android下无预览摄像

废话不多说，直接上代码

1，定义相机类kcamera

package com.kneron.kfaceservice;import android.graphics.ImageFormat;import android.graphics.SurfaceTexture;import android.hardware.Camera;import android.util.Log;import java.util.List;/** * Created by wayen on 18-8-25. */public class kcamera {    public kcamera(Camera.PreviewCallback cb){        mst = new SurfaceTexture(0);        this.mPreviewCb=cb;    }    private Camera.PreviewCallback mPreviewCb;    private final static String TAG="kcamera";    /**     * ASPECT_RATIO_W and ASPECT_RATIO_H define the aspect ratio     * of the Surface. They are used when {@link #onMeasure(int, int)}     * is called.     */    private final float ASPECT_RATIO_W = 4.0f;    private final float ASPECT_RATIO_H = 3.0f;    /**     * The maximum dimension (in pixels) of the preview frames that are produced     * by the Camera object. Note that this should not be intended as     * the final, exact, dimension because the device could not support     * it and a lower value is required (but the aspect ratio should remain the same).
     * See {@link CameraPreview#getBestSize(List, int)} for more information.     */    private final int PREVIEW_MAX_WIDTH = 640;    /**     * The maximum dimension (in pixels) of the images produced when a     * {@link Camera.PictureCallback#onPictureTaken(byte[], Camera)} event is     * fired. Again, this is a maximum value and could not be the     * real one implemented by the device.     */    private final int PICTURE_MAX_WIDTH = 640;    /**     * 'camera' is the object that references the hardware device     * installed on your Android phone.     */    private Camera camera;    /**     * Phone can have multiple cameras, so 'cameraID' is a     * useful variable to store which one of the camera is active.     * It starts with value -1     */    private int cameraID=-1;    SurfaceTexture mst;    /**     * [IMPORTANT!] The most important method of this Activity: it asks for an instance     * of the hardware camera(s) and save it to the private field {@link #camera}.     *     * @return TRUE if camera is set, FALSE if something bad happens     */    public boolean setCameraInstance() {        if (this.camera != null) {            // do the job only if the camera is not already set            Log.i(TAG, "setCameraInstance(): camera is already set, nothing to do");            return true;        }        // warning here! starting from API 9, we can retrieve one from the multiple        // hardware cameras (ex. front/back)        if (this.cameraID < 0) {            // at this point, it's the first time we request for a camera            Camera.CameraInfo camInfo = new Camera.CameraInfo();            for (int i = 0; i < Camera.getNumberOfCameras(); i++) {                Camera.getCameraInfo(i, camInfo);                if (camInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {                    // in this example we'll request specifically the back camera                    try {                        Log.d(TAG, "setCameraInstance(): trying to open camera #" + i);                        this.camera = Camera.open(i);                        this.cameraID = i; // assign to cameraID this camera's ID (O RLY?)                        this.camera.setPreviewCallback(mPreviewCb);                        camera.setPreviewTexture(mst);//int buffersize = 640 * 480* ImageFormat.getBitsPerPixel(ImageFormat.NV21) / 8;// previewBuffer = new byte[buffersize];// camera.addCallbackBuffer(previewBuffer);// camera.setPreviewCallbackWithBuffer(this);//SurfaceTexture mst = new SurfaceTexture(0);                        Camera.Parameters parameters = camera.getParameters();                        Camera.Size bestPreviewSize = getBestSize(parameters.getSupportedPreviewSizes(), PREVIEW_MAX_WIDTH);                        //Camera.Size bestPictureSize = getBestSize(parameters.getSupportedPictureSizes(), PICTURE_MAX_WIDTH);                        parameters.setPreviewSize(bestPreviewSize.width, bestPreviewSize.height);                        parameters.setPreviewFormat(ImageFormat.NV21); // NV21 is the most supported format for preview frames                        parameters.setPictureFormat(ImageFormat.JPEG); // JPEG for full resolution images                        try {                            parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);                        }                        catch (NoSuchMethodError e) {                            // remember that not all the devices support a given feature                            Log.e(TAG, "setupCamera(): this camera ignored some unsupported settings.", e);                        }                        camera.setParameters(parameters); // save everything                        camera.startPreview();                        return true;                    } catch (Exception e) {                        // something bad happened! this camera could be locked by other apps                        Log.e(TAG, "setCameraInstance(): trying to open camera #" + i + " but it's locked", e);                    }                }            }        }//         we could reach this point in two cases://         - the API is lower than 9//         - previous code block failed//         hence, we try the classic method, that doesn't ask for a particular camera        if (this.camera == null) {            try {                //openCameraBegin=System.currentTimeMillis();                Log.d(TAG, "setCameraInstance(): trying to open camera");                this.camera = Camera.open(1);                this.cameraID = 1;            } catch (RuntimeException e) {                // this is REALLY bad, the camera is definitely locked by the system.                Log.e(TAG,                        "setCameraInstance(): trying to open default camera but it's locked. "                                + "The camera is not available for this app at the moment.", e                );                return false;            }        }        // here, the open() went good and the camera is available        Log.i(TAG, "setCameraInstance(): successfully set camera #" + this.cameraID);        return true;    }    /**     * [IMPORTANT!] Another very important method: it releases all the resources and the locks     * we created while using the camera. It MUST be called everytime the app exits, crashes,     * is paused or whatever. The order of the called methods are the following: 
     *      * 1) stop any preview coming to the GUI, if running 
     * 2) call {@link Camera#release()} 
     * 3) set our camera object to null and invalidate its ID     */    public void releaseCameraInstance() {        if (this.camera != null) {            try {                this.camera.stopPreview();            } catch (Exception e) {                Log.i(TAG, "releaseCameraInstance(): tried to stop a non-existent preview, this is not an error");            }            this.camera.setPreviewCallback(null);            this.camera.release();            this.camera = null;            this.cameraID = -1;            Log.i(TAG, "releaseCameraInstance(): camera has been released.");        }    }    /**     * [IMPORTANT!] This is a convenient function to determine what's the proper     * preview/picture size to be assigned to the camera, by looking at     * the list of supported sizes and the maximum value given     * @param sizes sizes that are currently supported by the camera hardware,     * retrived with {@link Camera.Parameters#getSupportedPictureSizes()} or {@link Camera.Parameters#getSupportedPreviewSizes()}     * @param widthThreshold the maximum value we want to apply     * @return an optimal size <= widthThreshold     */    private Camera.Size getBestSize(List sizes, int widthThreshold) {        Camera.Size bestSize = null;        for (Camera.Size currentSize : sizes) {            boolean isDesiredRatio = ((currentSize.width / ASPECT_RATIO_W) == (currentSize.height / ASPECT_RATIO_H));            boolean isBetterSize = (bestSize == null || currentSize.width > bestSize.width);            boolean isInBounds = currentSize.width <= widthThreshold;            if (isDesiredRatio && isInBounds && isBetterSize) {                bestSize = currentSize;            }        }        if (bestSize == null) {            bestSize = sizes.get(0);            Log.e(TAG, "determineBestSize(): can't find a good size. Setting to the very first...");        }        Log.i(TAG, "determineBestSize(): bestSize is " + bestSize.width + "x" + bestSize.height);        return bestSize;    }}

2 实现 Camera.PreviewCallback，可以写在你的Activity里面

@Overridepublic void onPreviewFrame(byte[] data, Camera camera) {}

3 使用

mcamera=new kcamera(this);//一般写在oncreat里面即可boolean ret= mcamera.setCameraInstance();//开启预览mcamera.releaseCameraInstance();//别忘记关闭

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