必须初始化共享首选项错误

import android.content.Context;
import android.content.SharedPreferences;

public class PreferencesManager {
    private static final String PREF_NAME = "MyAppPreferences";
    private SharedPreferences sharedPreferences;
    private SharedPreferences.Editor editor;

    public PreferencesManager(Context context) {
        sharedPreferences = context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE);
        editor = sharedPreferences.edit();
    }

    public void saveData(String key, String value) {
        editor.putString(key, value);
        editor.apply();
    }

    public String getData(String key) {
        return sharedPreferences.getString(key, null);
    }
}

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);
}