App stürzt beim Start im Emulator ab

Question

Ich bin neu in der Android-Entwicklung und ich versuche, eine Art Buch zu erstellen, die Art von App für ein Projekt in meiner Klasse auflistet. Das Lieblingswort des Profs ist "was auch immer du nicht kennst google es". Das ist nicht schlecht, wenn man halb weiß, was zu tun ist, aber da wir Java zusammen mit Android-Entwicklung lernen, ist das nicht hilfreich, da Java ein wenig fremdartig wirken kann.

Sowieso meine app in einer Kontakt App stützt dies ist, wie mein MainActivity

//MainActivity.java 
package com.iekproject.siegfried.libraryapp; 

import android.net.Uri; 
import android.os.Bundle; 
import android.os.Environment; 
import android.support.v4.app.FragmentTransaction; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 

public class MainActivity extends AppCompatActivity 
    implements LibraryFragment.LibraryFragmentListener, DetailFragment.DetailFragmentListener, 
    AddEditFragment.AddEditFragmentListener { 

//key for storing a book's Uri in a Bundle passed to a fragment 
public static final String BOOK_URI = "book_uri"; 

private LibraryFragment libraryFragment; //displays library aka book list 

//displays LibraryFragment when MainActivity first loads 
@Override 
protected void onCreate(Bundle savedInstanceState) { 

    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(toolbar); 

    //if layout contains fragmentContainer, the phone layout is in use. Create and display 
    //a LibraryFragment 
    if (savedInstanceState == null && findViewById(R.id.fragmentContainer) != null) { 
     //create LibraryFragment 
     libraryFragment = new LibraryFragment(); 

     //add the fragment to the FrameLayout 
     FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); 
     transaction.add(R.id.fragmentContainer, libraryFragment); 
     transaction.commit(); //displays LibraryFragment 
    } 
    else { 
     libraryFragment = 
       (LibraryFragment) getSupportFragmentManager(). 
         findFragmentById(R.id.DetailFragment); 
    } 
} 

public boolean isExternalStorageReadable() { 
    String state = Environment.getExternalStorageState(); 
    if (Environment.MEDIA_MOUNTED.equals(state) || 
      Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
     return true; 
    } 
    return false; 
} 

//displays DetailFragment for selected book 
@Override 
public void onBookSelected(Uri bookUri) { 
     getSupportFragmentManager().popBackStack(); 
     displayBook(bookUri, R.id.rightPaneContainer); 
} 

//displays AddEditFragment to add a new book. Possibly what I'll also have to change to make it 
//scan/update the book list 
@Override 
public void onAddBook() { 
     displayAddEditFragment(R.id.rightPaneContainer, null); 
} 

//displays a book 
private void displayBook(Uri bookUri, int viewID) { 
    DetailFragment detailFragment = new DetailFragment(); 

    //specify book's Uri as an argument to the DetailFragment 
    Bundle arguments = new Bundle(); 
    arguments.putParcelable(BOOK_URI, bookUri); 
    detailFragment.setArguments(arguments); 

    //use a FragmentTransaction to display the DetailFragment 
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); 
    transaction.replace(viewID, detailFragment); 
    transaction.addToBackStack(null); 
    transaction.commit(); //causes DetailFragment to display 
} 

//displays fragment for adding new or editing existing book 
private void displayAddEditFragment(int viewID, Uri bookUri) { 
    AddEditFragment addEditFragment = new AddEditFragment(); 

    //if editing existing book, provide bookUri as an argument 
    if (bookUri != null) { 
     Bundle arguments = new Bundle(); 
     arguments.putParcelable(BOOK_URI, bookUri); 
     addEditFragment.setArguments(arguments); 
    } 

    //use a FragmentTransaction to display the AddEditFragment 
    FragmentTransaction transaction = 
      getSupportFragmentManager().beginTransaction(); 
    transaction.replace(viewID, addEditFragment); 
    transaction.addToBackStack(null); 
    transaction.commit(); //causes AddEditFragment to display 
} 

//return to book list when displayed book deleted 
@Override 
public void onBookDeleted() { 
    //removes top of back stack 
    getSupportFragmentManager().popBackStack(); 
    libraryFragment.updateLibrary(); //refresh book list 
} 

//displays the AddEditFragment to edit an existing book. Maybe it can be used as Move or sth 
/*@Override 
public void onEditBook(Uri bookUri) { 
    displayAddEditFragment(R.id.rightPaneContainer, bookUri); 
}*/ 

//update GUI after the new book or updated book saved 
@Override 
public void onAddEditCompleted(Uri bookUri) { 
    //removes top of back stack 
    getSupportFragmentManager().popBackStack(); 
    libraryFragment.updateLibrary(); //refresh book list 

    if (findViewById(R.id.fragmentContainer) == null){ //tablet 
     //removes top of back stack 
     getSupportFragmentManager().popBackStack(); 

     //on tablet, displays the book that was just added or edited 
     displayBook(bookUri, R.id.rightPaneContainer); 
    } 
    } 
} 

sieht und dies ist der logcat

04-12 16:14:38.807 5796-5796/? I/art: Not late-enabling -Xcheck:jni (already on) 
04-12 16:14:38.808 5796-5796/? W/art: Unexpected CPU variant for X86 using defaults: x86 
04-12 16:14:38.926 5796-5796/com.iekproject.siegfried.libraryapp W/System: ClassLoader referenced unknown path: /data/app/com.iekproject.siegfried.libraryapp-1/lib/x86 
04-12 16:14:38.945 5796-5796/com.iekproject.siegfried.libraryapp I/InstantRun: starting instant run server: is main process 
04-12 16:14:38.991 5796-5796/com.iekproject.siegfried.libraryapp 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$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable 
04-12 16:14:39.119 5796-5796/com.iekproject.siegfried.libraryapp D/AndroidRuntime: Shutting down VM 
04-12 16:14:39.119 5796-5796/com.iekproject.siegfried.libraryapp E/AndroidRuntime: FATAL EXCEPTION: main 
                        Process: com.iekproject.siegfried.libraryapp, PID: 5796 
                        java.lang.RuntimeException: Unable to start activity ComponentInfo{com.iekproject.siegfried.libraryapp/com.iekproject.siegfried.libraryapp.MainActivity}: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead. 
                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665) 
                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
                         at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
                         at android.os.Handler.dispatchMessage(Handler.java:102) 
                         at android.os.Looper.loop(Looper.java:154) 
                         at android.app.ActivityThread.main(ActivityThread.java:6119) 
                         at java.lang.reflect.Method.invoke(Native Method) 
                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
                        Caused by: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead. 
                         at android.support.v7.app.AppCompatDelegateImplV9.setSupportActionBar(AppCompatDelegateImplV9.java:207) 
                         at android.support.v7.app.AppCompatActivity.setSupportActionBar(AppCompatActivity.java:130) 
                         at com.iekproject.siegfried.libraryapp.MainActivity.onCreate(MainActivity.java:30) 
                         at android.app.Activity.performCreate(Activity.java:6679) 
                         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) 
                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618) 
                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)  
                         at android.app.ActivityThread.-wrap12(ActivityThread.java)  
                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)  
                         at android.os.Handler.dispatchMessage(Handler.java:102)  
                         at android.os.Looper.loop(Looper.java:154)  
                         at android.app.ActivityThread.main(ActivityThread.java:6119)  
                         at java.lang.reflect.Method.invoke(Native Method)  
                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)  
                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)  

jede Hilfe

Answer 1

geschätzt Sie müssen nur eingestellt die Inhaltsansicht nach dem Einstellen der Symbolleiste. Sie können wie folgt schreiben:

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
setSupportActionBar(toolbar); 
setContentView(R.layout.activity_main); 

Die App abstürzt, weil Sie zuerst die Ansicht einstellen und dann die Symbolleiste festlegen.