我的項目中有兩項活動。主活動中有一個按鈕，當我單擊它時，它會將我帶到第二個活動。當我按下后退按鈕時，它不會進入主要活動。它首先檢查互聯網，然后當我單擊按鈕時，它會將我帶到第二個活動。public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);        try {            this.getSupportActionBar().hide();        }catch (Exception e){        }        if (isNetworkConnected(this)) {            Button button = findViewById(R.id.button);            button.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View view) {                    Intent activity2Intent = new Intent(getApplicationContext(), playlive.class);                    startActivity(activity2Intent);                }            });        } else {            buildDialog(MainActivity.this).show();        }    }    public static boolean isNetworkConnected(Context context) {        boolean result = false;        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {            if (cm != null) {                NetworkCapabilities capabilities = cm.getNetworkCapabilities(cm.getActiveNetwork());                if (capabilities != null) {                    if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) {                        result = true;                    } else if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {                        result = true;                    }                }            }        }