Question

在我的Android应用中，我正在构建我的第一个自定义适配器。我现在遇到一个nullpointer在我膨胀convertView的行。请参阅以下代码：

private List<String> possibilitiesList = new ArrayList<String>();

public void setPossibilitiesList(List<String> possibilitiesList) {
    for (String possibility : possibilitiesList) {
        addItem(possibility);
    }
}

public void addItem (final String item) {
    possibilitiesList.add(item);
    notifyDataSetChanged();
}

private LayoutInflater inflater;

@Override
public View getView(final int position, View convertView, ViewGroup viewGroup) {
    Log.e(this, "is called here!!");
    ViewHolder holder = new ViewHolder();
    convertView = inflater.inflate(R.layout.list_item_posibility, viewGroup, false);
    holder.possibilityTitle = (TextView) convertView.findViewById(R.id.text_possibility);
    holder.possibilityTitle.setText(possibilitiesList.get(position));
    return convertView;
}

在我的片段中，我按如下方式设置了possibilitiesList：

List<String> list = Arrays.asList(getResources().getStringArray(R.array.the_possibilities));
Log.e(this, new Integer(list.size()).toString()); // outputs 8
adapter.setPossibilitiesList(list);

我100％确定list_item_posibility.xml存在（Android Studio也突出显示存在），所以我很遗憾为什么这会给出一个nullpointer。

有人知道我在这里做错了吗？

Answer 1

private LayoutInflater inflater;刚刚声明未初始化

您需要将上下文传递给适配器类的构造函数，然后使用它来初始化inflater。

 new Yourcustomadapter(ActivityName.this); 
// pass the context here and other params

然后

 private LayoutInflater inflater; 
 public Yourcustomadapterr(Context context)
 {
      inflater = LayoutInflater.from(context);
 }

同时检查此

http://developer.android.com/reference/android/view/View.html#getContext()

Answer 2

您的inflater为null，您需要将其设置为inflater的引用

private final LayoutInflater inflater;

public CustomAdapter(LayoutInflater inflater) {
  this.inflater = inflater;
}

@Override
public View getView(final int position, View convertView, ViewGroup viewGroup) {
    Log.e("this", "is called here!!");
    ViewHolder holder = new ViewHolder();
    convertView = inflater.inflate(R.layout.list_item_posibility, viewGroup, false);
    holder.possibilityTitle = (TextView) convertView.findViewById(R.id.text_possibility);
    holder.possibilityTitle.setText(possibilitiesList.get(position));
    return convertView;
}

然后，在你新增适配器的地方，:(取决于你启动适配器的位置）

new CustomAdapter(LayoutInflater.from(this));

或

new CustomAdapter(LayoutInflater.from(context));

或

new CustomAdapter(getActivity().getLayoutInflater());

或

new CustomAdapter((LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE));

inflater.inflate在Adapter getview方法中给出nullpointer。为什么？

2 个答案: