我正在嘗試使用設備Camera和Mobile Vision API掃描QR碼。爲此，我創建了一個SurfaceView並將圖像流提取到SurfaceView，並啓用BarcodeDetector，然後按需要的方法讀取檢測到的QR碼。下面是代碼的活動：使用相機掃描QR代碼崩潰應用程序|可能的修復？
QrScanActivity.class
public class QrScanActivity extends AppCompatActivity
{
private SurfaceView cameraView;
private TextView barcodeInfo;
private BarcodeDetector barcodeDetector;
private CameraSource cameraSource;
private static final String TAG = "QR_ACTIVITY";
private static final int REQUEST_CAMERA = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_qr_scan);
cameraView = (SurfaceView) findViewById(R.id.camera_view);
barcodeInfo = (TextView) findViewById(R.id.code_info);
barcodeDetector =
new BarcodeDetector.Builder(this)
.setBarcodeFormats(Barcode.QR_CODE)
.build();
cameraSource = new CameraSource
.Builder(this, barcodeDetector)
.setRequestedPreviewSize(640, 480)
.build();
cameraView.getHolder().addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
if (ActivityCompat.checkSelfPermission(QrScanActivity.this, Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED) {
requestCameraPermission();
}
try {
cameraSource.start(cameraView.getHolder());
} catch (IOException ie) {
Log.e("CAMERA SOURCE", ie.getMessage());
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
cameraSource.stop();
}
});
barcodeDetector.setProcessor(new Detector.Processor<Barcode>() {
@Override
public void release() {
}
@Override
public void receiveDetections(Detector.Detections<Barcode> detections) {
final SparseArray<Barcode> barcodes = detections.getDetectedItems();
if (barcodes.size() != 0) {
barcodeInfo.post(new Runnable() { // Use the post method of the TextView
public void run() {
barcodeInfo.setText( // Update the TextView
barcodes.valueAt(0).displayValue
);
}
});
}
}
});
}
private void requestCameraPermission() {
Log.i("CAM","CAMERA permission has NOT been granted. Requesting permission.");
// BEGIN_INCLUDE(camera_permission_request)
if (ActivityCompat.shouldShowRequestPermissionRationale(this,Manifest.permission.CAMERA))
{
Snackbar.make(findViewById(android.R.id.content), R.string.permission_camera_rationale,
Snackbar.LENGTH_INDEFINITE)
.setAction(R.string.ok, new View.OnClickListener() {
@Override
public void onClick(View view) {
ActivityCompat.requestPermissions(QrScanActivity.this,
new String[]{Manifest.permission.CAMERA},
REQUEST_CAMERA);
}
})
.show();
} else {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA},
REQUEST_CAMERA);
}
// END_INCLUDE(camera_permission_request)
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
@NonNull int[] grantResults) {
if (requestCode == REQUEST_CAMERA)
{
Log.i(TAG, "Received response for Camera permission request.");
if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
Log.i(TAG, "CAMERA permission has now been granted. Showing preview.");
Snackbar.make(findViewById(android.R.id.content), R.string.permision_available_camera,
Snackbar.LENGTH_SHORT).show();
} else {
Log.i(TAG, "CAMERA permission was NOT granted.");
Snackbar.make(findViewById(android.R.id.content), R.string.permissions_not_granted,
Snackbar.LENGTH_SHORT).show();
}
}
else {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
}
}
}
activity_qr_scan.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_qr_scan"
android:layout_width="match_parent"
android:layout_height="match_parent">
<SurfaceView
android:layout_width="400dp"
android:layout_height="280dp"
android:layout_marginTop="30dp"
android:id="@+id/camera_view"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/code_info"
android:layout_below="@+id/camera_view"
android:textSize="20sp"
android:layout_marginTop="30dp"
android:layout_centerHorizontal="true"
android:text="Nothing to read."
/>
</RelativeLayout>
，當應用程序運行中得到的logcat的：
Logcat
E/AndroidRuntime：致命異常：主 工藝：com.shreybank.shrey，PID：12044 了java.lang.RuntimeException：失敗在android.hardware.Camera（相機連接到相機服務 。 java：518） at com.google.android.gms.vision.CameraSource.zzBZ（Unknown Source）android.hardware.Camera.open .CameraSource.start（Unknown Source） at com.shreybank.shrey.activities.QrScanActivity $ 1.surfaceCreated（QrScanActivity.java:64） at android.view.SurfaceView.updateWindow（SurfaceView.java:583） 在android.view.SurfaceView $ 3.onPreDraw（SurfaceView.java:177） 在android.view.ViewTreeObserver.dispatchOnPreDraw（ViewTreeObserver.java:944） 在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:2055） at android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1107） at android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:6013） at android.view.Choreographer $ CallbackRecord.run（Choreographer.java:858 ） at android.view.Choreographer.doCallbacks（Choreographer.java:670） at android.view.Choreographer.doFrame（Choreographer.java:606） at android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:844） ） at android.os.Handler.handleCallback（Handler.java:739） 在android.os.Handler.dispatchMessage（Handler.java:95） 在android.os.Looper.loop（Looper.java:148） 在機器人。 （在本地方法） at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:726） 在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:616）
它說它無法打開相機。看着你的代碼，我看到你正在請求相機許可，並且在你開始相機預覽之後，這是不正確的。在授予權限時您應該只打開相機。 –
我是新來的運行時權限系統！我應該如何更改代碼，以便只有在授予許可時纔打開相機？ – OBX
查看下面的答案，它顯示了您在授予許可後如何啓動相機。 –