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Android開發(fā)中amera2 Preview使用詳解

 更新時間：2021年09月09日 09:43:21   作者：jgw2008  
這篇文章主要介紹了Android開發(fā)中amera2 Preview使用詳解，本文給大家介紹的非常詳細，對大家的學習或工作具有一定的參考借鑒價值，需要的朋友可以參考下

前言

Camera2是Android新的Camera框架，整體來講Camera2為應用程序提供了許多標準接口，使更多的功能可以通過參數(shù)控制；但是，靈活的同時也帶來了架構的復雜。本文通過討論實現(xiàn)Camera2的Preview功能，來和大家一起探討Camera2所用到的模塊最小集合。

一、Camera2 Preview需要用到哪些模塊

總結起來，用到了如下模塊，

  • SurfaceTexture之SurfaceTextureListener
  • CameraManager
  • CameraDevice之StateCallback
  • CameraDevice之createCaptureSession
  • CaptureRequest.Builder、 CaptureRequest

二、各個模塊的功能和之間的關系

下面詳細分析這幾個模塊的功能和之間的關系，

2.1 SurfaceTexture之SurfaceTextureListener

2.1.1 首先看關于SurfaceTexture的說明

主要目的是接收camera preview的數(shù)據(jù)并在UI上顯示。

Captures frames from an image stream as an OpenGL ES texture.
從圖像流捕獲幀, 作為OpenGL ES紋理.

The image stream may come from either camera preview or video decode. A android.view.Surface created from a SurfaceTexture can be used as an output destination for the android.hardware.camera2, android.media.MediaCodec, android.media.MediaPlayer, and android.renderscript.Allocation APIs. When updateTexImage is called, the contents of the texture object specified when the SurfaceTexture was created are updated to contain the most recent image from the image stream. This may cause some frames of the stream to be skipped.

2.1.2 SurfaceTextureListener的使用

當與此Surface Texture關聯(lián)的表面紋理可用時，可以使用此Listener來獲得通知。
當收到SurfaceTexture可用通知的時候，執(zhí)行初始化camera的動作。
示例代碼如下，

private final SurfaceTextureListener mSurfaceTextureListener = new SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(@NonNull SurfaceTexture surface, int width, int height) {
            Log.i(TAG, "onSurfaceTextureAvailable: ++");
            try {
                Log.i(TAG, "onCreate: call initCamera()");
                initCamera();
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }
 
        @Override
        public void onSurfaceTextureSizeChanged(@NonNull SurfaceTexture surface, int width, int height) {
            Log.i(TAG, "onSurfaceTextureSizeChanged: ++");
        }
 
        @Override
        public boolean onSurfaceTextureDestroyed(@NonNull SurfaceTexture surface) {
            Log.i(TAG, "onSurfaceTextureDestroyed: ++");
            return false;
        }
 
        @Override
        public void onSurfaceTextureUpdated(@NonNull SurfaceTexture surface) {
            Log.i(TAG, "onSurfaceTextureUpdated: ++");
        }
    };

2.2 CameraManager

2.2.1 CameraManager的作用

A system service manager for detecting, characterizing, and connecting to CameraDevices.
一種系統(tǒng)服務管理器，用于檢測、表征和連接攝像設備。

2.2.2 使用CameraManager打開Camera

示例代碼如下，

注意：
openCamera的第一個參數(shù)是打開哪一個攝像頭，0代表后置攝像頭；1代表前置攝像頭；2代表外接攝像頭。這里打開的是前置攝像頭。
第二個參數(shù)是CameraDevice之StateCallback，稍后解析；
第三個參數(shù)是Handler，這里我們把Handler放在一個新創(chuàng)建的thread中；

CameraManager manager = (CameraManager) this.getSystemService(Context.CAMERA_SERVICE);
manager.openCamera("1", stateCallback, mBackgroundHander);

2.3 CameraDevice之StateCallback

2.3.1 StateCallback的作用

A callback objects for receiving updates about the state of a camera device.
用于接收相機設備狀態(tài)更新的回調對象。

2.3.2 StateCallback的示例代碼

我們會在onOpened()函數(shù)中創(chuàng)建Preview Session！

 
            CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
                @Override
                public void onOpened(@NonNull CameraDevice camera) {
                    Log.i(TAG, "onOpened: ++");
                    mCameraDevice = camera;
                    createPreviewSession();
                }
 
                @Override
                public void onDisconnected(@NonNull CameraDevice camera) {
                    Log.i(TAG, "onDisconnected: ++");
                }
 
                @Override
                public void onError(@NonNull CameraDevice camera, int error) {
                    Log.i(TAG, "onError: ++");
                }
            };

2.4 CameraDevice之createCaptureSession

2.4.1 新建CaptureRequest.Builder

A builder for capture requests.

2.4.2 新建CameraDevice之createCaptureSession

A configured capture session for a CameraDevice, used for capturing images from the camera or reprocessing images captured from the camera in the same session previously.

2.4.3 創(chuàng)建CaptureRequest

An immutable package of settings and outputs needed to capture a single image from the camera device.

Contains the configuration for the capture hardware (sensor, lens, flash), the processing pipeline, the control algorithms, and the output buffers. Also contains the list of target Surfaces to send image data to for this capture.

這部分的示例代碼如下，

 
    private void createPreviewSession() {
        SurfaceTexture surfaceTexture = mTextureView.getSurfaceTexture();
        // should be preview size, will got it later
        surfaceTexture.setDefaultBufferSize(mTextureView.getWidth(), mTextureView.getHeight());
        mImageReader = ImageReader.newInstance(mTextureView.getWidth(), mTextureView.getHeight(),
                ImageFormat.JPEG, /*maxImages*/2);
 
        Surface surface =new Surface(surfaceTexture);
 
        try {
            mPreviewRequstBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            mPreviewRequstBuilder.addTarget(surface);
 
            mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
                    new CameraCaptureSession.StateCallback() {
                        @Override
                        public void onConfigured(@NonNull CameraCaptureSession session) {
                            Log.i(TAG, "onConfigured: ");
                            if (mCameraDevice == null) {
                                return;
                            } else {
                                mCaptureSession = session;
                            }
 
                            mPreviewRequest = mPreviewRequstBuilder.build();
                            try {
                                mCaptureSession.setRepeatingRequest(mPreviewRequest, null, mBackgroundHander);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }
 
                        @Override
                        public void onConfigureFailed(@NonNull CameraCaptureSession session) {
                            Log.i(TAG, "onConfigureFailed: ");
                        }
                    }, mBackgroundHander);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

小結

Camera2使用SurfaceTexture組件顯示Preview視頻流；
使用CameraManager打開CameraDevice之camera，同時塞入回調函數(shù)CameraDevice之StateCallback來反饋camera狀態(tài);
當Camera狀況為Opened時，創(chuàng)建CaptureRequest.Builder為preview，并將surface關聯(lián)至builder；之后創(chuàng)建CameraDevice之createCaptureSession，當收到onConfigured信息時，對諸如 sensor, lens, flash等進行配置，然后呼叫Builder的build函數(shù)完成配置CaptureRequest，最后設置session為repeat模式。

到此這篇關于Android開發(fā)中amera2 Preview使用詳解的文章就介紹到這了,更多相關Android Camera2 Preview內容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關文章希望大家以后多多支持腳本之家！

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