termux-app/float/src/main/java/com/termux/window/TermuxFloatPermissionActivity.java

package com.termux.window;

import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.provider.Settings;
import android.view.View;

@TargetApi(23)
public class TermuxFloatPermissionActivity extends Activity {

    public static int OVERLAY_PERMISSION_REQ_CODE = 1234;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_permission);
    }

    public void onOkButton(View view) {
        Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + getPackageName()));
        startActivityForResult(intent, OVERLAY_PERMISSION_REQ_CODE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == OVERLAY_PERMISSION_REQ_CODE) {
            startService(new Intent(this, TermuxFloatService.class));
            finish();
        }
    }

}