我在我的转换对话框以 DialogFragments 的过程。我下面的说明这里但看起来他们是在活动使用它，我用它在片段。我创建了监听器回到我的片段，但是当我打电话 getActivity（）则抛出一个 NullPointerException异常：

 公共类DialogTextAdd扩展DialogFragment实现OnEditorActionListener {

    私人的EditText行文字;

    公共接口DialogTextAddListener {
        无效onDialogTextAdd（最后弦乐的inputText）;
    }

    公共DialogTextAdd（）{
        //需要DialogFragment空的构造
    }

    @覆盖
    公共查看onCreateView（最终LayoutInflater吹气，最后的ViewGroup容器中，最后包savedInstanceState）{
        最终的视图中查看= inflater.inflate（R.layout.dialog_edit，集装箱）;
        多行文字=（EditText上）view.findViewById（R.id.Text_add）;
        getDialog（）的setTitle（添加文本）。

        //自动显示软键盘
        mText.requestFocus（）;
        getDialog（）getWindow（）setSoftInputMode（LayoutParams.SOFT_INPUT_STATE_VISIBLE）。
        mText.setOnEditorActionListener（本）;

        返回查看;
    }

    @覆盖
    公共布尔onEditorAction（最终的TextView V，最终诠释actionId，最终KeyEvent的事件）{
        如果（EditorInfo.IME_ACTION_DONE == actionId）{

            新MyFragment（）onDialogTextAdd（mText.getText（）的toString（））; //觉得这是我的问题
            this.dismiss（）;
            返回true;
        }
        返回false;
    }
}

公共类MyFragment扩展SherlockListFragment实现DialogKeywordAddListener
{
    @覆盖
    公共无效onDialogTextAdd（最终文本字符串）{
        Toast.makeText（getActivity（），文字+保存，Toast.LENGTH_SHORT）.show（）;
    }


@覆盖
公共无效onAttach（活动行为）{
    super.onAttach（行为）;
}


}
 

使用这个code得到它的工作：

  MyFragment MF =新MyFragment（）;
    捆绑的args =新包（）;
    args.putString（文本，mText.getText（）的toString（））;
    mf.setArguments（参数）;

    。getActivity（）getSupportFragmentManager（）的BeginTransaction（）加（MF，my_fragment）提交（）。;
 

解决方案

如果你不使用 getSupportFragmentManager（）并添加（。新增（片段，标签））的片段到 FragmentTransaction 的通过执行新的实例 .beginTransaction（），然后调用提交（）？我想这就是你正在努力做的事情。

getActivity（）返回空，因为新片段实例未连接到活动（本机 FragmentActivity /活动或 SherlockFragmentActivity / SherlockActivity ，不管它是什么）。

做关于使用部分片段阅读。该片段的Instantiantion是不够的。查找有关实例化后的基本操作。

I am in the process of converting my dialogs to DialogFragments. I'm following the instructions here but it looks like they are using it in an Activity and I'm using it in a Fragment. I've created the Listener back to my fragment, but when I call getActivity() it is throwing a NullPointerException:

public class DialogTextAdd extends DialogFragment implements OnEditorActionListener {

    private EditText mText;

    public interface DialogTextAddListener {
        void onDialogTextAdd(final String inputText);
    }

    public DialogTextAdd() {
        // Empty constructor required for DialogFragment
    }

    @Override
    public View onCreateView(final LayoutInflater inflater, final ViewGroup container, final Bundle savedInstanceState) {
        final View view = inflater.inflate(R.layout.dialog_edit, container);
        mText = (EditText)view.findViewById(R.id.Text_add);
        getDialog().setTitle("Add Text");

        // Show soft keyboard automatically
        mText.requestFocus();
        getDialog().getWindow().setSoftInputMode(LayoutParams.SOFT_INPUT_STATE_VISIBLE);
        mText.setOnEditorActionListener(this);

        return view;
    }

    @Override
    public boolean onEditorAction(final TextView v, final int actionId, final KeyEvent event) {
        if (EditorInfo.IME_ACTION_DONE == actionId) {

            new MyFragment().onDialogTextAdd(mText.getText().toString()); //think this is my problem
            this.dismiss();
            return true;
        }
        return false;
    }
}

public class MyFragment extends SherlockListFragment implements DialogKeywordAddListener
{
    @Override
    public void onDialogTextAdd(final String text) {
        Toast.makeText(getActivity(), text + " saved", Toast.LENGTH_SHORT).show();
    }


@Override
public void onAttach(Activity act) {
    super.onAttach(act);
}


}

Using this code got it to work:

    MyFragment mf = new MyFragment();
    Bundle args = new Bundle();
    args.putString("text", mText.getText().toString());
    mf.setArguments(args);

    getActivity().getSupportFragmentManager().beginTransaction().add(mf, "my_fragment").commit();

Shouldn't you use getSupportFragmentManager() and add (.add(fragment, tag)) the new instance of your fragment to the FragmentTransaction by doing .beginTransaction() and then call commit()? I guess thats what you are trying to do.

getActivity() returns null since your new Fragment instance is not attached to the Activity (native FragmentActivity/Activity or SherlockFragmentActivity/SherlockActivity, whatever it is).

Do some readings about using fragments. Instantiantion of the fragment is not enough. Find about underlying operations after instantiation.