didReceiveMemoryWarning

本文介绍当应用收到内存警告时,ViewController如何处理didReceiveMemoryWarning方法。默认实现会检查是否可以安全释放视图,若可以,则释放视图并调用viewDidUnload方法。开发者可根据需求重写此方法以释放更多内存。

摘要生成于 C知道 ,由 DeepSeek-R1 满血版支持, 前往体验 >

didReceiveMemoryWarning

Sent to the view controller when the application receives a memory warning.

- (void)didReceiveMemoryWarning
Discussion

The default implementation of this method checks to see if the view controller can safely release its view. This is possible if the view itself does not have a superview and can be reloaded either from a nib file or using a custom loadView method. If the view can be released, this method releases it and calls the viewDidUnload method.

You can override this method (as needed) to release any additional memory used by your view controller. If you do, be sure to call the super implementation at some point to allow the view controller to release its view. In iOS 3.0 and later, if your view controller holds references to objects in the view hierarchy, you should release those references in theviewDidUnload method instead. In earlier versions of iOS, you should continue to release them from this method. See the discussion in the viewDidUnload method for information about how to safely release outlets and other objects.

Availability
  • Available in iOS 2.0 and later.
#pragma mark -- UIImagePickerControllerDelegate- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info{ UIImage *pickImage = info[UIImagePickerControllerOriginalImage]; CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{CIDetectorAccuracy: CIDetectorAccuracyHigh}]; // 获取选择图片中识别结果 NSArray *features = [detector featuresInImage:[CIImage imageWithData:UIImagePNGRepresentation(pickImage)]]; [picker dismissViewControllerAnimated:YES completion:^{ if (features.count > 0) { CIQRCodeFeature *feature = features[0]; NSString *stringValue = feature.messageString; [self handleScanValue:stringValue]; } else { [self readFromAlbumFailed]; } }];}- (void)changeVideoScale:(AVMetadataMachineReadableCodeObject *)objc { NSArray *array = objc.corners; CGPoint point = CGPointZero; int index = 0; CFDictionaryRef dict = (__bridge CFDictionaryRef)(array[index++]); // 把点转换为不可变字典 // 把字典转换为点,存在point里,成功返回true 其他false CGPointMakeWithDictionaryRepresentation(dict, &point); NSLog(@"X:%f -- Y:%f",point.x,point.y); CGPoint point2 = CGPointZero; CGPointMakeWithDictionaryRepresentation((__bridge CFDictionaryRef)array[2], &point2); NSLog(@"X:%f -- Y:%f",point2.x,point2.y); NSLog(@"bounds:%@",NSStringFromCGRect(objc.bounds));}#pragma mark -- App 从后台进入前台- (void)appDidBecomeActive:(NSNotification *)notify { [self resumeScanning];}#pragma mark -- App 从前台进入后台- (void)appWillResignActive:(NSNotification *)notify { [self pauseScanning];}/** 恢复扫一扫功能 */- (void)resumeScanning { if (self.session) { [self.session startRunning]; [self.scannerView startLineAnimation]; }}/** 暂停扫一扫 */- (void)pauseScanning { if (self.session) { [self.session stopRunning]; [self.scannerView stopLineAnimation]; }}#pragma mark -- 扫一扫API/** 处理扫一扫结果 @param value 扫描结果 */- (void)handleScanValue:(NSString *)value { NSLog(@"handleScanValue === %@", value);}/** 相册选取图片无法读取数据 */- (void)readFromAlbumFailed { NSLog(@"readFromAlbumFailed");}- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated.}@end12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091929394959697989910010110210310410510610710810911011111211311411511611711811912012112212312412512612712812913013113213313413513613713813914014114214314414514614714814915015115215315415515615715815916016116216316416516616716816917017117217317417517617717817918018118218318418518618718818919019119219319419519619719819
04-03
评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值