Android 列表视图刷新

Question

在我的应用程序中，当用户单击“添加”菜单按钮时，会出现一个列表视图，其中填充了从文本文件加载的项目。 所以现在用户可以向列表视图添加一项了。将其添加到数组后，新项目将写入文本文件，但不会进入列表视图，因为我想通过将文件读取到数组然后用它填充 ListView 来实现。问题是这不起作用。 arrayadapter 填充位于 onCreate(Bundle savingInstanceState) {} 方法中，但添加位于该方法外部，因为它是通过按菜单调用的。

public class Connection extends Activity {
ListView lv1;
ArrayList<String> assignArr0 = new ArrayList<String>();
ArrayList<String> assignArr00 = new ArrayList<String>();
ArrayAdapter<String> adapter1;
ArrayAdapter<String> adapter2;

public void onCreate(Bundle savedInstanceState) {
...
//filereading to assingArr0. Lines of the file are added to the listview.
lv1 = (ListView) findViewById(R.id.ListView01);
adapter1 = new ArrayAdapter<String>(Connection.this,R.layout.list_black_text,R.id.list_content, assignArr0);
lv1.setAdapter(adapter1);
adapter1.notifyDataSetChanged();

//now, if there were any lines in the text file, the ListView is populated with them.
}

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.Menu1:
//this is where user adds an item to an array and item gets written out to the text file
//and this is also the part where the listview should be cleared, the lines of the text file should be read into an array, and the listview should be populated with the items of that array.

//The filereading is ok. Lines are read into assignArr00. Now what?

 break;
    }
    return true;
}
}

这是我在将行读入 allocateArr00 后尝试执行的方法：

 if (fileisempty == false) //i set this boolean var at the beginning
          {
              adapter1.clear();
            //  adapter1 = new ArrayAdapter<String>(Connection.this,R.layout.list_black_text,R.id.list_content, assignArr00);
              //lv1.setAdapter(adapter1);
              //adapter1.notifyDataSetChanged();
          }
          else
          {
              adapter1 = new ArrayAdapter<String>(Connection.this,R.layout.list_black_text,R.id.list_content, assignArr00);
              lv1.setAdapter(adapter1);
              adapter1.notifyDataSetChanged();
              }
          }

最后一个代码的 else 部分导致强制关闭（不要忘记这是第一次运行，因此文本文件是空的，这就是为什么else 部分已激活。

我对整个事情不太确定。 也许声明放错了地方。

任何帮助表示赞赏。

编辑：我已经设法解决它。解决方案可以在下面找到。

Answer 1

找到解决方案：我必须重新声明 lv1 = (ListView) findViewById(R.id.ListView01); 我不知道这背后的原因，但我花了 4 个小时才找到它。

if (fileisempty == false)
              {
                  adapter1.clear();
                  adapter1.notifyDataSetChanged();
                  lv1 = (ListView) findViewById(R.id.ListView01);
                  ArrayAdapter<String> adapter11;
                  adapter11 = new ArrayAdapter<String>(Connection.this,R.layout.list_black_text,R.id.list_content, assignArr00);
                  lv1.setAdapter(adapter11);
                  adapter11.notifyDataSetChanged();

              }
              else
              {
                  lv1 = (ListView) findViewById(R.id.ListView01);
                  ArrayAdapter<String> adapter11;
                  adapter11 = new ArrayAdapter<String>(Connection.this,R.layout.list_black_text,R.id.list_content, assignArr00);
                  lv1.setAdapter(adapter11);
                  adapter11.notifyDataSetChanged();
              }