ios定义全局变量
方法一：一般将服务器第一次返回的数据保存在沙盒里面。这样在手机断网的情况下可以从本地读取数据了。
1.保存到沙盒的代码：
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+ (void)saveCache:(int)type andID:(int)_id andString:(NSString *)str;
{
NSUserDefaults * setting = [NSUserDefaults standardUserDefaults];
NSString * key = [NSString stringWithFormat:@"detail-%d-%d",type, _id];
[setting setObject:str forKey:key];
[setting synchronize];
}
2.读取本地沙盒的代码
读取之前首先根据type和Id判断本地是否有
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+ (NSString *)getCache:(int)type andID:(int)_id
{
NSUserDefaults * settings = [NSUserDefaults standardUserDefaults];
NSString *key = [NSString stringWithFormat:@"detail-%d-%d",type, _id];
NSString *value = [settings objectForKey:key];
return value;
}
如果沙盒里面有数据
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NSString *value = [Tool getCache:5 andID:self.QiuTime];
if (value) {
NSDictionary *backdict = [value JSONValue];
if ([backdict objectForKey:@"items"]) {
NSArray *array=[NSArray arrayWithArray:[backdict objectForKey:@"items"]];
for (NSDictionary *qiushi in array) {
QiuShi *qs=[[[QiuShi alloc]initWithDictionary:qiushi] autorelease];
[self.list addObject:qs];
}
}
[self.tableView reloadData];
}
[self.tableView :@"数据全部加载完了.."];
self.tableView.reachedTheEnd = YES;
方法二：使用ASIHTTPRequest和ASIDownloadCache实现本地缓存
1、设置全局的Cache
在AppDelegate.h中添加一个全局变量
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@interface AppDelegate : UIResponder
{
ASIDownloadCache *myCache;
}
@property (strong, nonatomic) UIWindow *window;
@property (nonatomic,retain) ASIDownloadCache *myCache;
在AppDelegate.m中的- (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions方法中添加如下代码
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//自定义缓存
ASIDownloadCache *cache = [[ASIDownloadCache alloc] init];
self.myCache = cache;
[cache release];
//设置缓存路径
NSArray *paths = (NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDirectory = [paths objectAtIndex:0];
[self.myCache setStoragePath:[documentDirectory :@"resource"]];
[self.myCache setDefaultCachePolicy:];
在AppDelegate.m中的dealloc方法中添加如下语句
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[myCache release];
到这里为止，就完成了全局变量的声明。
2、设置缓存策略
在实现ASIHTTPRequest请求的地方设置request的存储方式，代码如下
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NSString *str = @"http://....../getPictureNews.aspx";
NSURL *url = [NSURL URLWithString:str];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
//获取全局变量
AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
//设置缓存方式
[request setDownloadCache:appDelegate.myCache];
//设置缓存数据存储策略，这里采取的是如果无更新或无法联网就读取缓存数据
[request setCacheStoragePolicy:];
request.delegate = self;
[request startAsynchronous];
3、清理缓存数据
我在这里采用的是手动清理数据的方式，在适当的地方添加如下代码，我将清理缓存放在了应用的设置模块：
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AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
[appDelegate.myCache :];
这里清理的是这种存储策略的缓存数据，如果更换其他的参数的话，即可清理对应存储策略的缓存数据。
㈡ ios开发怎么定义全局变量
ios开发中，全局变量设置和调用方法如下: 在AppDelegate.h文件中设置全局变量: @interface ***AppDelegate{ NSString *myName; } @property (nonatomic, retain) NSString *myName; @end 在AppDelegate.m文件中实现全局变量: @synthesize myName; 假如在 CallBack页面调用，在CallBack.m中包含AppDelegate.h文件，并定义一个代理实例，如下 #import "AppDelegate.h" 在 - (void)****{ AppDelegate *myDelegate = [[UIApplication sharedApplication] delegate]; myDelegte.myName = @"123 "; }
㈢ ios中uitextview怎么设置占位符
在UITextField中自带placeholder属性，可以用于提示输入框信息。但是并不具备此功能
介绍两种方法来实现：
第一种：
初始化UITextView
//首先定义UITextView
UITextView *textView = [[UITextView alloc] init];
textView.font = [UIFont systemFontOfSize:14];
textView.frame =CGRectMake(10, 0, cell.contentView.bounds.size.width-20, side);
textView.autoresizingMask = | ;
textView.backgroundColor = [UIColor whiteColor];
[cell.contentView addSubview:textView];
textView.hidden = NO;
textView.delegate = self;
//其次在UITextView上面覆盖个UILable,UILable设置为全局变量。
uilabel.frame =CGRectMake(17, 8, cell.contentView.bounds.size.width - side+10, 20);
uilabel.text = @"请填写审批意见...";
uilabel.enabled = NO;//lable必须设置为不可用
uilabel.backgroundColor = [UIColor clearColor];
[cell.contentView addSubview:uilabel];
实现UITextView的代理
-(void)textViewDidChange:(UITextView *)textView
{
self.examineText = textView.text;
if (textView.text.length == 0) {
uilabel.text = @"请填写审批意见...";
}else{
uilabel.text = @"";
}
}
第二种：
UITextView 实现 placeholder 及隐藏键盘
#import <Foundation/Foundation.h>
@interface UIPlaceHolderTextView : UITextView {
NSString *placeholder;
UIColor *placeholderColor;
@private
UILabel *placeHolderLabel;
}
@property(nonatomic, retain) UILabel *placeHolderLabel;
@property(nonatomic, retain) NSString *placeholder;
@property(nonatomic, retain) UIColor *placeholderColor;
-(void)textChanged:(NSNotification*)notification;
@end
#import "UIPlaceHolderTextView.h"
@implementation UIPlaceHolderTextView
@synthesize placeHolderLabel;
@synthesize placeholder;
@synthesize placeholderColor;
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
[placeHolderLabel release]; placeHolderLabel = nil;
[placeholderColor release]; placeholderColor = nil;
[placeholder release]; placeholder = nil;
[super dealloc];
}
- (void)awakeFromNib
{
[super awakeFromNib];
[self setPlaceholder:@""];
[self setPlaceholderColor:[UIColor lightGrayColor]];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name: object:nil];
}
- (id)initWithFrame:(CGRect)frame
{
if( (self = [super initWithFrame:frame]) )
{
[self setPlaceholder:@""];
[self setPlaceholderColor:[UIColor lightGrayColor]];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name: object:nil];
}
return self;
}
- (void)textChanged:(NSNotification *)notification
{
if([[self placeholder] length] == 0)
{
return;
}
if([[self text] length] == 0)
{
[[self viewWithTag:999] setAlpha:1];
}
else
{
[[self viewWithTag:999] setAlpha:0];
}
}
- (void)setText:(NSString *)text {
[super setText:text];
[self textChanged:nil];
}
- (void)drawRect:(CGRect)rect
{
if( [[self placeholder] length] > 0 )
{
if ( placeHolderLabel == nil )
{
placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];
placeHolderLabel.lineBreakMode = UILineBreakModeWordWrap;
placeHolderLabel.numberOfLines = 0;
placeHolderLabel.font = self.font;
placeHolderLabel.backgroundColor = [UIColor clearColor];
placeHolderLabel.textColor = self.placeholderColor;
placeHolderLabel.alpha = 0;
placeHolderLabel.tag = 999;
[self addSubview:placeHolderLabel];
}
placeHolderLabel.text = self.placeholder;
[placeHolderLabel sizeToFit];
[self sendSubviewToBack:placeHolderLabel];
}
if( [[self text] length] == 0 && [[self placeholder] length] > 0 )
{
[[self viewWithTag:999] setAlpha:1];
}
[super drawRect:rect];
}
@end
//隐藏键盘，实现UITextViewDelegate
-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString*)text
{
if ([text isEqualToString:@"\n"]) {
[m_textView resignFirstResponder];
return NO;
}
return YES;
}