Code improvements

* Replace unchecked casts with checked casts
 * remove Utility.finViewById
 * Fix return activity checking
 * Create UserAction enum
 * Fix typos
 * Add instrumented test for error info
 * ErrorInfo make fields final
 * Log exception using logger
 * Add inherited annotations
 * Resolve deprecation warnings
 * Remove unused methods from utility
 * Reformat code
 * Remove unused methods from Utility and improve getFileExt
 * Create OnScrollBelowItemsListener

app/src/test/java/org/schabi/newpipe/report/ErrorActivityTest.java

@@ -0,0 +1,38 @@
+package org.schabi.newpipe.report;
+
+import android.app.Activity;
+
+import org.junit.Test;
+import org.schabi.newpipe.MainActivity;
+import org.schabi.newpipe.RouterActivity;
+import org.schabi.newpipe.fragments.detail.VideoDetailFragment;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+/**
+ * Unit tests for {@link ErrorActivity}
+ */
+public class ErrorActivityTest {
+    @Test
+    public void getReturnActivity() throws Exception {
+        Class<? extends Activity> returnActivity;
+        returnActivity = ErrorActivity.getReturnActivity(MainActivity.class);
+        assertEquals(MainActivity.class, returnActivity);
+
+        returnActivity = ErrorActivity.getReturnActivity(RouterActivity.class);
+        assertEquals(RouterActivity.class, returnActivity);
+
+        returnActivity = ErrorActivity.getReturnActivity(null);
+        assertNull(returnActivity);
+
+        returnActivity = ErrorActivity.getReturnActivity(Integer.class);
+        assertEquals(MainActivity.class, returnActivity);
+
+        returnActivity = ErrorActivity.getReturnActivity(VideoDetailFragment.class);
+        assertEquals(MainActivity.class, returnActivity);
+    }
+
+
+
+}