UITableViewCell 如何与其 UITableView 通信? [英] How does UITableViewCell communicate with its UITableView?

问题描述

我目前正在创建一个自定义网格视图，这意味着我正在创建一个与 UITableView 有很多共同点的类.我想要做的一件事是单元格和网格视图的通信.

I am currently creating a custom grid view, which means that I am creating a class that has a lot in common with UITableView. One of the things that I want to get right is the communication of the cells and the grid view.

因此，我想知道表格视图单元格如何与其表格视图对话.比如cell如何通知table view它的delete按钮被点击了，cell需要从table view中移除?

I was therefore wondering how a table view cell talks to its table view. For example, how does the cell notify the table view that its delete button was tapped and the cell needs to be removed from the table view?

有几种可能的情况，但我不确定 Apple 正在使用哪一种，因为 UITableView 或 UITableViewCell 的标头揭示了这一点(或者我忽略了什么?).

There are several possible scenarios, but I am not sure which one is being used by Apple since the headers of UITableView or UITableViewCell reveal this (or am I overlooking something).

最终，目标是让单元格和网格视图私下通信，即不暴露任何公共方法或协议(如果可能的话).

Ultimately, the goal is to let the cell and the grid view communicate in private, that is, without exposing any public methods or protocols (if this is possible).

推荐答案

现在删除按钮可能是一个糟糕的例子，因为 iOS 有一个内置的方法，它允许你删除行并通知你的数据源调用:

Now a delete button might be a poor example because iOS has a built in method which allows you to delete rows and notify your datasource called:

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath

但是，为了便于理解，如果您想向 tableview 单元格添加按钮并让它执行标准 iOS 库中没有的操作，您将在单元格中创建一个委托并设置 tableview 的数据源文件作为代表.

However, for the sake of understanding if you wanted to add a button to your tableview cell and have it perform an action that isn't in the standard iOS library you would create a delegate in your cell and set your tableview's datasource file as the delegate.

基本上你会像这样子类化 UITableViewCell

Basically you would subclass UITableViewCell like so

MyCustomCell.h

MyCustomCell.h

@protocol MyCustomCellDelegate;
@interface MyCustomCell : UITableViewCell
@property (nonatomic, unsafe_unretained) id <MyCustomCellDelegate> delegate; //Holds a reference to our tableView class so we can call to it. 
@property (nonatomic, retain) NSIndexPath *indexPath; //Holds the indexPath of the cell so we know what cell had their delete button pressed
@end

/* Every class that has <MyCustomCellDelegate> in their .h must have these methods in them */
@protocol MyCustomCellDelegate <NSObject>
- (void)didTapDeleteButton:(MyCustomCell *)cell;
@end

MyCustomCell.m

MyCustomCell.m

@synthesize delegate = _delegate;
@synthesize indexPath = _indexPath;
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    if (self) 
    {
    /* Create a button and make it call to a method in THIS class called deleteButtonTapped */
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(5, 5, 25, 25);
    [button addTarget:self action:@selector(deleteButtonTapped:) forControlEvents:UIControlEventTouchUpInside];

    }
    return self;
}

/**
 * This is the method that is called when the button is clicked.
 * All it does is call to the delegate. (Whatever class we assigned to the 'delegate' property)
 */
- (void)deleteButtonTapped:(id)sender
{
    [self.delegate didTapDeleteButton:self];
}

您的 TableView 的数据源看起来像这样.

Your TableView's datasource would look something like this.

MyDataSource.h

MyDataSource.h

/* We conform to the delegate. Which basically means "Hey you know those methods that we defined in that @protocol I've got them and you can safely call to them" */
@interface MyDataSource : UIViewController <MyCustomCellDelegate, UITableViewDelegate, UITableViewDataSource>
 @property (nonatomic,retain) NSArray *tableData;//We will pretend this is the table data
 @property (nonatomic,retain) UITableView *tableView;// We will pretend this is the tableview

@end

MyDataSource.m

MyDataSource.m

//We will pretend we synthesized and initialized the properties
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{
    MyCustomCell *cell = [tableView dequeueReusableCellWithIdentifier: @"MyCustomCell"];
    if (!cell) 
        cell = [[DownloadQueueCell alloc] initWithStyle: UITableViewCellStyleDefault reuseIdentifier: @"MyCustomCell"];
    cell.delegate = self;      // Make sure we set the cell delegate property to this file so that it calls to this file when the button is pressed.
    cell.indexPath = indexPath;// Set the indexPath for later use so we know what row had it's button pressed.
    return cell;
}


- (void)didTapDeleteButton:(MyCustomCell *)cell;
{

   // From here we would likely call to the apple API to Delete a row cleanly and animated
   // However, since this example is ignoring the fact that they exist
   // We will remove the object from the tableData array and reload the data
   [self.tableData removeObjectAtIndexPath:cell.indexPath];
   [self.tableView reloadData];

}

基本上，长话短说.对于您的 gridview，您只需创建一个委托方法，告诉用户某个按钮被按下.

Basically, long story short. For your gridview you would just create a delegate method that tells the user a certain button was pressed.

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