Android CameraManager 类 _Android

少年击剑更吹箫，剑气箫心一例消。这篇文章主要讲述Android CameraManager 类相关的知识，希望能为你提供帮助。
先看代码：

private SurfaceView mSurfaceView; private SurfaceHolder mSurfaceHolder; private CameraManager cameraManager; cameraManager = new CameraManager(this); mSurfaceView = (SurfaceView) findViewById(R.id.java_surface_view); mSurfaceHolder = mSurfaceView.getHolder(); // mSurfaceView 不需要自己的缓冲区 mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); // mSurfaceView添加回调 mSurfaceHolder.addCallback(new SurfaceHolder.Callback() { @Override public void surfaceCreated(SurfaceHolder holder) { //SurfaceView创建 try { cameraManager.openDriver(mSurfaceHolder); cameraManager.startPreview(); } catch (IOException e) { e.printStackTrace(); } }@Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}@Override public void surfaceDestroyed(SurfaceHolder holder) { //SurfaceView销毁 holder.removeCallback(this); // Camera is being used after Camera.release() was called cameraManager.stopPreview(); cameraManager.closeDriver(); } });

自定义一个 CameraManager 类，在关闭当前页面，释放camera资源时偶尔报错

Camera is being used after Camera.release() was called

第一次，加了一句 holder.removeCallback(this); 运行发现还是时不时出现报错。
第二次在释放 camera前加 camera.setPreviewCallback(null); 问题解决。

/** * 关闭预览 */ public synchronized void stopPreview() { Log.e(TAG, "stopPreview"); if (autoFocusManager != null) { autoFocusManager.stop(); autoFocusManager = null; } if (camera != null & & previewing) { camera.stopPreview(); camera.setPreviewCallback(null); // Camera is being used after Camera.release() was called previewing = false; } }/** * 关闭camera */ public synchronized void closeDriver() { Log.e(TAG, "closeDriver"); if (camera != null) { camera.release(); camera = null; } }

原来：如果程序中加入了previewCallback，在surfaceDestroy释放camera的时候，最好执行myCamera.setOneShotPreviewCallback(null); 或者myCamera.setPreviewCallback(null); 中止这种回调，然后再释放camera更安全。否则可能会报错。

附：CameraManager类：

文章图片

package com.lemoncome.facedetection; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.ImageFormat; import android.graphics.Matrix; import android.hardware.Camera; import android.util.Log; import android.view.Display; import android.view.Surface; import android.view.SurfaceHolder; import android.view.WindowManager; import java.io.IOException; import java.util.List; /** * User:lizhangqu([email protected]) * Date:2015-09-05 * Time: 10:56 */ public class CameraManager implements Camera.PreviewCallback { private static final String TAG = CameraManager.class.getName(); private Camera camera; private Camera.Parameters parameters; private AutoFocusManager autoFocusManager; private int requestedCameraId = -1; private Context mContext; private boolean initialized; private boolean previewing; /** * 打开摄像头 * * @param cameraId 摄像头id * @return Camera */ public Camera open(int cameraId) { int numCameras = Camera.getNumberOfCameras(); if (numCameras == 0) { Log.e(TAG, "No cameras!"); return null; } boolean explicitRequest = cameraId > = 0; if (!explicitRequest) { // Select a camera if no explicit camera requested int index = 0; while (index < numCameras) { Camera.CameraInfo cameraInfo = new Camera.CameraInfo(); Camera.getCameraInfo(index, cameraInfo); if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_BACK) { break; } index++; } cameraId = index; } Camera camera; if (cameraId < numCameras) { Log.e(TAG, "Opening camera #" + cameraId); camera = Camera.open(cameraId); } else { if (explicitRequest) { Log.e(TAG, "Requested camera does not exist: " + cameraId); camera = null; } else { Log.e(TAG, "No camera facing back; returning camera #0"); camera = Camera.open(0); } } int rotation = getDisplayOrientation(); camera.setDisplayOrientation(rotation); camera.setPreviewCallback(this); return camera; }public int getDisplayOrientation() { Display display = ((WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay(); int rotation = display.getRotation(); int degrees = 0; switch (rotation) { case Surface.ROTATION_0: degrees = 0; break; case Surface.ROTATION_90: degrees = 90; break; case Surface.ROTATION_180: degrees = 180; break; case Surface.ROTATION_270: degrees = 270; break; }Camera.CameraInfo camInfo = new Camera.CameraInfo(); Camera.getCameraInfo(Camera.CameraInfo.CAMERA_FACING_BACK, camInfo); int result = (camInfo.orientation - degrees + 360) % 360; return result; }public CameraManager(Context context) { mContext = context; }/** * 打开camera * * @param holder SurfaceHolder * @throws IOException IOException */ public synchronized void openDriver(SurfaceHolder holder) throws IOException { Log.e(TAG, "openDriver"); Camera theCamera = camera; if (theCamera == null) { theCamera = open(requestedCameraId); if (theCamera == null) { throw new IOException(); } camera = theCamera; } theCamera.setPreviewDisplay(holder); if (!initialized) { initialized = true; parameters = camera.getParameters(); List< Camera.Size> previewSizes = parameters.getSupportedPreviewSizes(); int w = 800; int h = 600; for (Camera.Size size : previewSizes) { Log.e("TAG", "previewSizes width:" + size.width); Log.e("TAG", "previewSizes height:" + size.height); if (size.width - w < = 100 & size.width > = w) { w = size.width; h = size.height; break; } }parameters.setPreviewSize(w, h); parameters.setPictureFormat(ImageFormat.JPEG); parameters.setJpegQuality(100); parameters.setPictureSize(800, 600); theCamera.setParameters(parameters); } }/** * camera是否打开 * * @return camera是否打开 */ public synchronized boolean isOpen() { return camera != null; }/** * 关闭camera */ public synchronized void closeDriver() { Log.e(TAG, "closeDriver"); if (camera != null) { camera.release(); camera = null; } }/** * 开始预览 */ public synchronized void startPreview() { Log.e(TAG, "startPreview"); Camera theCamera = camera; if (theCamera != null & & !previewing) { theCamera.startPreview(); previewing = true; autoFocusManager = new AutoFocusManager(camera); } }/** * 关闭预览 */ public synchronized void stopPreview() { Log.e(TAG, "stopPreview"); if (autoFocusManager != null) { autoFocusManager.stop(); autoFocusManager = null; } if (camera != null & & previewing) { camera.stopPreview(); camera.setPreviewCallback(null); // Camera is being used after Camera.release() was called previewing = false; } }public void setPreviewCallback(Camera.PreviewCallback cb) { camera.setOneShotPreviewCallback(this); }/** * 打开闪光灯 */ public synchronized void openLight() { Log.e(TAG, "openLight"); if (camera != null) { parameters = camera.getParameters(); parameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH); camera.setParameters(parameters); } }/** * 关闭闪光灯 */ public synchronized void offLight() { Log.e(TAG, "offLight"); if (camera != null) { parameters = camera.getParameters(); parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF); camera.setParameters(parameters); } }/** * 拍照 * * @param shutter ShutterCallback * @param rawPictureCallback * @param jpegPictureCallback */ public synchronized void takePicture(final Camera.ShutterCallback shutter, final Camera.PictureCallback raw, final Camera.PictureCallback jpeg) { camera.takePicture(shutter, raw, jpeg); }@Override public void onPreviewFrame(byte[] bytes, Camera camera) {}private Bitmap reSize(byte[] data) { Log.i(TAG, "myJpegCallback:onPictureTaken..."); Bitmap cutMap = BitmapFactory.decodeByteArray(data, 0, data.length); //data是字节数据，将其解析成位图 //设置FOCUS_MODE_CONTINUOUS_VIDEO)之后，myParam.set("rotation", 90)失效。图片竟然不能旋转了，故这里要旋转下 Matrix matrix = new Matrix(); matrix.postRotate((float) 90.0); Bitmap rotaBitmap = Bitmap.createBitmap(cutMap, 0, 0, cutMap.getWidth(), cutMap.getHeight(), matrix, false); //旋转后rotaBitmap是960×1280.预览surfaview的大小是540×800 //将960×1280缩放到540×800 Bitmap sizeBitmap = Bitmap.createScaledBitmap(rotaBitmap, 540, 800, true); Bitmap rectBitmap = Bitmap.createBitmap(sizeBitmap, 100, 200, 300, 300); //截取 return rectBitmap; } }

CameraManager【Android CameraManager 类】