Add CameraActivity utility class to automate Camera permission request handling

modules/java/generator/android/java/org/opencv/android/CameraActivity.java

@@ -0,0 +1,60 @@
+package org.opencv.android;
+
+import android.annotation.TargetApi;
+import android.app.Activity;
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.os.Build;
+import android.util.AttributeSet;
+import android.view.View;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static android.Manifest.permission.CAMERA;
+
+public class CameraActivity extends Activity {
+
+    private static final int CAMERA_PERMISSION_REQUEST_CODE = 200;
+
+    protected List<? extends CameraBridgeViewBase> getCameraViewList() {
+        return new ArrayList<CameraBridgeViewBase>();
+    }
+
+    protected void onCameraPermissionGranted() {
+        List<? extends CameraBridgeViewBase> cameraViews = getCameraViewList();
+        if (cameraViews == null) {
+            return;
+        }
+        for (CameraBridgeViewBase cameraBridgeViewBase: cameraViews) {
+            if (cameraBridgeViewBase != null) {
+                cameraBridgeViewBase.setCameraPermissionGranted();
+            }
+        }
+    }
+
+    @Override
+    protected void onStart() {
+        super.onStart();
+        boolean havePermission = true;
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+            if (checkSelfPermission(CAMERA) != PackageManager.PERMISSION_GRANTED) {
+                requestPermissions(new String[]{CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
+                havePermission = false;
+            }
+        }
+        if (havePermission) {
+            onCameraPermissionGranted();
+        }
+    }
+
+    @Override
+    @TargetApi(Build.VERSION_CODES.M)
+    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
+        if (requestCode == CAMERA_PERMISSION_REQUEST_CODE && grantResults.length > 0
+                && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
+            onCameraPermissionGranted();
+        }
+        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
+    }
+}

modules/java/generator/android/java/org/opencv/android/CameraBridgeViewBase.java

@@ -48,6 +48,7 @@ public abstract class CameraBridgeViewBase extends SurfaceView implements Surfac
     protected int mPreviewFormat = RGBA;
     protected int mCameraIndex = CAMERA_ID_ANY;
     protected boolean mEnabled;
+    protected boolean mCameraPermissionGranted = false;
     protected FpsMeter mFpsMeter = null;
 
     public static final int CAMERA_ID_ANY   = -1;
@@ -219,9 +220,24 @@ public abstract class CameraBridgeViewBase extends SurfaceView implements Surfac
         }
     }
 
+
+    /**
+     * This method is provided for clients, so they can signal camera permission has been granted.
+     * The actual onCameraViewStarted callback will be delivered only after setCameraPermissionGranted
+     * and enableView have been called and surface is available
+     */
+    public void setCameraPermissionGranted() {
+        synchronized(mSyncObject) {
+            mCameraPermissionGranted = true;
+            checkCurrentState();
+        }
+    }
+
+
     /**
      * This method is provided for clients, so they can enable the camera connection.
-     * The actual onCameraViewStarted callback will be delivered only after both this method is called and surface is available
+     * The actual onCameraViewStarted callback will be delivered only after setCameraPermissionGranted
+     * and enableView have been called and surface is available
      */
     public void enableView() {
         synchronized(mSyncObject) {
@@ -300,7 +316,7 @@ public abstract class CameraBridgeViewBase extends SurfaceView implements Surfac
         Log.d(TAG, "call checkCurrentState");
         int targetState;
 
-        if (mEnabled && mSurfaceExist && getVisibility() == VISIBLE) {
+        if (mEnabled && mCameraPermissionGranted && mSurfaceExist && getVisibility() == VISIBLE) {
             targetState = STARTED;
         } else {
             targetState = STOPPED;