Java tutorial
package it.jaschke.alexandria.barcode; /** * Created by GIL on 22/09/2015 for alexandria. */ /* * Copyright (C) The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import android.Manifest; import android.app.Activity; import android.app.AlertDialog; import android.app.Dialog; import android.content.Context; import android.content.DialogInterface; import android.content.Intent; import android.content.IntentFilter; import android.content.pm.PackageManager; import android.os.Bundle; import android.support.design.widget.Snackbar; import android.support.v4.app.ActivityCompat; import android.support.v7.app.AppCompatActivity; import android.util.Log; import android.view.View; import android.widget.Toast; import com.google.android.gms.common.ConnectionResult; import com.google.android.gms.common.GoogleApiAvailability; import com.google.android.gms.vision.CameraSource; import com.google.android.gms.vision.MultiDetector; import com.google.android.gms.vision.MultiProcessor; import com.google.android.gms.vision.Tracker; import com.google.android.gms.vision.barcode.Barcode; import com.google.android.gms.vision.barcode.BarcodeDetector; import java.io.IOException; import it.jaschke.alexandria.R; /** * Activity for the multi-tracker app. This app detects faces and barcodes with the rear facing * camera, and draws overlay graphics to indicate the position, size, and ID of each face and * barcode. */ public final class BarcodeScanActivity extends AppCompatActivity { private static final String TAG = "MultiTracker"; private static final int RC_HANDLE_GMS = 9001; // permission request codes need to be < 256 private static final int RC_HANDLE_CAMERA_PERM = 2; public static final String BARCODE = "barcode"; private CameraSource mCameraSource = null; private CameraSourcePreview mPreview; /** * Initializes the UI and creates the detector pipeline. */ @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.activity_barcode_scan); mPreview = (CameraSourcePreview) findViewById(R.id.preview); // Check for the camera permission before accessing the camera. If the // permission is not granted yet, request permission. int rc = ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA); if (rc == PackageManager.PERMISSION_GRANTED) { createCameraSource(); } else { requestCameraPermission(); } } /** * Handles the requesting of the camera permission. This includes * showing a "Snackbar" message of why the permission is needed then * sending the request. */ private void requestCameraPermission() { Log.w(TAG, "Camera permission is not granted. Requesting permission"); final String[] permissions = new String[] { Manifest.permission.CAMERA }; if (!ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA)) { ActivityCompat.requestPermissions(this, permissions, RC_HANDLE_CAMERA_PERM); return; } final Activity thisActivity = this; View.OnClickListener listener = new View.OnClickListener() { @Override public void onClick(View view) { ActivityCompat.requestPermissions(thisActivity, permissions, RC_HANDLE_CAMERA_PERM); } }; Snackbar.make(mPreview, R.string.permission_camera_rationale, Snackbar.LENGTH_INDEFINITE) .setAction(R.string.ok, listener).show(); } /** * Creates and starts the camera. Note that this uses a higher resolution in comparison * to other detection examples to enable the barcode detector to detect small barcodes * at long distances. */ private void createCameraSource() { Context context = getApplicationContext(); // A barcode detector is created to track barcodes. An associated multi-processor instance // is set to receive the barcode detection results, track the barcodes, and maintain // graphics for each barcode on screen. The factory is used by the multi-processor to // create a separate tracker instance for each barcode. BarcodeDetector barcodeDetector = new BarcodeDetector.Builder(context).build(); //BarcodeTrackerFactory barcodeFactory = new BarcodeTrackerFactory(mGraphicOverlay); final MultiProcessor.Factory<Barcode> factory = new MultiProcessor.Factory<Barcode>() { @Override public Tracker<Barcode> create(final Barcode barcode) { final Intent intent = new Intent(); intent.putExtra(BARCODE, barcode); setResult(RESULT_OK, intent); finish(); return null; } }; barcodeDetector.setProcessor(new MultiProcessor.Builder<>(factory).build()); // A multi-detector groups the two detectors together as one detector. All images received // by this detector from the camera will be sent to each of the underlying detectors, which // will each do face and barcode detection, respectively. The detection results from each // are then sent to associated tracker instances which maintain per-item graphics on the // screen. MultiDetector multiDetector = new MultiDetector.Builder().add(barcodeDetector).build(); if (!multiDetector.isOperational()) { // Note: The first time that an app using the barcode or face API is installed on a // device, GMS will download a native libraries to the device in order to do detection. // Usually this completes before the app is run for the first time. But if that // download has not yet completed, then the above call will not detect any barcodes // and/or faces. // // isOperational() can be used to check if the required native libraries are currently // available. The detectors will automatically become operational once the library // downloads complete on device. Log.w(TAG, "Detector dependencies are not yet available."); // Check for low storage. If there is low storage, the native library will not be // downloaded, so detection will not become operational. IntentFilter lowstorageFilter = new IntentFilter(Intent.ACTION_DEVICE_STORAGE_LOW); boolean hasLowStorage = registerReceiver(null, lowstorageFilter) != null; if (hasLowStorage) { Toast.makeText(this, R.string.low_storage_error, Toast.LENGTH_LONG).show(); Log.w(TAG, getString(R.string.low_storage_error)); } } // Creates and starts the camera. Note that this uses a higher resolution in comparison // to other detection examples to enable the barcode detector to detect small barcodes // at long distances. mCameraSource = new CameraSource.Builder(getApplicationContext(), multiDetector) .setFacing(CameraSource.CAMERA_FACING_BACK).setRequestedPreviewSize(1600, 1024) .setRequestedFps(15.0f).build(); } /** * Restarts the camera. */ @Override protected void onResume() { super.onResume(); startCameraSource(); } /** * Stops the camera. */ @Override protected void onPause() { super.onPause(); mPreview.stop(); } /** * Releases the resources associated with the camera source, the associated detectors, and the * rest of the processing pipeline. */ @Override protected void onDestroy() { super.onDestroy(); if (mCameraSource != null) { mCameraSource.release(); } } @Override public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) { if (requestCode != RC_HANDLE_CAMERA_PERM) { Log.d(TAG, "Got unexpected permission result: " + requestCode); super.onRequestPermissionsResult(requestCode, permissions, grantResults); return; } if (grantResults.length != 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { Log.d(TAG, "Camera permission granted - initialize the camera source"); // we have permission, so create the camerasource createCameraSource(); return; } Log.e(TAG, "Permission not granted: results len = " + grantResults.length + " Result code = " + (grantResults.length > 0 ? grantResults[0] : "(empty)")); DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { finish(); } }; AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setTitle("Multitracker sample").setMessage(R.string.no_camera_permission) .setPositiveButton(R.string.ok, listener).show(); } /** * Starts or restarts the camera source, if it exists. If the camera source doesn't exist yet * (e.g., because onResume was called before the camera source was created), this will be called * again when the camera source is created. */ private void startCameraSource() { // check that the device has play services available. int code = GoogleApiAvailability.getInstance().isGooglePlayServicesAvailable(getApplicationContext()); if (code != ConnectionResult.SUCCESS) { Dialog dlg = GoogleApiAvailability.getInstance().getErrorDialog(this, code, RC_HANDLE_GMS); dlg.show(); } if (mCameraSource != null) { try { mPreview.start(mCameraSource); } catch (IOException e) { Log.e(TAG, "Unable to start camera source.", e); mCameraSource.release(); mCameraSource = null; } } } }