Android应用程序中的全局变量不持久

Posted 2023-04-17

【中文标题】Android应用程序中的全局变量不持久

【英文标题】：Global variable in Android application not persisting

【发布时间】：2016-09-27 06:04:18

【问题描述】：

我正在设计一个需要本地联系人列表的应用程序。我正在使用 cursorloader 来检索联系人并将其保存在我的应用程序类中全局的 hashmap 中

public class WoofyApp extends Application 
private static WoofyApp mInstance;
private FontFactory fontFactory;
private PreferenceService preferenceService;
private RequestQueue mRequestQueue;
private VolleyService mVolley;
private Validator mValidator;
private NetworkService mNetwork;
private DaoSession daoSession;
private HashMap<String,String> persons;
private ProgressDialog pdLoading;
private UserDao userDao;
private static final String WOOFYAPP = "WOOFYAPP";
@Override
public void onCreate() 
    super.onCreate();
    mInstance = this;
    persons = new HashMap<>();

 public  HashMap<String, String> getPersons()
        return persons;
    

public void setPersons(HashMap<String,String> per)
    persons = per;

我正在访问相关活动和片段中的联系人列表。我在 ContactService 类中设置它：

public class ContactService implements LoaderManager.LoaderCallbacks<Cursor> 


HashMap<String, String> hmContacts;
ArrayList<Person> alContacts;
private Context mContext;
private EventBus bus;
WoofyApp mApp;

private static final String[] PROJECTION = 
        ContactsContract.CommonDataKinds.Phone.NUMBER,
        ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME
;

public ContactService(AppCompatActivity context) 
    hmContacts = new HashMap<>();
    alContacts = new ArrayList<>();
    this.mContext = context;
    bus = EventBus.getDefault();
    mApp = WoofyApp.getApp();
    Log.d(Constants.LIFE_CYCLE,"ContactService called");
    if(mApp.getPersons().size()==0)
        context.getLoaderManager().initLoader(0,null,this);
        if(!context.getLoaderManager().getLoader(0).isReset()) 
            context.getLoaderManager().restartLoader(0, null, this);
        
        Log.d(Constants.LIFE_CYCLE,"ContactService loader called");
     else
        this.hmContacts = mApp.getPersons();
        this.alContacts = hashToArray(hmContacts);
        bus.post(hmContacts);
        bus.post(new ContactsAdapter(mContext, R.layout.row_contact_child, alContacts));
        Log.d(Constants.LIFE_CYCLE,"ContactService persons called");
    


@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) 
    Log.d(Constants.LIFE_CYCLE,"ContactService onCreateLoader called");
    return new CursorLoader(
            mContext,
            ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
            PROJECTION,
            null,
            null,
            null
    );




@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) 
    if (data.getCount() > 0) 
        while (data.moveToNext()) 
            String name = data.getString(
                    data.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
            String number = Validator.formatNumbers(data.getString(
                    data.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER)));
            if (!hmContacts.containsKey(number))
                alContacts.add(new Person(name, number));
            
            hmContacts.put(number, name);
        
        Log.d(Constants.LIFE_CYCLE,"onLoadFinished loader called "+hmContacts.size());
        mApp.setPersons(hmContacts);
        bus.post(hmContacts);
        bus.post(new ContactsAdapter(mContext, R.layout.row_contact_child, alContacts));
    


@Override
public void onLoaderReset(Loader<Cursor> loader) 



public static ArrayList<Person> hashToArray(HashMap<String,String>  hm)
    Iterator it = hm.entrySet().iterator();
    ArrayList<Person> persons = new ArrayList<>();
    while (it.hasNext()) 
        Map.Entry pair = (Map.Entry)it.next();
        persons.add(new Person((String)pair.getValue(),(String)pair.getKey()));
        it.remove();
    
    return persons;

奇怪的部分

当我第一次从主要活动及其片段访问它时，它正在正确加载。但是当我从不同的活动返回后尝试访问它时......即主要活动的 onResume 显示大小为 0。有什么想法会发生这种情况吗？

【参考方案1】：

添加您需要的设置模型：

public class SettingsModel 
    public String facebookToken;
    public String twitterToken;
    //... anything you need 

制作设置服务并在扩展应用程序类中将其初始化为

new SettingsService();

设置服务：

public class SettingsService 

    private static String KEY = "yourDesiredSettingsKey";
    private static Context mContext;

    public static SettingsModel settings;

    public SettingsService()
        mContext = YourApplication.getMainContext();
        //if(settings == null)
        settings = getSettings();
        //
    

    public static void saveSettings()
        if(settings == null)
            settings = new SettingsModel();
        
        SharedPreferences.Editor editor = mContext
                .getSharedPreferences(KEY, Activity.MODE_PRIVATE).edit();
        Gson gson = new Gson();
        String jsonSettings = gson.toJson(settings);
        editor.putString("settings", jsonSettings );
        editor.commit();
        settings = getSettings();
    


    public static SettingsModel getSettings() 
        SharedPreferences editor = mContext.getSharedPreferences(KEY,
                Activity.MODE_PRIVATE);
        try
            String jsonSettings = editor.getString("settings","settings");
            Gson gson = new Gson();
            settings = gson.fromJson(jsonSettings, SettingsModel.class);
        catch (Exception e)
            settings = new SettingsModel();
        

        return settings;
    

在毕业典礼中：

compile 'com.google.code.gson:gson:2.4'

就是这样，您可以从任何地方访问您的设置：

String token = SettingsService.settings.facebookToken;

或更新它们：

SettingsService.settings.facebookToken = "yourToken";
SettingsService.saveSettings();

【参考方案2】：

我明白了..我正在使用一种方法将 hasmap 转换为其中包含 iterator.remove() 的数组列表..它删除了联系人并将哈希图留空。很抱歉用这个愚蠢的问题打扰您。