Merge pull request #213 from misaochan/category-back-button

Add warning when pressing 'back' on category screen

app/src/main/java/fr/free/nrw/commons/category/CategorizationFragment.java

@@ -3,6 +3,7 @@ package fr.free.nrw.commons.category;
 import android.app.Activity;
 import android.content.ContentProviderClient;
 import android.content.Context;
+import android.content.DialogInterface;
 import android.database.Cursor;
 import android.os.AsyncTask;
 import android.os.Bundle;
@@ -10,10 +11,12 @@ import android.os.Parcel;
 import android.os.Parcelable;
 import android.os.RemoteException;
 import android.support.v4.app.Fragment;
+import android.support.v7.app.AlertDialog;
 import android.text.Editable;
 import android.text.TextUtils;
 import android.text.TextWatcher;
 import android.util.Log;
+import android.view.KeyEvent;
 import android.view.LayoutInflater;
 import android.view.Menu;
 import android.view.MenuItem;
@@ -26,6 +29,7 @@ import android.widget.EditText;
 import android.widget.ListView;
 import android.widget.ProgressBar;
 import android.widget.TextView;
+import android.widget.Toast;
 
 import java.util.ArrayList;
 import java.util.Date;
@@ -447,6 +451,47 @@ public class CategorizationFragment extends Fragment {
         client = getActivity().getContentResolver().acquireContentProviderClient(CategoryContentProvider.AUTHORITY);
     }
 
+    @Override
+    public void onResume() {
+        super.onResume();
+
+        View rootView = getView();
+        if (rootView != null) {
+            rootView.setFocusableInTouchMode(true);
+            rootView.requestFocus();
+            rootView.setOnKeyListener(new View.OnKeyListener() {
+                @Override
+                public boolean onKey(View v, int keyCode, KeyEvent event) {
+                    if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK) {
+                        backButtonDialog();
+                        return true;
+                    }
+                    return false;
+                }
+            });
+        }
+    }
+
+    private void backButtonDialog() {
+        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+
+        builder.setMessage("Are you sure you want to go back? The image will not have any categories saved.")
+                .setTitle("Warning");
+        builder.setPositiveButton("No", new DialogInterface.OnClickListener() {
+            public void onClick(DialogInterface dialog, int id) {
+                //No need to do anything, user remains on categorization screen
+            }
+        });
+        builder.setNegativeButton("Yes", new DialogInterface.OnClickListener() {
+            public void onClick(DialogInterface dialog, int id) {
+                getActivity().finish();
+            }
+        });
+
+        AlertDialog dialog = builder.create();
+        dialog.show();
+    }
+
     @Override
     public void onDestroy() {
         super.onDestroy();