Optional app PIN, settings header, pink selection ring

- A PIN (4 to 8 digits, salted SHA-256 in prefs) set in Settings shows
  a logo splash with a PIN prompt at start and whenever the app returns
  after leaving the screen; Back there leaves the app.
- Settings gets the back-arrow header shared with the folder grid
  (Ui.header) and scrolls, since the PIN fields overflow the screen.
- Tile and list focus rings use the icon pink.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 43 insertions, 1 deletions

diff --git a/app/src/main/java/mygram/droid/App.java b/app/src/main/java/mygram/droid/App.java
index ffbdd8d..1919343 100644
--- a/app/src/main/java/mygram/droid/App.java
+++ b/app/src/main/java/mygram/droid/App.java
@@ -14,19 +14,61 @@
 
 package mygram.droid;
 
+import android.app.Activity;
 import android.app.Application;
+import android.content.Intent;
+import android.os.Bundle;
 
 import java.net.CookieHandler;
 import java.net.CookieManager;
 import java.net.CookiePolicy;
 
-public final class App extends Application {
+public final class App extends Application implements Application.ActivityLifecycleCallbacks {
+	/** Until the PIN is entered; set again whenever the app leaves the screen. */
+	static boolean locked = true;
+	private int started;
+
 	@Override
 	public void onCreate() {
 		super.onCreate();
 		Prefs.init(this);
+		registerActivityLifecycleCallbacks(this);
 		// One cookie jar for the Foldergram session: Api, Glide and ExoPlayer
 		// all use HttpURLConnection, which consults the default handler.
 		CookieHandler.setDefault(new CookieManager(null, CookiePolicy.ACCEPT_ALL));
 	}
+
+	/** Before any screen draws, cover it with the PIN prompt if the app is locked. */
+	@Override
+	public void onActivityStarted(Activity a) {
+		started++;
+		if (locked && Prefs.hasPin() && !(a instanceof LockActivity))
+			a.startActivity(new Intent(a, LockActivity.class));
+	}
+
+	@Override
+	public void onActivityStopped(Activity a) {
+		if (--started == 0)
+			locked = true;
+	}
+
+	@Override
+	public void onActivityCreated(Activity a, Bundle state) {
+	}
+
+	@Override
+	public void onActivityResumed(Activity a) {
+	}
+
+	@Override
+	public void onActivityPaused(Activity a) {
+	}
+
+	@Override
+	public void onActivitySaveInstanceState(Activity a, Bundle state) {
+	}
+
+	@Override
+	public void onActivityDestroyed(Activity a) {
+	}
 }