fix: blank page at start — SSL, HTTP errors, old-key migration

- WebView background set to #F5F5F5 to avoid white flash
- SSL certificate errors now show a dialog (user can accept self-signed)
- HTTP errors (4xx/5xx) shown with status code
- Migrates old 'public_url' key to 'server_url' automatically
- Better error messages with troubleshooting tips
- Progress bar shows real page load progress
- No-server-configured state shows clear instructions

android/app/src/main/java/com/mealtracker/app/MainActivity.java

@@ -6,13 +6,16 @@ import android.content.SharedPreferences;
 import android.graphics.Bitmap;
 import android.net.ConnectivityManager;
 import android.net.NetworkInfo;
+import android.net.http.SslError;
 import android.os.Bundle;
 import android.view.KeyEvent;
 import android.view.View;
 import android.webkit.CookieManager;
+import android.webkit.SslErrorHandler;
 import android.webkit.WebChromeClient;
 import android.webkit.WebResourceError;
 import android.webkit.WebResourceRequest;
+import android.webkit.WebResourceResponse;
 import android.webkit.WebSettings;
 import android.webkit.WebView;
 import android.webkit.WebViewClient;
@@ -30,6 +33,7 @@ public class MainActivity extends AppCompatActivity {
 
     private static final String PREFS_NAME = "mealtracker_prefs";
     private static final String KEY_SERVER_URL = "server_url";
+    private static final String KEY_PUBLIC_URL = "public_url"; // migrate old key
 
     private WebView webView;
     private SwipeRefreshLayout swipeRefresh;
@@ -38,6 +42,7 @@ public class MainActivity extends AppCompatActivity {
     private TextView toolbarTitle;
     private String serverUrl;
     private String currentUrl;
+    private boolean firstLoad = true;
 
     @SuppressLint("SetJavaScriptEnabled")
     @Override
@@ -61,11 +66,22 @@ public class MainActivity extends AppCompatActivity {
 
         SharedPreferences prefs = getSharedPreferences(PREFS_NAME, MODE_PRIVATE);
         serverUrl = prefs.getString(KEY_SERVER_URL, "");
+
+        // Migrate from old public_url key if present
+        if (serverUrl.isEmpty()) {
+            String oldUrl = prefs.getString(KEY_PUBLIC_URL, "");
+            if (!oldUrl.isEmpty()) {
+                prefs.edit().putString(KEY_SERVER_URL, oldUrl).remove(KEY_PUBLIC_URL).apply();
+                serverUrl = oldUrl;
+            }
+        }
+
         if (!serverUrl.isEmpty()) {
             loadUrl(serverUrl);
-            toolbarTitle.setText(getString(R.string.app_name));
         } else {
-            toolbarTitle.setText(R.string.app_name);
+            errorView.setText(R.string.server_not_configured);
+            errorView.setVisibility(View.VISIBLE);
+            webView.setVisibility(View.GONE);
             showSettingsDialog();
         }
     }
@@ -86,7 +102,9 @@ public class MainActivity extends AppCompatActivity {
         settings.setAllowFileAccess(false);
         settings.setSaveFormData(true);
 
-        // Accept all cookies so login sessions persist
+        // Avoid blank flash — match the site background
+        webView.setBackgroundColor(0xFFF5F5F5);
+
         CookieManager.getInstance().setAcceptCookie(true);
         CookieManager.getInstance().setAcceptThirdPartyCookies(webView, true);
 
@@ -96,6 +114,7 @@ public class MainActivity extends AppCompatActivity {
         webView.setWebViewClient(new WebViewClient() {
             @Override
             public void onPageStarted(WebView view, String url, Bitmap favicon) {
+                firstLoad = false;
                 progressBar.setVisibility(View.VISIBLE);
                 errorView.setVisibility(View.GONE);
                 webView.setVisibility(View.VISIBLE);
@@ -112,23 +131,39 @@ public class MainActivity extends AppCompatActivity {
             public void onReceivedError(WebView view, WebResourceRequest request,
                                         WebResourceError error) {
                 if (request.isForMainFrame()) {
-                    progressBar.setVisibility(View.GONE);
-                    swipeRefresh.setRefreshing(false);
-                    if (!isNetworkAvailable()) {
-                        errorView.setText(R.string.error_no_network);
-                    } else {
-                        errorView.setText(R.string.error_load_failed);
-                    }
-                    errorView.setVisibility(View.VISIBLE);
-                    webView.setVisibility(View.GONE);
+                    showError(isNetworkAvailable()
+                        ? R.string.error_load_failed : R.string.error_no_network);
                 }
             }
 
+            @Override
+            public void onReceivedHttpError(WebView view, WebResourceRequest request,
+                                            WebResourceResponse errorResponse) {
+                // Only show error for the main page, not subresources
+                if (request.isForMainFrame() && firstLoad) {
+                    int code = errorResponse.getStatusCode();
+                    errorView.setText(getString(R.string.error_http, code));
+                    showError(0); // 0 means keep the text we just set
+                }
+            }
+
+            @Override
+            public void onReceivedSslError(WebView view, SslErrorHandler handler,
+                                           SslError error) {
+                // Let the user decide — some self-hosted instances use self-signed certs
+                new AlertDialog.Builder(MainActivity.this)
+                    .setTitle(R.string.ssl_error_title)
+                    .setMessage(getString(R.string.ssl_error_msg,
+                        error.getUrl(), error.getPrimaryError()))
+                    .setPositiveButton(R.string.ssl_proceed, (d, w) -> handler.proceed())
+                    .setNegativeButton(R.string.ssl_cancel, (d, w) -> handler.cancel())
+                    .setCancelable(false)
+                    .show();
+            }
+
             @Override
             public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
-                String url = request.getUrl().toString();
-                // Keep all navigation inside the WebView
-                view.loadUrl(url);
+                view.loadUrl(request.getUrl().toString());
                 return true;
             }
         });
@@ -136,6 +171,7 @@ public class MainActivity extends AppCompatActivity {
         webView.setWebChromeClient(new WebChromeClient() {
             @Override
             public void onProgressChanged(WebView view, int newProgress) {
+                progressBar.setProgress(newProgress);
                 if (newProgress == 100) {
                     progressBar.setVisibility(View.GONE);
                     swipeRefresh.setRefreshing(false);
@@ -151,17 +187,32 @@ public class MainActivity extends AppCompatActivity {
         });
 
         errorView.setOnClickListener(v -> {
-            if (serverUrl != null) {
+            if (serverUrl != null && !serverUrl.isEmpty()) {
+                firstLoad = true;
                 loadUrl(serverUrl);
+            } else {
+                showSettingsDialog();
             }
         });
     }
 
+    private void showError(int resId) {
+        progressBar.setVisibility(View.GONE);
+        swipeRefresh.setRefreshing(false);
+        if (resId != 0) {
+            errorView.setText(resId);
+        }
+        errorView.setVisibility(View.VISIBLE);
+        webView.setVisibility(View.GONE);
+    }
+
     private void loadUrl(String url) {
         serverUrl = url;
         currentUrl = url;
+        firstLoad = true;
         errorView.setVisibility(View.GONE);
         webView.setVisibility(View.VISIBLE);
+        progressBar.setVisibility(View.VISIBLE);
         webView.loadUrl(url);
     }
 
@@ -182,13 +233,14 @@ public class MainActivity extends AppCompatActivity {
         builder.setPositiveButton(R.string.save, (dialog, which) -> {
             String url = urlInput.getText().toString().trim();
             if (!url.isEmpty()) {
-                // Normalize: strip trailing slashes, auto-add https://
                 url = url.replaceAll("/+$", "");
                 if (!url.startsWith("http://") && !url.startsWith("https://")) {
                     url = "https://" + url;
                 }
                 prefs.edit().putString(KEY_SERVER_URL, url).apply();
+                firstLoad = true;
                 loadUrl(url);
+                toolbarTitle.setText(R.string.app_name);
                 Toast.makeText(this, R.string.url_saved, Toast.LENGTH_SHORT).show();
             } else {
                 Toast.makeText(this, R.string.url_empty, Toast.LENGTH_SHORT).show();
@@ -220,9 +272,7 @@ public class MainActivity extends AppCompatActivity {
         webView.clearFormData();
         CookieManager.getInstance().removeAllCookies(null);
         CookieManager.getInstance().flush();
-        // Clear WebView storage
         webView.clearSslPreferences();
-        // Nuke DOM/local storage
         webView.evaluateJavascript("localStorage.clear(); sessionStorage.clear();", null);
     }
 

android/app/src/main/res/layout/activity_main.xml

@@ -60,9 +60,10 @@
                 style="?android:attr/progressBarStyleHorizontal"
                 android:layout_width="match_parent"
                 android:layout_height="3dp"
-                android:indeterminate="true"
+                android:max="100"
                 android:visibility="gone"
-                android:indeterminateTint="@color/colorAccent" />
+                android:indeterminateTint="@color/colorAccent"
+                android:progressTint="@color/colorAccent" />
 
         </com.google.android.material.appbar.AppBarLayout>
 

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

@@ -5,14 +5,19 @@
     <string name="settings">Settings</string>
     <string name="settings_title">Server Configuration</string>
     <string name="url_label">Enter your Meal Tracker server URL:</string>
-    <string name="url_hint_text">This is the URL where your household\'s meal tracker is hosted.\nExample: https://meals.example.com</string>
+    <string name="url_hint_text">The address where your meal tracker is hosted.\nExample: https://meals.example.com</string>
     <string name="save">Save</string>
     <string name="cancel">Cancel</string>
     <string name="clear_data">Clear Data</string>
     <string name="url_saved">Connected to server</string>
     <string name="url_empty">Please enter a server URL</string>
     <string name="error_no_network">No network connection.\nTap to retry.</string>
-    <string name="error_load_failed">Could not reach the server.\nCheck the URL and tap to retry.</string>
-    <string name="server_not_configured">No server configured.\nTap the gear icon to set up.</string>
+    <string name="error_load_failed">Could not reach the server.\nCheck the URL and tap to retry.\n\nTip: make sure the URL opens in a browser first.</string>
+    <string name="error_http">Server returned HTTP %d.\nCheck your server URL and tap to retry.</string>
+    <string name="server_not_configured">No server configured.\nTap the gear icon ⚙ to enter your server URL.</string>
     <string name="data_cleared">Local data cleared</string>
+    <string name="ssl_error_title">⚠ Certificate Warning</string>
+    <string name="ssl_error_msg">The server at %1$s uses an untrusted certificate (error %2$d).\n\nThis is common for self-hosted servers. Proceed only if you trust this server.</string>
+    <string name="ssl_proceed">Proceed</string>
+    <string name="ssl_cancel">Cancel</string>
 </resources>