iOS 小知识2
隐藏导航栏的正确姿势
方法一
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[self.navigationController setNavigationBarHidden:YES animated:YES];
}
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[self.navigationController setNavigationBarHidden:NO animated:YES];
}
方法二（契合左滑返回手势）
- (void)viewDidLoad {
[super viewDidLoad];
// 设置导航控制器的代理为self
self.navigationController.delegate = self;
}
#pragma mark - UINavigationControllerDelegate
// 将要显示控制器
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
// 判断要显示的控制器是否是自己
BOOL isShowHomePage = [viewController isKindOfClass:[self class]];
[self.navigationController setNavigationBarHidden:isShowHomePage animated:YES];
}
iOS 生成PDF
生成PDF文件步骤：
1创建PDF上下文
//1>.获取沙盒路径
NSString *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
//2>.拼接路径
NSString *PDFPath = [path stringByAppendingPathComponent:@"123.pdf"];
//3>.创建PDF上下文
UIGraphicsBeginPDFContextToFile(PDFPath, CGRectZero, NULL);
2.创建PDF页面
1.初始化image，画image；
for (int i = 0; i < 6; i++) {
if (i % 2 == 0) {
//创建PDF页
UIGraphicsBeginPDFPage();
}
UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"NatGeo%02d",i+1]];
[image drawInRect:CGRectMake(0, (i % 2) * h, w, h)];
}
2.1添加文字水印
// 添加文字
NSString *text = @"www.baidu.com";
NSMutableParagraphStyle *paragraph = [[NSMutableParagraphStyle alloc] init];
paragraph.alignment = NSTextAlignmentCenter;
NSDictionary *dict = @{NSFontAttributeName: [UIFont systemFontOfSize:18],
NSParagraphStyleAttributeName: paragraph,
NSForegroundColorAttributeName: [UIColor whiteColor]};
[text drawInRect:CGRectMake(0, (i % 2) * h + h - 40, w, 40) withAttributes:dict];
3.关闭上下文
UIGraphicsEndPDFContext();
二、渐变
1>线性渐变
//1.获得上下文
CGContextRef context = UIGraphicsGetCurrentContext();
//绘制渐性渐变
//创建色彩空间
CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
//颜色组件，每四个一组
CGFloat components[] = {1.0,0.0,0.0,1.0,1.0,1.0,1.0,1.0};
//开始和结束的位置数组，以百分比来表示的
CGFloat location[] = {0.0,1.0};
//创建渐变
CGGradientRef gradinet = CGGradientCreateWithColorComponents(space,components, location, 2);
//裁剪
// CGContextClipToRect(context, CGRectMake(0, 20, 100, 100));
//开始绘制
CGContextDrawLinearGradient(context, gradinet, CGPointMake(0, 0), CGPointMake(320, 460), kCGGradientDrawsAfterEndLocation);
//释放内容
CGGradientRelease(gradinet);
CGColorSpaceRelease(space);
2>绘制径向渐变
CGContextDrawRadialGradient(context, gradinet, CGPointMake(200, 240), 80, CGPointMake(160, 300), 200, kCGGradientDrawsBeforeStartLocation);
其他的步骤和线性渐变都一样。
用此种方式生成的 PDF 文件的大小主要看 PDF 中图片的大小，我一开始用的时候，生成的 PDF 一直很大，后来发现是图片本身就很大了，在压缩图片之后，达到了十张图片才不到1M，而且图片在电脑上查看依然比较清晰；
压缩图片可以使用 UIImageJPEGRepresentation 或者是压缩 size。
参考1
参考2
autolayout动画
[self.view layoutIfNeeded];
[UIView animateWithDuration:1.0 animations:^{
[self updateConstraintsForMode];
[self.view layoutIfNeeded];
}];
for循环导致的内存暴涨
在我的一个项目中，需要通过 for 循环来将用户选中或者拍照的图片全部经过复杂的处理，这过程需要消耗大量的 CPU 和 memory（memory 会一直递涨），当选中的照片超过60张的时候（iPhone6 Plus），APP 就会崩溃了，而老板的需要时至少100张，进过查阅后，加一个自动释放池就可以了，如下：
for (NSInteger i = 0; i < self.data.count; i++) {
@autoreleasepool {
//以下为非常耗资源的操作
ScanModel *model = self.data[i];
UIImage *image = [UIImage imageWithData: model.originData];
[cropImageView setOriginImage: image];
UIImage *cropImage = [cropImageView cropPhoto];
//压缩剪裁后的图片
cropImage = [cropImage see_compressImageWithMaxSize: CGSizeMake(cropImage.size.width / 2, cropImage.size.height / 2)];
NSData *imageData = UIImageJPEGRepresentation(cropImage, 0.5);
cropImage = [UIImage imageWithData: imageData];
model.cropImage = cropImage;
hud.labelText = [NSString stringWithFormat: @"%zd/%zd", i + 1, self.data.count];
// sleep(1);
}
}
collectionView的headerView
1、在UICollectionViewFlowLayout中headerReferenceSize设置headView的大小
2、注册headerView：
[self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView"];
3、设置headerView的样式：
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
UICollectionReusableView *reusableView = nil;
if (kind == UICollectionElementKindSectionHeader) {
UICollectionReusableView *header = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView" forIndexPath:indexPath];
reusableView = header;
}
reusableView.backgroundColor = [UIColor greenColor];
if (kind == UICollectionElementKindSectionFooter)
{
UICollectionReusableView *footerview = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"FooterView" forIndexPath:indexPath];
footerview.backgroundColor = [UIColor purpleColor];
reusableView = footerview;
}
return reusableView;
}
旋转动画
- (IBAction)rotateImage:(UIButton *)sender {
CGFloat value = (int)floorf((self.rotateSlider + 1)*2) + 1;
if(value>4){ value -= 4; }
self.rotateSlider = value / 2 - 1;
[UIView animateWithDuration:0.5 animations:^{
[self rotateStateDidChange];
}];
self.model.cropImage = [UIImage getRotationImageWithImage: self.model.cropImage Angle: self.angle];
}
#pragma mark - 旋转动画操作
- (CATransform3D)rotateTransform:(CATransform3D)initialTransform clockwise:(BOOL)clockwise
{
CGFloat arg = self.rotateSlider*M_PI;
if(!clockwise){
arg *= -1;
}
CATransform3D transform = initialTransform;
transform = CATransform3DRotate(transform, arg, 0, 0, 1);
transform = CATransform3DRotate(transform, 0*M_PI, 0, 1, 0);
transform = CATransform3DRotate(transform, 0*M_PI, 1, 0, 0);
return transform;
}
- (void)rotateStateDidChange{
CATransform3D transform = [self rotateTransform:CATransform3DIdentity clockwise:YES];
CGFloat arg = self.rotateSlider*M_PI;
CGFloat Wnew = fabs(self.imageView.frame.size.width * cos(arg)) + fabs(self.imageView.frame.size.height * sin(arg));
CGFloat Hnew = fabs(self.imageView.frame.size.width * sin(arg)) + fabs(self.imageView.frame.size.height * cos(arg));
CGFloat Rw = self.imageView.frame.size.width / Wnew;
CGFloat Rh = self.imageView.frame.size.height / Hnew;
CGFloat scale;
//为了在旋转的过程中和旋转结束后看到完整的图像做的处理
if (self.imageView.bounds.size.width < self.imageView.bounds.size.height) {
scale = MIN(Rw, Rh) * 1;
}else{
scale = MAX(Rw, Rh) * 1;
}
transform = CATransform3DScale(transform, scale, scale, 1);
self.imageView.layer.transform = transform;
}
获取旋转之后的图片
/**
* 得到旋转后的图片
*
* @param image 原图
* @param Angle 角度（0~360）
*
* @return 新生成的图片
*/
+(UIImage *)getRotationImageWithImage:(UIImage *)image Angle:(CGFloat)Angle
{
UIView *RootBackView = [[UIView alloc] initWithFrame:CGRectMake(0,0, image.size.width, image.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation( Angle* M_PI / 180);
RootBackView.transform = t;
CGSize rotatedSize = RootBackView.frame.size;
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef theContext = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(theContext, rotatedSize.width/2, rotatedSize.height/2);
CGContextRotateCTM(theContext, Angle * M_PI / 180);
CGContextScaleCTM(theContext, 1.0, -1.0);
CGContextDrawImage(theContext,
CGRectMake(-image.size.width / 2,
-image.size.height / 2,
image.size.width,
image.size.height),
[image CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
StoryBoard & Xib拖线错误
今天在给 IBOutlet 拖线的时候报出如下错误：
could not insert new outlet connection
解决办法：将此控制器或者 View 对应的 .h .m .swift 文件删除 （Remove Reference）,然后到对应文件夹中重新添加即可
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