Baseadapter与ViewHolder，在Scroll上崩溃

Question

我使用listview与baseadapter和滚动的listview它崩溃。

我getView的BaseAdapter类

@Override 
public View getView(final int arg0, View arg1, ViewGroup arg2) { 
    // TODO Auto-generated method stub 

    LayoutInflater inflater = activity.getLayoutInflater(); 
    ViewHolder holder=null; 

    if(arg1 == null){ 

     //Login category 
     if(categoryList.get(arg0).getType()==1){ 
      arg1 = inflater.inflate(R.layout.switch_profile_header, null); 
      holder=new ViewHolder(); 
      holder.layout=(RelativeLayout)arg1.findViewById(R.id.switch_profile_header_view); 
      holder.categoryName =(TextView)arg1.findViewById(R.id.categoryName); 
      holder.isLogin=categoryList.get(arg0).getIsLogin(); 
      arg1.setTag(holder); 
     } 
     //Other category 
     else if(categoryList.get(arg0).getType()==0){ 
      arg1 = inflater.inflate(R.layout.switch_profile_listrow, null); 
      holder=new ViewHolder(); 
      holder.layout=(RelativeLayout)arg1.findViewById(R.id.switch_profile_listrow_view); 
      holder.categoryName =(TextView)arg1.findViewById(R.id.categoryName); 
      holder.isLogin=categoryList.get(arg0).getIsLogin(); 
      holder.isDelete=(ImageView)arg1.findViewById(R.id.categoryDelete); 
      holder.login=(ImageView)arg1.findViewById(R.id.categoryLogin); 
      arg1.setTag(holder); 
     } 


    }else { 
     holder = (ViewHolder) arg1.getTag(); 
    } 
    //Login category 
    if(categoryList.get(arg0).getType()==1){ 
     holder.categoryName.setText(Html.fromHtml(categoryList.get(arg0).getCategoryName())); 
     holder.layout.setBackgroundColor(Color.parseColor("#efefef")); 
    } 
    //Login category 
    else if(categoryList.get(arg0).getType()==0){ 
     if(flag==false){ 
      holder.isDelete.setVisibility(View.INVISIBLE); 
     }else{ 
      holder.isDelete.setVisibility(View.VISIBLE); 
     } 

     if(categoryList.get(arg0).getIsLogin().equalsIgnoreCase("1")){ 
      holder.isDelete.setVisibility(View.INVISIBLE); 
      holder.login.setVisibility(View.INVISIBLE); 
     }else if(flag) { 
      holder.isDelete.setVisibility(View.VISIBLE); 
      holder.login.setVisibility(View.VISIBLE); 
     } 

     holder.categoryName.setText(Html.fromHtml(categoryList.get(arg0).getCategoryName())); 
     if(categoryList.get(arg0).getIsLogin().equalsIgnoreCase("1")){ 
      holder.layout.setBackgroundColor(Color.parseColor("#efefef")); 
     }else{ 
      holder.layout.setBackgroundColor(Color.parseColor("#f0f0f0")); 
     } 


    return arg1; 
} 

我的logcat

Process: com.Tiger.Tiger, PID: 14059 
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setVisibility(int)' on a null object reference 
     at com.TenderTiger.Adapter.SwitchProfileAdapter.getView(SwitchProfileAdapter.java:117) 
     at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:220) 
     at android.widget.AbsListView.obtainView(AbsListView.java:2344) 
     at android.widget.ListView.makeAndAddView(ListView.java:1864) 
     at android.widget.ListView.fillDown(ListView.java:698) 
     at android.widget.ListView.correctTooLow(ListView.java:1474) 

Answer 1

正如我曾在getView方法膨胀两个不同的布局的方法。
正如Blackbelt所建议的，我必须在BaseAdapter类中实现getViewTypeCount方法。
我做了上述，它工作正常，但是当我滚动它会强制关闭。

我们必须实现

getViewTypeCount，也getItemViewType得到它的工作

1）getViewTypeCount方法返回布局的总数
2）getItemViewType方法返回与膨胀哪一行适当的条件。

所以最后我的代码看起来像这样

private static final int TYPE_HEADER = 0; 
private static final int TYPE_ROW = 1; 

@Override 
public int getViewTypeCount() { 
    return 2; 
} 

@Override 
public int getItemViewType(int position) { 
    return (categoryList.get(position).getType()==1)?TYPE_HEADER :TYPE_ROW; 
} 

最后我getView方法

@Override 
public View getView(final int position, View convertView, ViewGroup arg2) { 
    // TODO Auto-generated method stub 

    LayoutInflater inflater = activity.getLayoutInflater(); 
    ViewHolder holder=null; 
    if(convertView == null) { 
     if (getItemViewType(position) == TYPE_HEADER) { // Header 
      convertView = inflater.inflate(R.layout.switch_profile_header, null); 
      holder = new ViewHolder(); 
      holder.layout = (RelativeLayout) convertView.findViewById(R.id.switch_profile_header_view); 
      holder.categoryName = (TextView) convertView.findViewById(R.id.categoryName); 
      holder.isLogin = categoryList.get(position).getIsLogin(); 
      convertView.setTag(holder); 

     } else { 
      //row 
      convertView = inflater.inflate(R.layout.switch_profile_listrow, null); 
      holder = new ViewHolder(); 
      holder.layout = (RelativeLayout) convertView.findViewById(R.id.switch_profile_listrow_view); 
      holder.categoryName = (TextView) convertView.findViewById(R.id.categoryName); 
      holder.isLogin = categoryList.get(position).getIsLogin(); 
      holder.isDelete = (ImageView) convertView.findViewById(R.id.categoryDelete); 
      holder.login = (ImageView) convertView.findViewById(R.id.categoryLogin); 
      convertView.setTag(holder); 
     } 
    }else { 
     holder = (ViewHolder) convertView.getTag(); 
    } 

    //Header 
    if(getItemViewType(position) == TYPE_HEADER){ 

    } 
    //row 
    else if(getItemViewType(position) == TYPE_ROW){ 

    } 

    return convertView; 
}