NPE durante il gonfiaggio del layout (Tentativo di richiamare il metodo virtuale 'boolean java.lang.String.equals (java.lang.Object)' su un riferimento a oggetto nullo)

Question

Continuo a ricevere java.lang.NullPointerException quando provo a utilizzare ScrollView in un'attività .

La cosa strana è che ho utilizzato la stessa identica installazione Scrollview in altre attività. E all'improvviso ho degli errori. Ho provato a ripulire il progetto e a ricostruirlo.

E ho provato il buon vecchio riavviare il programma. Ho imparato molto su Null Pointer Exceptions oggi, ma non sono stato in grado di capire perché continuo a ricevere Problemi di rendering.

Questo è il java.lang.NullPointerException che viene gettato sulla XML:

java.lang.NullPointerException 
    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:738) 
    at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:149) 
    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704) 
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:835) 
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:70) 
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:811) 
    at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798) 
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:838) 
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:70) 
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:811) 
    at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798) 
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:838) 
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:70) 
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:811) 
    at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798) 
    at android.view.LayoutInflater.inflate(LayoutInflater.java:515) 
    at android.view.LayoutInflater.inflate(LayoutInflater.java:394) 
    at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:223) 
    at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:426) 
    at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:350) 
    at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:510) 
    at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:498) 
    at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:888) 
    at com.android.tools.idea.rendering.RenderTask.createRenderSession(RenderTask.java:498) 
    at com.android.tools.idea.rendering.RenderTask.access$600(RenderTask.java:72) 
    at com.android.tools.idea.rendering.RenderTask$3.call(RenderTask.java:610) 
    at com.android.tools.idea.rendering.RenderTask$3.call(RenderTask.java:607) 
    at com.android.tools.idea.rendering.RenderService.runRenderAction(RenderService.java:362) 
    at com.android.tools.idea.rendering.RenderTask.render(RenderTask.java:607) 
    at com.android.tools.idea.rendering.RenderTask.render(RenderTask.java:629) 
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.doRender(AndroidLayoutPreviewToolWindowManager.java:652) 
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.access$1700(AndroidLayoutPreviewToolWindowManager.java:80) 
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7$1.run(AndroidLayoutPreviewToolWindowManager.java:594) 
    at com.intellij.openapi.progress.impl.CoreProgressManager$2.run(CoreProgressManager.java:152) 
    at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:452) 
    at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:402) 
    at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:54) 
    at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:137) 
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7.run(AndroidLayoutPreviewToolWindowManager.java:589) 
    at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:320) 
    at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:310) 
    at com.intellij.util.ui.update.MergingUpdateQueue$2.run(MergingUpdateQueue.java:254) 
    at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:269) 
    at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:227) 
    at com.intellij.util.ui.update.MergingUpdateQueue.run(MergingUpdateQueue.java:217) 
    at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:238) 
    at com.intellij.util.Alarm$Request$1.run(Alarm.java:351) 
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) 
    at java.util.concurrent.FutureTask.run(FutureTask.java:266) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 
    at java.lang.Thread.run(Thread.java:745) 

Quindi, niente di tutto questo è il codice che ho scritto. Così mi sono tuffato nella traccia dello stack ed ho trovato questo:

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325) 
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
     at android.app.ActivityThread.access$800(ActivityThread.java:151) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:135) 
     at android.app.ActivityThread.main(ActivityThread.java:5254) 
     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:903) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference 
       at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:715) 
       at android.view.LayoutInflater.rInflate(LayoutInflater.java:806) 
       at android.view.LayoutInflater.rInflate(LayoutInflater.java:809) 
       at android.view.LayoutInflater.rInflate(LayoutInflater.java:809) 
       at android.view.LayoutInflater.inflate(LayoutInflater.java:504) 
       at android.view.LayoutInflater.inflate(LayoutInflater.java:414) 
       at android.view.LayoutInflater.inflate(LayoutInflater.java:365) 
       at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:378) 
       at android.app.Activity.setContentView(Activity.java:2145) 
       at com.mitchellpalermo.tutroubleshooting.ContactPage.onCreate(ContactPage.java:11) 
       at android.app.Activity.performCreate(Activity.java:5990) 
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) 
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278) 
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)  
       at android.app.ActivityThread.access$800(ActivityThread.java:151)  
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)  
       at android.os.Handler.dispatchMessage(Handler.java:102)  
       at android.os.Looper.loop(Looper.java:135)  
       at android.app.ActivityThread.main(ActivityThread.java:5254)  
       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:903)  
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 

che punta al linea 11 sul file Contact.java. Che assomiglia a questo (ho messo indicatori attorno alla riga 11):

package com.mitchellpalermo.tutroubleshooting; 

    import android.app.Activity; 
    import android.os.Bundle; 

    public class Contact extends Activity { 

     @Override 
     protected void onCreate(Bundle savedInstanceState) { 
       super.onCreate(savedInstanceState); 
       setContentView(R.layout.activity_contact); // line 11 
     } 
    } 

non vedo un problema con linea 11.

Ora, non riesco a capire cosa c'è di sbagliato nel mio codice. Tra Problemi di rendering e NullPointerExceptions, non riesco a capire cosa c'è di veramente sbagliato nel mio codice.

Questo è un esempio di XML in un'attività in cui la ScrollView non gettare eventuali errori:

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" 
    tools:context="com.mitchellpalermo.tutroubleshooting.ComputerOrProjector"> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_gravity="center" 
     android:orientation="vertical"> 

     <TextView 
      style="@style/HeaderStyle" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_gravity="center" 
      android:text="@string/solutions" 
      android:textStyle="bold" /> 

     <!-- A CardView that contains a TextView --> 
     <android.support.v7.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:layout_gravity="center" 
      android:layout_margin="15dp" 
      card_view:cardBackgroundColor="#FFFFFF" 
      card_view:cardCornerRadius="4dp" 
      card_view:cardElevation="5dp"> 

      <LinearLayout 
       android:layout_width="match_parent" 
       android:layout_height="wrap_content" 
       android:orientation="vertical"> 

       <TextView 
        style="@style/Solution" 
        android:text="@string/pc_v_fifth" /> 

       <View 
        android:layout_width="match_parent" 
        android:layout_height="2dp" 
        android:background="@android:color/darker_gray" /> 

       <TextView 
        style="@style/Solution" 
        android:text="@string/pc_v_first" /> 

       <View 
        android:layout_width="match_parent" 
        android:layout_height="2dp" 
        android:background="@android:color/darker_gray" /> 

       <TextView 
        style="@style/Solution" 
        android:text="@string/pc_v_second" /> 

       <View 
        android:layout_width="match_parent" 
        android:layout_height="2dp" 
        android:background="@android:color/darker_gray" /> 

       <TextView 
        style="@style/Solution" 
        android:text="@string/pc_v_third" /> 

       <View 
        android:layout_width="match_parent" 
        android:layout_height="2dp" 
        android:background="@android:color/darker_gray" /> 


       <TextView 
        style="@style/Solution" 
        android:text="@string/pc_v_fourth" /> 

       <View 
        android:layout_width="match_parent" 
        android:layout_height="2dp" 
        android:background="@android:color/darker_gray" /> 

      </LinearLayout> 
     </android.support.v7.widget.CardView> 

     <LinearLayout 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:orientation="horizontal"> 

      <Button 
       style="@style/NextButton" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_gravity="center" 
       android:onClick="sendEmail" 
       android:text="@string/fixed" 
       android:textStyle="bold" /> 

      <Button 
       style="@style/NextButton" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_gravity="center" 
       android:onClick="notFixedButton" 
       android:text="@string/not_fixed" 
       android:textStyle="bold" /> 

     </LinearLayout> 

    </LinearLayout> 

</ScrollView> 

Ed ecco la attività in cui ricevo errori:

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:fillViewport="false"> 


    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:orientation="vertical"> 

     <TextView 
      style="@style/HeaderStyle" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_gravity="center" 
      android:text="@string/still_not_fixed" /> 

     <!-- A CardView that contains a TextView --> 
     <android.support.v7.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:layout_gravity="center" 
      android:layout_margin="15dp" 
      card_view:cardBackgroundColor="#FFFFFF" 
      card_view:cardCornerRadius="4dp" 
      card_view:cardElevation="5dp"> 

      <TextView 
       android:layout_width="match_parent" 
       android:layout_height="wrap_content" 
       android:text="@string/hector" /> 

      <view 
       android:layout_width="match_parent" 
       android:layout_height="2dp" 
       android:backgroundTint="@android:color/darker_gray" /> 

      <TextView 
       android:layout_width="match_parent" 
       android:layout_height="wrap_content" 
       android:text="@string/robert" /> 

      <view 
       android:layout_width="match_parent" 
       android:layout_height="2dp" 
       android:backgroundTint="@android:color/darker_gray" /> 

      <TextView 
       android:layout_width="match_parent" 
       android:layout_height="wrap_content" 
       android:text="@string/mitch" /> 

     </android.support.v7.widget.CardView> 

    </LinearLayout> 

</ScrollView> 

Qualche suggerimento? E grazie mille in anticipo!

Answer 1

Change <view a <View, perché view non è circa vuoto vista.E 'per visualizzazione personalizzata definita attraverso class attr, come di seguito:

<view 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    class="com.your.package.YourCustomView" /> 

e hai ottenuto

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference 

a causa della LayoutInflater tenta di analizzare class attr:

LayoutInflater codice sorgente

//... 
View createViewFromTag(View parent, String name, Context context, AttributeSet attrs, 
     boolean ignoreThemeAttr) { 
    if (name.equals("view")) { // line 724 
     name = attrs.getAttributeValue(null, "class"); // line 725 
    } 

    // Apply a theme wrapper, if allowed and one is specified. 
    if (!ignoreThemeAttr) { 
     final TypedArray ta = context.obtainStyledAttributes(attrs, ATTRS_THEME); 
     final int themeResId = ta.getResourceId(0, 0); 
     if (themeResId != 0) { 
      context = new ContextThemeWrapper(context, themeResId); 
     } 
     ta.recycle(); 
    } 

    if (name.equals(TAG_1995)) { // line 738 
     // Let's party like it's 1995! 
     return new BlinkLayout(context, attrs); 
    } 
//... 

• on line 724 è verificare che il tag è view e ottiene true
• on line 725 si cerca di ottenere classe attraverso class attr e ottiene null
• on line 738 si cerca di verificare la presenza di blink tag e ottiene incidente

Inoltre, v'è una cosa curiosa, gli sviluppatori di Android aggiunto uovo di Pasqua, si può provare:

<view 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    class="blink"> 
    <TextView 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:gravity="center" 
     android:text="Some text" /> 
</view> 

Answer 2

Dopo 2 giorni ho risolto questo problema utilizzare Vista invece di vista

<View 
    android:layout_width="match_parent" 
    android:layout_height="1dp" 
    android:background="#faf4f4"></View>