java - 从 BaseAdapter 访问 Activity 的变量

Question

我想从 BaseAdapter 类中的 Activity 访问变量，我用该类设置了 Activity 的 ListView。但我总是收到此错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Integer.toString()' on a null object reference

这些是我的代码的相关部分:

public class GetAllEntrysListViewAdapter extends BaseAdapter {

Integer markerID;
PinboardActivity pinboard = new PinboardActivity();

public GetAllEntrysListViewAdapter(JSONArray jsonArray, Context context) {
    this.dataArray = jsonArray;
    this.context= context;
    //I want to get the markerID variable from pinboardActivity:
    markerID = pinboard.markerID;
    inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
//...
public Cursor getLikes(DbHelper dbh) {
    //The following line is the one the error occurs
    String args[] = {markerID.toString(), pos};
    //...
}

Answer 1

这是因为 markerID 为 null。
检查您的以下行

//I want to get the markerID variable from pinboardActivity:
    markerID = pinboard.markerID;

这里 pinboard.markerID 返回一个空对象。