App 2.6.0: floating button to open the app

The MG4's launcher does not list third-party apps, so the app could
only be opened by reinstalling it. Now a small round MG-red button
floats over the car's screens: tap opens the app, drag moves it (the
position is kept and clamped to the screen), and it hides while the
app itself is open. A switch in the Upload tab turns it off.

The always-on service owns the overlay, so the button is there from
boot. It needs the overlay permission (SYSTEM_ALERT_WINDOW), which the
car build has through the system UID; without it, or if the window
manager refuses, the button stays away and nothing crashes, and the
Upload tab offers the system permission screen.

Tested on an Android 9 AOSP emulator at the head unit's 1920x1080 /
160 dpi with the car APK (installs as UID 1000): button appears over
the home screen, tap opens the app, hidden while open, drag moves it
without opening the app, position survives a force-stop, the switch
works through the UI. FloatingButtonGeometry has 3 unit tests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QLJfZQZeAKAwSqViTmLzki

app/src/main/java/com/evsuite/abrp/MainActivity.java

@@ -120,7 +120,8 @@ public class MainActivity extends AppCompatActivity {
     private TextView connectionStatusText;
 
     /** Upload page: live telemetry switch and cadence. */
-    private SwitchMaterial liveTelemetrySwitch, boostSwitch;
+    private SwitchMaterial liveTelemetrySwitch, boostSwitch, floatingButtonSwitch;
+    private View overlayPermissionNote;
     private android.widget.Spinner intervalSpinner;
     private TextInputLayout lowSocLayout;
     private TextInputEditText lowSocInput;
@@ -303,6 +304,8 @@ public class MainActivity extends AppCompatActivity {
         super.onResume();
         // Poll state and log only while the screen is up; onPause cancels it.
         uiHandler.post(uiRefresh);
+        FloatingButton.setAppInForeground(true);
+        refreshOverlayPermissionNote();
     }
 
     @Override
@@ -310,6 +313,7 @@ public class MainActivity extends AppCompatActivity {
         super.onPause();
         // Stop polling off-screen: this activity has no reason to spend cycles then.
         uiHandler.removeCallbacks(uiRefresh);
+        FloatingButton.setAppInForeground(false);
     }
 
     // ---------- Update check ----------
@@ -791,6 +795,22 @@ public class MainActivity extends AppCompatActivity {
     // ---------- Upload page ----------
 
     private void bindServicePane() {
+        floatingButtonSwitch = servicePane.findViewById(R.id.floating_button_switch);
+        overlayPermissionNote = servicePane.findViewById(R.id.overlay_permission_note);
+        floatingButtonSwitch.setChecked(UploadSettings.floatingButtonEnabled(prefs));
+        floatingButtonSwitch.setOnCheckedChangeListener((btn, checked) -> {
+            prefs.edit().putBoolean(UploadSettings.KEY_FLOATING_BUTTON, checked).apply();
+            FloatingButton.refresh();
+            refreshOverlayPermissionNote();
+        });
+        servicePane.findViewById(R.id.overlay_permission_button).setOnClickListener(v -> {
+            try {
+                startActivity(new Intent(android.provider.Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
+                        Uri.parse("package:" + getPackageName())));
+            } catch (android.content.ActivityNotFoundException e) {
+                Toast.makeText(this, R.string.overlay_settings_missing, Toast.LENGTH_LONG).show();
+            }
+        });
         liveTelemetrySwitch = servicePane.findViewById(R.id.abrp_upload_switch);
         intervalSpinner = servicePane.findViewById(R.id.interval_spinner);
         boostSwitch = servicePane.findViewById(R.id.boost_switch);
@@ -847,6 +867,16 @@ public class MainActivity extends AppCompatActivity {
         });
     }
 
+    /**
+     * The note under the floating-button switch: only when the button is wanted but this build
+     * may not draw over other apps (the car build may, through the system UID).
+     */
+    private void refreshOverlayPermissionNote() {
+        if (overlayPermissionNote == null) return;
+        boolean missing = UploadSettings.floatingButtonEnabled(prefs) && !FloatingButton.canDraw(this);
+        overlayPermissionNote.setVisibility(missing ? View.VISIBLE : View.GONE);
+    }
+
     /** Clamped to 1-99: 0 would never trigger and 100 would boost permanently. */
     private void saveLowSocThreshold() {
         CharSequence raw = lowSocInput.getText();