如何在碎片导航底栏中调用登录活动

Question

i制作一个具有3个底部导航栏的应用程序

这是我的主要活动Java

public class MainActivity extends AppCompatActivity {
    private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            FragmentTransaction transaction = fragmentManager.beginTransaction();
            switch (item.getItemId()) {
                case R.id.navigation_home:
                    transaction.replace(R.id.content, new LoginFragment()).commit();
                    return true;
                case R.id.navigation_dashboard:
                    transaction.replace(R.id.content, new DashboardFragment()).commit();
                    return true;
                case R.id.navigation_notifications:
                    transaction.replace(R.id.content, new NotificationsFragment()).commit();
                    return true;
            }
            return false;
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
        navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        transaction.replace(R.id.content, new LoginFragment()).commit();
    }
}

和xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.network.poeja.diskusiku.MainActivity">
    <FrameLayout
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1">
    </FrameLayout>
    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:background="?android:attr/windowBackground"
        app:menu="@menu/navigation" />
</LinearLayout>

然后我创建一个登录范围来显示第一个导航

public class LoginFragment extends Fragment {
    Button btn_logout;
    TextView txt_id, txt_username;
    String id, username;
    SharedPreferences sharedpreferences;
    public static final String TAG_ID = "id";
    public static final String TAG_USERNAME = "username";
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";
    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;
    private OnFragmentInteractionListener mListener;
    public LoginFragment() {
        // Required empty public constructor
    }
    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment LoginFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static LoginFragment newInstance(String param1, String param2) {
        LoginFragment fragment = new LoginFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        txt_id = (TextView) getView().findViewById(R.id.txt_id);
        txt_username = (TextView) getView().findViewById(R.id.txt_username);
        btn_logout = (Button) getView().findViewById(R.id.btn_logout);
        sharedpreferences = getActivity().getSharedPreferences(Login.my_shared_preferences, Context.MODE_PRIVATE);
        id = getActivity().getIntent().getStringExtra(TAG_ID);
        username = getActivity().getIntent().getStringExtra(TAG_USERNAME);
        txt_id.setText("ID : " + id);
        txt_username.setText("USERNAME : " + username);
        btn_logout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                // update login session ke FALSE dan mengosongkan nilai id dan username
                SharedPreferences.Editor editor = sharedpreferences.edit();
                editor.putBoolean(Login.session_status, false);
                editor.putString(TAG_ID, null);
                editor.putString(TAG_USERNAME, null);
                editor.commit();
                Intent intent = new Intent(getActivity(), Login.class);
                startActivity(intent);
            }
        });
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_login, container, false);

        return view;
    }
    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
        }
    }
    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }
    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

这是loginfragment的XML

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.network.poeja.diskusiku.LoginFragment">
<!-- TODO: Update blank fragment layout -->
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:orientation="vertical">
    <ImageView
        android:id="@+id/logo"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_gravity="center"
        android:background="@mipmap/ic_launcher" />
    <TextView
        android:id="@+id/TextView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginBottom="5dp"
        android:layout_marginTop="5dp"
        android:text="www.dedykuncoro.com"
        android:textSize="18dip"
        android:textStyle="bold" />
    <View
        android:id="@+id/View1"
        android:layout_width="fill_parent"
        android:layout_height="1dp"
        android:layout_gravity="center"
        android:background="#448AFF" />
    <TextView
        android:id="@+id/txt_id"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="10dp"
        android:text="ID"/>
    <TextView
        android:id="@+id/txt_username"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="10dp"
        android:text="Username"/>
    <Button
        android:id="@+id/btn_logout"
        style="@style/Widget.AppCompat.Button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="50dp"
        android:background="#f5f5f5"
        android:text="Logout"
        android:textStyle="bold" />
    <Button
        android:id="@+id/btn_home"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/title_home" />
</LinearLayout>

我将登录Java进行检查

public class Login extends AppCompatActivity {
    ProgressDialog pDialog;
    Button btn_register, btn_login;
    EditText txt_username, txt_password;
    Intent intent;
    int success;
    ConnectivityManager conMgr;
    private String url = Server.URL + "login.php";
    private static final String TAG = Login.class.getSimpleName();
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_MESSAGE = "message";
    public final static String TAG_USERNAME = "username";
    public final static String TAG_ID = "id";
    String tag_json_obj = "json_obj_req";
    SharedPreferences sharedpreferences;
    Boolean session = false;
    String id, username;
    public static final String my_shared_preferences = "my_shared_preferences";
    public static final String session_status = "session_status";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        conMgr = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        {
            if (conMgr.getActiveNetworkInfo() != null
                    && conMgr.getActiveNetworkInfo().isAvailable()
                    && conMgr.getActiveNetworkInfo().isConnected()) {
            } else {
                Toast.makeText(getApplicationContext(), "No Internet Connection",
                        Toast.LENGTH_LONG).show();
            }
        }
        btn_login = (Button) findViewById(R.id.btn_login);
        btn_register = (Button) findViewById(R.id.btn_register);
        txt_username = (EditText) findViewById(R.id.txt_username);
        txt_password = (EditText) findViewById(R.id.txt_password);
        // Chek session login if TRUE then directly open LoginFragment
        sharedpreferences = getSharedPreferences(my_shared_preferences, Context.MODE_PRIVATE);
        session = sharedpreferences.getBoolean(session_status, false);
        id = sharedpreferences.getString(TAG_ID, null);
        username = sharedpreferences.getString(TAG_USERNAME, null);
        if (session) {
            Intent intent = new Intent(Login.this, LoginFragment.class);
            intent.putExtra(TAG_ID, id);
            intent.putExtra(TAG_USERNAME, username);
            finish();
            startActivity(intent);
        }

        btn_login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                String username = txt_username.getText().toString();
                String password = txt_password.getText().toString();
                // check if field is empty
                if (username.trim().length() > 0 && password.trim().length() > 0) {
                    if (conMgr.getActiveNetworkInfo() != null
                            && conMgr.getActiveNetworkInfo().isAvailable()
                            && conMgr.getActiveNetworkInfo().isConnected()) {
                        checkLogin(username, password);
                    } else {
                        Toast.makeText(getApplicationContext() ,"No Internet Connection", Toast.LENGTH_LONG).show();
                    }
                } else {
                    // Prompt user to enter credentials
                    Toast.makeText(getApplicationContext() ,"Kolom tidak boleh kosong", Toast.LENGTH_LONG).show();
                }
            }
        });
        btn_register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                intent = new Intent(Login.this, Register.class);
                finish();
                startActivity(intent);
            }
        });
    }
    private void checkLogin(final String username, final String password) {
        pDialog = new ProgressDialog(this);
        pDialog.setCancelable(false);
        pDialog.setMessage("Logging in ...");
        showDialog();
        StringRequest strReq = new StringRequest(Request.Method.POST, url, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                Log.e(TAG, "Login Response: " + response.toString());
                hideDialog();
                try {
                    JSONObject jObj = new JSONObject(response);
                    success = jObj.getInt(TAG_SUCCESS);
                    // Check for error node in json
                    if (success == 1) {
                        String username = jObj.getString(TAG_USERNAME);
                        String id = jObj.getString(TAG_ID);
                        Log.e("Successfully Login!", jObj.toString());
                        Toast.makeText(getApplicationContext(), jObj.getString(TAG_MESSAGE), Toast.LENGTH_LONG).show();
                        // Save login to session
                        SharedPreferences.Editor editor = sharedpreferences.edit();
                        editor.putBoolean(session_status, true);
                        editor.putString(TAG_ID, id);
                        editor.putString(TAG_USERNAME, username);
                        editor.commit();
                        // Call main activity
                        Intent intent = new Intent(Login.this, LoginFragment.class);
                        intent.putExtra(TAG_ID, id);
                        intent.putExtra(TAG_USERNAME, username);
                        finish();
                        startActivity(intent);
                    } else {
                        Toast.makeText(getApplicationContext(),
                                jObj.getString(TAG_MESSAGE), Toast.LENGTH_LONG).show();
                    }
                } catch (JSONException e) {
                    // JSON error
                    e.printStackTrace();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e(TAG, "Login Error: " + error.getMessage());
                Toast.makeText(getApplicationContext(),
                        error.getMessage(), Toast.LENGTH_LONG).show();
                hideDialog();
            }
        }) {
            @Override
            protected Map<String, String> getParams() {
                // Posting parameters to login url
                Map<String, String> params = new HashMap<String, String>();
                params.put("username", username);
                params.put("password", password);
                return params;
            }
        };
        // Adding request to request queue
        AppController.getInstance().addToRequestQueue(strReq, tag_json_obj);
    }
    private void showDialog() {
        if (!pDialog.isShowing())
            pDialog.show();
    }
    private void hideDialog() {
        if (pDialog.isShowing())
            pDialog.dismiss();
    }
}

和这里的登录XML

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.network.poeja.diskusiku.LoginFragment">
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:orientation="vertical">
    <ImageView
        android:id="@+id/logo"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_gravity="center"
        android:background="@mipmap/ic_launcher" />
    <TextView
        android:id="@+id/TextView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginBottom="5dp"
        android:layout_marginTop="5dp"
        android:text="www.dedykuncoro.com"
        android:textSize="18dip"
        android:textStyle="bold" />
    <View
        android:id="@+id/View1"
        android:layout_width="fill_parent"
        android:layout_height="1dp"
        android:layout_gravity="center"
        android:background="#448AFF" />
    <TextView
        android:id="@+id/TextView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="30dip"
        android:text="WELCOME, LOGIN BELOW"
        android:textSize="16dip" />
    <EditText
        android:id="@+id/txt_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="10dp"
        android:hint="Username"
        android:inputType="textEmailAddress"
        android:singleLine="true" />
    <EditText
        android:id="@+id/txt_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="10dp"
        android:hint="Password"
        android:password="true"
        android:singleLine="true" />
    <Button
        android:id="@+id/btn_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginBottom="15dp"
        android:text="Login"
        android:background="#448AFF"
        android:textColor="#fff"
        android:textStyle="bold" />
    <Button
        android:id="@+id/btn_register"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginBottom="15dp"
        android:background="#00555555"
        android:text="Register"
        android:textStyle="bold" />
</LinearLayout>

但是我仍然面临一些错误，当我开始运行应用程序时，它是 force Close ，我不知道该如何修复

我想要的是，当用户单击家庭导航时，它将检查他是否登录，

如果登录，他将显示他的ID和用户名如果否，请显示登录页面

任何人请帮助，如果您想要完整的代码代码，请与我联系，我将其发送给您

Answer 1

您的问题来自登录片段。您不应该从 increate 中进行 findViewById ，而是来自 increateview 。

碎片生命周期与活动的生命周期有些不同。只需将UI初始化移至 oncreateview 方法，您应该很好地进行：）