当在导航抽屉中打开另一个活动时,应用程序崩溃

问题描述:

我有一个导航抽屉,并且具有正在打开碎片的项目,但是当我尝试使用导航抽屉上的项目打开另一个活动时,它会崩溃并打开上述活动。这里是我的代码:当在导航抽屉中打开另一个活动时,应用程序崩溃

MainActivity.java

package application.cedie.myapplication; 

import android.app.Activity; 
import android.content.Intent; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentTransaction; 
import android.support.v7.app.NotificationCompat; 
import android.text.InputType; 
import android.view.View; 
import android.support.design.widget.NavigationView; 
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.view.Menu; 
import android.view.MenuItem; 
import android.view.inputmethod.EditorInfo; 
import android.widget.EditText; 

import layout.BlankFragment; 
import layout.DrugList; 
import layout.HerbalMedicineList; 
import layout.Home; 

public class MainActivity extends AppCompatActivity 
     implements NavigationView.OnNavigationItemSelectedListener, Home.OnFragmentInteractionListener, BlankFragment.OnFragmentInteractionListener, DrugList.OnFragmentInteractionListener 
, HerbalMedicineList.OnFragmentInteractionListener{ 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 


     Fragment fragment = null; 
     Class fragmentClass = null; 
     fragmentClass = BlankFragment.class; 
     try { 
      fragment = (Fragment) fragmentClass.newInstance(); 
     }catch (Exception e){ 
      e.printStackTrace(); 
     } 

     FragmentManager fragmentManager = getSupportFragmentManager(); 
     fragmentManager.beginTransaction().replace(R.id.Fragment_container, fragment).commit(); 

     NavigationView nw = (NavigationView) 
       findViewById(R.id.nav_view); 
       nw.setItemIconTintList(null); 


     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
     fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Snackbar.make(view, "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.setDrawerListener(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 

     return super.onOptionsItemSelected(item); 
    } 



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

     if (id == R.id.nav_home) { 
      fragmentClass = Home.class; 
      FragmentManager fragmentManager = getSupportFragmentManager(); 
      fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).commit(); 
     } else if (id == R.id.nav_reminder) { 
      fragmentClass = BlankFragment.class; 
      FragmentManager fragmentManager = getSupportFragmentManager(); 
      fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).commit(); 
     } else if (id == R.id.nav_druglist) { 
      fragmentClass = DrugList.class; 
      FragmentManager fragmentManager = getSupportFragmentManager(); 
      fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).commit(); 
     } else if (id == R.id.nav_herbdrug) { 
      fragmentClass = HerbalMedicineList.class; 
      FragmentManager fragmentManager = getSupportFragmentManager(); 
      fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).commit(); 
     } else if (id == R.id.nav_settings) { 

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

     } else if (id == R.id.nav_about) { 
      Intent newAct = new Intent(getApplicationContext(), About.class); 
      startActivity(newAct); 

    } 
     try { 
      fragment = (Fragment) fragmentClass.newInstance(); 
     }catch (Exception e){ 
      e.printStackTrace(); 
     } 



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

    @Override 
    public void onFragmentInteraction(Uri uri) { 

    } 
} 

About.java

package application.cedie.myapplication; 

import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 

public class About extends AppCompatActivity { 

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

logcat的

07-06 03:28:23.426 1760-1760/application.cedie.myapplication I/Process: Sending signal. PID: 1760 SIG: 9 
07-06 03:28:30.049 3855-3876/application.cedie.myapplication I/OpenGLRenderer: Initialized EGL, version 1.4 
07-06 03:28:30.049 3855-3876/application.cedie.myapplication W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without... 
07-06 03:28:30.059 3855-3876/application.cedie.myapplication D/OpenGLRenderer: Enabling debug mode 0 
07-06 03:28:33.043 3855-3855/application.cedie.myapplication V/Monotype: SetAppTypeFace- try to flip, app = application.cedie.myapplication 
07-06 03:28:33.044 3855-3855/application.cedie.myapplication V/Monotype:  Typeface getFontPathFlipFont - systemFont = /data/data/flipfont/app_fonts/Felbridge#Felbridge 
07-06 03:28:33.256 3855-3855/application.cedie.myapplication W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable 
07-06 03:28:34.020 3855-3871/application.cedie.myapplication W/art: Suspending all threads took: 6.224ms 
07-06 03:28:38.532 3855-3855/application.cedie.myapplication D/AndroidRuntime: Shutting down VM 
07-06 03:28:38.533 3855-3855/application.cedie.myapplication E/AndroidRuntime: FATAL EXCEPTION: main 
                       Process: application.cedie.myapplication, PID: 3855 
                       java.lang.NullPointerException: Attempt to write to field 'android.support.v4.app.FragmentManagerImpl android.support.v4.app.Fragment.mFragmentManager' on a null object reference 
                        at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:418) 
                        at android.support.v4.app.BackStackRecord.replace(BackStackRecord.java:453) 
                        at android.support.v4.app.BackStackRecord.replace(BackStackRecord.java:445) 
                        at application.cedie.myapplication.MainActivity.onNavigationItemSelected(MainActivity.java:128) 
                        at android.support.design.widget.NavigationView$1.onMenuItemSelected(NavigationView.java:151) 
                        at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:811) 
                        at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152) 
                        at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:958) 
                        at android.support.design.internal.NavigationMenuPresenter$1.onClick(NavigationMenuPresenter.java:318) 
                        at android.view.View.performClick(View.java:4756) 
                        at android.view.View$PerformClick.run(View.java:19761) 
                        at android.os.Handler.handleCallback(Handler.java:739) 
                        at android.os.Handler.dispatchMessage(Handler.java:95) 
                        at android.os.Looper.loop(Looper.java:135) 
                        at android.app.ActivityThread.main(ActivityThread.java:5253) 
                        at java.lang.reflect.Method.invoke(Native Method) 
                        at java.lang.reflect.Method.invoke(Method.java:372) 
                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:949) 
                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:744) 

片段类: Home.java

package layout; 

import android.content.Context; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.EditText; 

import application.cedie.myapplication.R; 

/** 
* A simple {@link Fragment} subclass. 
* Activities that contain this fragment must implement the 
* {@link Home.OnFragmentInteractionListener} interface 
* to handle interaction events. 
* Use the {@link Home#newInstance} factory method to 
* create an instance of this fragment. 
*/ 
public class Home extends Fragment { 
    // 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 Home() { 
     // 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 Home. 
    */ 
    // TODO: Rename and change types and number of parameters 
    public static Home newInstance(String param1, String param2) { 
     Home fragment = new Home(); 
     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); 
     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 
     return inflater.inflate(R.layout.fragment_home, container, false); 
    } 

    // 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 { 
      throw new RuntimeException(context.toString() 
        + " must implement OnFragmentInteractionListener"); 
     } 
    } 

    @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); 
    } 
} 
+0

尝试创建[mcve]。 – fracz

试试这个

Fragment fragment = null; 
    if (id == R.id.nav_home) { 
       fragment = Home.class; 
    FragmentManager fragmentManager = getSupportFragmentManager(); 
fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).comit(); 

} else if (id == R.id.nav_reminder) { 
    fragment = BlankFragment.class; 
    FragmentManager fragmentManager = getSupportFragmentManager(); 
fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).comit(); 
} else if (id == R.id.nav_druglist) { 
    fragment = DrugList.class; 
    FragmentManager fragmentManager = getSupportFragmentManager(); 
fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).comit(); 
} else if (id == R.id.nav_herbdrug) { 
    fragment = HerbalMedicineList.class; 
    FragmentManager fragmentManager = getSupportFragmentManager(); 
    fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).commit(); 
} else if (id == R.id.nav_settings) { 

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

} else if (id == R.id.nav_about) { 
    Intent newAct = new Intent(getApplicationContext(), About.class); 
    startActivity(newAct); 

}

+0

我如何设置该条件?谢谢您的回答 – RoyalCediee

+0

@RoyalCediee尝试编辑答案 – Nisarg

+0

当我打开片段 – RoyalCediee

这解决了我的问题:

if (id == R.id.nav_home) { 
      fragmentClass = Home.class; 
      try { 
       fragment = (Fragment) fragmentClass.newInstance(); 
      }catch (Exception e){ 
       e.printStackTrace(); 
      } 

      FragmentManager fragmentManager = getSupportFragmentManager(); 
      fragmentManager.beginTransaction().replace(R.id.Fragment_container,fragment).commit(); 
     } 

我把它时,我打开一个片段。