在理想情况下，您会希望 Apple 只提供几个可以做到这一点的代表。例如：
- (void)imagePickerControllerDidStartVideoCapturing:(UIImagePickerController *)picker
- (void)imagePickerControllerDidStopVideoCapturing:(UIImagePickerController *)picker
然而（根据苹果文档）现实是：
- UIImagePickerController 的协议太基础了，无法做到这一点
- 此类旨在按原样使用，不支持子类化
- 此类的视图层次结构是私有的，不得修改
文档还指出：“您可以将自定义视图分配给 cameraOverlayView 属性，并使用该视图来呈现附加信息或管理相机界面和代码之间的交互”。
在我的应用程序中，我需要显示“UIProgressView”来指示视频可以录制多长时间。为了实现这一点，我需要能够检测到视频捕获开始的时刻。
我不想禁用原生相机控件，因为它们很酷而且我很懒，所以我不想花太多时间重新发明轮子。我只需要捕捉一个大红色按钮被点击以开始或停止录制的事实。
我的解决方案是用自定义视图“覆盖”原始开始/停止录制按钮，并为该视图启用用户交互，如下所示：
overlayView = [[UIView alloc] initWithFrame:self.view.frame];
// Start/ Stop fake button
UIView *ssView = [[UIView alloc] initWithFrame:CGRectMake(self.view.frame.size.width / 2 - 35, self.view.frame.size.height - 71, 70, 70)];
[ssView setUserInteractionEnabled:YES];
// Background color below is only there to make sure my pseudo-button overlaps native Start/Stop button. Comment out the line below to leave it transparent
[ssView setBackgroundColor:[UIColor colorWithRed:0 green:1 blue:0 alpha:0.5f]];
UITapGestureRecognizer *t = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)];
[ssView addGestureRecognizer:t];
[overlayView addSubview:ssView];
// My own progress bar
UIProgressView *p = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleDefault];
[p setTintColor:[UIColor redColor]];
[p setCenter:CGPointMake(30, 130)];
[p setTransform:CGAffineTransformMakeRotation( M_PI / 2 )];
[p setProgress:0];
[overlayView addSubview:p];
pickerController.cameraOverlayView = overlayView;
然后我为点击定义了事件处理程序，如下所示：
-(void)tapped:(id)sender {
if (isRecording) {
[pickerController stopVideoCapture];
NSLog(@"Video capturing stopped...");
// add your business logic here ie stop updating progress bar etc...
[pickerController.cameraOverlayView setHidden:YES];
isRecording = NO;
return;
}
if ([pickerController startVideoCapture]) {
NSLog(@"Video capturing started...");
// add your business logic here ie start updating progress bar etc...
isRecording = YES;
}
}
接口文件的完整代码：
#import <UIKit/UIKit.h>
#import <MobileCoreServices/MobileCoreServices.h>
@interface ViewController : UIViewController <UIImagePickerControllerDelegate>
- (IBAction)openCamera:(id)sender;
@end
实现文件：
#import "ViewController.h"
@interface ViewController () {
UIImagePickerController *pickerController;
UIView* overlayView;
BOOL isRecording;
}
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
isRecording = NO;
pickerController = [[UIImagePickerController alloc] init];
pickerController.delegate = self;
pickerController.allowsEditing = NO;
pickerController.videoMaximumDuration = 30.0f;
pickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
pickerController.mediaTypes = [[NSArray alloc] initWithObjects: (NSString *) kUTTypeMovie, nil];
// I want default controls be available here...
pickerController.showsCameraControls = YES;
overlayView = [[UIView alloc] initWithFrame:self.view.frame];
// Start/ Stop fake button
UIView *ssView = [[UIView alloc] initWithFrame:CGRectMake(self.view.frame.size.width / 2 - 35, self.view.frame.size.height - 71, 70, 70)];
[ssView setUserInteractionEnabled:YES];
// Background color below is only there to make sure myt pseudo-button overlaps native Start/Stop button
[ssView setBackgroundColor:[UIColor colorWithRed:0 green:1 blue:0 alpha:0.5f]];
UITapGestureRecognizer *t = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)];
[ssView addGestureRecognizer:t];
[overlayView addSubview:ssView];
// My own progress bar
UIProgressView *p = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleDefault];
[p setTintColor:[UIColor redColor]];
[p setCenter:CGPointMake(30, 130)];
[p setTransform:CGAffineTransformMakeRotation( M_PI / 2 )];
[p setProgress:0];
[overlayView addSubview:p];
pickerController.cameraOverlayView = overlayView;
}
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {
// Cancel button tapped
[picker dismissViewControllerAnimated:YES completion:nil];
}
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
NSLog(@"Got image : %@", info);
[picker dismissViewControllerAnimated:YES completion:nil];
// Do something with video captured
}
-(void)tapped:(id)sender {
if (isRecording) {
[pickerController stopVideoCapture];
NSLog(@"Video capturing stopped...");
// add your business logic here ie stop updating progress bar etc...
[pickerController.cameraOverlayView setHidden:YES];
isRecording = NO;
return;
}
if ([pickerController startVideoCapture]) {
NSLog(@"Video capturing started...");
// add your business logic here ie start updating progress bar etc...
isRecording = YES;
}
}
- (IBAction)openCamera:(id)sender {
[pickerController.cameraOverlayView setHidden:NO];
[self presentViewController:pickerController animated:YES completion:nil];
}
@end
您可能已经注意到，一旦视频捕获停止，我将隐藏 cameraOverlayView。
[pickerController.cameraOverlayView setHidden:YES];
这是为了让“重拍/播放和使用”原生控件在录制视频后正常工作。