无法在外部存储中创建文件夹，Android

File directory = new File(Environment.getExternalStorageDirectory(), "MyFolder");
if (!directory.exists()) {
    directory.mkdirs();
}

if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
    File directory = new File(Environment.getExternalStorageDirectory(), "MyFolder");
    if (!directory.exists()) {
        directory.mkdirs();
    }
} else {
    // 处理外部存储不可用的情况
}

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import java.io.File;

public class MainActivity extends AppCompatActivity {
    private static final int REQUEST_CODE = 123;

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

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);
            } else {
                createDirectory();
            }
        } else {
            createDirectory();
        }
    }

    private void createDirectory() {
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File directory = new File(Environment.getExternalStorageDirectory(), "MyFolder");
            if (!directory.exists()) {
                directory.mkdirs();
            }
        } else {
            // 处理外部存储不可用的情况
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                createDirectory();
            } else {
                // 处理权限被拒绝的情况
            }
        }
    }
}