的Android NullPointerException異常Toolbar.setNavigationOnClickListener空對象引用

Question

這是錯誤

java.lang.NullPointerException: Attempt to invoke virtual method 'void 
android.support.v7.widget.Toolbar.setNavigationOnClickListener(android.view.View$ 
OnClickListener)' on a null object reference 

它發生在

toolBar.setNavigationOnClickListener(new View.OnClickListener() 
imageView.setOnClickListener(new View.OnClickListener() 
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() 

有同樣的問題， 「空對象引用」。

我的團隊單獨的文件片段在MainActivity所有動作偵聽器壞了，但我們要分開，這樣的片段，但我找不到爲什麼單獨的文件，將其分解將空對象引用

這裏XML fragment_main.xml

<?xml version="1.0" encoding="utf-8"?> 
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layoutDirection="rtl"><!--set tool bar right to left set drawer to right--> 



    <android.support.v7.widget.Toolbar 
     android:id="@+id/toolbar" 
     android:layout_width="0dp" 
     android:layout_height="56dp" 
     android:background="@color/colorPrimary" 
     app:layout_constraintLeft_toLeftOf="parent" 
     app:layout_constraintRight_toRightOf="parent" 
     tools:layout_editor_absoluteY="0dp" 
     app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" /> 

    <ImageView 
     android:id="@+id/pamba_icon_id" 
     android:layout_width="50dp" 
     android:layout_height="50dp" 
     android:layout_marginLeft="16dp" 
     android:layout_marginTop="0dp" 
     app:layout_constraintLeft_toLeftOf="@+id/toolbar" 
     app:layout_constraintTop_toTopOf="parent" 
     app:srcCompat="@drawable/pambaicon" 
     app:layout_constraintBottom_toBottomOf="@+id/toolbar" 
     android:layout_marginBottom="0dp" 
     app:layout_constraintVertical_bias="0.0" /> 

    <ImageView 
     android:id="@+id/filter_icon_id" 
     android:clickable="true" 
     android:layout_width="25dp" 
     android:layout_height="25dp" 
     android:layout_marginBottom="8dp" 
     android:layout_marginRight="48dp" 
     android:layout_marginTop="8dp" 
     app:layout_constraintBottom_toBottomOf="@+id/toolbar" 
     app:layout_constraintRight_toRightOf="@+id/toolbar" 
     app:layout_constraintTop_toTopOf="@+id/toolbar" 
     app:srcCompat="@drawable/filter" 
     app:layout_constraintVertical_bias="0.533" /> 

    <android.support.v4.view.ViewPager 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:id="@+id/viewPaper_id" 
     android:layout_below="@id/toolbar"> 

    </android.support.v4.view.ViewPager> 


    <android.support.design.widget.CoordinatorLayout 
     android:layout_width="match_parent" 
     android:layout_height="match_parent"> 

     <android.support.design.widget.BottomNavigationView 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:id="@+id/bottomNavigation_id" 
      android:layout_gravity="bottom" 
      android:background="?android:attr/windowBackground" 
      app:menu="@menu/bottom_navigation_menu" 
      app:theme="@style/BottomNavigationTheme" 
      app:itemBackground="@color/colorGray"/> 

    </android.support.design.widget.CoordinatorLayout> 


</android.support.constraint.ConstraintLayout> 

這裏activity_main.xml中

<?xml version="1.0" encoding="utf-8"?> 
<android.support.constraint.ConstraintLayout 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" 
    android:layoutDirection="rtl"><!--set tool bar right to left set drawer to right--> 

    <android.support.constraint.ConstraintLayout 
     android:id="@+id/contentContainer" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" /> 


</android.support.constraint.ConstraintLayout> 

這裏MainFragment

import... 

public class MainFragment extends Fragment { 

    public MainFragment() { 
     super(); 
    } 

    public static MainFragment newInstance() { 
     MainFragment fragment = new MainFragment(); 
     Bundle args = new Bundle(); 
     fragment.setArguments(args); 
     return fragment; 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.fragment_main, container, false); 
     initInstances(rootView); 
     return rootView; 
    } 

    private void initInstances(View rootView) { 
     // Init 'View' instance(s) with rootView.findViewById here 
    } 

    @Override 
    public void onStart() { 
     super.onStart(); 
    } 

    @Override 
    public void onStop() { 
     super.onStop(); 
    } 

    /* 
    * Save Instance State Here 
    */ 
    @Override 
    public void onSaveInstanceState(Bundle outState) { 
     super.onSaveInstanceState(outState); 
     // Save Instance State here 
    } 

    /* 
    * Restore Instance State Here 
    */ 
    @Override 
    public void onActivityCreated(Bundle savedInstanceState) { 
     super.onActivityCreated(savedInstanceState); 
     if (savedInstanceState != null) { 
      // Restore Instance State here 
     } 
    } 
} 

和MainActivity

import... 


public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener{ 

    Toolbar toolBar; 
    DrawerLayout drawerLayout; 
    NavigationView navigationView; 
    ImageView imageView; 
    BottomNavigationView bottomNavigationView; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.navigation_drawer); 
     setTitle(R.string.title); 

     drawerLayout = (DrawerLayout) findViewById(R.id.drawe_layout); 
     navigationView = (NavigationView) findViewById(R.id.navigation_view); 
     imageView = (ImageView) findViewById(R.id.filter_icon_id); 

     navigationView.setNavigationItemSelectedListener(this); 

     final ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawerLayout, toolBar, R.string.open_drawer, R.string.close_drawer); 
     drawerLayout.setDrawerListener(toggle); 
     toggle.syncState(); 


//  set own toolbar 
     toolBar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolBar); 
     toolBar.setNavigationOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 
       if (drawerLayout.isDrawerOpen(Gravity.RIGHT)) { 
        drawerLayout.closeDrawer(Gravity.RIGHT); 
       } else { 
        drawerLayout.openDrawer(Gravity.RIGHT); 
       } 
      } 
     }); 

     imageView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       Toast.makeText(getApplicationContext(), "filter click", Toast.LENGTH_SHORT).show(); 
      } 
     }); 

     bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottomNavigation_id); 

//  select item from bottom navigation 
     bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() { 
      @Override 
      public boolean onNavigationItemSelected(@NonNull MenuItem item) { 
       int id = item.getItemId(); 
       switch (id){ 
        case R.id.firstpage_id: 
         Toast.makeText(getApplicationContext(), "home", Toast.LENGTH_SHORT).show(); 
         break; 

        case R.id.offergape_id: 
         Toast.makeText(getApplicationContext(), "offer", Toast.LENGTH_SHORT).show(); 
         break; 

        case R.id.needpage_id: 

         Toast.makeText(getApplicationContext(), "need", Toast.LENGTH_SHORT).show(); 
         break; 

        case R.id.searchpage_id: 
         Toast.makeText(getApplicationContext(), "search", Toast.LENGTH_SHORT).show(); 
         break; 
       } 

       return true; 
      } 
     }); 

    } 

    //close drawer when click back 
    @Override 
    public void onBackPressed() { 

     if(drawerLayout.isDrawerOpen(GravityCompat.END)){ 

      drawerLayout.closeDrawer(GravityCompat.END); 
     }else { 
      super.onBackPressed(); 
     } 
    } 

// select item from drawer 
    @Override 
    public boolean onNavigationItemSelected(@NonNull MenuItem item) { 
     int id = item.getItemId(); 
     switch (id){ 
      case R.id.account_detail_id: 

       Toast.makeText(getApplicationContext(), "account", Toast.LENGTH_SHORT).show(); 
       break; 

      case R.id.trip_detail_id: 

       Toast.makeText(getApplicationContext(), "detail", Toast.LENGTH_SHORT).show(); 
       break; 

      case R.id.mail_id: 
       Toast.makeText(getApplicationContext(), "mail", Toast.LENGTH_SHORT).show(); 
       break; 

      case R.id.logout_id: 
       Toast.makeText(getApplicationContext(), "logout", Toast.LENGTH_SHORT).show(); 
       break; 


     } 

     drawerLayout.closeDrawer(GravityCompat.END); 

     return true; 
    } 


} 

編輯附加navigation_drawer.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:orientation="vertical" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:id="@+id/drawe_layout" 
    android:fitsSystemWindows="true" 
    tools:openDrawer="end"> 
    <!--set drawer open from right--> 

    <include layout="@layout/activity_main"/> 

    <android.support.design.widget.NavigationView 
     android:layout_width="wrap_content" 
     android:layout_height="match_parent" 
     android:id="@+id/navigation_view" 
     android:background="@color/colorGray" 
     android:fitsSystemWindows="true" 
     app:headerLayout="@layout/navigation_header" 
     app:menu="@menu/navigation_menu" 
     app:theme="@style/NavigationDrawerStyle" 
     android:layout_gravity="end"/> 
    <!--set drawer open from right--> 


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

Answer 1

你在的onCreate的setContentView是將其設置爲R.layout.navigation_drawer。你沒有提供這方面的例子，而是提供了R.layout.fragment_main的例子。我想你想讓那個人成爲你的佈局。因此，在中的onCreate您的活動設置你的內容，以便該佈局來代替：

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.fragment_main); 
    ... // The rest of your code here 
}