SDLPAL/android/app/src/main/java/io/github/sdlpal/MainActivity.java

package io.github.sdlpal;

import android.Manifest;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.*;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.widget.Toast;

import java.io.*;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "sdlpal-debug";

    public static native void setAppPath(String basepath, String datapath, String cachepath);

    public static boolean crashed = false;

    private final static int REQUEST_FILESYSTEM_ACCESS_CODE = 101;

    private boolean checkIfAlreadyhavePermission() {
        int result = ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
        if (result == PackageManager.PERMISSION_GRANTED) {
            return true;
        } else {
            return false;
        }
    }
    private void requestForSpecificPermission() {
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_FILESYSTEM_ACCESS_CODE);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            case REQUEST_FILESYSTEM_ACCESS_CODE:
                if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    StartGame();
                } else {
                    AlertDialog.Builder builder = new AlertDialog.Builder(this);
                    builder.setMessage(R.string.toast_requestpermission);
                    builder.setCancelable(false);
                    builder.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            requestForSpecificPermission();
                        }
                    });
                    builder.create().show();
                }
                break;
        }
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        int MyVersion = Build.VERSION.SDK_INT;
        if (MyVersion < Build.VERSION_CODES.M || checkIfAlreadyhavePermission())
            StartGame();
        else
            requestForSpecificPermission();
    }

    public void StartGame() {

        System.loadLibrary("SDL2");
        System.loadLibrary("main");

        String dataPath = getApplicationContext().getFilesDir().getPath();
        String cachePath = getApplicationContext().getCacheDir().getPath();
        String sdcardState = Environment.getExternalStorageState();
        if (sdcardState.equals(Environment.MEDIA_MOUNTED)){
            setAppPath(Environment.getExternalStorageDirectory().getPath() + "/sdlpal/", dataPath, cachePath);
        } else {
            setAppPath("/sdcard/sdlpal/", dataPath, cachePath);
        }

        File runningFile = new File(cachePath + "/running");
        crashed = runningFile.exists();

        Intent intent;
        if (SettingsActivity.loadConfigFile() || crashed) {
            runningFile.delete();

            intent = new Intent(this, SettingsActivity.class);
        } else {
            intent = new Intent(this, PalActivity.class);
        }
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(intent);
        finish();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }
}