Android samples are updated: onPause()/onResume() release/open camera, a message is shown on camera open error, minor fixes in code and resources

samples/android/face-detection/src/org/opencv/samples/fd/FdActivity.java

@@ -1,6 +1,8 @@
 package org.opencv.samples.fd;
 
 import android.app.Activity;
+import android.app.AlertDialog;
+import android.content.DialogInterface;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.Menu;
@@ -14,6 +16,8 @@ public class FdActivity extends Activity {
     private MenuItem            mItemFace40;
     private MenuItem            mItemFace30;
     private MenuItem            mItemFace20;
+    
+    private FdView				mView;
 
     public static float         minFaceSize = 0.5f;
 
@@ -21,13 +25,39 @@ public class FdActivity extends Activity {
         Log.i(TAG, "Instantiated new " + this.getClass());
     }
 
+    @Override
+	protected void onPause() {
+        Log.i(TAG, "onPause");
+		super.onPause();
+		mView.releaseCamera();
+	}
+
+	@Override
+	protected void onResume() {
+        Log.i(TAG, "onResume");
+		super.onResume();
+		if( !mView.openCamera() ) {
+			AlertDialog ad = new AlertDialog.Builder(this).create();  
+			ad.setCancelable(false); // This blocks the 'BACK' button  
+			ad.setMessage("Fatal error: can't open camera!");  
+			ad.setButton("OK", new DialogInterface.OnClickListener() {  
+			    public void onClick(DialogInterface dialog, int which) {  
+			        dialog.dismiss();                      
+					finish();
+			    }  
+			});  
+			ad.show();
+		}
+	}
+
     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         Log.i(TAG, "onCreate");
         super.onCreate(savedInstanceState);
         requestWindowFeature(Window.FEATURE_NO_TITLE);
-        setContentView(new FdView(this));
+        mView = new FdView(this);
+        setContentView(mView);
     }
 
     @Override

samples/android/face-detection/src/org/opencv/samples/fd/FdView.java

@@ -62,17 +62,17 @@ class FdView extends SampleCvViewBase {
     }
 
     @Override
-    public void surfaceChanged(SurfaceHolder _holder, int format, int width, int height) {
-        super.surfaceChanged(_holder, format, width, height);
-
+	public void surfaceCreated(SurfaceHolder holder) {
         synchronized (this) {
             // initialize Mats before usage
             mGray = new Mat();
             mRgba = new Mat();
         }
-    }
 
-    @Override
+        super.surfaceCreated(holder);
+	}
+
+	@Override
     protected Bitmap processFrame(VideoCapture capture) {
         capture.retrieve(mRgba, Highgui.CV_CAP_ANDROID_COLOR_FRAME_RGBA);
         capture.retrieve(mGray, Highgui.CV_CAP_ANDROID_GREY_FRAME);

samples/android/face-detection/src/org/opencv/samples/fd/SampleCvViewBase.java

@@ -28,13 +28,36 @@ public abstract class SampleCvViewBase extends SurfaceView implements SurfaceHol
         Log.i(TAG, "Instantiated new " + this.getClass());
     }
 
-    public void surfaceChanged(SurfaceHolder _holder, int format, int width, int height) {
-        Log.i(TAG, "surfaceCreated");
+    public boolean openCamera() {
+        Log.i(TAG, "openCamera");
+        synchronized (this) {
+	        releaseCamera();
+	        mCamera = new VideoCapture(Highgui.CV_CAP_ANDROID);
+	        if (!mCamera.isOpened()) {
+	            mCamera.release();
+	            mCamera = null;
+	            Log.e(TAG, "Failed to open native camera");
+	            return false;
+	        }
+	    }
+        return true;
+    }
+    
+    public void releaseCamera() {
+        Log.i(TAG, "releaseCamera");
+        synchronized (this) {
+	        if (mCamera != null) {
+	                mCamera.release();
+	                mCamera = null;
+            }
+        }
+    }
+    
+    public void setupCamera(int width, int height) {
+        Log.i(TAG, "setupCamera("+width+", "+height+")");
         synchronized (this) {
             if (mCamera != null && mCamera.isOpened()) {
-                Log.i(TAG, "before mCamera.getSupportedPreviewSizes()");
                 List<Size> sizes = mCamera.getSupportedPreviewSizes();
-                Log.i(TAG, "after mCamera.getSupportedPreviewSizes()");
                 int mFrameWidth = width;
                 int mFrameHeight = height;
 
@@ -54,28 +77,22 @@ public abstract class SampleCvViewBase extends SurfaceView implements SurfaceHol
                 mCamera.set(Highgui.CV_CAP_PROP_FRAME_HEIGHT, mFrameHeight);
             }
         }
+
+    }
+    
+    public void surfaceChanged(SurfaceHolder _holder, int format, int width, int height) {
+        Log.i(TAG, "surfaceChanged");
+        setupCamera(width, height);
     }
 
     public void surfaceCreated(SurfaceHolder holder) {
         Log.i(TAG, "surfaceCreated");
-        mCamera = new VideoCapture(Highgui.CV_CAP_ANDROID);
-        if (mCamera.isOpened()) {
-            (new Thread(this)).start();
-        } else {
-            mCamera.release();
-            mCamera = null;
-            Log.e(TAG, "Failed to open native camera");
-        }
+        (new Thread(this)).start();
     }
 
     public void surfaceDestroyed(SurfaceHolder holder) {
         Log.i(TAG, "surfaceDestroyed");
-        if (mCamera != null) {
-            synchronized (this) {
-                mCamera.release();
-                mCamera = null;
-            }
-        }
+        releaseCamera();
     }
 
     protected abstract Bitmap processFrame(VideoCapture capture);