onBindViewHolder找不到視圖

Question

我在recyclerview適配器中充氣我的佈局xml。但我每次都碰到一個NPE，似乎無法找到問題的根源。

這裏是我的logcat：

E/AndroidRuntime: FATAL EXCEPTION: main 
 
java.lang.NullPointerException 
 
at com.softtech.stevekamau.buyathome.adapter.RecomGridAdapter.onBindViewHolder(RecomGridAdapter.java:159) 
 
at com.softtech.stevekamau.buyathome.adapter.RecomGridAdapter.onBindViewHolder(RecomGridAdapter.java:120) 
 
    at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:5217) 
 
    at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:5250) 
 
    at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4487) 
 
    at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4363) 
 
    at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1961) 
 
    at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1370) 
 
    at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1333) 
 
    at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:562) 
 
    at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2900) 
 
    at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3071) 
 
    at android.view.View.layout(View.java:13754) 
 
    at android.view.ViewGroup.layout(ViewGroup.java:4362) 
 
     
 
    .......

而且我的適配器：

public class RecomGridAdapter extends RecyclerView.Adapter<RecomGridAdapter.ViewHolder> { 
 
    private List<NewModel> modelItems; 
 

 
    // Provide a reference to the views for each data item 
 
    // Complex data items may need more than one view per item, and 
 
    // you provide access to all the views for a data item in a view holder 
 
    public static class ViewHolder extends RecyclerView.ViewHolder { 
 
     // each data item is just a string in this case 
 
     public TextView mTextView; 
 

 
     public ViewHolder(View v) { 
 
      super(v); 
 
      mTextView = (TextView) v.findViewById(R.id.name); 
 
     } 
 
    } 
 

 
    // Provide a suitable constructor (depends on the kind of dataset) 
 
    public RecomGridAdapter(List<NewModel> modelItems) { 
 
     this.modelItems = modelItems; 
 
    } 
 

 
    // Create new views (invoked by the layout manager) 
 
    @Override 
 
    public RecomGridAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, 
 
                 int viewType) { 
 
     // create a new view 
 
     View v = LayoutInflater.from(parent.getContext()) 
 
       .inflate(R.layout.grid_cell, parent, false); 
 
     // set the view's size, margins, paddings and layout parameters 
 

 
     return new ViewHolder(v); 
 
    } 
 

 
    // Replace the contents of a view (invoked by the layout manager) 
 
    @Override 
 
    public void onBindViewHolder(ViewHolder holder, int position) { 
 
     // - get element from your dataset at this position 
 
     // - replace the contents of the view with that element 
 
     NewModel m = modelItems.get(position); 
 
     holder.mTextView.setText(m.getName()); 
 

 
    } 
 

 
    // Return the size of your dataset (invoked by the layout manager) 
 
    @Override 
 
    public int getItemCount() { 
 
     return modelItems.size(); 
 
    } 
 
}

而且我grid_cell.xml：

<?xml version="1.0" encoding="utf-8"?> 
 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
 
    xmlns:card_view="http://schemas.android.com/apk/res-auto" 
 
    xmlns:foobar="http://schemas.android.com/apk/res-auto" 
 
    android:layout_width="118dp" 
 
    android:layout_height="wrap_content" 
 
    android:layout_marginLeft="5dp"> 
 

 
    <android.support.v7.widget.CardView 
 
     android:layout_width="wrap_content" 
 
     android:layout_height="wrap_content" 
 
     android:background="@drawable/list_row_selector" 
 
     card_view:cardCornerRadius="3dp"> 
 

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

 
      <com.android.volley.toolbox.NetworkImageView 
 
       android:id="@+id/thumbnail" 
 
       android:layout_width="100dp" 
 
       android:layout_height="100dp" 
 
       android:layout_centerHorizontal="true" 
 
       android:layout_margin="5dp" 
 
       android:scaleType="centerCrop" 
 
       android:src="@drawable/loading4" /> 
 

 
      <RelativeLayout 
 
       android:layout_width="110dp" 
 
       android:layout_height="60dp"> 
 

 
       <ImageView 
 
        android:id="@+id/options" 
 
        android:layout_width="30dp" 
 
        android:layout_height="30dp" 
 
        android:layout_alignParentRight="true" 
 
        android:src="@drawable/options" /> 
 

 
       <com.ctrlplusz.anytextview.AnyTextView 
 
        android:id="@+id/title" 
 
        android:layout_width="70dp" 
 
        android:layout_height="35dp" 
 
        android:ellipsize="end" 
 
        android:ems="10" 
 
        android:gravity="start" 
 
        android:maxLines="2" 
 
        android:paddingLeft="5dp" 
 
        android:text="Samsungf usb cablexvndvnsddvjdbv" 
 
        android:textSize="14dp" 
 
        android:textStyle="bold" 
 
        foobar:typeface="Gudea-Regular.ttf" /> 
 

 
       <com.ctrlplusz.anytextview.AnyTextView 
 
        android:id="@+id/amount" 
 
        android:layout_width="110dp" 
 
        android:layout_height="wrap_content" 
 
        android:layout_below="@+id/title" 
 
        android:ellipsize="end" 
 
        android:ems="10" 
 
        android:paddingLeft="5dp" 
 
        android:singleLine="true" 
 
        android:text="10000000000" 
 
        android:textColor="#cf5862" 
 
        android:textSize="18dp" 
 
        foobar:typeface="Gudea-Bold.ttf" /> 
 
      </RelativeLayout> 
 
     </LinearLayout> 
 
    </android.support.v7.widget.CardView> 
 
</LinearLayout>

的logcat的建議，這條線：

holder.mTextView.setText(m.getName()); 

是我的異常發生。 而m.getName()肯定不是空或者甚至是問題，因爲我試過holder.mTextView.setText("Test");。

任何想法究竟發生了什麼？

Answer 1

grid_cell.xml中的文字的ID是標題和數量，請嘗試使用其中的一個而不是名稱。事情是這樣的

mTextView = (TextView) v.findViewById(R.id.title); 

Answer 2

的問題是TextView = (TextView) v.findViewById(R.id.name); return null;因爲在XML文件中沒有TextView與ID名稱。有兩種解決方案：添加一個textView與id="name"，或者您可以使用 AnyTextView TextView = (AnyTextView) v.findViewById(R.id.title);代替textview的初始化。

Answer 3

mTextView爲空，因爲在grid_cell.xml中，您沒有ID爲name的視圖。嘗試將作業更改爲：

mTextView = (TextView) v.findViewById(R.id.title); 

當然假設「標題」是您打算獲得的視圖。

道歉，米格爾在那之前就到了那裏！

Answer 4

在你的xml文件中，你沒有任何帶'name'id的TextView！如何在findViewById中使用R.id.name？你必須改變你的ViewHolder類：？什麼是空指針異常，以及如何解決呢]

mTextView = (TextView) v.findViewById(R.id.title); 

OR

mTextView = (TextView) v.findViewById(R.id.amount);