Android中CameraManager类的作用是什么
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具体内容如下
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;
}
}附：CameraManager类：
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(513163535@qq.com)
* 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 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 raw PictureCallback
* @param jpeg PictureCallback
*/
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;
}
} 以上就是Android中CameraManager类的作用是什么，小编相信有部分知识点可能是我们日常工作会见到或用到的。希望你能通过这篇文章学到更多知识。更多详情敬请关注创新互联行业资讯频道。
标题名称：Android中CameraManager类的作用是什么
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