我创建了一个 AsyncTask用于在调用 onClick() 后处理多个相机帧，但相机会卡住，直到 AsyncTask已完成执行。
有没有办法避免这种行为？我的意思是，在执行 AsyncTask 期间是否可以不断更新相机帧？ ?
异步任务代码:
private class ReadCodeTask extends AsyncTask<Mat[], List<Mat>, List<Bitmap>> {
protected Mat[] onPreExecute(List<Mat> frames){
Mat[] output = new Mat[4];;
for(int i=0; i<frames.size(); i++){
mH = new Mat();
List<Mat> channels = new ArrayList<Mat>(3);
// convert inputFrame to HSV for segmentation
Mat hsvFrame = new Mat(frames.get(i).height(), frames.get(i).width(), CvType.CV_8UC3, new Scalar(4));
Imgproc.cvtColor(frames.get(i), hsvFrame, Imgproc.COLOR_RGB2HSV, 0);
Core.split(hsvFrame, channels);
// get H channel of the input image
mH = channels.get(0);
if(mH!=null){
double meanH = 0;
double size = mH.rows()*mH.cols();
// average saturation in frame
for(int k=0; k<mH.rows(); k++){
for(int j=0; j<mH.cols(); j++){
meanH += mH.get(k, j)[0]/size;
}
}
if(meanH<=0.2*180){ // if WHITE BACKGROUND
output[i] = frames.get(i);
continue;
}
}else{
Log.e("ERR", "Error converting to HSV");
}
gray = new Mat(frames.get(i).height(), frames.get(i).width(), CvType.CV_8UC1, new Scalar(4));
Imgproc.cvtColor(frames.get(i), gray, Imgproc.COLOR_RGB2GRAY, 0);
Mat grayBin = new Mat();
Scalar lowG = new Scalar(0.9*255);
Scalar highG = new Scalar(1*255);
Core.inRange(gray, lowG, highG, grayBin);
Imgproc.findContours(grayBin, contours, hierarchy, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_NONE);
for(int c=0; c<contours.size(); c++){
if(couldItBeASquare(contours.get(c))){
boundingRect = Imgproc.boundingRect(contours.get(c));
}
}
Mat qrSubIm = new Mat();
try{
qrSubIm = frames.get(i).submat(boundingRect);
}catch(NullPointerException e){
// Log.e("ERR", e.getMessage());
}
if(qrSubIm != null){
output[i] = qrSubIm;
}else{
output[i] = frames.get(i);
}
}
return output;
}
@Override
protected List<Bitmap> doInBackground(Mat[]... params) {
List<Bitmap> bmp = new ArrayList<Bitmap>();
for(int i=0; i<params.length; i++){
Mat mRgb = params[0][i];
qr = new Mat();
mQrFinder.qrFindJNI(mRgb.getNativeObjAddr(), qr.getNativeObjAddr());
Bitmap aux = null;
if(qr.cols()!=0 || qr.rows()!=0){
try {
aux = Bitmap.createBitmap(qr.cols(), qr.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(qr, aux);
bmp.add(aux);
}catch (CvException e){
Log.e("Exception",e.getMessage());
}
}
}
return bmp;
}
@Override
protected void onPostExecute(List<Bitmap> bmp) {
List<String> results = new ArrayList<String>(bmp.size());
for(int i=0; i<bmp.size(); i++){
try {
String aux = readQRCode(bmp.get(i));
results.add(aux);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
for(int i=0; i<results.size(); i++){
if(!results.get(i).contentEquals("NOTHING")){
Toast toast = Toast.makeText(mContext, results.get(i), android.widget.Toast.LENGTH_SHORT);
toast.show();
}
}
return;
}
}
注意
onPreExecute()方法没有被覆盖，我必须像这样手动调用它:ReadCodeTask task = new ReadCodeTask();
task.execute(task.onPreExecute(frames));
为了完成，以下代码对应于
camera listener我用于检索帧:camListener = new CvCameraViewListener2() {
@Override
public void onCameraViewStopped() {
// TODO Auto-generated method stub
}
@Override
public void onCameraViewStarted(int width, int height) {
//
}
@Override
public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
rgb = inputFrame.rgba();
if(frames != null){
if(frames.size()<4){
frames.add(rgb);
}
if(frames.size()==4){
List<Mat> aux = frames;
for (int k = 0; k<aux.size()-1; k++){
frames.set(k, aux.get(k+1));
}
frames.set(aux.size()-1, rgb);
}
}
return rgb;
}
};
最佳答案
我的意思是这样的。请注意 mContext，您应该传递一个上下文，或者如果您的 asynctask 是扩展 Activiti 的类中的私有(private)类，那么您可以将“.this”传递给 toast。
private class ReadCodeTask extends AsyncTask<List<Mat>, Void, List<Bitmap>> {
@Override
protected List<Bitmap> doInBackground(List<Mat>... frames) {
Mat[] output = new Mat[4];;
for(int i=0; i<frames.length; i++){
mH = new Mat();
List<Mat> channels = new ArrayList<Mat>(3);
// convert inputFrame to HSV for segmentation
Mat hsvFrame = new Mat(frames[0].get(i).height(), frames[0].get(i).width(), CvType.CV_8UC3, new Scalar(4));
Imgproc.cvtColor(frames[0].get(i), hsvFrame, Imgproc.COLOR_RGB2HSV, 0);
Core.split(hsvFrame, channels);
// get H channel of the input image
mH = channels.get(0);
if(mH!=null){
double meanH = 0;
double size = mH.rows()*mH.cols();
// average saturation in frame
for(int k=0; k<mH.rows(); k++){
for(int j=0; j<mH.cols(); j++){
meanH += mH.get(k, j)[0]/size;
}
}
if(meanH<=0.2*180){ // if WHITE BACKGROUND
output[i] = frames[0].get(i);
continue;
}
}else{
Log.e("ERR", "Error converting to HSV");
}
gray = new Mat(frames[0].get(i).height(), frames[0].get(i).width(), CvType.CV_8UC1, new Scalar(4));
Imgproc.cvtColor(frames[0].get(i), gray, Imgproc.COLOR_RGB2GRAY, 0);
Mat grayBin = new Mat();
Scalar lowG = new Scalar(0.9*255);
Scalar highG = new Scalar(1*255);
Core.inRange(gray, lowG, highG, grayBin);
Imgproc.findContours(grayBin, contours, hierarchy, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_NONE);
for(int c=0; c<contours.size(); c++){
if(couldItBeASquare(contours.get(c))){
boundingRect = Imgproc.boundingRect(contours.get(c));
}
}
Mat qrSubIm = new Mat();
try{
qrSubIm = frames[0].get(i).submat(boundingRect);
}catch(NullPointerException e){
// Log.e("ERR", e.getMessage());
}
if(qrSubIm != null){
output[i] = qrSubIm;
}else{
output[i] = frames[0].get(i);
}
}
List<Bitmap> bmp = new ArrayList<Bitmap>();
for(int i=0; output.length; i++){
Mat mRgb = output[i];
qr = new Mat();
mQrFinder.qrFindJNI(mRgb.getNativeObjAddr(), qr.getNativeObjAddr());
Bitmap aux = null;
if(qr.cols()!=0 || qr.rows()!=0){
try {
aux = Bitmap.createBitmap(qr.cols(), qr.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(qr, aux);
bmp.add(aux);
}catch (CvException e){
Log.e("Exception",e.getMessage());
}
}
}
return bmp;
}
@Override
protected void onPostExecute(List<Bitmap> bmp) {
List<String> results = new ArrayList<String>(bmp.size());
for(int i=0; i<bmp.size(); i++){
try {
String aux = readQRCode(bmp.get(i));
results.add(aux);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
for(int i=0; i<results.size(); i++){
if(!results.get(i).contentEquals("NOTHING")){
Toast toast = Toast.makeText(mContext, results.get(i), android.widget.Toast.LENGTH_SHORT);
toast.show();
}
}
return;
}
}
我不确定我是否拼错了什么。为什么会这样？通常 onPreExceute 的类型为 void，因此当您重载此方法时，UI 可能会被阻塞。反正我会试一试。
请记住，onPreExecute 方法在 UI 线程中运行。参见文档:http://developer.android.com/reference/android/os/AsyncTask.html#onPreExecute()
关于Android OpenCV : update camera frames while executing AsyncTask，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24861360/