Chez Bob

levelsOfDetail是指，从UIScrollView的1倍zoomScale开始，能够支持细节刷新的缩小级数。每一级是上一级的1/2，所 以假设levelsOfDetail = n，levelsOfDetailBias不指定的话，CATiledLayer将会在UIScrollView的zoomScale为以下数字时重新 drawLayer
2^-1 -> 2^-2 -> … -> 2^-n
也就是
1/2, 1/4, 1/8, 1/16, … , 1/2^n

在levelsOfDetailBias不指定的情况下，zoomScale大于0.5后就不会再drawLayer，所以若继续放大UIScrollView的话，画面将越来越模糊。

这个时候levelsOfDetailBias就有用了。
levelsOfDetailBias = m表示，将原来的1/2，移到2^m倍的位置。
假设levelsOfDetail = n，levelsOfDetailBias = m的话，会有如下队列：
2^m * 2^-1 -> 2^m * 2^-2 -> … -> 2^m * 2^-n
简化一下即
2^(m – 1) -> 2^(m – 2) -> 2^(m – 3) ->… -> 2^(m – n)

举例，levelsOfDetail = 3，levelsOfDetailBias = 3，则你的UIScrollView将会在以下zoomScale时drawLayer
2^(3 – 1) -> 2^(3 – 2) -> 2^(3 – 3)
即4 -> 2 -> 1

特例是，levelsOfDetailBias > levelsOfDetail时，则每相差2倍就会drawLayer一下。

可以简单理解成：
levelsOfDetail表示一共有多少个drawLayer的位置
levelsOfDetailBias表示比1大的位置里有多少个drawLayer的位置（包括1）

以上若还没看懂的话，以下是图(点开看原始大小)
图中灰色的格子表示跨界的格子，它们本来是同一个格子，被1这条线分割了。

I find out that, the API for UISearchDisplayerController in SDK 3.0b is different from 3.0. And there’s no sample code for UISearchDisplayerController anywhere else until now. (Yes, there is one in Apple’s sample code web page, but it uses Interface Builder to realize it. And there is one from the source code of “three20″, but it’s based on SDK 3.0b. )

So I wrote this sample based on “Table Search” sample code.It realizes UISearchDisplayerController programmatically without Interface Builder. It supports landscape screen and search scopes, and integrate one UITabBarController with two UITableViewControllers.

Here is the tutorial .

@interface

1. Declare an instance of UISearchDisplayerController and set as property.
2. Prepare two arrays to hold original data and filtered data.

@implementation

1. Set up viewDidLoadmethod
   1. Create an UISearchBar.
   2. Initialize the UISearchDisplayController based on the UISearchBar:

      1	[[UISearchDisplayController alloc] initWithSearchBar:mySearchBar contentsController:self];

   3. Set the UISearchDisplayController instance:

      1 2 3

      [self setSearchDisplayController:searchDisplayController]; [searchDisplayController setDelegate:self]; [searchDisplayController setSearchResultsDataSource:self];

2. Set up UISearchDisplayController delegate methods:

   1 2 3

   - (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString - (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchScope:(NSInteger)searchOption - (void)searchDisplayControllerDidBeginSearch:(UISearchDisplayController *)controller

   Be careful, we need to set the delegate for self.searchDisplayController.searchResultsTableView each time we begin to search. Because the instance of searchResultsTableView is allocated and released automatically.

3. Set up UITableView data source and delegate methods, we distinguish filtered or not filtered table by

   1	if (tableView == self.searchDisplayController.searchResultsTableView)

4. Remember to return YES in shouldAutorotateToInterfaceOrientation to support landscape screen.

Some details need to be cared:

1. self.searchDisplayController.searchResultsTableView is created and release automatically, so its delegate should be setted each time it’s created.
2. Every time we turn to a landscape UITableViewController, the UISearchBar in the tableHeaderView has only a width of 320 even we have already setted sizeToFit. It’s may be caused by UITabBarController, I don’t know. So I set the frame of tableHeaderView based on the screen orientation manually in the viewDidLoad method.

Sample Code(.zip)

I use base64 encoder and decoder to put binary data of images into xml data, then transfer the non-text data as text data between server and client.

Here’s an example in my iPhone project.

base64.zip

Download these two files and import them in your project and include the head file in your class file.

(Thanks to Jonathan Wight, who wrote it on Mar 18, 2003)

There are four methods in the base64 head file.

extern size_t EstimateBas64EncodedDataSize(size_t inDataSize);
extern size_t EstimateBas64DecodedDataSize(size_t inDataSize);
extern bool Base64EncodeData(const void *inInputData, size_t inInputDataSize, char *outOutputData, size_t *ioOutputDataSize, BOOL wrapped);
extern bool Base64DecodeData(const void *inInputData, size_t inInputDataSize, void *ioOutputData, size_t *ioOutputDataSize)

Here’s the usage of decoding a string data.

NSString *stringValue = /*the UTF8 string parsed from xml data*/
Byte inputData[[stringValue lengthOfBytesUsingEncoding:NSUTF8StringEncoding]];//prepare a Byte[]
[[stringValue dataUsingEncoding:NSUTF8StringEncoding] getBytes:inputData];//get the pointer of the data
size_t inputDataSize = (size_t)[stringValue length];
size_t outputDataSize = EstimateBas64DecodedDataSize(inputDataSize);//calculate the decoded data size
Byte outputData[outputDataSize];//prepare a Byte[] for the decoded data
Base64DecodeData(inputData, inputDataSize, outputData, &outputDataSize);//decode the data
NSData *theData = [[NSData alloc] initWithBytes:outputData length:outputDataSize];//create a NSData object from the decoded data

Open Terminal, type

sudo /Developer/Library/uninstall-devtools --mode=all