Downgrades to SDL2 2.0.9

Actually simply reverted few files:
```sh
git checkout master -- \
    pythonforandroid/recipes/sdl2/__init__.py \
    pythonforandroid/bootstraps/sdl2/build/src/patches/SDLActivity.java.patch \
    pythonforandroid/bootstraps/sdl2/build/src/main/java/org/kivy/android/PythonActivity.java
```
- fixes kivy#2167
- fixes kivy#2169

pythonforandroid/bootstraps/sdl2/build/src/main/java/org/kivy/android/PythonActivity.java

@@ -193,7 +193,7 @@ protected void onPostExecute(String result) {
                         mActivity.getPackageName(), PackageManager.GET_META_DATA).metaData;
 
                 PowerManager pm = (PowerManager) mActivity.getSystemService(Context.POWER_SERVICE);
-                if (mActivity.mMetaData.getInt("wakelock") == 1) {
+                if ( mActivity.mMetaData.getInt("wakelock") == 1 ) {
                     mActivity.mWakeLock = pm.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK, "Screen On");
                     mActivity.mWakeLock.acquire();
                 }
@@ -450,32 +450,35 @@ public void appConfirmedActive() {
     public void considerLoadingScreenRemoval() {
         if (loadingScreenRemovalTimer != null)
             return;
-        if (PythonActivity.mSingleton != null &&
-                mAppConfirmedActive &&
-                loadingScreenRemovalTimer == null) {
-            Log.v(TAG, "loading screen timer Runnable() launched.");
-            // Remove loading screen but with a delay.
-            // (app can use p4a's android.loadingscreen module to
-            // do it quicker if it wants to)
-            TimerTask removalTask = new TimerTask() {
-                @Override
-                public void run() {
-                    // post a runnable to the handler
-                    runOnUiThread(new Runnable() {
+        runOnUiThread(new Runnable() {
+            public void run() {
+                if (((PythonActivity)PythonActivity.mSingleton).mAppConfirmedActive &&
+                        loadingScreenRemovalTimer == null) {
+                    // Remove loading screen but with a delay.
+                    // (app can use p4a's android.loadingscreen module to
+                    // do it quicker if it wants to)
+                    // get a handler (call from main thread)
+                    // this will run when timer elapses
+                    TimerTask removalTask = new TimerTask() {
                         @Override
                         public void run() {
-                            Log.v(TAG, "loading screen timer Runnable() finished.");
-                            PythonActivity activity =
-                                ((PythonActivity)PythonActivity.mSingleton);
-                            if (activity != null)
-                                activity.removeLoadingScreen();
+                            // post a runnable to the handler
+                            runOnUiThread(new Runnable() {
+                                @Override
+                                public void run() {
+                                    PythonActivity activity =
+                                        ((PythonActivity)PythonActivity.mSingleton);
+                                    if (activity != null)
+                                        activity.removeLoadingScreen();
+                                }
+                            });
                         }
-                    });
+                    };
+                    loadingScreenRemovalTimer = new Timer();
+                    loadingScreenRemovalTimer.schedule(removalTask, 5000);
                 }
-            };
-            loadingScreenRemovalTimer = new Timer();
-            loadingScreenRemovalTimer.schedule(removalTask, 5000);
-        }
+            }
+        });
     }
 
     public void removeLoadingScreen() {
@@ -586,30 +589,14 @@ protected void onResume() {
         if (this.mWakeLock != null) {
             this.mWakeLock.acquire();
         }
-        Log.v(TAG, "onResume(), mSDLThread exists yet: " + (mSDLThread != null));
+        Log.v(TAG, "onResume()");
         try {
             super.onResume();
-            if (mSDLThread == null && !mIsResumedCalled) {
-                // Ok so SDL2's onStart() usually launches the native code.
-                // However, this may fail if native libs aren't loaded yet at that point
-                // (due ot our loading screen) so we may need to manually trigger this,
-                // otherwise code would only launch by leaving & re-entering the app:
-                Log.v(TAG, "Loading screen workaround: triggering native resume");
-                if (mSDLThread == null && mCurrentNativeState == NativeState.RESUMED) {
-                    // Force a state change so SDL2 doesn't just ignore the resume:
-                    mCurrentNativeState = NativeState.PAUSED;
-                }
-                resumeNativeThread();  // native resume to call native code
-            }
         } catch (UnsatisfiedLinkError e) {
             // Catch resume while still in loading screen failing to
             // call native function (since it's not yet loaded)
-            Log.v(TAG, "failed to call native onResume() because libs " +
-                       "aren't loaded yet. this is expected to happen");
         }
         considerLoadingScreenRemoval();
-        Log.v(TAG, "onResume() done in PythonActivity, " +
-                   "mSDLThread exists yet: " + (mSDLThread != null));
     }
 
     @Override
@@ -619,7 +606,6 @@ public void onWindowFocusChanged(boolean hasFocus) {
         } catch (UnsatisfiedLinkError e) {
             // Catch window focus while still in loading screen failing to
             // call native function (since it's not yet loaded)
-            return;  // no point in barging further
         }
         considerLoadingScreenRemoval();
     }

pythonforandroid/bootstraps/sdl2/build/src/patches/SDLActivity.java.patch

@@ -1,13 +1,12 @@
 --- a/src/main/java/org/libsdl/app/SDLActivity.java
 +++ b/src/main/java/org/libsdl/app/SDLActivity.java
-@@ -196,6 +196,16 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
+@@ -196,6 +196,15 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
          Log.v(TAG, "onCreate()");
          super.onCreate(savedInstanceState);
 
++        SDLActivity.initialize();
 +        // So we can call stuff from static callbacks
 +        mSingleton = this;
-+
-+        SDLActivity.initialize();
 +    }
 +
 +    // We don't do this in onCreate because we unpack and load the app data on a thread
@@ -17,16 +16,6 @@
          // Load shared libraries
          String errorMsgBrokenLib = "";
          try {
-@@ -508,7 +508,8 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
-         }
-
-         // Try a transition to resumed state
--        if (mNextNativeState == NativeState.RESUMED) {
-+        // python-for-android: we delay finishLoad() -> mSurface can be null!
-+        if (mNextNativeState == NativeState.RESUMED && mSurface != null) {
-             if (mSurface.mIsSurfaceReady && mHasFocus && mIsResumedCalled) {
-                 if (mSDLThread == null) {
-                     // This is the entry point to the C app.
 @@ -639,7 +648,7 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
      Handler commandHandler = new SDLCommandHandler();
 
@@ -58,11 +47,28 @@
      // APK expansion files support
 
      /** com.android.vending.expansion.zipfile.ZipResourceFile object or null. */
-@@ -1475,5 +1475,7 @@ class SDLMain implements Runnable {
+@@ -1341,14 +1366,13 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
+     };
+
+     public void onSystemUiVisibilityChange(int visibility) {
+-        if (SDLActivity.mFullscreenModeActive && (visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0 || (visibility & View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) == 0) {
+-
++        // SDL2 BUGFIX (see sdl bug #4424 ) - REMOVE WHEN FIXED IN UPSTREAM !!
++        if (SDLActivity.mFullscreenModeActive && ((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0 || (visibility & View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) == 0)) {
+             Handler handler = getWindow().getDecorView().getHandler();
+             if (handler != null) {
+                 handler.removeCallbacks(rehideSystemUi); // Prevent a hide loop.
+                 handler.postDelayed(rehideSystemUi, 2000);
+             }
+-
+         }
+     }    
+
+@@ -1475,6 +1499,7 @@ class SDLMain implements Runnable {
+         String[] arguments = SDLActivity.mSingleton.getArguments();
+
          Log.v("SDL", "Running main function " + function + " from library " + library);
-
 +        SDLActivity.mSingleton.appConfirmedActive();
-+        Log.v("SDL", "(python-for-android: appConfirmedActive() was called)");
          SDLActivity.nativeRunMain(library, function, arguments);
 
          Log.v("SDL", "Finished main function");

pythonforandroid/recipes/sdl2/__init__.py

@@ -4,9 +4,9 @@
 
 
 class LibSDL2Recipe(BootstrapNDKRecipe):
-    version = "2.0.10"
-    url = "https://www.libsdl.org/release/SDL2-{version}.zip"
-    md5sum = "6b2e9a4a2faba4ff277062cf669724f4"
+    version = "2.0.9"
+    url = "https://www.libsdl.org/release/SDL2-{version}.tar.gz"
+    md5sum = 'f2ecfba915c54f7200f504d8b48a5dfe'
 
     dir_name = 'SDL'