エラーナビゲーションドロワーの実装時に発生する

Question

ユーザがログインボタンをクリックすると自動的にナビゲーションドロワに移動するのではなく、エラーが発生しました。このエラーから私を助けてください。

MainActivity.java

import android.content.Intent; 
import android.os.Bundle; 
import android.support.design.widget.NavigationView; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.view.GravityCompat; 
import android.support.v4.widget.DrawerLayout; 
import android.support.v7.app.ActionBarDrawerToggle; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 
import android.util.Log; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.inputmethod.InputMethodManager; 
import android.widget.AdapterView; 
import android.widget.Toast; 


public class MainActivity extends AppCompatActivity 
     implements NavigationView.OnNavigationItemSelectedListener, AdapterView.OnItemSelectedListener, AdapterView.OnItemClickListener { 


    private Toolbar toolbar; 
    private DrawerLayout drawer; 
    public String emailRegistration; 





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

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


     //toolbar.setTitle("toolbar"); 
     setSupportActionBar(toolbar); 



     //Set adapter to AutoCompleteTextView 

     // FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 

//  if (!emailRegistration.matches("[a-zA-Z0-9._-]+@[a-z]+.[a-z]+")) { 
// 
//   email.setError("Invalid Email Address"); 
// 
//  } 

//  fab.setOnClickListener(new View.OnClickListener() { 
//   @Override 
//   public void onClick(View v) { 
//    Snackbar.make(v, "Replace with your own action", Snackbar.LENGTH_LONG) 
//      .setAction("Action", null).show(); 
//   } 
//  }); 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
       this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); 
     drawer.addDrawerListener(toggle); 
     toggle.syncState(); 

     NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); 
     navigationView.setNavigationItemSelectedListener(this); 
    } 

    @Override 
    public void onBackPressed() { 
     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     if (drawer.isDrawerOpen(GravityCompat.START)) { 
      drawer.closeDrawer(GravityCompat.START); 
     } else { 
      super.onBackPressed(); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 

    @SuppressWarnings("StatementWithEmptyBody") 
    @Override 
    public boolean onNavigationItemSelected(MenuItem item) { 
     // Handle navigation view item clicks here. 
     int id = item.getItemId(); 

     if (id == R.id.nav_camera) { 
     setTitle("Home"); 
      Intent i = new Intent(MainActivity.this, HomeFragment.class); 
      startActivity(i); 
     } else if (id == R.id.nav_gallery) { 
      setTitle("Edit Profile"); 
      EditFragment editFragment = new EditFragment(); 
      FragmentManager fragmentManager = getSupportFragmentManager(); 
      fragmentManager.beginTransaction().replace(R.id.fragment,editFragment).commit(); 

     } else if (id == R.id.nav_slideshow) { 
      setTitle("Business"); 
      BusinessFragment businessFragment = new BusinessFragment(); 
      FragmentManager fragmentManager = getSupportFragmentManager(); 
      fragmentManager.beginTransaction().replace(R.id.fragment,businessFragment).commit(); 

     } else if (id == R.id.nav_manage) { 
      setTitle("Message"); 
      MessageFragment messageFragment = new MessageFragment(); 
      FragmentManager fragmentManager = getSupportFragmentManager(); 
      fragmentManager.beginTransaction().replace(R.id.fragment,messageFragment).commit(); 

     } else if (id == R.id.nav_share) { 

     } else if (id == R.id.nav_send) { 

     } 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     drawer.closeDrawer(GravityCompat.START); 
     return true; 
    } 

    @Override 
    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) { 
     // TODO Auto-generated method stub 
     //Log.d("AutocompleteContacts", "onItemSelected() position " + position); 

    } 

    @Override 
    public void onNothingSelected(AdapterView<?> adapterView) { 
     InputMethodManager imm = (InputMethodManager) getSystemService(
       INPUT_METHOD_SERVICE); 
     imm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0); 

    } 

    @Override 
    public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) { 
     // TODO Auto-generated method stub 

     // Show Alert 
     Toast.makeText(getBaseContext(), "Position:"+i+" Country:"+adapterView.getItemAtPosition(i), 
       Toast.LENGTH_LONG).show(); 

     Log.d("AutocompleteContacts", "Position:"+i+" Country:"+adapterView.getItemAtPosition(i)); 

    } 
} 

LoginActivity.java

import android.content.Intent; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.TextView; 



public class LoginActivity extends AppCompatActivity { 
    public EditText email, password; 
    public TextView textView; 
    public Button login; 


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

     email = (EditText) findViewById(R.id.email); 
//  if(email.getText().toString().length() == 0) 
//   email.setError("Email is required!"); 
     password = (EditText) findViewById(R.id.text_input_password_toggle); 
//  if(password.getText().toString().length() == 0) 
//   password.setError("Password is required!"); 
     textView = (TextView) findViewById(R.id.text2); 
     login = (Button) findViewById(R.id.login); 

     login.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Intent intent = new Intent(LoginActivity.this, MainActivity.class); 
       startActivity(intent); 
      } 
     }); 

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



    } 

activity_main.xml

<?xml version="1.0" encoding="utf-8"?> 
<android.support.v4.widget.DrawerLayout 
    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/drawer_layout" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:fitsSystemWindows="true" 
    tools:openDrawer="start"> 

    <include 
     layout="@layout/app_bar_main" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" /> 

    <android.support.design.widget.NavigationView 
     android:id="@+id/nav_view" 
     android:layout_width="wrap_content" 
     android:layout_height="match_parent" 
     android:layout_gravity="start" 
     android:fitsSystemWindows="true" 
     app:headerLayout="@layout/nav_header_main" 
     app:menu="@menu/activity_main_drawer" /> 

</android.support.v4.widget.DrawerLayout> 

エラー

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.DrawerLayout.addDrawerListener(android.support.v4.widget.DrawerLayout$DrawerListener)' on a null object reference 

SignupActivity。あなたのMainActivity.javaでJava

import android.content.Intent; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.view.View; 
import android.widget.ArrayAdapter; 
import android.widget.AutoCompleteTextView; 
import android.widget.Button; 
import android.widget.EditText; 

import java.util.ArrayList; 
import java.util.List; 


public class signupactivity extends AppCompatActivity { 
    public EditText firstname, lastname, email; 
    private AutoCompleteTextView actv; 
    public Button signup; 
    String[] languages={"Indore","Ujjain","Bhopal","Delhi","Bangalore","Chennai"}; 
    List<CharSequence> list = new ArrayList<CharSequence>(); 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.content_main); 
     for (int i=0;i<20;i++){ 
      list.add("test " + i); // Add the item in the list 
     } 
     firstname = (EditText)findViewById(R.id.firstname); 
     lastname = (EditText)findViewById(R.id.lastname); 
     actv = (AutoCompleteTextView) findViewById(R.id.autoCompleteTextView1); 
     email = (EditText) findViewById(R.id.email); 
     signup = (Button)findViewById(R.id.signup); 
     ArrayAdapter adapter = new 
       ArrayAdapter(this,android.R.layout.simple_list_item_1,languages); 
     actv.setAdapter(adapter); 
     actv.setThreshold(1); 

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

} 

画像I want the blank fragment when i click on the home, edit profile but its show everywhere signup activity because my content_main framelayout id is fragment and its call in mainactivity and its my signup page too (fragmentManager.beginTransaction().replace(R.id.fragment,editFragment).commit();) So how to solve this problem

Answer 1

あなたは

setContentView(R.layout.fragment_business); 

を使用しているしかし、あなたの引き出しがactivity_main.xml

は、だからあなたの引き出しがnullであり、あなたがすることはできませんnullオブジェクトにリスナーを追加します。

変更するには、setContentView（R.layout.fragment_business）を使用しているあなたのMainActivity.javaで

setContentView(R.layout.activity_main);