用到的IOS知识点小结（1）

以下内容是在ios6模拟器运行成功的，或者与我自己的开发环境有关系。

1.强制转屏，不过不推荐，是私有方法

//    if ([[UIDevice currentDevice] respondsToSelector:@selector(setOrientation:)]) {

//        [[UIDevice currentDevice] performSelector:@selector(setOrientation:)

//                                       withObject:(id)UIDeviceOrientationPortrait];

//    }

2.给导航条添加自定义的图片按钮，并且要有点击事件

先建立个按钮：

UIButton *button1 = [UIButtonbuttonWithType:UIButtonTypeCustom];

[button1 setImage:[UIImageimageNamed:@"btu_shop.png"] forState:UIControlStateNormal];

[button1 addTarget:selfaction:@selector(gotoShop) forControlEvents:UIControlEventTouchUpInside];

button1.frame = CGRectMake(0, 0, 60, 40);

然后把按钮作为一个view加入
UIBarButtonItem中：

UIBarButtonItem *shopButton = [[UIBarButtonItemalloc]initWithCustomView:button1];

self.navigationItem.leftBarButtonItems = [NSArrayarrayWithObjects:shopButton,storeButton, nil];

3.把一张图片作为背景

UIImageView *imageView = [[UIImageViewalloc]initWithFrame:CGRectMake(0, 0, 1024, 768)];

imageView.image = [UIImageimageNamed:@"background.png"];

[self.viewinsertSubview:imageView belowSubview:self.table];

4.读取图片，不存在图片则下载

- (UIImage *)getPictureWithURL:(NSString *)str {

UIImage *image = nil;

NSString *picURLWithMD5 = [[Cell class]md5:str];//先把图片的路径加密

NSString *picPath =  [[Cell class]makeUserFilePath:picURLWithMD5];

if ([[NSFileManagerdefaultManager] fileExistsAtPath:picPath]) {

//存在图片的时候直接读取

NSData *data = [NSDatadataWithContentsOfFile:picPath];

image = [UIImage imageWithData:data];

}

else{

//下载图片

NSURL *url=[NSURLURLWithString:str];

image = [[[UIImagealloc] initWithData:[NSDatadataWithContentsOfURL:url]]autorelease];

//将图片写到文件中

[UIImagePNGRepresentation(image) writeToFile: picPath  atomically:YES];

}

return image;

}

5.输入框有字的时候再进行操作

if(self.textField.text.length != 0){

6.想去除一个modalView的同时跳转，必须用：

[selfdismissViewControllerAnimated:YEScompletion:^{

UINavigationController *nav = [[UINavigationControlleralloc] initWithRootViewController:detailView];

[selfpresentModalViewController:nav animated:YES];

[nav release];

}];

7.sqlite更新自增值

//    char *update = "update sqlite_sequence set seq = 0 ";//更新自增的值

//    sqlite3_prepare_v2(database, update , -1, &statement, nil) ;

//    if (sqlite3_step(statement) != SQLITE_DONE)

//    {

//        NSLog(@"error update!");

//    }

8.把UIView转成Image，导入<QuartzCore/QuartzCore.h>

-(UIImage *)makeScreenshot:(UIView*) tView{

[tView retain];

@try {

if(UIGraphicsBeginImageContextWithOptions != NULL)

{

UIGraphicsBeginImageContextWithOptions(tView.bounds.size, NO, 1);

} else {

UIGraphicsBeginImageContext(tView.bounds.size);

}

}

@catch (NSException *exception) {

[tView release];

return nil;

}

[tView.layerrenderInContext:UIGraphicsGetCurrentContext()];

UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

[tView release];

return viewImage;

}