如何在Ubuntu手機中使用前置照相機，ubuntu照相機

如何在Ubuntu手機中使用前置照相機，ubuntu照相機

我們可以在Ubuntu QML的API文檔中看到Camera的用法，但是裡面沒有寫到任何的前置Camera的調用方法。對於一些應用來說，前置Camera的使用是重要的。我們必須使用Qt C++代碼來實現這個功能。在這篇文章中，我們來介紹如何使用Ubuntu手機中的前置照相機。

１）建立一個最基本的QML應用
   

   

這樣我們就產生了一個含有plugin的項目。
２）在項目中加入CameraSelector來選擇照相機
為了能夠調用Camera的一些API，我們在plugin中加入如下的CameraSelector類：

#ifndef CAMERA_SELECTOR_H#define CAMERA_SELECTOR_H#include <QObject>#include <QCamera>#include <QVideoDeviceSelectorControl>class CameraSelector : public QObject{    Q_OBJECT    Q_PROPERTY(QObject* cameraObject READ cameraObject WRITE setCameraObject)    Q_PROPERTY(int selectedCameraDevice READ selectedCameraDevice WRITE setSelectedCameraDevice)public:    QObject* cameraObject() const;    void setCameraObject(QObject *cam);    int selectedCameraDevice() const;    void setSelectedCameraDevice(const int cameraId);private:    QCamera *m_camera;    QVideoDeviceSelectorControl *m_deviceSelector;};#endif // CAMERA_SELECTOR_H

#include "cameraselector.h"#include <QMediaService>void CameraSelector::setCameraObject(QObject *cam){    // get the QCamera from the declarative camera's mediaObject property.    m_camera = qvariant_cast<QCamera*>(cam->property("mediaObject"));    // get the video device selector control    QMediaService *service = m_camera->service();    m_deviceSelector = qobject_cast<QVideoDeviceSelectorControl*>(service->requestControl(QVideoDeviceSelectorControl_iid));}QObject *CameraSelector::cameraObject() const{    return m_camera;}int CameraSelector::selectedCameraDevice() const{     return 0;}void CameraSelector::setSelectedCameraDevice(const int cameraId){    // A camera might already be started, make sure it's unloaded    m_camera->unload();    m_deviceSelector->setSelectedDevice(cameraId);}

我們在“backend”中的CMakeLists.txt中加入“MultiMedia"庫以調用QCamera。

include_directories(    ${CMAKE_CURRENT_SOURCE_DIR})set(    FrontCamerabackend_SRCS    modules/FrontCamera/backend.cpp    modules/FrontCamera/mytype.cpp    modules/FrontCamera/cameraselector.cpp)add_library(FrontCamerabackend MODULE    ${FrontCamerabackend_SRCS})set_target_properties(FrontCamerabackend PROPERTIES         LIBRARY_OUTPUT_DIRECTORY FrontCamera)qt5_use_modules(FrontCamerabackend Gui Qml Quick Multimedia)# Copy qmldir file to build dir for running in QtCreatoradd_custom_target(FrontCamerabackend-qmldir ALL    COMMAND cp ${CMAKE_CURRENT_SOURCE_DIR}/modules/FrontCamera/qmldir ${CMAKE_CURRENT_BINARY_DIR}/FrontCamera    DEPENDS ${QMLFILES})# Install plugin fileinstall(TARGETS FrontCamerabackend DESTINATION ${QT_IMPORTS_DIR}/FrontCamera/)install(FILES   modules/FrontCamera/qmldir DESTINATION ${QT_IMPORTS_DIR}/FrontCamera/)

同時在backend.cpp中加入如下的句子：

 qmlRegisterType<CameraSelector>(uri, 1, 0, "CameraSelector");

為了使用Camera，我們對我們的FrontCamera.qml做如下的修改：

import QtQuick 2.0import Ubuntu.Components 1.1import FrontCamera 1.0import QtMultimedia 5.0/*!    \brief MainView with Tabs element.           First Tab has a single Label and           second Tab has a single ToolbarAction.*/MainView {    // objectName for functional testing purposes (autopilot-qt5)    objectName: "mainView"    // Note! applicationName needs to match the "name" field of the click manifest    applicationName: "frontcamera.liu-xiao-guo"    /*     This property enables the application to change orientation     when the device is rotated. The default is false.    */    //automaticOrientation: true    // Removes the old toolbar and enables new features of the new header.    useDeprecatedToolbar: false    width: units.gu(100)    height: units.gu(76)    Page {        title: i18n.tr("App with backend")        Button {            id: activateRearCamera            text: "Rear Camera"            onClicked: {                selector. selectedCameraDevice = 0;                camera.start();            }        }        Button {            id: activateFrontCamera            text: "Front camera"            anchors.left : activateRearCamera.right            anchors.leftMargin: units.gu(2)            onClicked: {                selector. selectedCameraDevice = 1;                camera.start();            }        }        Camera {            id: camera            imageProcessing.whiteBalanceMode: CameraImageProcessing.WhiteBalanceFlash            exposure {                exposureCompensation: -1.0                exposureMode: Camera.ExposurePortrait            }            flash.mode: Camera.FlashRedEyeReduction            imageCapture {                onImageCaptured: {                    photoPreview.source = preview  // Show the preview in an Image                }            }        }        CameraSelector {            id: selector            cameraObject: camera        }        VideoOutput {            source: camera            anchors.fill: parent            focus : visible // to receive focus and capture key events when visible        }        Image {            id: photoPreview        }    }}

運行我們的應用：
  


整個項目的源碼在：git clone https://gitcafe.com/ubuntu/frontcamera.git