Question

我创建了一个ListView，其中包含一个项目列表，每个项目都有自己的删除按钮。

我已经覆盖了ArrayAdapter中的getView方法，并将处理程序附加到了delete按钮。

问题是，getView方法被调用两次。第二次，v.findViewById（DeleteButton）调用返回null。我已经检查过视图，ImageButton在层次结构中，但Id为0。

有人可以解释为什么会这样吗？

ManualFragment.java

public class ManualFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            final Bundle savedInstanceState) {
        View view = inflater
                .inflate(R.layout.fragment_manual, container, false);
        Button addButton = (Button) view.findViewById(R.id.AddButton);
        ListView listView = (ListView) view.findViewById(R.id.ListView);
        final List<String> items = new ArrayList<String>();
        final ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                getActivity(), R.layout.list_item, R.id.TextItem, items) {
            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                View v = convertView;
                if (v == null) {
                    LayoutInflater vi = (LayoutInflater) ManualFragment.this.getLayoutInflater(savedInstanceState);
                    v = vi.inflate(R.layout.list_item, null);
                }

                TextView time = (TextView) v.findViewById(R.id.TextItem);
                time.setText(items.get(position));
                ImageButton delete = (ImageButton) v
                        .findViewById(R.id.DeleteButton);
                //THIS LINE THROWS A NULLREF ON SECOND CALL
                delete.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        ImageButton deleteButton = (ImageButton) v;
                        items.remove(deleteButton.getId());
                        notifyDataSetChanged();
                    }
                });
                delete.setId(position);

                return v;
            }
        };
        listView.setAdapter(adapter);
        final EditText addText = (EditText) view.findViewById(R.id.AddText);
        addButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                String value = addText.getText().toString();
                if (!"".equals(value)) {
                    items.add(value);
                    adapter.notifyDataSetChanged();
                    addText.setText("");
                }
            }
        });

        return view;
    }
}

list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:focusable="false" >

        <TextView
            android:id="@+id/TextItem"
            android:layout_width="267dp"
            android:layout_height="match_parent"
            android:layout_weight="0.89"
            android:focusable="false"
            android:gravity="center_vertical"
            android:text="Item"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <ImageButton
            android:id="@+id/DeleteButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@null"
            android:focusable="false"
            android:src="@drawable/delete" />

    </LinearLayout>

</LinearLayout>

Answer 1

您正在使用

进行设置

delete.setId(position)

我认为你想用位置标记buttojn

delete.setTag(position)

findViewById在第二次调用时返回null

1 个答案: