qt for ios扫描二维码功能实现

浏览数：41 / 时间：2015年06月11日

问题:　　

公司项目考虑到跨平台一直都是用qt做,由于项目需求,项目上要增加一个二维码扫描功能,在安卓可以用QVideoProbe实现抓取摄像头视频帧,用QZxing解码图片,从而实现二维码扫描,但是在ios上,QVideProbe并不支持,所以只好选择其他抓取视频帧的方法,考虑使用OPencv实现抓取视频帧,但是在查看ios文档时,ios7 以上直接支持二维码扫描功能,所以放弃使用opencv抓取 + zxing解码的方法.从而采取ios官方提供的二维码解码功能.

实现:

由于我们项目ui一直是用qml实现,但是要实现扫描二维码功能,需要调用AVFoundation中的方法,同时要显示ios中的ui显示摄像头及返回qml 键.所以这里需要结合oc 和 qt编程.

直接上代码:

pro文件增加

ios {

　　OBJECTIVE_SOURCES += IOSView.mm　　\ # object c++ file

　　　　　　IOSCamera.mm　

　　HEADER += 　IOSView.h \

　　　　　　IOSCamera.h \

　　　　　　IOSCameraViewProtocol.h　

　　QMAKE_LFLAGS += -framework AVFoundation　　#add AVfoundation framework

　　QT += gui private

}

重新qmake生成xcode project

IOSView.#include <QQuickItem>

class IOSView : public QQuickItem
{
    Q_OBJECT
    Q_PROPERTY(QString qrcodeText READ qrcodeText WRITE setQrcodeText NOTIFY qrcodeTextChanged)
        
public:
    explicit IOSView(QQuickItem *parent = 0);
        
    QString qrcodeText() {
       return m_qrcodeText;
    }
    
    void setQrcodeText(QString text){
        m_qrcodeText = text;
        emit qrcodeTextChanged();
    }
        
   QString m_qrcodeText;
        
        
public slots:
    void startScan();　　//for open ios camera scan and ui
        
private:
    void *m_delegate;　　//for communication with qt
        
signals:
    void qrcodeTextChanged();　　
    void stopCameraScan();　　//show qml
};

IOSView..mm

#include <UIKit/UIKit.h>
#include <QtQuick>
#include <QtGui>
#include <QtGui/qpa/qplatformnativeinterface.h>
#include "IOSView.h"
#include "IOSCamera.h"

@interface IOSCameraDelegate : NSObject <IOSCameraProtocol> {
    IOSView *m_iosView;
}
@end

@implementation IOSCameraDelegate

- (id) initWithIOSCamera:(IOSView *)iosView
{
    self = [super init];
    if (self) {
        m_iosView = iosView;
    }
    return self;
}

-(void) scanCancel{
    emit m_iosView->stopCameraScan();
}

-(void) scanResult :(NSString *) result{
    m_iosView->setQrcodeText(QString::fromNSString(result));
}

@end

IOSView::IOSView(QQuickItem *parent) :
    QQuickItem(parent), m_delegate([[IOSCameraDelegate alloc] initWithIOSCamera:this])
{
}
    
void IOSView::startScan()
{
    // Get the UIView that backs our QQuickWindow:
    UIView *view = static_cast<UIView *>(QGuiApplication::platformNativeInterface()->nativeResourceForWindow("uiview", window()));
    UIViewController *qtController = [[view window] rootViewController];

    IOSCamera *iosCamera = [[[IOSCameraView alloc] init ]autorelease];
    iosCamera.delegate = (id)m_delegate;
    // Tell the imagecontroller to animate on top:
    [qtController presentViewController:iosCamera animated:YES completion:nil];
    [iosCamera startScan];
}

IOSCameraViewProtocol.h

#import <Foundation/Foundation.h>

@protocol CameraScanViewProtocol <NSObject>

@required
-(void) scanCancel;
-(void) scanResult :(NSString *) result;


@end

IOSCamera.h

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#import "CameraViewProtocol.h"

@interface IOSCamera : UIViewController <AVCaptureMetadataOutputObjectsDelegate>{
    id<CameraScanViewProtocol> delegate;
}
@property (retain, nonatomic) IBOutlet UIView *viewPreview;
- (IBAction)backQtApp:(id)sender;

-(void) startScan;

@property (retain) id<CameraScanViewProtocol> delegate;

@end

IOSCamera.cpp#import "IOSCamera.h"


@interface IOSCamera ()
@property (nonatomic,strong) AVCaptureSession * captureSession;
@property (nonatomic,strong) AVCaptureVideoPreviewLayer * videoPreviewLayer;-(BOOL) startReading;
-(void) stopReading;
-(void) openQtLayer;
@end

@implementation CameraScanView
@synthesize delegate;　　　　//Sync delegate for interactive with qt

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    
    // Initially make the captureSession object nil.
    _captureSession = nil;
    
    // Set the initial value of the flag to NO.
    _isReading = NO;
    
    // Begin loading the sound effect so to have it ready for playback when it‘s needed.
    [self loadBeepSound];
  
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
#pragma mark - Navigation

- (void)dealloc {
    [_viewPreview release];
    [super dealloc];
}
- (void)viewDidUnload {
    [self setViewPreview:nil];
    [super viewDidUnload];
}- (IBAction)backQtApp:(id)sender {    [delegate scanCancel];

    [self stopReading];
}

-(void) openQtLayer{
    // Bring back Qt‘s view controller:
    UIViewController *rvc = [[[UIApplication sharedApplication] keyWindow] rootViewController];
    [rvc dismissViewControllerAnimated:YES completion:nil];
}

-(void) startScan{
    if (!_isReading) {
        // This is the case where the app should read a QR code when the start button is tapped.
        if ([self startReading]) {
            // If the startReading methods returns YES and the capture session is successfully
            // running, then change the start button title and the status message.
            NSLog(@"Start Reading !!");
        }
    }
}

#pragma mark - Private method implementation

- (BOOL)startReading {
    NSError *error;

    // Get an instance of the AVCaptureDevice class to initialize a device object and provide the video
    // as the media type parameter.
    AVCaptureDevice *captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    // Get an instance of the AVCaptureDeviceInput class using the previous device object.
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:&error];

    if (!input) {
        // If any error occurs, simply log the description of it and don‘t continue any more.
        NSLog(@"%@", [error localizedDescription]);
        return NO;
    }

    // Initialize the captureSession object.
    _captureSession = [[AVCaptureSession alloc] init];
    // Set the input device on the capture session.
    [_captureSession addInput:input];


    // Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
    AVCaptureMetadataOutput *captureMetadataOutput = [[AVCaptureMetadataOutput alloc] init];
    [_captureSession addOutput:captureMetadataOutput];

    // Create a new serial dispatch queue.
    dispatch_queue_t dispatchQueue;
    dispatchQueue = dispatch_queue_create("myQueue", NULL);
    [captureMetadataOutput setMetadataObjectsDelegate:self queue:dispatchQueue];
    [captureMetadataOutput setMetadataObjectTypes:[NSArray arrayWithObject:AVMetadataObjectTypeQRCode]];

    // Initialize the video preview layer and add it as a sublayer to the viewPreview view‘s layer.
    _videoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:_captureSession];
    [_videoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [_videoPreviewLayer setFrame:_viewPreview.layer.bounds];
    [_viewPreview.layer addSublayer:_videoPreviewLayer];


    // Start video capture.
    [_captureSession startRunning];
    _isReading = YES;
    return YES;
}

-(void)stopReading{
    // Stop video capture and make the capture session object nil.
    [_captureSession stopRunning];
    _captureSession = nil;

// Remove the video preview layer from the viewPreview view‘s layer.
[_videoPreviewLayer removeFromSuperlayer];
_isReading = NO;
[self openQtLayer];
}

#pragma mark - AVCaptureMetadataOutputObjectsDelegate method implementation

-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{

    // Check if the metadataObjects array is not nil and it contains at least one object.
    if (metadataObjects != nil && [metadataObjects count] > 0) {
        // Get the metadata object.
        AVMetadataMachineReadableCodeObject *metadataObj = [metadataObjects objectAtIndex:0];
        if ([[metadataObj type] isEqualToString:AVMetadataObjectTypeQRCode]) {
            // If the found metadata is equal to the QR code metadata then update the status label‘s text,
            // stop reading and change the bar button item‘s title and the flag‘s value.
            // Everything is done on the main thread.
            [delegate scanResult:[metadataObj stringValue]];　　//send scan result to qt show

            [self performSelectorOnMainThread:@selector(stopReading) withObject:nil waitUntilDone:NO];

            _isReading = NO;
        }
    }
}

@end