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;
}