Android共享首选项重启应用

Question

所以我一直在跟随教程，一切正常，直到我运行该应用程序并遇到此问题。 每次我重新启动应用程序时，我的活动都会回到LoginActivity而不是MainActivity。 这是我的代码

会议经理

SharedPreferences pref;
SharedPreferences.Editor editor;
Context _context;

int PRIVATE_MODE = 0;

private static final String PREF_NAME = "users";

private static final String IS_LOGIN = "IsLoggedIn";
//userID and userName
public static final String KEY_USERNAME = "name";
// public static final String KEY_USERID = "userid";

//Constructor
public SessionManager(Context context) {
    this._context = context;
    this.pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
    this.editor = pref.edit();
    this.editor.commit();
    this.editor.clear();
}

public void createLoginSession(String username) {
    editor.putBoolean(IS_LOGIN, true);
    editor.putString(KEY_USERNAME, username);
    editor.commit();
    // editor.putString(KEY_USERID, userID);
}

public void checkLogin() {
    if (!this.isLoggedIn()) {
        Intent i = new Intent(_context, SplashScreen.class);
        i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
        this._context.startActivity(i);
    }
}


public HashMap<String, String> getUserDetails() {
    HashMap<String, String> user = new HashMap<>();
    user.put(KEY_USERNAME, pref.getString(KEY_USERNAME, null));
    return user;
}

public void logoutUser() {
    editor.clear();
    editor.commit();
    Intent i = new Intent(_context, SplashScreen.class);
    i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    _context.startActivity(i);
}

public boolean isLoggedIn() {
    return pref.getBoolean(IS_LOGIN, false);
}

登录活动

TextView register_link;
Button btnLogin;
EditText eTxtUsername, eTxtPassword;
SessionManager session;

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

    this.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);
    //
    register_link = (TextView) findViewById(R.id.tv_register_link);
    btnLogin = (Button) findViewById(R.id.buttonSignIn);
    eTxtUsername = (EditText) findViewById(R.id.eTxt_username);
    eTxtPassword = (EditText) findViewById(R.id.eTxt_password);
    session = new SessionManager(getApplicationContext());
    //
    final AlertDialog.Builder builder = new AlertDialog.Builder(LoginActivity.this);

    Toast.makeText(this, "Login status: " + session.isLoggedIn(), Toast.LENGTH_LONG).show();


    register_link.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent i = new Intent(LoginActivity.this, RegisterActivity.class);
            LoginActivity.this.startActivity(i);
        }
    });

    btnLogin.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            final String username_ = eTxtUsername.getText().toString();
            final String password_ = eTxtPassword.getText().toString();

            if (isEmptyFields(username_, password_)) {
                builder.setMessage("Please provide all fields")
                        .setNegativeButton("Retry", null)
                        .create()
                        .show();
            } else {
                Response.Listener<String> responseListener = new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        try {
                            JSONObject jsonResponse = new JSONObject(response);
                            final boolean success = jsonResponse.getBoolean("success");

                            if (success) {
                                final String userid_ = String.valueOf(jsonResponse.getInt("userid"));

                                session.createLoginSession(username_);
                                Toast.makeText(getApplicationContext(), "Login Success",
                                        Toast.LENGTH_SHORT).show();
                                Intent i = new Intent(getApplicationContext(), MainActivity.class);
                                i.putExtra("userId", userid_);
                                startActivity(i);
                                finish();
                            } else {
                                builder.setMessage("Login Failed")
                                        .setNegativeButton("Retry", null)
                                        .create()
                                        .show();
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                };

                LoginRequest loginRequest = new LoginRequest(username_, password_, responseListener);
                RequestQueue queue = Volley.newRequestQueue(LoginActivity.this);
                queue.add(loginRequest);
            }
        }
    });
}

static boolean isEmptyFields(String n1, String pw1) {
    final boolean result;

    if (n1.isEmpty() || pw1.isEmpty())
        result = true;
    else
        result = false;

    return result;
}

主要活动

private Drawer result = null;
private String userid;
SessionManager session;

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    final Button btn_showlist = (Button) findViewById(R.id.btn_showlist);
    session = new SessionManager(this);

    Toast.makeText(this, "Login status: " + session.isLoggedIn(), Toast.LENGTH_LONG).show();

    session.checkLogin();
    HashMap<String, String> user = session.getUserDetails();
    // userid = user.get(SessionManager.KEY_USERID);
    String username = user.get(SessionManager.KEY_USERNAME);

    //create drawer
    new DrawerBuilder().withActivity(this).build();
    CreateDrawer(CreateAccountDrawer(), toolbar);

    btn_showlist.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent i = new Intent(MainActivity.this, ListActivity.class);
            startActivity(i);
        }
    });
}

@Override
protected void onResume() {
    super.onResume();
    result.deselect();
}

//CREATE DRAWER
@Override
protected void attachBaseContext(Context newBase) {
    super.attachBaseContext(IconicsContextWrapper.wrap(newBase));
}

private AccountHeader CreateAccountDrawer() {

    AccountHeader headerResult = new AccountHeaderBuilder()
            .withActivity(this)
            .withSelectionListEnabledForSingleProfile(false)
            .withHeaderBackground(R.drawable.header1)
            .addProfiles(
                    new ProfileDrawerItem().withName("New User").withIcon(getResources()
                            .getDrawable(R.drawable.profile))
            )
            .withOnAccountHeaderListener(new AccountHeader.OnAccountHeaderListener() {
                @Override
                public boolean onProfileChanged(View view, IProfile profile, boolean currentProfile) {
                    return false;
                }
            })
            .build();

    return headerResult;

}

private void CreateDrawer(AccountHeader header, Toolbar toolbar) {

    PrimaryDrawerItem p_item1 = new PrimaryDrawerItem().withSetSelected(true).withIdentifier(1)
            .withName(R.string.map).withIcon(FontAwesome.Icon.faw_map);
    PrimaryDrawerItem p_item2 = new PrimaryDrawerItem().withIdentifier(2)
            .withName(R.string.analyze_soil).withIcon(FontAwesome.Icon.faw_bullseye);
    PrimaryDrawerItem p_item3 = new PrimaryDrawerItem().withIdentifier(3)
            .withName(R.string.drawer_item_statistic).withIcon(FontAwesome.Icon.faw_line_chart);
    //
    SecondaryDrawerItem s_item1 = new SecondaryDrawerItem().withIdentifier(4)
            .withName(R.string.drawer_item_app_settings).withIcon(FontAwesome.Icon.faw_cog);
    SecondaryDrawerItem s_item2 = new SecondaryDrawerItem().withIdentifier(5)
            .withName(R.string.drawer_item_account_settings).withIcon(FontAwesome.Icon.faw_cog);
    SecondaryDrawerItem s_item3 = new SecondaryDrawerItem().withIdentifier(6)
            .withName(R.string.logout).withIcon(FontAwesome.Icon.faw_sign_out);

    //Create the drawer and remember the `Drawer` result object
    result = new DrawerBuilder()
            .withActivity(this)
            .withAccountHeader(header)
            .withToolbar(toolbar)
            .addDrawerItems(
                    p_item2,
                    p_item1,
                    p_item3,
                    new DividerDrawerItem(),
                    s_item1,
                    s_item2,
                    new DividerDrawerItem(),
                    s_item3
            )
            .withOnDrawerItemClickListener(new Drawer.OnDrawerItemClickListener() {
                @Override
                public boolean onItemClick(View view, int position, IDrawerItem drawerItem) {

                    int clickedID = (int) drawerItem.getIdentifier();
                    Intent i;
                    switch (clickedID) {
                        case 1:
                            drawerItem.withSetSelected(false);
                            i = new Intent(MainActivity.this, MapsActivity.class);
                            startActivity(i);
                            break;
                        case 2:
                            drawerItem.withSetSelected(false);
                            i = new Intent(MainActivity.this, AnalyzeSoilActivity.class);
                            startActivity(i);
                            break;
                        case 3:
                            drawerItem.withSetSelected(false);
                            i = new Intent(MainActivity.this, StatisticActivity.class);
                            startActivity(i);
                            break;
                        case 4:
                            drawerItem.withSetSelected(false);
                            i = new Intent(MainActivity.this, AppSettingActivity.class);
                            startActivity(i);
                            break;
                        case 5:
                            drawerItem.withSetSelected(false);
                            i = new Intent(MainActivity.this, AccountSettingActivity.class);
                            startActivity(i);
                            break;
                        case 6:
                            session.logoutUser();
                            break;
                    }
                    return false;
                }
            })
            .build();
}

Answer 1

嘿，您似乎正在为每个活动创建会话实例。 尝试创建共享首选项的单例类。 在这里，当您调用构造函数时

//Constructor
public SessionManager(Context context) {
    this._context = context;
    this.pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
    this.editor = pref.edit();
    this.editor.commit();
    this.editor.clear();
}

调用editor.clear（）可以在您达到主要活动时清除您的偏好

Answer 2

您必须像下面那样更改SessionManager构造函数：

public SessionManager(Context context) {
    this._context = context;
    this.pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
    this.editor = pref.edit();
    this.editor.commit();
} 

您在编辑器上调用了clear方法，因此每次运行MainActivity时，会话管理器都会先读取共享的pref值，然后再清除它们。 就像您正在清除值，然后您要从中获取数据！

Answer 3

公共类MyPreferences实现AppConstants，VCardStorage {

private static final String TAG = "MyPreferences";
private static final String APP_PREFS = "my_prefs";

private static MyPreferences mPreferences;
private SharedPreferences mPreferences;
private Editor mEditor;
private Context mContext;


private MyPreferences(Context context) {
    mContext = context;
    mPreferences = context.getSharedPreferences(APP_PREFS, Context.MODE_PRIVATE);
    mEditor = mPreferences.edit();
}

public static MyPreferences getInstance(Context context) {
    if (mPreferences == null) {
        mPreferences = new MyPreferences(context);
    }
    return mPreferences;
}

public void removeKey(String key) {
    mEditor.remove(key).apply();
}

public void clear() {
    mEditor.clear().commit();
    ciaoPreferences = null;
}

public AppState getAppState() {
    String state = mPreferences.getString(PREFS_APP_STATE, AppState.INSTALLED.name());
    return AppState.valueOf(state);
}

public void setAppState(AppState state) {
    mEditor.putString(PREFS_APP_STATE, state.name()).apply();
}

Answer 4

每次我重新启动应用程序时，我的活动都会回到LoginActivity而不是MainActivity

可能是因为LoginActivity（或SplashActivity）是清单中设置的主要活动。

在onCreate中没有代码可以在单击登录活动按钮之外启动MainActivity。 实现SharedPreferences不仅会为您做到这一点。

// top of onCreate 
super.onCreate(savedInstanceState);
session = new SessionManager(getApplicationContext());
boolean loggedIn = session.isLoggedIn()
Toast.makeText(this, "Login status: "  + loggedIn, Toast.LENGTH_LONG).show();
if (loggedIn) {
    // start MainActivity
    finish(); // don't need this activity 
} else {
    // load LoginActivity 
} 

---

同时从构造函数中删除

this.editor.clear();