UITableViewCell的重用

可能的错误分析：

在使用UITableViewCell的时候，一般都会重用Cell以提高性能和节省内存开销。但是每个Cell的子控件或者子控件的内容可能会不同，这时重用会导致显示错误(新显示的cell，拥有了它重用的cell的子控件等错误)。

解决办法：

1.子控件不同时，重用时删除cell的子控件，显示新的cell时，重新创建子控件。

2.子控件相同时，无需删除子控件，但重用时对每个子控件重新赋值。

3.cell较少时，无需使用重用机制。

Demo1：这里是错误分析的第一种情况

正确代码，间隔显示如下图色块。

当不考虑去重时，会出现如下情况

其实，核心代码只在ViewController.m中，重用cell的时候删除cell的子控件(或者只删除其子控件的子控件，具体视情况而定)

while ([cell.cellImgView.subviews lastObject] != nil)

    {

     [[cell.cellImgView.subviewslastObject] removeFromSuperview];

    }

下面贴出代码

<pre name="code" class="objc"><pre name="code" class="objc">////  XYDTableViewCell.h//  UITableViewCell重用////  Created by  laisenmi on 10/23/14.//  Copyright (c) 2014 laisenmi. All rights reserved.//  自定义的 Cell#import <UIKit/UIKit.h>@interface XYDTableViewCell : UITableViewCell{    UIView *cellImgView;}@property(nonatomic,strong) UIView *cellImgView;@end

<pre name="code" class="objc">////  XYDTableViewCell.m//  UITableViewCell重用////  Created by  laisenmi on 10/23/14.//  Copyright (c) 2014 laisenmi. All rights reserved.//  自定义的 Cell#import "XYDTableViewCell.h"@implementation XYDTableViewCell@synthesize cellImgView;-(id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier{    if (self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]) {        self.cellImgView = [[UIView alloc]initWithFrame:self.frame];        [self addSubview:self.cellImgView];    }    return self;}@end

<pre name="code" class="objc">////  ViewController.h//  UITableViewCell重用////  Created by  laisenmi on 10/23/14.//  Copyright (c) 2014 laisenmi. All rights reserved.//#import <UIKit/UIKit.h>@interface ViewController : UIViewController<UITableViewDataSource,UITableViewDelegate>{    UITableView *myTableView;}@property(nonatomic,strong) UITableView *myTableView;@end

<pre name="code" class="objc">////  ViewController.m//  UITableViewCell重用////  Created by  laisenmi on 10/23/14.//  Copyright (c) 2014 laisenmi. All rights reserved.//#import "ViewController.h"#import "XYDTableViewCell.h"@interface ViewController ()@end@implementation ViewController@synthesize myTableView;- (void)viewDidLoad {    [super viewDidLoad];        float contentViewW = 305;    float contentViewH = 337;    float contentViewX = 7.5;    float contentViewY = 79;    CGRect contentViewFrame = CGRectMake(contentViewX, contentViewY, contentViewW, contentViewH);    self.myTableView = [[UITableView alloc]initWithFrame:contentViewFrame];    [self.view addSubview:self.myTableView];        self.myTableView.backgroundColor = [UIColor clearColor];    self.myTableView.separatorStyle = UITableViewCellSeparatorStyleNone;    self.myTableView.delegate = self;    self.myTableView.dataSource = self;    // Do any additional setup after loading the view, typically from a nib.}-(XYDTableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{    static NSString *ID = @"cell";    XYDTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];    if (cell == nil) {        cell = [[XYDTableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:ID];    }        while ([cell.cellImgView.subviews lastObject] != nil) {        [[cell.cellImgView.subviews lastObject] removeFromSuperview];    }        if (indexPath.row == 0 || indexPath.row == 2 || indexPath.row == 4 || indexPath.row  == 6 || indexPath.row  == 8 || indexPath.row  == 10  ) {        float BgOfCoverX = 0;        float BgOfCoverY = 0;        float BgOfCoverW = 305;        float BgOfCoverH = 130;        CGRect BgOfCoverFrame = CGRectMake(BgOfCoverX, BgOfCoverY, BgOfCoverW, BgOfCoverH);        UIImageView *BgOfCover = [[UIImageView  alloc]initWithFrame:BgOfCoverFrame];        BgOfCover.backgroundColor = [UIColor orangeColor];        [cell.cellImgView addSubview:BgOfCover];    }        if (indexPath.row == 1 || indexPath.row == 3 || indexPath.row == 5 || indexPath.row == 7 || indexPath.row == 9 || indexPath.row == 11 ) {        float BgOfCover1X = 0;        float BgOfCover1Y = 0;        float BgOfCover1W = 150;        float BgOfCover1H = 100;        CGRect BgOfCover1Frame = CGRectMake(BgOfCover1X, BgOfCover1Y, BgOfCover1W, BgOfCover1H);                UIImageView  *BgOfCover1 = [[UIImageView  alloc]initWithFrame:BgOfCover1Frame]; BgOfCover1.backgroundColor = [UIColor greenColor];        BgOfCover1.backgroundColor = [UIColor redColor];        [cell.cellImgView addSubview:BgOfCover1];                        float BgOfCover2X = 155;        float BgOfCover2Y = 0;        float BgOfCover2W = 150;        float BgOfCover2H = 100;        CGRect BgOfCover2Frame = CGRectMake(BgOfCover2X, BgOfCover2Y, BgOfCover2W, BgOfCover2H);                UIImageView  *BgOfCover2 = [[UIImageView  alloc]initWithFrame:BgOfCover2Frame];        BgOfCover2.backgroundColor = [UIColor greenColor];        [cell.cellImgView addSubview:BgOfCover2];    }        cell.backgroundColor = [UIColor clearColor];    cell.selectionStyle = UITableViewCellSelectionStyleNone;    return cell;}-(float)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{    return 135;}-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{    return 12;}@end