Android: handle the back button / gesture on API level 33+ in a way that preserves backward compatibility

Author: alemart

android/gradle_project/allegro/src/main/java/org/liballeg/android/AllegroActivity.java

@@ -25,6 +25,9 @@
 import java.util.Vector;
 import android.os.Build;
 import android.view.View;
+import android.view.KeyEvent;
+import android.window.OnBackInvokedCallback;
+import android.window.OnBackInvokedDispatcher;
 
 public class AllegroActivity extends Activity
 {
@@ -339,6 +342,22 @@ public void onCreate(Bundle savedInstanceState)
       requestWindowFeature(Window.FEATURE_NO_TITLE);
       this.getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
 
+      if(Build.VERSION.SDK_INT >= 33) {
+         // handle the back button / gesture on API level 33+
+         getOnBackInvokedDispatcher().registerOnBackInvokedCallback(
+            OnBackInvokedDispatcher.PRIORITY_DEFAULT, new OnBackInvokedCallback() {
+               @Override
+               public void onBackInvoked() {
+                  // these will be mapped to ALLEGRO_KEY_BACK
+                  KeyEvent keyDown = new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_BACK);
+                  KeyEvent keyUp = new KeyEvent(KeyEvent.ACTION_UP, KeyEvent.KEYCODE_BACK);
+                  dispatchKeyEvent(keyDown);
+                  dispatchKeyEvent(keyUp);
+               }
+            }
+         );
+      }
+
       Log.d("AllegroActivity", "onCreate end");
    }
 

android/gradle_project/app/src/main/AndroidManifest.xml

@@ -4,7 +4,8 @@
       android:versionCode="1"
       android:versionName="1.0">
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
-    <application android:label="${APP_ID}">
+    <application android:label="${APP_ID}"
+                 android:enableOnBackInvokedCallback="true">
         <activity android:name=".MainActivity"
                   android:launchMode="singleTask"
                   android:screenOrientation="unspecified"