如何使条形码扫描仪只扫描一次(谷歌移动视觉API)?

Question

我正在开发一个应用程序，该应用程序使用谷歌移动视觉api的条形码扫描仪。我应该只能在ScannerClassy中扫描一次.java并将结果保存在MainActivity中。问题是当我扫描条形码时，它打开了 MainActivity.java 5-7 次。我尝试使用camerasource.release()，但它不起作用。

扫描仪类.java

import com.example.MashapeHello.R;
import com.google.android.gms.vision.Detector;
import android.Manifest;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Looper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.util.Log;
import android.util.SparseArray;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.TextView;
import com.google.android.gms.vision.CameraSource;
import com.google.android.gms.vision.barcode.Barcode;
import com.google.android.gms.vision.barcode.BarcodeDetector;
import java.io.IOException;

public class ScannerClass extends AppCompatActivity implements Detector.Processor {
private TextView textView;
private SurfaceView surfaceView;
private BarcodeDetector barcodeDetector;
private CameraSource cameraSource;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
surfaceView = (SurfaceView) this.findViewById(R.id.surfaceView);
barcodeDetector = new BarcodeDetector.Builder(this).setBarcodeFormats(Barcode.ALL_FORMATS).build();
barcodeDetector.setProcessor(this);
cameraSource = new CameraSource.Builder(getApplicationContext(), barcodeDetector).
setRequestedPreviewSize(1024,1024).setAutoFocusEnabled(true)
.build();
final Activity activity = this;
surfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
try{
if(ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions(activity, new String[]{Manifest.permission.CAMERA},1024);
return;
}
cameraSource.start(surfaceView.getHolder());
} catch (IOException ie){
Log.e("Camera start problem", ie.getMessage());
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
cameraSource.stop();
}
});
}

@Override
public void release(){
}

@Override
public void receiveDetections(Detector.Detections detections) {
final SparseArray<Barcode> barcodes = detections.getDetectedItems();
if (barcodes.size() != 0) {
final StringBuilder sb = new StringBuilder();
for (int i = 0; i < barcodes.size(); ++i) {
sb.append(barcodes.valueAt(i).rawValue).append("n");
}
Intent intent = new Intent(this, MainActivity.class);
intent.putExtra("barcodevalue", sb.toString());
startActivity(intent);
cameraSource.release();

}
}
}

Answer 1

您可以通过创建自己的条形码检测器类来解决此问题，该类在内部使用 BarcodeDetector 类。 下面是一个简单的示例：

public class LimitToOneBarcodeDetector extends Detector<Barcode> {
private BarcodeDetector internalDetector;
public LimitToOneBarcodeDetector(Context context) {
this.internalDetector = new BarcodeDetector.Builder(App.getContext())
.setBarcodeFormats(Barcode.ALL_FORMATS)
.build();
}
@Override
public SparseArray<Barcode> detect(Frame frame) {
SparseArray<Barcode> detected = this.internalDetector.detect(frame);
if (detected == null) {
// Nothing detected, kick out an empty array 
return new SparseArray<>();
}
if (detected.size() == 0) {
// Detected size = 0 , kick out an empty array
return new SparseArray<>();
}
if (detected.size() > 1) {
// Detected more than one barcode, kick out an empty array
return new SparseArray<>();
}
// If we're here, there is only one barcode, return the array
return detected;
}

然后，您只需替换"活动"中的此行：

barcodeDetector = new BarcodeDetector.Builder(this).setBarcodeFormats(Barcode.ALL_FORMATS).build();

有了这个或类似的东西：

barcodeDetector = new LimitToOneBarcodeDetector(this);

Answer 2

这个问题是，你不断用startActivity(intent);开始新的活动

而不是用检测结果完成当前活动......

最好从startActivityForResult()开始ScannerClass并传回所有条形码：

if (barcodes.size() > 0) {
cameraSource.release();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < barcodes.size(); ++i) {
sb.append(barcodes.valueAt(i).rawValue).append("n");
}
Intent data = new Intent();
data.putExtra("barcodes", sb.toString());
this.setResult(AppCompatActivity.RESULT_OK, data);
this.finish();
}

然后可以在方法MainActivity.onActivityResult()中处理这些。