didReceiveMemoryWarning 处理总结

本文介绍了一个iOS应用在内存警告时的处理方法,包括如何避免不必要的内存占用并确保关键数据的安全。通过判断当前视图是否处于活跃状态来决定是否释放资源,并在需要时重新加载视图。

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一、

-(void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];//即使没有显示在window上,也不会自动的将self.view释放。
// Add code to clean up any of your own resources that are no longer necessary.

// 此处做兼容处理需要加上ios6.0的宏开关,保证是在6.0下使用的,6.0以前屏蔽以下代码,否则会在下面使用self.view时自动加载viewDidLoad
if ([self.view window] == nil)// 是否是正在使用的视图
{
// Add code to preserve data stored in the views that might be
// needed later.

// Add code to clean up other strong references to the view in
// the view hierarchy.
self.view = nil;// 目的是再次进入时能够重新加载调用viewDidLoad函数。
}
}

参考 http://zhidao.baidu.com/link?

url=cCmmW4DEd_eWcY_P0rbOs4EWlXXi1asDSy3Ka8ks3CYgxgwOsk7ANzOkbKlz0RkME_s97kYAT8g0JavrV_iXGFiE9_R4TcQZYHPwV44IQHC


#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
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