片段间的Android通信
'我试图通过活动将数据从一个片段发送到另一个片段。 可以将数据从GroupFragment发送到包含正确值的ChatActivity id,但当其达到以下值时:片段间的Android通信,android,android-fragments,Android,Android Fragments,'我试图通过活动将数据从一个片段发送到另一个片段。 可以将数据从GroupFragment发送到包含正确值的ChatActivity id,但当其达到以下值时: @Override public void respond(String id) { interfaceDataCommunicatorFromActivity.respond(id); } 在我的聊天活动中,它抛出一个NUllPointException,我不知道如何使它工作 当我只粘贴代码的一部分时,我试图让你更容易阅读,
@Override
public void respond(String id) {
interfaceDataCommunicatorFromActivity.respond(id);
}
在我的聊天活动中,它抛出一个NUllPointException,我不知道如何使它工作
当我只粘贴代码的一部分时,我试图让你更容易阅读,如果没有帮助,我会友好地纠正我!对于所有代码:
聊天活动:
public class ChatActivity extends Activity implements
GroupFragment.OnFragmentInteractionListener,
//ChatFragment.OnFragmentInteractionListener,
GroupFragment.InterfaceDataCommunicator {
public InterfaceDataCommunicatorFromActivity interfaceDataCommunicatorFromActivity;
@Override
public void respond(String id) {
interfaceDataCommunicatorFromActivity.respond(id);
}
public interface InterfaceDataCommunicatorFromActivity {
public void respond(String id);
}
}
组片段:
public class GroupFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
public InterfaceDataCommunicator interfaceDataCommunicater;
...../
public void CreateNewGroup(String groupName) {
Map<String, Group> newGroup = new HashMap<>();
Firebase firebaserootRef = new Firebase("https://luminous-heat-420.firebaseio.com");
Firebase firebaseGroup = firebaserootRef.child("").push();
Group group = new Group();
group.SetID(firebaseGroup.getKey());
group.SetName(groupName);
String id = firebaseGroup.getKey();
firebaseGroup.child("id").setValue(group.GetId());
firebaseGroup.child("name").setValue(group.GetName());
newGroup.put(id, group);
interfaceDataCommunicater.respond(group.GetId());
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mListener = (OnFragmentInteractionListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnFragmentInteractionListener");
}
try {
interfaceDataCommunicater = (InterfaceDataCommunicator) activity;
} catch (ClassCastException c) {
throw new ClassCastException(activity.toString()
+ " must implement InterfaceDataCommunicator");
}
}
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
public void onFragmentInteraction(Uri uri);
}
public interface InterfaceDataCommunicator{
public void respond(String id);
}
}
你的活动中的interfaceDataComunicatorFromActivity是无用的,你会得到一个NPE,因为没有引用它。如果您只想在ChatFragment中输入组的id,只需通过ChangeToChatFragment中的setter传递即可:
public class ChatFragment extends Fragment implements
View.OnClickListener,
ChatActivity.InterfaceDataCommunicatorFromActivity {
public ChatActivity.InterfaceDataCommunicatorFromActivity
interfaceDataCommunicatorFromActivity;
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mListener = (OnFragmentInteractionListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnFragmentInteractionListener");
}
try {
interfaceDataCommunicatorFromActivity = (ChatActivity
.InterfaceDataCommunicatorFromActivity) activity;
} catch (ClassCastException c) {
throw new ClassCastException(activity.toString()
+ " must implement InterfaceDataCommunicator");
}
}
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
public void onFragmentInteraction(Uri uri);
}
@Override
public void respond(String id) {
this.groupID = id;
}
}
编辑:
在聊天室中添加:
然后将您的groupId作为参数传递给ChangeToChatFragment考虑使用广播而不是接口在哪里初始化field InterfacedataCommunicationorFromActivity?我的意思是,您没有在活动中为该字段设置任何值,因此很明显在那里会出现空指针异常。Thx对于快速答案和您的解决方案有效,但只是为了澄清其他有相同问题的人,我需要添加一个SetGroupIDString groupId{return this.group=groupId;}在我的聊天片段中,我在课堂上寻找字符串。。。
public void ChangeToChatFragment(String groupId) {
ChatFragment groupFragment = ChatFragment.newInstance("", "");
groupFragment.setGroupId(groupId);
FragmentManager fM = getFragmentManager();
FragmentTransaction fT = fM.beginTransaction();
fT.replace(R.id.container_chat, groupFragment, null);
fT.addToBackStack("go to chat fragmement");
fT.commit();
}
public void setGroupId(String groupId){
this.groupId = groupId;
}