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, 49 insertions, 6 deletions

diff --git a/app/src/main/java/mygram/droid/SettingsActivity.java b/app/src/main/java/mygram/droid/SettingsActivity.java
index a8839bb..3783058 100644
--- a/app/src/main/java/mygram/droid/SettingsActivity.java
+++ b/app/src/main/java/mygram/droid/SettingsActivity.java
@@ -18,12 +18,16 @@ import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.text.InputType;
+import android.view.ViewGroup;
 import android.widget.EditText;
 import android.widget.LinearLayout;
+import android.widget.ScrollView;
 import android.widget.Toast;
 
-/** Viewer password, photo and background durations, change instance. */
+/** Viewer password, durations, app PIN, change instance. */
 public final class SettingsActivity extends Activity {
+	private static final int PIN_INPUT = InputType.TYPE_CLASS_NUMBER | InputType.TYPE_NUMBER_VARIATION_PASSWORD;
+
 	@Override
 	protected void onCreate(Bundle state) {
 		super.onCreate(state);
@@ -41,23 +45,58 @@ public final class SettingsActivity extends Activity {
 		EditText bg = Ui.field(this, "15", InputType.TYPE_CLASS_NUMBER);
 		bg.setText(String.valueOf(Prefs.backgroundSeconds()));
 		box.addView(bg);
+		box.addView(Ui.text(this, Prefs.hasPin() ? "New app PIN, 4 to 8 digits (empty keeps it)"
+				: "App PIN, 4 to 8 digits (empty for none)", 14));
+		EditText pin = Ui.field(this, "PIN", PIN_INPUT);
+		box.addView(pin);
+		EditText again = Ui.field(this, "Repeat PIN", PIN_INPUT);
+		box.addView(again);
 		LinearLayout row = Ui.row(this);
 		row.addView(Ui.iconButton(this, R.drawable.ic_check, "Save", v -> save(pw.getText().toString(),
-				photo.getText().toString(), bg.getText().toString())));
+				photo.getText().toString(), bg.getText().toString(), pin.getText().toString(),
+				again.getText().toString())));
+		if (Prefs.hasPin())
+			row.addView(Ui.iconButton(this, R.drawable.ic_lock_open, "Remove PIN", v -> {
+				Prefs.setPin(null);
+				Toast.makeText(this, "PIN removed", Toast.LENGTH_SHORT).show();
+				finish();
+			}));
 		row.addView(Ui.iconButton(this, R.drawable.ic_swap, "Change instance",
 				v -> startActivity(new Intent(this, SetupActivity.class))));
 		box.addView(row);
-		setContentView(box);
+
+		// Taller than the screen with the PIN fields; the scroll view follows focus.
+		ScrollView scroll = new ScrollView(this);
+		scroll.addView(box);
+		LinearLayout column = new LinearLayout(this);
+		column.setOrientation(LinearLayout.VERTICAL);
+		column.addView(Ui.header(this, "Settings"));
+		column.addView(scroll, new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 0, 1));
+		setContentView(column);
 		row.getChildAt(0).requestFocus();
 	}
 
-	private void save(String password, String photo, String background) {
+	private void save(String password, String photo, String background, String pin, String again) {
 		int p = seconds(photo), b = seconds(background);
 		if (p < 1 || b < 1) {
-			Toast.makeText(this, "Durations must be 1 to 600 seconds", Toast.LENGTH_LONG).show();
+			toast("Durations must be 1 to 600 seconds");
 			return;
 		}
+		if (!pin.isEmpty() || !again.isEmpty()) {
+			if (!Prefs.validPin(pin)) {
+				toast("The PIN must be 4 to 8 digits");
+				return;
+			}
+			if (!pin.equals(again)) {
+				toast("The two PINs differ");
+				return;
+			}
+		}
 		Prefs.setTimes(p, b);
+		if (!pin.isEmpty()) {
+			Prefs.setPin(pin);
+			App.locked = false; // just typed it; ask from the next time the app leaves the screen
+		}
 		if (password.equals(Prefs.password())) {
 			finish();
 			return;
@@ -68,7 +107,11 @@ public final class SettingsActivity extends Activity {
 		}, ok -> {
 			Prefs.setPassword(password);
 			finish();
-		}, e -> Toast.makeText(this, "Login failed: " + e.getMessage(), Toast.LENGTH_LONG).show());
+		}, e -> toast("Login failed: " + e.getMessage()));
+	}
+
+	private void toast(String s) {
+		Toast.makeText(this, s, Toast.LENGTH_LONG).show();
 	}
 
 	private static int seconds(String s) {