @"CellIdentifier";
// Dequeue or create a cell of the appropriate type.
UITableViewCell *cell = [tableView1 dequeueReusableCellWithIdentifier:CellIdentifier];
cell= nil;
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
[[cell.contentView viewWithTag:100+indexPath.row] removeFromSuperview];
UIView *selectview = [[UIView alloc]initWithFrame:CGRectMake(0, 0, cell.frame.size.width, 30)];
[selectview setBackgroundColor:[UIColor colorWithPatternImage:[UIImage imageNamed:@"strip_s12A-1_h.png"]]];
cell.selectedBackgroundView = selectview;
[selectview release];
UILabel *cellTitle=[[UILabel alloc]initWithFrame:CGRectMake(40, 0, 300, 30)];
//cellTitle.adjustsFontSizeToFitWidth=YES;
[cellTitle setBackgroundColor:[UIColor clearColor]];
[cellTitle setFont:[UIFont fontWithName:@"Arial Rounded MT Bold" size:17]];
[cellTitle setTextColor:[UIColor blackColor]];
cellTitle.tag = 100+indexPath.row;
cellTitle.text= [[[cellArray objectAtIndex:indexPath.section]objectAtIndex:indexPath.row] valueForKey:@"Des2"];
[cell.contentView addSubview:cellTitle];
[cellTitle release];
}
return cell;
}
我认为足够了
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