Android view.getTag（）返回null而不是holder对象请回答

然后单击出现错误的地方

@Override
public View getView(int position, View view, ViewGroup parent)
{
    ViewHolder holder;
    if (view == null ) {
        // We must create a new view if we're not given a recycle view or
        // if the recycle view has the wrong layout.
        view = mInflater.inflate(mExpandable ? R.layout.library_row_expandable : R.layout.library_row, null);
        holder = new ViewHolder();  
        view.setTag(holder);
        if (mExpandable) {
            holder.text = (TextView)view.findViewById(R.id.text);
            holder.arrow = (ImageView)view.findViewById(R.id.arrow);
            holder.arrow.setOnClickListener(this);
        } else {
            holder.text = (TextView)view.findViewById(R.id.title_row);
            holder.text.setLongClickable(true);
        }
        holder.text.setOnClickListener(this);
    } else {
        holder = (ViewHolder)view.getTag();
    }
    Cursor cursor = mCursor;
    cursor.moveToPosition(position);
    holder.id = cursor.getLong(0);
    if (mFields.length > 1) {
        String line1 = cursor.getString(1);
        String line2 = cursor.getString(2);
        SpannableStringBuilder sb = new SpannableStringBuilder(line1);
        sb.append('\n');
        sb.append(line2);
        sb.setSpan(new ForegroundColorSpan(Color.GRAY), line1.length() + 1, sb.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        holder.text.setText(sb);
        holder.title = line1;
    } else {
        String title = cursor.getString(1);
        holder.text.setText(title);
        holder.title = title;
    }

    return view;
}

然后是xml

@Override
public Intent createData(View view)
{
    ViewHolder holder = new ViewHolder();
    holder = (ViewHolder)view.getTag();//returns null   
    Intent intent = new Intent();
    intent.putExtra(LibraryAdapter.DATA_TYPE, mType);
    intent.putExtra(LibraryAdapter.DATA_ID, (long)holder.id);//nullpointerexception
    intent.putExtra(LibraryAdapter.DATA_TITLE,holder.text.getText());//exception
    intent.putExtra(LibraryAdapter.DATA_EXPANDABLE, mExpandable);
    return intent;
}

@Override
public void onClick(View view)
{
    int id = view.getId();
    if (mExpandable)
        view = (View)view.getParent();      
    Intent intent;      
        intent = createData(view);
        if (id == R.id.arrow) {
            mActivity.onItemExpanded(intent);
        } else {
            mActivity.onItemClicked(intent);
        }       

}

---

然而，OnlongPress项现在工作得很完美，我认为应该为linearlayout中的每个元素设置ClickListner。您认为如何。

当它崩溃时，mExpandable是true还是false？发布longPress方法以供引用False当它崩溃时它不会崩溃当它为true时它也不会崩溃当它为LongClickItem时错误为空指针异常。。。。。。。。。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
> 
<TextView android:id="@+id/title_row"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
 android:minHeight="44dip"
 android:padding="3dip"
  android:background="@drawable/selectable_item_bg"
  android:layout_weight="1"
  android:gravity="center_vertical"
  android:textStyle="bold"
  android:maxLines="2"
  android:textColor="#ffff"
  android:ellipsize="end"
/>

02-27 13:32:33.664: E/AndroidRuntime(8239): FATAL EXCEPTION: main
02-27 13:32:33.664: E/AndroidRuntime(8239): java.lang.NullPointerException
02-27 13:32:33.664: E/AndroidRuntime(8239):     at com.applicationpackge.MediaAdapter.createData(MediaAdapter.java:550)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at com.applicationpackge.MediaAdapter.onClick(MediaAdapter.java:563)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at android.view.View.performClick(View.java:4084)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at android.view.View$PerformClick.run(View.java:16987)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at android.os.Handler.handleCallback(Handler.java:615)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at android.os.Handler.dispatchMessage(Handler.java:92)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at android.os.Looper.loop(Looper.java:137)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at android.app.ActivityThread.main(ActivityThread.java:4794)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at java.lang.reflect.Method.invokeNative(Native Method)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at java.lang.reflect.Method.invoke(Method.java:511)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
02-27 13:32:33.664: E/AndroidRuntime(8239):     at dalvik.system.NativeStart.main(Native Method)