UILog

有時候呈現多個 View 時,用的資料會有相關性,此例以兩個 UITableViewController 為例,他們的 dataSource 是同一個來源,當透過底下的 TabBar 進行接換時,會自動增加 dataSource 的資料,接著呈現最新的清單列表,並且在 Console 上印出從哪個 View 新增的資料,以及目前 dataSource 的個數。此作法是共用記憶體資料,另一種作法是每次讀資料都從 databases 或 file 更新。

程式碼:

DataConnectAppDelegate.h

#import <UIKit/UIKit.h>

@interface DataConnectAppDelegate : NSObject <UIApplicationDelegate> {
    UIWindow *window;
    NSMutableArray *dataSource;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;

@end

DataConnectAppDelegate.m

#import "DataConnectAppDelegate.h"
#import "MyTableViewController.h"

@implementation DataConnectAppDelegate

@synthesize window;

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

    // Override point for customization after application launch
    dataSource = [[NSMutableArray alloc] init];
    
    MyTableViewController *a = [[MyTableViewController alloc] init];
    a.dataSource = dataSource;
    a.title = @"View A";
    
    MyTableViewController *b = [[MyTableViewController alloc] init];
    b.dataSource = dataSource;
    b.title = @"View B";
    
    UITabBarController *tabBar = [[UITabBarController alloc] init];

    tabBar.viewControllers = [NSArray arrayWithObjects:a, b, nil];
    [window addSubview:tabBar.view];
    [window makeKeyAndVisible];

    
    return YES;
}

- (void)dealloc {
    [dataSource release];
    [window release];
    [super dealloc];
}

@end

 MyTableViewController.h

#import <UIKit/UIKit.h>

@interface MyTableViewController : UITableViewController {
    NSMutableArray *dataSource;
}

@property (nonatomic ,assign) NSMutableArray *dataSource;


@end

 MyTableViewController.m

#import "MyTableViewController.h"

@implementation MyTableViewController

@synthesize dataSource;
#pragma mark -
#pragma mark Initialization

#pragma mark -
#pragma mark View lifecycle

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    NSLog( @"In,%3@, %d" , self.title , [self.dataSource count]);
    [self.dataSource addObject:[NSString stringWithFormat:@"%d) %@" , [self.dataSource count] , self.title ]];
    [[self tableView] reloadData];

}

#pragma mark -
#pragma mark Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // Return the number of sections.
    return 1;
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    if( dataSource == nil )
        return 0;
    return [dataSource count];

}

// Customize the appearance of table view cells.
- (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];
    }
    
    // Configure the cell...
    cell.textLabel.text = (NSString*)[dataSource objectAtIndex:indexPath.row];
    return cell;
}

#pragma mark -
#pragma mark Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    // Navigation logic may go here. Create and push another view controller.
    /*
     <#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc] initWithNibName:@"<#Nib name#>" bundle:nil];
     // ...
     // Pass the selected object to the new view controller.
     [self.navigationController pushViewController:detailViewController animated:YES];
     [detailViewController release];
     */
}

#pragma mark -
#pragma mark Memory management

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];
    
    // Relinquish ownership any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    // Relinquish ownership of anything that can be recreated in viewDidLoad or on demand.
    // For example: self.myOutlet = nil;
}

- (void)dealloc {
    [super dealloc];
}

@end

成果:

UI1 UI2
左邊一開始執行程式時,由於預設是進入 View A ,故一開始是新增一筆 View A 資料,接著點選下方的 TabBar 切換到 View B 時,則會新增另一筆資料 View B ,接著再 Table View 就會呈現出兩筆資料,最後,不斷掉交替切換到 View A 或 View B 那則會呈現以下的資料列表

UI3

此例在 UITableViewController 中的 - (void)viewWillAppear:(BOOL)animated; 進行實作的,要記得呼叫 [[self tableView] reloadData]; 才會更新 Table View 的資料,否則不斷地切換就只會顯示上面兩個小圖而已,那就是因為沒有叫 tableView 更新資料。


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