1 概述
通过Android Camera拍摄预览中设置setPreviewCallback实现onPreviewFrame接口，实时截取每一帧视频流数据
2 知识点
① Android Camera使用： 参考 Refs/Related 0-4
Camera 支持格式
拍照流程
② Android SurfaceView使用： 参考 Refs/Related 5-10
③ Camera权限
3 核心源码
① SurfaceView相关
// 定义对象
private SurfaceView mSurfaceview = null; // SurfaceView对象：(视图组件)视频显示
private SurfaceHolder mSurfaceHolder = null; // SurfaceHolder对象：(抽象接口)SurfaceView支持类
private Camera mCamera =null; // Camera对象，相机预览
复制代码
// InitSurfaceView
private void initSurfaceView() {
mSurfaceview = (SurfaceView) this.findViewById(R.id.Surfaceview);
mSurfaceHolder = mSurfaceview.getHolder(); // 绑定SurfaceView，取得SurfaceHolder对象
mSurfaceHolder.addCallback(mainActivity.this); // SurfaceHolder加入回调接口
// mSurfaceHolder.setFixedSize(176, 144); // 预览大小設置
mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);// 設置顯示器類型，setType必须设置
}
② 主Activity实现SurfaceHolder.Callback接口，编写回调函数
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public void surfaceCreated(SurfaceHolder holder) <span style="font-family: Arial, Helvetica, sans-serif;">{</span>
// SurfaceView启动时/初次实例化，预览界面被创建时，该方法被调用。
// TODO Auto-generated method stub
mCamera = Camera.open();// 开启摄像头（2.3版本后支持多摄像头,需传入参数）
try {
Log.i(TAG, "SurfaceHolder.Callback：surface Created");
mCamera.setPreviewDisplay(mSurfaceHolder);//set the surface to be used for live preview
} catch (Exception ex) {
<span style="white-space:pre"></span>if(null != mCamera){
<span style="white-space:pre"></span>mCamera.release();
<span style="white-space:pre"></span>mCamera = null;
<span style="white-space:pre"></span>}
<span style="white-space:pre"></span>Log.i(TAG+"initCamera", ex.getMessage());
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height){
// 当SurfaceView/预览界面的格式和大小发生改变时，该方法被调用
// TODO Auto-generated method stub
Log.i(TAG, "SurfaceHolder.Callback：Surface Changed");
//mPreviewHeight = height;
//mPreviewWidth = width;
initCamera();
}
public void surfaceDestroyed(SurfaceHolder holder) {
// SurfaceView销毁时，该方法被调用
// TODO Auto-generated method stub
Log.i(TAG, "SurfaceHolder.Callback：Surface Destroyed");
if(null != mCamera) {
mCamera.setPreviewCallback(null); //！！这个必须在前，不然退出出错
mCamera.stopPreview();
bIfPreview = false;
mCamera.release();
mCamera = null;
}
}
核心子函数: 相机预览
private void initCamera() <a target=_blank title="复制代码" style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);"></a><pre name="code" class="java" style="display: inline !important;">{
//surfaceChanged中调用 Log.i(TAG, "going into initCamera"); if (bIfPreview) { mCamera.stopPreview();//stopCamera(); } if(null != mCamera) { try{
<span style="white-space:pre"></span>Camera.Parameters parameters = mCamera.getParameters();
// parameters.setFlashMode("off"); // 无闪光灯
parameters.setPictureFormat(PixelFormat.JPEG); //Sets the image format for picture 设定相片格式为JPEG，默认为NV21
parameters.setPreviewFormat(PixelFormat.YCbCr_420_SP); //Sets the image format for preview picture，默认为NV21
// 【调试】获取caera支持的PictrueSize，看看能否设置？？
List pictureSizes = mCamera.getParameters().getSupportedPictureSizes();
List previewSizes = mCamera.getParameters().getSupportedPreviewSizes();
List previewFormats = mCamera.getParameters().getSupportedPreviewFormats();
List previewFrameRates = mCamera.getParameters().getSupportedPreviewFrameRates();
Log.i(TAG+"initCamera", "cyy support parameters is ");
Size psize = null;
for (int i = 0; i < pictureSizes.size(); i++) {
psize = pictureSizes.get(i);
Log.i(TAG+"initCamera", "PictrueSize,width: " + psize.width + " height" + psize.height);
}
for (int i = 0; i < previewSizes.size(); i++) <a target=_blank title="复制代码" style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);"></a><pre name="code" class="java" style="display: inline !important;">{
psize = previewSizes.get(i); Log.i(TAG+"initCamera", "PreviewSize,width: " + psize.width + " height" + psize.height); } Integer pf = null; for (int i = 0; i < previewFormats.size(); i++) { pf = previewFormats.get(i); Log.i(TAG+"initCamera", "previewformates:" + pf); } // 设置拍照和预览图片大小 parameters.setPictureSize(640, 480); //指定拍照图片的大小 parameters.setPreviewSize(mPreviewWidth, mPreviewHeight); // 指定preview的大小 //这两个属性 如果这两个属性设置的和真实手机的不一样时，就会报错 // 横竖屏镜头自动调整 if (this.getResources().getConfiguration().orientation != Configuration.ORIENTATION_LANDSCAPE) { parameters.set("orientation", "portrait"); // parameters.set("rotation", 90); // 镜头角度转90度（默认摄像头是横拍） mCamera.setDisplayOrientation(90); // 在2.2以上可以使用 } else
{
// 如果是横屏 parameters.set("orientation", "landscape"); // mCamera.setDisplayOrientation(0); // 在2.2以上可以使用 } //添加对视频流处理函数 // 设定配置参数并开启预览 mCamera.setParameters(parameters); // 将Camera.Parameters设定予Camera mCamera.startPreview(); // 打开预览画面 bIfPreview = true; // 【调试】设置后的图片大小和预览大小以及帧率 Camera.Size csize = mCamera.getParameters().getPreviewSize(); mPreviewHeight = csize.height; // mPreviewWidth = csize.width; Log.i(TAG+"initCamera", "after setting, previewSize:width: " + csize.width + " height: " + csize.height); csize = mCamera.getParameters().getPictureSize(); Log.i(TAG+"initCamera", "after setting, pictruesize:width: " + csize.width + " height: " + csize.height); Log.i(TAG+"initCamera", "after setting, previewformate is " + mCamera.getParameters().getPreviewFormat()); Log.i(TAG+"initCamera", "after setting, previewframetate is " + mCamera.getParameters().getPreviewFrameRate()); } catch (Exception e) { e.printStackTrace(); } } }
③视频帧回调接
// 【获取视频预览帧的接口】
mJpegPreviewCallback = new Camera.PreviewCallback(){
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
//传递进来的data,默认是YUV420SP的
// TODO Auto-generated method stub
try {
Log.i(TAG, "going into onPreviewFrame");
//mYUV420sp = data; // 获取原生的YUV420SP数据
YUVIMGLEN = data.length;
// 拷贝原生yuv420sp数据
mYuvBufferlock.acquire();
System.arraycopy(data, 0, mYUV420SPSendBuffer, 0, data.length);
//System.arraycopy(data, 0, mWrtieBuffer, 0, data.length);
mYuvBufferlock.release();
// 开启编码线程，如开启PEG编码方式线程
mSendThread1.start();
} catch (Exception e){
Log.v("System.out", e.toString());
}// endtry
}// endonPriview
};