我正在尝试将Activity
转换为Fragment
,但我仍想了解如何正确地将其转换为public class RoomMarkdownActivity extends Fragment implements NotesAdapter.OnNoteItemClick {
public static RoomMarkdownActivity newInstance() { return new RoomMarkdownActivity(); }
public RecyclerView recyclerView;
public TextView textViewMsg;
public NoteDatabase noteDatabase;
public List<Note> notes;
public NotesAdapter notesAdapter;
public int pos;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.room_markdown_activity, container, false);
textViewMsg = view.findViewById(R.id.textview_empty);
FloatingActionButton fab = view.findViewById(R.id.fab);
fab.setOnClickListener(listener);
recyclerView = view.findViewById(R.id.recycler_view);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
notes = new ArrayList<>();
notesAdapter = new NotesAdapter(notes, getActivity());
recyclerView.setAdapter(notesAdapter);
noteDatabase = NoteDatabase.getInstance(getActivity());
new RetrieveTask(this).execute();
return view;
}
private static class RetrieveTask extends AsyncTask<Void, Void, List<Note>> {
private WeakReference<RoomMarkdownActivity> activityReference;
RetrieveTask(RoomMarkdownActivity context) {
activityReference = new WeakReference<>(context);
}
@Override
protected List<Note> doInBackground(Void... voids) {
if (activityReference.get() != null)
return activityReference.get().noteDatabase.getNoteDao().getNotes();
else
return null;
}
@Override
protected void onPostExecute(List<Note> notes) {
if (notes != null && notes.size() > 0) {
activityReference.get().notes.clear();
activityReference.get().notes.addAll(notes);
activityReference.get().textViewMsg.setVisibility(View.GONE);
activityReference.get().notesAdapter.notifyDataSetChanged();
}
}
}
private View.OnClickListener listener = new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivityForResult(new Intent(getActivity(), RoomMarkdownAddNoteActivity.class), 100);
}
};
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 100 && resultCode > 0) {
if (resultCode == 1) {
notes.add((Note) data.getSerializableExtra("note"));
} else if (resultCode == 2) {
notes.set(pos, (Note) data.getSerializableExtra("note"));
}
listVisibility();
}
}
@Override
public void onNoteClick(final int pos) {
new AlertDialog.Builder(recyclerView.getContext())
.setTitle("Select:")
.setItems(new String[]{"Read", "Update", "Delete"}, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
switch (i) {
case 0:
RoomMarkdownActivity.this.pos = pos;
startActivityForResult(
new Intent(getActivity(),
RoomMarkdownViewNoteActivity.class).putExtra(
"note", notes.get(pos)), 100);
break;
case 1:
RoomMarkdownActivity.this.pos = pos;
startActivityForResult(
new Intent(getActivity(),
RoomMarkdownAddNoteActivity.class).putExtra(
"note", notes.get(pos)), 100);
break;
case 2:
noteDatabase.getNoteDao().deleteNote(notes.get(pos));
notes.remove(pos);
listVisibility();
break;
}
}
}).show();
}
private void listVisibility() {
int emptyMsgVisibility = View.GONE;
if (notes.size() == 0) {
if (textViewMsg.getVisibility() == View.GONE)
emptyMsgVisibility = View.VISIBLE;
}
textViewMsg.setVisibility(emptyMsgVisibility);
notesAdapter.notifyDataSetChanged();
}
@Override
public void onDestroy() {
noteDatabase.cleanUp();
super.onDestroy();
}
}
。
基本上,我正在尝试适应this MainActivity,使其适合底部导航栏,除了在上下文中迷路以外,我还处理以下特定问题:
E / Android运行时:致命异常:主要 流程:com.example.com,PID:5213 java.lang.ClassCastException:com.example.com.MainActivity无法转换为com.example.com.adapter.NotesAdapter $ OnNoteItemClick 在com.example.com.adapter.NotesAdapter。(NotesAdapter.java:27) 在com.example.com.RoomMarkdownActivity.onCreateView(RoomMarkdownActivity.java:54) 在android.support.v4.app.Fragment.performCreateView(Fragment.java:2439) 在android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1460) 在android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784) 在android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852) 在android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:802) 在android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625) 在android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411) 在android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366) 在android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273) 在android.support.v4.app.FragmentManagerImpl $ 1.run(FragmentManager.java:733) 在android.os.Handler.handleCallback(Handler.java:873) 在android.os.Handler.dispatchMessage(Handler.java:99) 在android.os.Looper.loop(Looper.java:193) 在android.app.ActivityThread.main(ActivityThread.java:6669) 在java.lang.reflect.Method.invoke(本机方法) 在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run(RuntimeInit.java:493) 在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
I / Process:正在发送信号。 PID:5213 SIG:9应用程序终止。
这是我正在处理的代码的副本:
public class NotesAdapter extends RecyclerView.Adapter<NotesAdapter.BeanHolder> {
private List<Note> list;
public Context context;
private LayoutInflater layoutInflater;
private OnNoteItemClick onNoteItemClick;
public NotesAdapter(List<Note> list, Context context) {
layoutInflater = LayoutInflater.from(context);
this.list = list;
this.context = context;
this.onNoteItemClick = (OnNoteItemClick) context;
}
@Override
public BeanHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = layoutInflater.inflate(R.layout.room_markdown_note_list_item, parent, false);
return new BeanHolder(view);
}
@Override
public void onBindViewHolder(BeanHolder holder, int position) {
Log.e("bind", "onBindViewHolder: " + list.get(position));
holder.textViewTitle.setText(list.get(position).getTitle());
}
@Override
public int getItemCount() {
return list.size();
}
public class BeanHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
TextView textViewTitle;
private BeanHolder(View itemView) {
super(itemView);
itemView.setOnClickListener(this);
textViewTitle = itemView.findViewById(R.id.textview_title);
}
@Override
public void onClick(View view) {
onNoteItemClick.onNoteClick(getAdapterPosition());
}
}
public interface OnNoteItemClick {
void onNoteClick(int pos);
}
}
这是适配器:
notesAdapter = new NotesAdapter(notes, getActivity());
在this.onNoteItemClick = (OnNoteItemClick) context;
和getActivity()
之间似乎有一些分歧,但是我找不到this
的替代品,但是我想我已经用另一种方法解决了这个问题,如果我没有记错的话,它仍然会引发另一个类似的错误(此文件已充满getActivity()
,我不确定某些Fragment
的位置是否正确)。
按原样编译代码,但是,一旦单击了将调用特定MyHttpsClient
到屏幕上的按钮,就会引发错误,并且应用程序立即停止运行。
在此先感谢您的关注和帮助,如果您需要更多有关此问题的信息,请告诉我,以便在此处提供更多信息。
答案 0 :(得分:1)
您不能将Activity转换为OnNoteItemClick,因为您在片段中实现了它,因此可以将OnNoteItemClick分配给适配器,以便将代码更改为: 适配器:
public NotesAdapter(List<Note> list, OnNoteItemClick onNoteItemClick) {
layoutInflater = LayoutInflater.from(context);
this.list = list;
this.context = context;
this.onNoteItemClick = onNoteItemClick;
}
以这种方式初始化您的适配器:
notesAdapter = new NotesAdapter(notes, this); //Your class implements OnNoteItemClick interface so you can use 'this'
答案 1 :(得分:0)
替换
notesAdapter = new NotesAdapter(notes, getActivity());
使用
notesAdapter = new NotesAdapter(notes, RoomMarkdownActivity.this);
答案 2 :(得分:0)
感谢Mike M.和Reza.Abedini在回答和评论中所说的话,我能够理解正在发生的事情并克服了这个问题。
问题出在Adapter
,它准备从Context
那里获得Activity
,所以我不得不将参数转换为Fragment
,结果最终像这样工作:
public NotesAdapter(List<Note> list, RoomMarkdownActivity fragment) {
this.layoutInflater = LayoutInflater.from(fragment.getActivity());
this.list = list;
this.fragment = fragment;
this.onNoteItemClick = fragment;
}
和Fragment
一样:
public class RoomMarkdownActivity extends Fragment implements NotesAdapter.OnNoteItemClick {
public static RoomMarkdownActivity newInstance() {
return new RoomMarkdownActivity();
}
RecyclerView recyclerView;
TextView textViewMsg;
NoteDatabase noteDatabase;
List<Note> notes;
NotesAdapter notesAdapter;
int pos;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.room_markdown_activity, container, false);
textViewMsg = view.findViewById(R.id.textview_empty);
FloatingActionButton fab = view.findViewById(R.id.fab);
fab.setOnClickListener(listener);
recyclerView = view.findViewById(R.id.recycler_view);
initializeViews();
displayList();
return view;
}
private void displayList() {
noteDatabase = NoteDatabase.getInstance(getActivity());
new RetrieveTask(this).execute();
}
private static class RetrieveTask extends AsyncTask<Void, Void, List<Note>> {
private WeakReference<RoomMarkdownActivity> activityReference;
RetrieveTask(RoomMarkdownActivity context) {
activityReference = new WeakReference<>(context);
}
@Override
protected List<Note> doInBackground(Void... voids) {
if (activityReference.get() != null)
return activityReference.get().noteDatabase.getNoteDao().getNotes();
else
return null;
}
@Override
protected void onPostExecute(List<Note> notes) {
if (notes != null && notes.size() > 0) {
activityReference.get().notes.clear();
activityReference.get().notes.addAll(notes);
activityReference.get().textViewMsg.setVisibility(View.GONE);
activityReference.get().notesAdapter.notifyDataSetChanged();
}
}
}
public void initializeViews() {
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
notes = new ArrayList<>();
notesAdapter = new NotesAdapter(notes, this);
recyclerView.setAdapter(notesAdapter);
}
private View.OnClickListener listener = new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivityForResult(new Intent(getActivity(), RoomMarkdownAddNoteActivity.class), 100);
}
};
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 100 && resultCode > 0) {
if (resultCode == 1) {
notes.add((Note) data.getSerializableExtra("note"));
} else if (resultCode == 2) {
notes.set(pos, (Note) data.getSerializableExtra("note"));
}
listVisibility();
}
}
@Override
public void onNoteClick(final int pos) {
new AlertDialog.Builder(getActivity())
.setTitle("Select:")
.setItems(new String[]{"Read", "Update", "Delete"}, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
switch (i) {
case 0:
RoomMarkdownActivity.this.pos = pos;
startActivityForResult(
new Intent(getActivity(),
RoomMarkdownViewNoteActivity.class).putExtra(
"note", notes.get(pos)), 100);
break;
case 1:
RoomMarkdownActivity.this.pos = pos;
startActivityForResult(
new Intent(getActivity(),
RoomMarkdownAddNoteActivity.class).putExtra(
"note", notes.get(pos)), 100);
break;
case 2:
noteDatabase.getNoteDao().deleteNote(notes.get(pos));
notes.remove(pos);
listVisibility();
break;
}
}
}).show();
}
public void listVisibility() {
int emptyMsgVisibility = View.GONE;
if (notes.size() == 0) {
if (textViewMsg.getVisibility() == View.GONE)
emptyMsgVisibility = View.VISIBLE;
}
textViewMsg.setVisibility(emptyMsgVisibility);
notesAdapter.notifyDataSetChanged();
}
@Override
public void onDestroy() {
noteDatabase.cleanUp();
super.onDestroy();
}
}
非常感谢您的帮助,我希望这个问题/答案也能对其他人有所帮助!