133自动滚动到被选中单元格（扩展知识：滚动到头部和底部）

效果如下：

ViewController.h

1 #import <UIKit/UIKit.h>

2 

3 @interface ViewController : UITableViewController

4 @property (strong, nonatomic) NSMutableArray *mArrDataSource;

5 

6 @end

ViewController.m

  1 #import "ViewController.h"

  2 

  3 @interface ViewController ()

  4 - (void)layoutUI;

  5 - (UIBarButtonItem *)barButtonItemForToolbar:(NSString *)title selectorName:(NSString *)selectorName;

  6 - (void)scrollToTopDidPush:(UIBarButtonItem *)sender;

  7 - (void)scrollToSelectedRowDidPush:(UIBarButtonItem *)sender;

  8 - (void)scrollToBottomDidPush:(UIBarButtonItem *)sender;

  9 @end

 10 

 11 @implementation ViewController

 12 #define kRowCount 64

 13 

 14 - (void)viewDidLoad {

 15     [super viewDidLoad];

 16     

 17     [self layoutUI];

 18 }

 19 

 20 - (void)didReceiveMemoryWarning {

 21     [super didReceiveMemoryWarning];

 22     // Dispose of any resources that can be recreated.

 23 }

 24 

 25 - (void)viewDidAppear:(BOOL)animated {

 26     [super viewDidAppear:animated];

 27     

 28     [self.navigationController setNavigationBarHidden:NO animated:animated];

 29     [self.navigationController setToolbarHidden:NO animated:animated];

 30 }

 31 

 32 - (void)layoutUI {

 33     _mArrDataSource = [[NSMutableArray alloc] initWithCapacity:kRowCount];

 34     for (NSUInteger i=0; i<kRowCount; i++) {

 35         [_mArrDataSource addObject:[NSNumber numberWithUnsignedInteger:i]];

 36     }

 37     [self.tableView setAllowsSelection:YES]; //设置在普通状态中，是否允许选中；默认值为YES

 38     [self.tableView setAllowsSelectionDuringEditing:YES]; //设置在编辑状态中，是否允许选中；默认值为YES

 39     

 40     self.navigationItem.title = @"自动滚动到被选中单元格";

 41     UIBarButtonItem *barBtnScrollToTop = [self barButtonItemForToolbar:@"滚动到头部" selectorName:@"scrollToTopDidPush:"];

 42     UIBarButtonItem *barBtnScrollToSelectedRow = [self barButtonItemForToolbar:@"滚动到被选中单元格" selectorName:@"scrollToSelectedRowDidPush:"];

 43     UIBarButtonItem *barBtnScrollToBottom = [self barButtonItemForToolbar:@"滚动到底部" selectorName:@"scrollToBottomDidPush:"];

 44     self.toolbarItems = @[barBtnScrollToTop, barBtnScrollToSelectedRow, barBtnScrollToBottom];

 45 }

 46 

 47 - (UIBarButtonItem *)barButtonItemForToolbar:(NSString *)title selectorName:(NSString *)selectorName {

 48     UIBarButtonItem *barBtnItem = [[UIBarButtonItem alloc] initWithTitle:title

 49                                                                    style:UIBarButtonItemStyleDone

 50                                                                   target:self

 51                                                                   action:NSSelectorFromString(selectorName)];

 52     return barBtnItem;

 53 }

 54 

 55 - (void)scrollToTopDidPush:(UIBarButtonItem *)sender {

 56     [self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]

 57                           atScrollPosition:UITableViewScrollPositionTop

 58                                                       animated:YES];

 59 }

 60 

 61 - (void)scrollToSelectedRowDidPush:(UIBarButtonItem *)sender {

 62     [self.tableView scrollToNearestSelectedRowAtScrollPosition:UITableViewScrollPositionNone

 63                                                       animated:YES];

 64     

 65     /*

 66      typedef NS_ENUM(NSInteger, UITableViewScrollPosition) {

 67      UITableViewScrollPositionNone,

 68      UITableViewScrollPositionTop,

 69      UITableViewScrollPositionMiddle,

 70      UITableViewScrollPositionBottom

 71      };                // scroll so row of interest is completely visible at top/center/bottom of view

 72      */

 73 }

 74 

 75 - (void)scrollToBottomDidPush:(UIBarButtonItem *)sender {

 76     [self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:(kRowCount - 1) inSection:0]

 77                           atScrollPosition:UITableViewScrollPositionBottom

 78                                   animated:YES];

 79 }

 80 

 81 #pragma mark - TableView

 82 - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {

 83     return @"列表";

 84 }

 85 

 86 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {

 87     return 1;

 88 }

 89 

 90 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

 91     return kRowCount;

 92 }

 93 

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

 95     static NSString *cellIdentifier = @"cellIdentifier";

 96     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

 97     if (!cell) {

 98         cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];

 99     }

100     

101     NSInteger row = indexPath.row;

102     cell.textLabel.text = [_mArrDataSource[row] stringValue];

103     

104     return cell;

105 }

106 

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

108     

109 }

110 

111 @end

AppDelegate.h

1 #import <UIKit/UIKit.h>

2 

3 @interface AppDelegate : UIResponder <UIApplicationDelegate>

4 @property (strong, nonatomic) UIWindow *window;

5 @property (strong, nonatomic) UINavigationController *navigationController;

6 

7 @end

AppDelegate.m

 1 #import "AppDelegate.h"

 2 #import "ViewController.h"

 3 

 4 @interface AppDelegate ()

 5 @end

 6 

 7 @implementation AppDelegate

 8 

 9 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

10     _window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

11     ViewController *viewController = [[ViewController alloc] init];

12     _navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];

13     _window.rootViewController = _navigationController;

14     //[_window addSubview:_navigationController.view]; //当_window.rootViewController关联时，这一句可有可无

15     [_window makeKeyAndVisible];

16     return YES;

17 }

18 

19 - (void)applicationWillResignActive:(UIApplication *)application {

20 }

21 

22 - (void)applicationDidEnterBackground:(UIApplication *)application {

23 }

24 

25 - (void)applicationWillEnterForeground:(UIApplication *)application {

26 }

27 

28 - (void)applicationDidBecomeActive:(UIApplication *)application {

29 }

30 

31 - (void)applicationWillTerminate:(UIApplication *)application {

32 }

33 

34 @end