十分钟实现 Android Camera2 相机预览

╰+哭是因爲堅強的太久メ 2023-10-12 20:36 67阅读 0赞

### 1. 前言 ###

因为工作中要使用`Android Camera2 API`，但因为`Camera2`比较复杂，网上资料也比较乱，有一定入门门槛，所以花了几天时间系统研究了下，并在`CSDN`上记录了下，希望能帮助到更多的小伙伴。

### 2. Camera2 API 概述 ###

`Camera2 API`的包名是`android.hardware.camera2`，是`Android 5.0`后推出的一套调用摄像头设备的接口，用来替换原有的`Camera`。`Camera2 API`采用管道式的设计，使数据流从摄像头流向`Surface`，使用`Camera2 API`实现拍照录制视频功能时，主要涉及到以下几个类：

*  `CameraManager` : `Camera`设备的管理类，通过该对象可以查询设备的`Camera`设备信息，得到`CameraDevice`对象
 *  `CameraDevice`:`CameraDevice`提供了`Camera`设备相关的一系列固定参数，例如基础的设置和输出格式等。这些信息包含在`CameraCharacteristic`类中，可以通过`getCameraCharacteristics(String)`获得该类对象。
 *  `CaptureSession` : 在`Camera API`中，如何需要从`Camera`设备中获取视频或图片流，首先需要使用输出的`Surface`和`CameraDevice`创建一个`CameraCaptureSession`
 *  `CaptureRequest` : 该类中定义了一个`Camera`设备获取帧数据所需要的参数，可以通过`CameraDevice`的工厂方法创建一个`Request Builder`，用于获取`CaptureRequest`
 *  `CaptureResult` : 当处理完一个请求后，会返回一个`TotalCaptureResult`对象，其中包含`Camera`设备执行该次`Request`所使用的参数以及自身状态。

一个`Android`设备可以有多个摄像头。每个摄像头都是一个摄像头设备，摄像头设备可以同时输出多个流。  
![在这里插入图片描述][9b240482b7fc43068922a298432d6bff.png]

### 3. 前置设置 ###

#### 3.1 添加权限 ####

在`AndroidManifest.xml`中声明权限

<uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-permission android:name="android.permission.CAMERA" />

#### 3.2 申请权限 ####

ActivityCompat.requestPermissions(
            this@MainActivity,
            arrayOf(
                Manifest.permission.CAMERA,
                Manifest.permission.WRITE_EXTERNAL_STORAGE,
                Manifest.permission.RECORD_AUDIO
            ), 123
        )

### 4. 获取相机列表 ###

#### 4.1 获取摄像头列表 ####

获取摄像头列表需要使用到`CameraManager`，通过`cameraManager.cameraIdList`可以获取到摄像头列表

private val cameraManager =
            context.getSystemService(Context.CAMERA_SERVICE) as CameraManager
    
    // 获取所有摄像头的CameraID
    fun getCameraIds(): Array<String> {
        
        return cameraManager.cameraIdList
    }

#### 4.2 判断 前/后 摄像头 ####

通过该方法可以获取摄像头的方位，判定是前摄还是后摄

/**
    * 获取摄像头方向
    */
    fun getCameraOrientationString(cameraId: String): String {
        
       val characteristics = cameraManager.getCameraCharacteristics(cameraId)
       val lensFacing = characteristics.get(CameraCharacteristics.LENS_FACING)!!
       return when (lensFacing) {
        
           CameraCharacteristics.LENS_FACING_BACK -> "后摄(Back)"
           CameraCharacteristics.LENS_FACING_FRONT -> "前摄(Front)"
           CameraCharacteristics.LENS_FACING_EXTERNAL -> "外置(External)"
           else -> "Unknown"
       }
    }

> 还有一个简易的判断方式，一般情况下`cameraId`为`0`是后摄，`cameraId`为`1`是前摄。

#### 4.3 获取一下试试 ####

我们来获取一下试试

val cameraIds = viewModel.getCameraIds()
    cameraIds.forEach{
         cameraId ->
        val orientation = viewModel.getCameraOrientationString(cameraId)
        Log.i(TAG,"cameraId : $cameraId - $orientation")
    }

运行后可以发现打印了日志

cameraId : 0 - 后摄(Back)
    cameraId : 1 - 前摄(Front)

### 5. 实现相机预览 ###

#### 5.1 修改布局 ####

来修改一下`XML`布局

<?xml version="1.0" encoding="utf-8"?>
    <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/black"
        xmlns:app="http://schemas.android.com/apk/res-auto">
    
        <SurfaceView
            android:id="@+id/surface_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent" />
    
        <Button
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintBottom_toBottomOf="parent"
            android:id="@+id/btn_take_picture"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|center"
            android:layout_marginBottom="64dp"
            android:text="拍照"/>
    
    </FrameLayout>

#### 5.2 声明相机参数和成员变量 ####

//后摄 : 0 ，前摄 : 1
    private val cameraId = "0"
    private val TAG = CameraActivity::class.java.simpleName
    private lateinit var cameraDevice: CameraDevice
    private val cameraThread = HandlerThread("CameraThread").apply {
         start() }
    private val cameraHandler = Handler(cameraThread.looper)
    private val cameraManager: CameraManager by lazy {
        
        getSystemService(Context.CAMERA_SERVICE) as CameraManager
    }
    private val characteristics: CameraCharacteristics by lazy {
        
        cameraManager.getCameraCharacteristics(cameraId)
    }
    private lateinit var session: CameraCaptureSession

#### 5.3 添加SurfaceView回调 ####

添加`SurfaceView`回调，并在`SurfaceView`创建的时候，去初始化相机

override fun onCreate(savedInstanceState: Bundle?) {
        
    	super.onCreate(savedInstanceState)
    	binding = ActivityCameraBinding.inflate(layoutInflater)
    	setContentView(binding.root)
    	binding.surfaceView.holder.addCallback(object : SurfaceHolder.Callback {
        
    	    override fun surfaceChanged(holder: SurfaceHolder,format: Int, width: Int,height: Int) = Unit
    	
    	    override fun surfaceDestroyed(holder: SurfaceHolder) = Unit
    	
    	    override fun surfaceCreated(holder: SurfaceHolder) {
        
    		    //为了确保设置了大小，需要在主线程中初始化camera
    	        binding.root.post {
        
    	             openCamera(cameraId)
    	        }
    	    }
    	})
    }

#### 5.4 打开相机 ####

@SuppressLint("MissingPermission")
    private fun openCamera(cameraId: String) {
        
        cameraManager.openCamera(cameraId, object : CameraDevice.StateCallback() {
        
            override fun onOpened(camera: CameraDevice) {
        
    			cameraDevice = camera
    			startPreview()
            }
    
            override fun onDisconnected(camera: CameraDevice) {
        
                this@CameraActivity.finish()
            }
    
            override fun onError(camera: CameraDevice, error: Int) {
        
                Toast.makeText(application, "openCamera Failed:$error", Toast.LENGTH_SHORT).show()
            }
        }, cameraHandler)
    }

#### 5.5 开始预览 ####

private fun startPreview() {
        
    	//因为摄像头设备可以同时输出多个流，所以可以传入多个surface
        val targets = listOf(binding.surfaceView.holder.surface /*,这里可以传入多个surface*/)
        cameraDevice.createCaptureSession(targets, object : CameraCaptureSession.StateCallback() {
        
            override fun onConfigured(captureSession: CameraCaptureSession) {
        
            	//赋值session
                session = captureSession
    
                val captureRequest = cameraDevice.createCaptureRequest(
                    CameraDevice.TEMPLATE_PREVIEW
                ).apply {
         addTarget(binding.surfaceView.holder.surface) }
    
                //这将不断地实时发送视频流，直到会话断开或调用session.stoprepeat()
                session.setRepeatingRequest(captureRequest.build(), null, cameraHandler)
            }
    
            override fun onConfigureFailed(session: CameraCaptureSession) {
        
                Toast.makeText(application,"session configuration failed",Toast.LENGTH_SHORT).show()
            }
        }, cameraHandler)
    }

#### 5.6 来看下效果 ####

可以看到预览画面是出来了，但是比例不对，有拉伸形变，下面我们会来解决这个问题

![在这里插入图片描述][f3de4b3f5b1a4c90a260da8dca3d827f.png]

#### 5.7 修正拉伸形变 ####

##### 5.7.1 新建AutoFitSurfaceView #####

新建`AutoFitSurfaceView`继承自`SurfaceView`，这个类可以调整为我们指定的宽高比，在显示画面的时候进行中心裁剪。

class AutoFitSurfaceView @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyle: Int = 0
    ) : SurfaceView(context, attrs, defStyle) {
        
    
        private var aspectRatio = 0f
    
        /**
         * 设置此视图的宽高比。视图的大小将基于从参数中计算的比率来测量。
         *
         * @param width  相机水平分辨率
         * @param height 相机垂直分辨率
         */
        fun setAspectRatio(width: Int, height: Int) {
        
            require(width > 0 && height > 0) {
         "Size cannot be negative" }
            aspectRatio = width.toFloat() / height.toFloat()
            holder.setFixedSize(width, height)
            requestLayout()
        }
    
        override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        
            super.onMeasure(widthMeasureSpec, heightMeasureSpec)
            val width = MeasureSpec.getSize(widthMeasureSpec)
            val height = MeasureSpec.getSize(heightMeasureSpec)
            if (aspectRatio == 0f) {
        
                setMeasuredDimension(width, height)
            } else {
        
    
                // Performs center-crop transformation of the camera frames
                val newWidth: Int
                val newHeight: Int
                val actualRatio = if (width > height) aspectRatio else 1f / aspectRatio
                if (width < height * actualRatio) {
        
                    newHeight = height
                    newWidth = (height * actualRatio).roundToInt()
                } else {
        
                    newWidth = width
                    newHeight = (width / actualRatio).roundToInt()
                }
    
                Log.d(TAG, "Measured dimensions set: $newWidth x $newHeight")
                setMeasuredDimension(newWidth, newHeight)
            }
        }
    
        companion object {
        
            private val TAG = AutoFitSurfaceView::class.java.simpleName
        }
    }

##### 5.7.2 `XML`布局中将`SurfaceView`替换为`AutoFitSurfaceView` #####

<?xml version="1.0" encoding="utf-8"?>
    <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/black"
        xmlns:app="http://schemas.android.com/apk/res-auto">
    
        
        <com.heiko.mycamera2test.AutoFitSurfaceView
            android:id="@+id/surface_view"
            android:layout_width="match_parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent"
            android:layout_height="match_parent" />
    
        <Button
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintBottom_toBottomOf="parent"
            android:id="@+id/btn_take_picture"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|center"
            android:layout_marginBottom="64dp"
            android:text="拍照"/>
    
    </FrameLayout>

> 注意这里根布局不能使用`ConstraintLayout`，否则宽高比还是会出现问题

##### 5.7.3 获取最大支持的预览大小 #####

新建`SmartSize`类，这个类通过比较显示的`SurfaceView`和摄像头支持的分辨率，匹配出最大支持的预览大小

import android.graphics.Point
    import android.hardware.camera2.CameraCharacteristics
    import android.hardware.camera2.params.StreamConfigurationMap
    import android.util.Size
    import android.view.Display
    import java.lang.Math.max
    import java.lang.Math.min
    
    /** Helper class used to pre-compute shortest and longest sides of a [Size] */
    class SmartSize(width: Int, height: Int) {
        
        var size = Size(width, height)
        var long = max(size.width, size.height)
        var short = min(size.width, size.height)
        override fun toString() = "SmartSize(${
          long}x${
          short})"
    }
    
    /** Standard High Definition size for pictures and video */
    val SIZE_1080P: SmartSize = SmartSize(1920, 1080)
    
    /** Returns a [SmartSize] object for the given [Display] */
    fun getDisplaySmartSize(display: Display): SmartSize {
        
        val outPoint = Point()
        display.getRealSize(outPoint)
        return SmartSize(outPoint.x, outPoint.y)
    }
    
    /**
     * Returns the largest available PREVIEW size. For more information, see:
     * https://d.android.com/reference/android/hardware/camera2/CameraDevice and
     * https://developer.android.com/reference/android/hardware/camera2/params/StreamConfigurationMap
     */
    fun <T>getPreviewOutputSize(
            display: Display,
            characteristics: CameraCharacteristics,
            targetClass: Class<T>,
            format: Int? = null
    ): Size {
        
    
        // Find which is smaller: screen or 1080p
        val screenSize = getDisplaySmartSize(display)
        val hdScreen = screenSize.long >= SIZE_1080P.long || screenSize.short >= SIZE_1080P.short
        val maxSize = if (hdScreen) SIZE_1080P else screenSize
    
        // If image format is provided, use it to determine supported sizes; else use target class
        val config = characteristics.get(
                CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP)!!
        if (format == null)
            assert(StreamConfigurationMap.isOutputSupportedFor(targetClass))
        else
            assert(config.isOutputSupportedFor(format))
        val allSizes = if (format == null)
            config.getOutputSizes(targetClass) else config.getOutputSizes(format)
    
        // Get available sizes and sort them by area from largest to smallest
        val validSizes = allSizes
                .sortedWith(compareBy {
         it.height * it.width })
                .map {
         SmartSize(it.width, it.height) }.reversed()
    
        // Then, get the largest output size that is smaller or equal than our max size
        return validSizes.first {
         it.long <= maxSize.long && it.short <= maxSize.short }.size
    }

##### 5.7.4 设置宽高比 #####

我们在原本调用`openCamera()`方法之前的地方，先去设置一下宽高比`setAspectRatio()`

binding.surfaceView.holder.addCallback(object : SurfaceHolder.Callback {
        
        //...省略了代码....
        override fun surfaceCreated(holder: SurfaceHolder) {
        
    	    //设置宽高比
    	    setAspectRatio()
            //为了确保设置了大小，需要在主线程中初始化camera
            binding.root.post {
        
                openCamera2(cameraId)
            }
        }
    })
    	
    private fun setAspectRatio() {
        
    	val previewSize = getPreviewOutputSize(
    	    binding.surfaceView.display,
    	    characteristics,
    	    SurfaceHolder::class.java
    	)
    	Log.d(TAG, "Selected preview size: $previewSize")
    	binding.surfaceView.setAspectRatio(previewSize.width, previewSize.height)
    }

##### 5.7.5 再次运行预览 #####

可以看到，现在比例显示正常了  
![在这里插入图片描述][7d55cb58e16c4711884eba583680fded.png]

#### 5.8 销毁相机 ####

在`Activity`销毁的时候，我们也要去销毁相机，代码如下

override fun onStop() {
        
        super.onStop()
        try {
        
            cameraDevice.close()
        } catch (exc: Throwable) {
        
            Log.e(TAG, "Error closing camera", exc)
        }
    }
    
    override fun onDestroy() {
        
        super.onDestroy()
        cameraThread.quitSafely()
        //imageReaderThread.quitSafely()
    }

### 6. 其他 ###

#### 6.1 本文源码下载 ####

下载地址 : [Android Camera2 Demo - 实现相机预览、拍照、录制视频功能][Android Camera2 Demo -]

#### 6.2 Android Camera2 系列 ####

更多Camera2相关文章，请看  
[十分钟实现 Android Camera2 相机预览\_氦客的博客-CSDN博客][Android Camera2 _-CSDN]  
[十分钟实现 Android Camera2 相机拍照\_氦客的博客-CSDN博客][Android Camera2 _-CSDN 1]  
[十分钟实现 Android Camera2 视频录制\_氦客的博客-CSDN博客][Android Camera2 _-CSDN 1]

#### 6.3 Android 相机相关文章 ####

[Android 使用CameraX实现预览/拍照/录制视频/图片分析/对焦/缩放/切换摄像头等操作\_氦客的博客-CSDN博客][Android _CameraX_-CSDN]  
[Android 从零开发一个简易的相机App\_android开发简易app\_氦客的博客-CSDN博客][Android _App_android_app_-CSDN]

#### 6.4 参考 ####

本文参考文章  
[\[Android进阶\] 使用Camera2 API实现一个相机预览页面][Android_ _Camera2 API]  
[实现预览 | Android 开发者 | Android Developers (google.cn)][_ Android _ _ Android Developers _google.cn]

[9b240482b7fc43068922a298432d6bff.png]: https://img-blog.csdnimg.cn/9b240482b7fc43068922a298432d6bff.png
[f3de4b3f5b1a4c90a260da8dca3d827f.png]: https://img-blog.csdnimg.cn/f3de4b3f5b1a4c90a260da8dca3d827f.png
[7d55cb58e16c4711884eba583680fded.png]: https://img-blog.csdnimg.cn/7d55cb58e16c4711884eba583680fded.png
[Android Camera2 Demo -]: https://download.csdn.net/download/EthanCo/87960340
[Android Camera2 _-CSDN]: https://blog.csdn.net/EthanCo/article/details/131371887
[Android Camera2 _-CSDN 1]: https://blog.csdn.net/EthanCo/article/details/131414981
[Android _CameraX_-CSDN]: https://blog.csdn.net/EthanCo/article/details/125603671
[Android _App_android_app_-CSDN]: https://blog.csdn.net/EthanCo/article/details/126260794
[Android_ _Camera2 API]: https://mp.weixin.qq.com/s?src=11&timestamp=1686793261&ver=4591&signature=1XOaxRy504Pv8rIGoLoq1-xTZ7UnDtOl2mJlicDIekNCWpe7D-GCgcj7JJsyOYa*O5ZaavZCBXGGL*9I3IgdLq5*WCEsCRQ1Nsq7Tr6Dv*c-vYv0v3UuGBCvrOk4rNuz&new=1
[_ Android _ _ Android Developers _google.cn]: https://developer.android.google.cn/training/camerax/preview?hl=zh-cn