1.25 Warn user about losing unsaved changes

app/src/main/java/com/example/android/pets/EditorActivity.java

@@ -15,9 +15,11 @@
  */
 package com.example.android.pets;
 
+import android.app.AlertDialog;
 import android.app.LoaderManager;
 import android.content.ContentValues;
 import android.content.CursorLoader;
+import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.Loader;
 import android.database.Cursor;
@@ -28,6 +30,7 @@
 import android.text.TextUtils;
 import android.view.Menu;
 import android.view.MenuItem;
+import android.view.MotionEvent;
 import android.view.View;
 import android.widget.AdapterView;
 import android.widget.ArrayAdapter;
@@ -68,6 +71,21 @@ public class EditorActivity extends AppCompatActivity implements
      */
     private int mGender = PetEntry.GENDER_UNKNOWN;
 
+    /** Boolean flag that keeps track of whether the pet has been edited (true) or not (false) */
+    private boolean mPetHasChanged = false;
+
+    /**
+     * OnTouchListener that listens for any user touches on a View, implying that they are modifying
+     * the view, and we change the mPetHasChanged boolean to true.
+     */
+    private View.OnTouchListener mTouchListener = new View.OnTouchListener() {
+        @Override
+        public boolean onTouch(View view, MotionEvent motionEvent) {
+            mPetHasChanged = true;
+            return false;
+        }
+    };
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -98,6 +116,14 @@ protected void onCreate(Bundle savedInstanceState) {
         mWeightEditText = (EditText) findViewById(R.id.edit_pet_weight);
         mGenderSpinner = (Spinner) findViewById(R.id.spinner_gender);
 
+        // Setup OnTouchListeners on all the input fields, so we can determine if the user
+        // has touched or modified them. This will let us know if there are unsaved changes
+        // or not, if the user tries to leave the editor without saving.
+        mNameEditText.setOnTouchListener(mTouchListener);
+        mBreedEditText.setOnTouchListener(mTouchListener);
+        mWeightEditText.setOnTouchListener(mTouchListener);
+        mGenderSpinner.setOnTouchListener(mTouchListener);
+
         setupSpinner();
     }
 
@@ -235,13 +261,58 @@ public boolean onOptionsItemSelected(MenuItem item) {
                 return true;
             // Respond to a click on the "Up" arrow button in the app bar
             case android.R.id.home:
-                // Navigate back to parent activity (CatalogActivity)
-                NavUtils.navigateUpFromSameTask(this);
+                // If the pet hasn't changed, continue with navigating up to parent activity
+                // which is the {@link CatalogActivity}.
+                if (!mPetHasChanged) {
+                    NavUtils.navigateUpFromSameTask(EditorActivity.this);
+                    return true;
+                }
+
+                // Otherwise if there are unsaved changes, setup a dialog to warn the user.
+                // Create a click listener to handle the user confirming that
+                // changes should be discarded.
+                DialogInterface.OnClickListener discardButtonClickListener =
+                        new DialogInterface.OnClickListener() {
+                            @Override
+                            public void onClick(DialogInterface dialogInterface, int i) {
+                                // User clicked "Discard" button, navigate to parent activity.
+                                NavUtils.navigateUpFromSameTask(EditorActivity.this);
+                            }
+                        };
+
+                // Show a dialog that notifies the user they have unsaved changes
+                showUnsavedChangesDialog(discardButtonClickListener);
                 return true;
         }
         return super.onOptionsItemSelected(item);
     }
 
+    /**
+     * This method is called when the back button is pressed.
+     */
+    @Override
+    public void onBackPressed() {
+        // If the pet hasn't changed, continue with handling back button press
+        if (!mPetHasChanged) {
+            super.onBackPressed();
+            return;
+        }
+
+        // Otherwise if there are unsaved changes, setup a dialog to warn the user.
+        // Create a click listener to handle the user confirming that changes should be discarded.
+        DialogInterface.OnClickListener discardButtonClickListener =
+                new DialogInterface.OnClickListener() {
+                    @Override
+                    public void onClick(DialogInterface dialogInterface, int i) {
+                        // User clicked "Discard" button, close the current activity.
+                        finish();
+                    }
+                };
+
+        // Show dialog that there are unsaved changes
+        showUnsavedChangesDialog(discardButtonClickListener);
+    }
+
     @Override
     public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
         // Since the editor shows all pet attributes, define a projection that contains
@@ -314,4 +385,33 @@ public void onLoaderReset(Loader<Cursor> loader) {
         mWeightEditText.setText("");
         mGenderSpinner.setSelection(0); // Select "Unknown" gender
     }
+
+    /**
+     * Show a dialog that warns the user there are unsaved changes that will be lost
+     * if they continue leaving the editor.
+     *
+     * @param discardButtonClickListener is the click listener for what to do when
+     *                                   the user confirms they want to discard their changes
+     */
+    private void showUnsavedChangesDialog(
+            DialogInterface.OnClickListener discardButtonClickListener) {
+        // Create an AlertDialog.Builder and set the message, and click listeners
+        // for the postivie and negative buttons on the dialog.
+        AlertDialog.Builder builder = new AlertDialog.Builder(this);
+        builder.setMessage(R.string.unsaved_changes_dialog_msg);
+        builder.setPositiveButton(R.string.discard, discardButtonClickListener);
+        builder.setNegativeButton(R.string.keep_editing, new DialogInterface.OnClickListener() {
+            public void onClick(DialogInterface dialog, int id) {
+                // User clicked the "Keep editing" button, so dismiss the dialog
+                // and continue editing the pet.
+                if (dialog != null) {
+                    dialog.dismiss();
+                }
+            }
+        });
+
+        // Create and show the AlertDialog
+        AlertDialog alertDialog = builder.create();
+        alertDialog.show();
+    }
 }

app/src/main/res/values/strings.xml

@@ -50,6 +50,15 @@
     <!-- Toast message in editor when current pet has failed to be updated [CHAR LIMIT=NONE] -->
     <string name="editor_update_pet_failed">Error with updating pet</string>
 
+    <!-- Dialog message when user is leaving editor but hasn't saved changes [CHAR LIMIT=NONE] -->
+    <string name="unsaved_changes_dialog_msg">Discard your changes and quit editing?</string>
+
+    <!-- Dialog button text for the option to discard a user's changes [CHAR LIMIT=20] -->
+    <string name="discard">Discard</string>
+
+    <!-- Dialog button text for the option to keep editing the current pet [CHAR LIMIT=20] -->
+    <string name="keep_editing">Keep Editing</string>
+
     <!-- Label for overview category of attributes in the editor [CHAR LIMIT=30] -->
     <string name="category_overview">Overview</string>