Add huge performance improvements

- Address potential activity memory leaks, by allowing callers to unregister handlers, listeners or validators. Actually, MaoniActivity will auto-clear strong references when it exits. This requires callers to reset their handlers when they are done. Furthermore, Maoni#start(...) can no longer be called twice.

- Reduce memory footprint when loading image views (especially, screen captures). Thumbnail preview has been reduced to a 100x100 size, since it does not need to be loaded at full resolution.

maoni-sample/src/main/java/org/rm3l/maoni/sample/ui/MaoniSampleMainActivity.java

@@ -43,6 +43,8 @@ public class MaoniSampleMainActivity extends AppCompatActivity {
     private static final String MY_FILE_PROVIDER_AUTHORITY =
             (BuildConfig.APPLICATION_ID + ".fileprovider");
 
+    private Maoni mMaoni;
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -53,30 +55,42 @@ protected void onCreate(Bundle savedInstanceState) {
             setSupportActionBar(toolbar);
         }
 
+        final MyHandlerForMaoni handlerForMaoni = new MyHandlerForMaoni(this);
+        final Maoni.Builder maoniBuilder = new Maoni.Builder(MY_FILE_PROVIDER_AUTHORITY)
+                .withWindowTitle("Feedback") //Set to an empty string to clear it
+                .withMessage("Hey! Love or hate this app? We would love to hear from you.\n\n" +
+                        "Note: Almost everything in Maoni is customizable.")
+                .withExtraLayout(R.layout.my_feedback_activity_extra_content)
+                .withFeedbackContentHint("[Custom hint] Write your feedback here")
+                .withIncludeLogsText("[Custom text] Include system logs")
+                .withIncludeScreenshotText("[Custom text] Include screenshot")
+                .withTouchToPreviewScreenshotText("Touch To Preview")
+                .withContentErrorMessage("Custom error message")
+                .withScreenshotHint("Custom test: Lorem Ipsum Dolor Sit Amet...");
+
         final FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
         if (fab != null) {
-            final MyHandlerForMaoni handlerForMaoni = new MyHandlerForMaoni(this);
             fab.setOnClickListener(new View.OnClickListener() {
                 @Override
                 public void onClick(View view) {
-                    new Maoni.Builder(MY_FILE_PROVIDER_AUTHORITY)
-                            .withWindowTitle("Feedback") //Set to an empty string to clear it
-                            .withMessage("Hey! Love or hate this app? We would love to hear from you.\n\n" +
-                                    "Note: Almost everything in Maoni is customizable.")
-                            .withExtraLayout(R.layout.my_feedback_activity_extra_content)
-                            .withHandler(handlerForMaoni)
-                            .withFeedbackContentHint("[Custom hint] Write your feedback here")
-                            .withIncludeScreenshotText("[Custom text] Include screenshot")
-                            .withTouchToPreviewScreenshotText("Touch To Preview")
-                            .withContentErrorMessage("Custom error message")
-                            .withScreenshotHint("Custom test: Lorem Ipsum Dolor Sit Amet...")
-                            .build()
-                            .start(MaoniSampleMainActivity.this);
+                    // MaoniActivity de-registers handlers, listeners and validators upon activity destroy,
+                    // so we need to re-register it again by reconstructing a new Maoni instance.
+                    //Also, Maoni.start(...) cannot be called twice,
+                    // but we are reusing the Builder to construct a new instance along with its handler.
+                    mMaoni = maoniBuilder.withHandler(handlerForMaoni).build();
+                    mMaoni.start(MaoniSampleMainActivity.this);
                 }
             });
         }
     }
 
+    @Override
+    protected void onDestroy() {
+        //Clear strong references used in Maoni, by de-registering any handlers, listeners and validators
+        mMaoni.clear();
+        super.onDestroy();
+    }
+
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.menu_maoni_sample, menu);

maoni/src/main/java/org/rm3l/maoni/Maoni.java

@@ -42,6 +42,7 @@
 import org.rm3l.maoni.utils.ViewUtils;
 
 import java.io.File;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import static org.rm3l.maoni.Maoni.CallbacksConfiguration.getInstance;
 import static org.rm3l.maoni.ui.MaoniActivity.APPLICATION_INFO_BUILD_CONFIG_BUILD_TYPE;
@@ -160,6 +161,8 @@ public class Maoni {
     private final String fileProviderAuthority;
     private File maoniWorkingDir;
 
+    private final AtomicBoolean mUsed = new AtomicBoolean(false);
+
     /**
      * Constructor
      * @param fileProviderAuthority        the file provider authority.
@@ -226,6 +229,14 @@ public Maoni(
      * @param callerActivity the caller activity
      */
     public void start(@Nullable final Activity callerActivity) {
+
+        if (mUsed.getAndSet(true)) {
+            this.clear();
+            throw new UnsupportedOperationException(
+                    "Maoni instance cannot be reused to start a new activity. " +
+                            "Please build a new Maoni instance.");
+        }
+
         if (callerActivity == null) {
             Log.d(LOG_TAG, "Target activity is undefined");
             return;
@@ -343,6 +354,32 @@ public void start(@Nullable final Activity callerActivity) {
         callerActivity.startActivity(maoniIntent);
     }
 
+
+    public Maoni unregisterListener() {
+        getInstance().setListener(null);
+        return this;
+    }
+
+    public Maoni unregisterUiListener() {
+        getInstance().setUiListener(null);
+        return this;
+    }
+
+    public Maoni unregisterValidator() {
+        getInstance().setValidator(null);
+        return this;
+    }
+
+    public Maoni unregisterHandler() {
+        return this.unregisterListener()
+                .unregisterUiListener()
+                .unregisterValidator();
+    }
+
+    public Maoni clear() {
+        return this.unregisterHandler();
+    }
+
     /**
      * Maoni Builder
      */
@@ -650,6 +687,12 @@ public CallbacksConfiguration setUiListener(@Nullable final UiListener uiListene
             this.uiListener = uiListener;
             return this;
         }
+
+        public CallbacksConfiguration reset() {
+            return this.setUiListener(null)
+                    .setListener(null)
+                    .setValidator(null);
+        }
     }
 
 }

maoni/src/main/java/org/rm3l/maoni/ui/MaoniActivity.java

@@ -56,6 +56,7 @@
 import org.rm3l.maoni.common.contract.Validator;
 import org.rm3l.maoni.common.model.Feedback;
 import org.rm3l.maoni.utils.LogcatUtils;
+import org.rm3l.maoni.utils.ViewUtils;
 
 import java.io.File;
 import java.util.UUID;
@@ -264,9 +265,11 @@ protected void onCreate(Bundle savedInstanceState) {
                 if (screenshotContentView != null) {
                     screenshotContentView.setVisibility(View.VISIBLE);
                 }
-                final Bitmap mBitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
                 if (screenshotThumb != null) {
-                    screenshotThumb.setImageBitmap(mBitmap);
+                    //Thumbnail - load with smaller resolution so as to reduce memory footprint
+                    screenshotThumb.setImageBitmap(
+                            ViewUtils.decodeSampledBitmapFromFilePath(
+                                    file.getAbsolutePath(), 100, 100));
                 }
 
                 // Hook up clicks on the thumbnail views.
@@ -299,7 +302,7 @@ public void onClick(View v) {
 
                             final ImageView imageView = (ImageView)
                                     imagePreviewDialog.findViewById(R.id.maoni_screenshot_preview_image);
-                            imageView.setImageBitmap(mBitmap);
+                            imageView.setImageURI(Uri.fromFile(file));
                             imageView.setOnClickListener(clickListener);
                             imagePreviewDialog.findViewById(R.id.maoni_screenshot_preview_close)
                                     .setOnClickListener(clickListener);
@@ -369,6 +372,12 @@ public void onClick(View view) {
         }
     }
 
+    @Override
+    protected void onDestroy() {
+        CallbacksConfiguration.getInstance().reset();
+        super.onDestroy();
+    }
+
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.maoni_activity_menu, menu);

maoni/src/main/java/org/rm3l/maoni/utils/ViewUtils.java

@@ -22,7 +22,9 @@
 package org.rm3l.maoni.utils;
 
 import android.content.Context;
+import android.content.res.Resources;
 import android.graphics.Bitmap;
+import android.graphics.BitmapFactory;
 import android.graphics.Canvas;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
@@ -110,4 +112,77 @@ public static void exportBitmapToFile(@NonNull final Context context,
             }
         }
     }
+
+    private static int calculateInSampleSize(
+            BitmapFactory.Options options, int reqWidth, int reqHeight) {
+        // Raw height and width of image
+        final int height = options.outHeight;
+        final int width = options.outWidth;
+        int inSampleSize = 1;
+
+        if (height > reqHeight || width > reqWidth) {
+
+            final int halfHeight = height / 2;
+            final int halfWidth = width / 2;
+
+            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
+            // height and width larger than the requested height and width.
+            while ((halfHeight / inSampleSize) >= reqHeight
+                    && (halfWidth / inSampleSize) >= reqWidth) {
+                inSampleSize *= 2;
+            }
+        }
+
+        return inSampleSize;
+    }
+
+    /**
+     * Decode a given drawable resource with the specified dimensions
+     *
+     * @param res the app resources
+     * @param resId the drawable resource ID
+     * @param reqWidth the required width
+     * @param reqHeight the required height
+     * @return the bitmap
+     */
+    public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,
+                                                         int reqWidth, int reqHeight) {
+
+        // First decode with inJustDecodeBounds=true to check dimensions
+        final BitmapFactory.Options options = new BitmapFactory.Options();
+        options.inJustDecodeBounds = true;
+        BitmapFactory.decodeResource(res, resId, options);
+
+        // Calculate inSampleSize
+        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
+
+        // Decode bitmap with inSampleSize set
+        options.inJustDecodeBounds = false;
+        return BitmapFactory.decodeResource(res, resId, options);
+    }
+
+    /**
+     * Decode a given image file with the specified dimensions
+     *
+     * @param filePath the file resource path
+     * @param reqWidth the required width
+     * @param reqHeight the required height
+     * @return the bitmap
+     */
+    public static Bitmap decodeSampledBitmapFromFilePath(String filePath,
+                                                         int reqWidth, int reqHeight) {
+
+        // First decode with inJustDecodeBounds=true to check dimensions
+        final BitmapFactory.Options options = new BitmapFactory.Options();
+        options.inJustDecodeBounds = true;
+        BitmapFactory.decodeFile(filePath, options);
+
+        // Calculate inSampleSize
+        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
+
+        // Decode bitmap with inSampleSize set
+        options.inJustDecodeBounds = false;
+        return BitmapFactory.decodeFile(filePath, options);
+
+    }
 }