An upward swipe now closes the photo viewer. Closes #31

app/src/main/java/com/keylesspalace/tusky/ViewMediaFragment.java

@@ -19,6 +19,7 @@ import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.v4.app.DialogFragment;
 import android.view.LayoutInflater;
+import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.WindowManager;
@@ -71,6 +72,7 @@ public class ViewMediaFragment extends DialogFragment {
 
         attacher = new PhotoViewAttacher(photoView);
 
+        // Clicking outside the photo closes the viewer.
         attacher.setOnPhotoTapListener(new PhotoViewAttacher.OnPhotoTapListener() {
             @Override
             public void onPhotoTap(View view, float x, float y) {
@@ -83,6 +85,20 @@ public class ViewMediaFragment extends DialogFragment {
             }
         });
 
+        /* An upward swipe motion also closes the viewer. This is especially useful when the photo
+         * mostly fills the screen so clicking outside is difficult. */
+        attacher.setOnSingleFlingListener(new PhotoViewAttacher.OnSingleFlingListener() {
+            @Override
+            public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
+                    float velocityY) {
+                if (velocityY < 0.0 && Math.abs(velocityY) > Math.abs(velocityX)) {
+                    dismiss();
+                    return true;
+                }
+                return false;
+            }
+        });
+
         Picasso.with(getContext())
                 .load(url)
                 .into(photoView, new Callback() {