Question

我需要将 ListAdapterA onClick方法中的列表项添加到 DoneListAdapter ，所以我需要在 ListAdapterA DoneListAdapter >调用方法添加添加列表项和notifyDataSetChanged（）但 DoneListAdapter 返回null并且我的应用程序崩溃，为什么它返回null？

public class ListAdapterA extends ArrayAdapter<Abc> {

private Context context;
private String testString = "a";
DoneListAdapter doneListAdapter;
List<Abc> abc;
List<DoneAbc> doneAbc;


public ListAdapter(Context context, List<Abc> cbA) {
    super(context, R.layout.list_item, cbA);
    this.context = context;
    this.abc = cbA;
    doneListAdapter = new DoneListAdapter(context,doneAbc);
    doneActionHandler = new DoneActionHandler(context);
    actionHandler = new ActionHandler(context);
}

private class ViewHolder {
    ImageButton abcDoneBtn;
}

@Override
public Abc getItem(int position) {
    return abc.get(position);
}

@Override
public long getItemId(int position) {
    return 0;
}

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

@Override
public int getItemViewType(int position) {

    return (testString == "a") ? 0:1;
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    ViewHolder holder = null;
    int type = getItemViewType(position);

    if (convertView == null) {

        if (type == 0){
            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.list_item_finished, null);
        }else {
            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.list_item, null);
        }

        holder = new ViewHolder();

        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    if (type == 0){

    holder.abcDoneBtn= (ImageButton)convertView.findViewById(R.id.finished_abc);
        holder.abcDoneBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                Abc abc = (Abc) getItem(position);


        DoneABC doneabc = new DoneAC();
                DoneABC.setId(abc.getId());
                doneabc.setName(abc.getName());

                doneActionHandler.save(doneabc);

                doneListAdapter.add(doneabc);
                remove(abc);
                actionHandler.delete(abc);
                notifyDataSetChanged();
                doneListAdapter.notifyDataSetChanged();

            }
        }); 
    }
    return convertView;
}

@Override
public void add(Abc abc) {
    dreams.add(abc);
    notifyDataSetChanged();
    super.add(abc);
}

@Override
public void remove(Abc abc) {
    dreams.remove(abc);
    notifyDataSetChanged();
    super.remove(abc);
}

}

DoneAdapter：

public class DoneListAdapter extends ArrayAdapter<DoneAbc> {

private Context context;
List<DoneAbc> adoneAbc;


public DoneListAdapter(Context context, List<DoneAbc> doneAbc) {
    super(context, R.layout.list_item, doneAbc);
    this.context = context;
    this.adoneAbc = doneAbc;
}

private class ViewHolder {

}

@Override
public int getCount() {
    return adoneAbc.size();
}

@Override
public DoneAbc getItem(int position) {
    return adoneAbc.get(position);
}

@Override
public long getItemId(int position) {
    return 0;
}


@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder = null;
    int type = getItemViewType(position);

    if (convertView == null) {

            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.list_item, null);


        holder = new ViewHolder();

        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    return convertView;
}

@Override
public void add(DoneAbc doneAbc) {
    adoneAbc.add(doneAbc);
    notifyDataSetChanged();
    super.add(doneAbc);
}

@Override
public void remove(DoneAbc doneAbc) {
    adoneAbc.remove(doneAbc);
    notifyDataSetChanged();
    super.remove(doneAbc);
}
}

致命的例外：主要过程：com.teamkosas.cloudv05，PID：30693 java.lang.NullPointerException：尝试调用接口方法＆＃39; boolean java.util.List.add（java.lang.Object）＆＃39;在null对象引用上在com.teamkosas.cloudv05.adapters.DoneListAdapter.add（DoneListAdapter.java:123）在com.teamkosas.cloudv05.adapters.ListAdapterA $ 1.onClick（ListAdapterA.java:152）在android.view.View.performClick（View.java:5697）在android.view.View $ PerformClick.run（View.java:22526）在android.os.Handler.handleCallback（Handler.java:739）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:158）在android.app.ActivityThread.main（ActivityThread.java:7224） at java.lang.reflect.Method.invoke（Native Method）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1230）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:1120）

Answer 1

您正在DoneListAdapter构造函数中传递空列表。

在您的班级ListAdapterA中替换此行：

doneListAdapter = new DoneListAdapter(context,doneAbc);

有了这个：

doneListAdapter = new DoneListAdapter(context,new ArrayList<DoneAbc>())

当在其他数组适配器中实例化数组适配器时，我得到了空

1 个答案: