Java tutorial
/* * 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. */ package it.jaschke.alexandria.barcodes; import android.Manifest; import android.annotation.SuppressLint; 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.hardware.Camera; import android.os.Build; import android.os.Bundle; import android.support.annotation.NonNull; 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.GestureDetector; import android.view.MotionEvent; import android.view.ScaleGestureDetector; 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.common.api.CommonStatusCodes; import it.jaschke.alexandria.R; import it.jaschke.alexandria.camera.CameraSource; import it.jaschke.alexandria.camera.CameraSourcePreview; import it.jaschke.alexandria.camera.GraphicOverlay; import com.google.android.gms.vision.MultiProcessor; import com.google.android.gms.vision.barcode.Barcode; import com.google.android.gms.vision.barcode.BarcodeDetector; import java.io.IOException; /** * Activity for the multi-tracker app. This app detects barcodes and displays the value with the * rear facing camera. During detection overlay graphics are drawn to indicate the position, * size, and ID of each barcode. */ public final class BarcodeCaptureActivity extends AppCompatActivity { private static final String TAG = "Barcode-reader"; // intent request code to handle updating play services if needed. private static final int RC_HANDLE_GMS = 9001; // permission request codes need to be < 256 private static final int RC_HANDLE_CAMERA_PERM = 2; // constants used to pass extra data in the intent public static final String AutoFocus = "AutoFocus"; public static final String UseFlash = "UseFlash"; public static final String BarcodeObject = "Barcode"; private CameraSource mCameraSource; private CameraSourcePreview mPreview; private GraphicOverlay<BarcodeGraphic> mGraphicOverlay; // helper objects for detecting taps and pinches. private ScaleGestureDetector scaleGestureDetector; private GestureDetector gestureDetector; /** * Initializes the UI and creates the detector pipeline. */ @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.barcode_capture); mPreview = (CameraSourcePreview) findViewById(R.id.preview); mGraphicOverlay = (GraphicOverlay<BarcodeGraphic>) findViewById(R.id.graphicOverlay); // read parameters from the intent used to launch the activity. boolean autoFocus = getIntent().getBooleanExtra(AutoFocus, false); boolean useFlash = getIntent().getBooleanExtra(UseFlash, false); // 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(autoFocus, useFlash); } else { requestCameraPermission(); } gestureDetector = new GestureDetector(this, new CaptureGestureListener()); scaleGestureDetector = new ScaleGestureDetector(this, new ScaleListener()); Snackbar.make(mGraphicOverlay, "Tap to capture. Pinch/Stretch to zoom", Snackbar.LENGTH_LONG).show(); } /** * 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(mGraphicOverlay, R.string.permission_camera_rationale, Snackbar.LENGTH_INDEFINITE) .setAction(R.string.ok, listener).show(); } @Override public boolean onTouchEvent(MotionEvent e) { boolean b = scaleGestureDetector.onTouchEvent(e); boolean c = gestureDetector.onTouchEvent(e); return b || c || super.onTouchEvent(e); } /** * 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. * * Suppressing InlinedApi since there is a check that the minimum version is met before using * the constant. */ @SuppressLint("InlinedApi") private void createCameraSource(boolean autoFocus, boolean useFlash) { 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).setBarcodeFormats(Barcode.EAN_13) .build(); BarcodeTrackerFactory barcodeFactory = new BarcodeTrackerFactory(mGraphicOverlay); barcodeDetector.setProcessor(new MultiProcessor.Builder<>(barcodeFactory).build()); if (!barcodeDetector.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. // continuous-picture // 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. CameraSource.Builder builder = new CameraSource.Builder(getApplicationContext(), barcodeDetector) .setFacing(CameraSource.CAMERA_FACING_BACK).setRequestedPreviewSize(1600, 1024) .setRequestedFps(15.0f); // make sure that auto focus is an available option if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) { builder = builder.setFocusMode(autoFocus ? Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE : null); } mCameraSource = builder.setFlashMode(useFlash ? Camera.Parameters.FLASH_MODE_TORCH : null).build(); } /** * Restarts the camera. */ @Override protected void onResume() { super.onResume(); startCameraSource(); } /** * Stops the camera. */ @Override protected void onPause() { super.onPause(); if (mPreview != null) { 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 (mPreview != null) { mPreview.release(); } } /** * Callback for the result from requesting permissions. This method * is invoked for every call on {@link #requestPermissions(String[], int)}. * <p> * <strong>Note:</strong> It is possible that the permissions request interaction * with the user is interrupted. In this case you will receive empty permissions * and results arrays which should be treated as a cancellation. * </p> * * @param requestCode The request code passed in {@link #requestPermissions(String[], int)}. * @param permissions The requested permissions. Never null. * @param grantResults The grant results for the corresponding permissions * which is either {@link PackageManager#PERMISSION_GRANTED} * or {@link PackageManager#PERMISSION_DENIED}. Never null. * @see #requestPermissions(String[], int) */ @Override public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull 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 boolean autoFocus = getIntent().getBooleanExtra(AutoFocus, false); boolean useFlash = getIntent().getBooleanExtra(UseFlash, false); createCameraSource(autoFocus, useFlash); 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() throws SecurityException { // 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, mGraphicOverlay); } catch (IOException e) { Log.e(TAG, "Unable to start camera source.", e); mCameraSource.release(); mCameraSource = null; } } } /** * onTap is called to capture the oldest barcode currently detected and * return it to the caller. * * @param rawX - the raw position of the tap * @param rawY - the raw position of the tap. * @return true if the activity is ending. */ private boolean onTap(float rawX, float rawY) { BarcodeGraphic graphic = mGraphicOverlay.getFirstGraphic(); Barcode barcode = null; if (graphic != null) { barcode = graphic.getBarcode(); if (barcode != null) { Intent data = new Intent(); data.putExtra(BarcodeObject, barcode); setResult(CommonStatusCodes.SUCCESS, data); finish(); } else { Log.d(TAG, "barcode data is null"); } } else { Log.d(TAG, "no barcode detected"); } return barcode != null; } private class CaptureGestureListener extends GestureDetector.SimpleOnGestureListener { @Override public boolean onSingleTapConfirmed(MotionEvent e) { return onTap(e.getRawX(), e.getRawY()) || super.onSingleTapConfirmed(e); } } private class ScaleListener implements ScaleGestureDetector.OnScaleGestureListener { /** * Responds to scaling events for a gesture in progress. * Reported by pointer motion. * * @param detector The detector reporting the event - use this to * retrieve extended info about event state. * @return Whether or not the detector should consider this event * as handled. If an event was not handled, the detector * will continue to accumulate movement until an event is * handled. This can be useful if an application, for example, * only wants to update scaling factors if the change is * greater than 0.01. */ @Override public boolean onScale(ScaleGestureDetector detector) { return false; } /** * Responds to the beginning of a scaling gesture. Reported by * new pointers going down. * * @param detector The detector reporting the event - use this to * retrieve extended info about event state. * @return Whether or not the detector should continue recognizing * this gesture. For example, if a gesture is beginning * with a focal point outside of a region where it makes * sense, onScaleBegin() may return false to ignore the * rest of the gesture. */ @Override public boolean onScaleBegin(ScaleGestureDetector detector) { return true; } /** * Responds to the end of a scale gesture. Reported by existing * pointers going up. * <p/> * Once a scale has ended, {@link ScaleGestureDetector#getFocusX()} * and {@link ScaleGestureDetector#getFocusY()} will return focal point * of the pointers remaining on the screen. * * @param detector The detector reporting the event - use this to * retrieve extended info about event state. */ @Override public void onScaleEnd(ScaleGestureDetector detector) { mCameraSource.doZoom(detector.getScaleFactor()); } } }