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我在试图弄清楚这个阵列适配器的东西时遇到了很多麻烦。

我已经在一些教程和这个页面的帮助下把它放在了一起点击项目列表视图中的按钮时如何在 android 的列表视图中添加/删除项目

但是我遇到了一个问题，即当 getView 运行时“适配器”设置为“null”。我不知道这是怎么回事。我已经解决了将适配器备份到backupAdapter的可怕hacky解决方案，然后在我需要调用adapter.notifyDataSetChanged（）时将其复制回来；

我发现第一次使用 deleteButton 时，resetAdapter 发现适配器为空，并从 backupAdapter 复制值。之后就好了，不需要再恢复了。所以我的代码有效，但它很可怕。我究竟做错了什么？

public class EditTaskList extends Activity {
    private static ArrayList<Something> list;
    private CustomAdapter adapter;
    private CustomAdapter backupAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.list_task_edit);
        ListView listView = (ListView)findViewById(R.id.edit_task_listview);
        list = MainActivity.getMasterList();

        CustomAdapter adapter = new CustomAdapter(this, list);
        listView.setAdapter(adapter);
        adapter.notifyDataSetChanged();
        backupAdapter = adapter;
    }

    public void resetAdapter(){
        if(adapter == null){
            System.out.println("Not fixed");
            adapter = backupAdapter;
        }
        else{System.out.println("Fixed!");}
        adapter.notifyDataSetChanged();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.edit_task_list, menu);
        return true;
    }

    public class CustomAdapter extends ArrayAdapter<Something>{
        //private Context context;
        private ArrayList<Something> things;
        private LayoutInflater inflater;

        class ViewHolder {
            public TextView text;
            public Button editButton;
            public Button deleteButton;
        }

        public CustomAdapter(Context context, ArrayList<Something> things) {
            super(context, R.layout.edit_task_list_item, things);
            inflater = LayoutInflater.from(context);
            this.things = things;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            // reuse views
            ViewHolder viewHolder;
            if (convertView == null) {
                viewHolder = new ViewHolder();
                convertView = inflater.inflate(R.layout.edit_task_list_item, null);
                // configure view holder
                viewHolder.text = (TextView) ConvertView.findViewById(R.id.edit_task_name);
                viewHolder.editButton = (Button) convertView.findViewById(R.id.edit_task_edit);
                viewHolder.deleteButton = (Button) convertView.findViewById(R.id.edit_task_delete);
                convertView.setTag(viewHolder);
            }

            else {
                viewHolder = (ViewHolder) convertView.getTag();
        }

        viewHolder.text.setTag(position);
        viewHolder.text.setText(things.get(position).toString());
        viewHolder.deleteButton.setTag(position);
        viewHolder.editButton.setTag(position);
        viewHolder.deleteButton.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View view) {
                int tag = (Integer)view.getTag();
                things.remove(tag);
                resetAdapter();
                }
        });

        return convertView;
    }
    }
}
4

1 回答 1

2

这一行：

CustomAdapter adapter = new CustomAdapter(this, list);

创建一个局部变量，因此字段适配器永远不会被初始化。相反，您希望将新创建的适配器分配给该字段：

adapter = new CustomAdapter(this, list);
于 2014-05-01T11:03:10.720 回答