Handle runtime permission in the demo app

Also move a test layout resource to where it should have been.

Change-Id: Ifdc7868bd86defb71324f5f6d500eff999856043

demo/src/main/java/com/google/android/cameraview/demo/MainActivity.java

@@ -18,13 +18,26 @@
 
 import com.google.android.cameraview.CameraView;
 
+import android.Manifest;
+import android.app.Dialog;
+import android.content.DialogInterface;
+import android.content.pm.PackageManager;
 import android.os.Bundle;
+import android.support.annotation.NonNull;
+import android.support.v4.app.ActivityCompat;
+import android.support.v4.app.DialogFragment;
+import android.support.v4.content.ContextCompat;
+import android.support.v7.app.AlertDialog;
 import android.support.v7.app.AppCompatActivity;
 import android.util.Log;
+import android.widget.Toast;
 
-public class MainActivity extends AppCompatActivity {
+public class MainActivity extends AppCompatActivity implements
+        ActivityCompat.OnRequestPermissionsResultCallback {
 
     private static final String TAG = "MainActivity";
+    private static final int REQUEST_CAMERA_PERMISSION = 1;
+    private static final String FRAGMENT_DIALOG = "dialog";
 
     private CameraView mCameraView;
 
@@ -41,7 +54,16 @@ protected void onCreate(Bundle savedInstanceState) {
     @Override
     protected void onResume() {
         super.onResume();
-        mCameraView.start();
+        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
+                == PackageManager.PERMISSION_GRANTED) {
+            mCameraView.start();
+        } else if (ActivityCompat.shouldShowRequestPermissionRationale(this,
+                Manifest.permission.CAMERA)) {
+            new ConfirmationDialogFragment().show(getSupportFragmentManager(), FRAGMENT_DIALOG);
+        } else {
+            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA},
+                    REQUEST_CAMERA_PERMISSION);
+        }
     }
 
     @Override
@@ -50,6 +72,20 @@ protected void onPause() {
         super.onPause();
     }
 
+    @Override
+    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
+                                           @NonNull int[] grantResults) {
+        if (requestCode == REQUEST_CAMERA_PERMISSION) {
+            if (permissions.length != 1 || grantResults.length != 1) {
+                throw new RuntimeException("Error on requesting permission.");
+            }
+            if (grantResults[0] != PackageManager.PERMISSION_GRANTED) {
+                Toast.makeText(this, R.string.permission_not_granted, Toast.LENGTH_SHORT).show();
+                // No need to start camera here; it is handled by onResume
+            }
+        }
+    }
+
     private CameraView.Callback mCallback
             = new CameraView.Callback() {
 
@@ -65,4 +101,33 @@ public void onCameraClosed(CameraView cameraView) {
 
     };
 
+    public static class ConfirmationDialogFragment extends DialogFragment {
+
+        @NonNull
+        @Override
+        public Dialog onCreateDialog(Bundle savedInstanceState) {
+            return new AlertDialog.Builder(getActivity())
+                    .setMessage(R.string.permission_confirmation)
+                    .setPositiveButton(android.R.string.ok,
+                            new DialogInterface.OnClickListener() {
+                                @Override
+                                public void onClick(DialogInterface dialog, int which) {
+                                    ActivityCompat.requestPermissions(getActivity(),
+                                            new String[]{Manifest.permission.CAMERA},
+                                            REQUEST_CAMERA_PERMISSION);
+                                }
+                            })
+                    .setNegativeButton(android.R.string.cancel,
+                            new DialogInterface.OnClickListener() {
+                                @Override
+                                public void onClick(DialogInterface dialog, int which) {
+                                    Toast.makeText(getActivity(), R.string.permission_not_granted,
+                                            Toast.LENGTH_SHORT).show();
+                                }
+                            })
+                    .create();
+        }
+
+    }
+
 }

demo/src/main/res/values/strings.xml

@@ -13,4 +13,6 @@
 -->
 <resources>
     <string name="app_name">CameraView Demo</string>
+    <string name="permission_confirmation">This app demonstrates the usage of CameraView. In order to do that, it needs permission to access camera.</string>
+    <string name="permission_not_granted">Camera app cannot do anything without camera permission.</string>
 </resources>

library/src/main/camera1/com/google/android/cameraview/Camera1.java

@@ -52,6 +52,8 @@ class Camera1 extends CameraViewImpl {
 
     private int mDisplayOrientation;
 
+    private boolean mShowingPreview;
+
     private static class PreviewInfo {
         SurfaceTexture surface;
         int width;
@@ -113,12 +115,16 @@ void start() {
         if (mPreviewInfo.surface != null) {
             setUpPreview();
         }
+        mShowingPreview = true;
         mCamera.startPreview();
     }
 
     @Override
     void stop() {
-        mCamera.stopPreview();
+        if (mCamera != null) {
+            mCamera.stopPreview();
+        }
+        mShowingPreview = false;
         releaseCamera();
     }
 
@@ -220,8 +226,17 @@ private void adjustPreviewSize() {
             mAspectRatio = chooseAspectRatio();
         }
         Size size = chooseOptimalSize(sizes);
-        mCameraParameters.setPreviewSize(size.getWidth(), size.getHeight());
-        mCamera.setParameters(mCameraParameters);
+        final Camera.Size currentSize = mCameraParameters.getPictureSize();
+        if (currentSize.width != size.getWidth() || currentSize.height != size.getHeight()) {
+            if (mShowingPreview) {
+                mCamera.stopPreview();
+            }
+            mCameraParameters.setPreviewSize(size.getWidth(), size.getHeight());
+            mCamera.setParameters(mCameraParameters);
+            if (mShowingPreview) {
+                mCamera.startPreview();
+            }
+        }
     }
 
     @SuppressWarnings("SuspiciousNameCombination")