如何在RecyclerView适配器中选择每个项目，以便通过转到活动来编辑该列表中的项目

Question

这是我的第一个问题，所以我会尽可能做到最好。

目标是有一个列表，允许我单击每个项目，以便打开一个新的活动，我可以在其中编辑或删除此项目。

目前我有一个选项卡式应用程序，其中有代表每个选项卡的不同片段，在这些片段中，我有要显示的所有项目的回收视图。我还有一个浮动按钮，可以在第一个选项卡(客户端(中添加新客户端。它看起来像这样：

应用程序默认主页

我在YouTube和博客上尝试了几个视频来解决这个问题，但我无法让它发挥作用。我的愿望是，如果我能让点击开始工作，当它打开UpdateClient活动时，它会从该项目中获取必要的详细信息。请参阅此处的结构和UpdateClient活动：

应用程序文件结构更新客户端活动

到目前为止，我已经尝试在片段本身中创建一个按钮，但当尝试引用编辑按钮的id(称为"更新"(时，这会返回一个null对象。我也尝试过在RecyclerViewAdapter中实现OnClickListener，但也没有成功，它只是偶尔让我点击，但仍然没有解决我的需求。

这是迄今为止的代码：

主要活动

public class MainActivity extends AppCompatActivity {
private AdminDB_Manager db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
SectionsPagerAdapter sectionsPagerAdapter = new SectionsPagerAdapter(this, getSupportFragmentManager());
ViewPager viewPager = findViewById(R.id.view_pager);
viewPager.setAdapter(sectionsPagerAdapter);
TabLayout tabs = findViewById(R.id.tabs);
tabs.setupWithViewPager(viewPager);
FloatingActionButton fab = findViewById(R.id.fab);
// Crear base de datos
db = new AdminDB_Manager(this);
db.open();
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(MainActivity.this, "Adding Client", Toast.LENGTH_LONG).show();
addClient(view);
}
});
}
public void addClient(android.view.View v) {
Intent intent = new Intent(this, AddClient.class);
startActivity(intent);
}
}

客户端片段

public class ClientsFragment extends Fragment {
// TODO: Customize parameter argument names
private static final String ARG_COLUMN_COUNT = "column-count";
// TODO: Customize parameters
private int mColumnCount = 1;
/**
* Mandatory empty constructor for the fragment manager to instantiate the
* fragment (e.g. upon screen orientation changes).
*/
public ClientsFragment() {
}
// TODO: Customize parameter initialization
@SuppressWarnings("unused")
public static ClientsFragment newInstance(int columnCount) {
ClientsFragment fragment = new ClientsFragment();
Bundle args = new Bundle();
args.putInt(ARG_COLUMN_COUNT, columnCount);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_client_list, container, false);
Button update = view.findViewById(R.id.update);
if(update != null){
update.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(getActivity(), "Adding Client", Toast.LENGTH_LONG).show();
Intent intent = new Intent(getActivity(), MainActivity.class);
startActivity(intent);
}
});
}
// Set the adapter
if (view instanceof RecyclerView) {
Context context = view.getContext();
RecyclerView recyclerView = (RecyclerView) view;
if (mColumnCount <= 1) {
recyclerView.setLayoutManager(new LinearLayoutManager(context));
} else {
recyclerView.setLayoutManager(new GridLayoutManager(context, mColumnCount));
}
recyclerView.setAdapter(new MyClientsRecyclerViewAdapter(DummyContent.ITEMS));
}
return view;
}
}

MyClientsCyclerViewAdapter

public class MyClientsRecyclerViewAdapter extends RecyclerView.Adapter<MyClientsRecyclerViewAdapter.ViewHolder> {
private final List<DummyItem> mValues;
public MyClientsRecyclerViewAdapter(List<DummyItem> items) {
mValues = items;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.fragment_clients, parent, false);

return new ViewHolder(view);
}
@Override
public void onBindViewHolder(final ViewHolder holder, int position) {
holder.mItem = mValues.get(position);
holder.mIdView.setText(mValues.get(position).id);
holder.mContentView.setText(mValues.get(position).content);
}
@Override
public int getItemCount() {
return mValues.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public final View mView;
public final TextView mIdView;
public final TextView mContentView;
public DummyItem mItem;
public ViewHolder(View view) {
super(view);
mView = view;
mIdView = (TextView) view.findViewById(R.id.item_number);
mContentView = (TextView) view.findViewById(R.id.content);
}
@Override
public String toString() {
return super.toString() + " '" + mContentView.getText() + "'";
}
}
}

以下是布局：

fragment_clients.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:id="@+id/item_number"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="@dimen/text_margin"
android:textAppearance="?attr/textAppearanceListItem" />
<TextView
android:id="@+id/content"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="@dimen/text_margin"
android:textAppearance="?attr/textAppearanceListItem" />
</LinearLayout>

fragment_clients_list.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView     xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/list"
android:name="com.example.app.fragments.ClientsFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
app:layoutManager="LinearLayoutManager"
tools:context=".fragments.ClientsFragment"
tools:listitem="@layout/fragment_clients">
</androidx.recyclerview.widget.RecyclerView>

Answer 1

我已经找到了解决方案，只做了一点调整。现在，每个viewHolder都有一个onClickListener，这样当我点击项目(网格中的任何位置(时，它都会打开活动，而不是为每个项目都设置一个按钮。更改发生在：

客户端碎片

public class ClientsFragment extends Fragment implements MyClientsRecyclerViewAdapter.OnClientListenser {
// TODO: Customize parameter argument names
private static final String ARG_COLUMN_COUNT = "column-count";
// TODO: Customize parameters
private int mColumnCount = 1;
// Vars
private List<DummyContent.DummyItem> mValues = new ArrayList<>();
/**
* Mandatory empty constructor for the fragment manager to instantiate the
* fragment (e.g. upon screen orientation changes).
*/
public ClientsFragment() {
}
// TODO: Customize parameter initialization
@SuppressWarnings("unused")
public static ClientsFragment newInstance(int columnCount) {
ClientsFragment fragment = new ClientsFragment();
Bundle args = new Bundle();
args.putInt(ARG_COLUMN_COUNT, columnCount);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_client_list, container, false);
// Set the adapter
if (view instanceof RecyclerView) {
Context context = view.getContext();
RecyclerView recyclerView = (RecyclerView) view;
if (mColumnCount <= 1) {
recyclerView.setLayoutManager(new LinearLayoutManager(context));
} else {
recyclerView.setLayoutManager(new GridLayoutManager(context, mColumnCount));
}
recyclerView.setAdapter(new MyClientsRecyclerViewAdapter(DummyContent.ITEMS, this));
}
return view;
}
@Override
public void onClientClick(int position) {
Toast.makeText(getActivity(), "Editing Client", Toast.LENGTH_LONG).show();
Intent intent = new Intent(getActivity(), UpdateClient.class);
// intent.putExtra("Some info", "something else");
startActivity(intent);
}
}

MyClientsCyclerViewAdapter

public class MyClientsRecyclerViewAdapter extends RecyclerView.Adapter<MyClientsRecyclerViewAdapter.ViewHolder> {
private final List<DummyItem> mValues;
private OnClientListenser mOnClientListener;
public MyClientsRecyclerViewAdapter(List<DummyItem> items, OnClientListenser onClientListenser) {
mValues = items;
this.mOnClientListener = onClientListenser;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.fragment_clients, parent, false);

return new ViewHolder(view, mOnClientListener);
}
@Override
public void onBindViewHolder(final ViewHolder holder, int position) {
holder.mItem = mValues.get(position);
holder.mIdView.setText(mValues.get(position).id);
holder.mContentView.setText(mValues.get(position).content);
}
@Override
public int getItemCount() {
return mValues.size();
}
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public final View mView;
public final TextView mIdView;
public final TextView mContentView;
public DummyItem mItem;
OnClientListenser onClientListener;
public ViewHolder(View view, OnClientListenser onClientListener) {
super(view);
mView = view;
mIdView = (TextView) view.findViewById(R.id.item_number);
mContentView = (TextView) view.findViewById(R.id.content);
this.onClientListener = onClientListener;
itemView.setOnClickListener(this);
}
@Override
public String toString() {
return super.toString() + " '" + mContentView.getText() + "'";
}
// Implementation of interface
@Override
public void onClick(View v) {
onClientListener.onClientClick(getAdapterPosition());
}
}
public interface OnClientListenser{
public void onClientClick(int position);
}
}

感谢所有在Facebook上帮忙的人，我找到了这个视频(https://www.youtube.com/watch?v=69C1ljfDvl0&feature=emb_logo(，他帮助我取得了进步！