在我的应用程序中，我有一个Mysql，并通过凌空获取数据并使用它来填充recyclerView，并且要明确地说，我有一个餐厅列表，其中填充了recyclerView，如果您长按餐厅，则可以在该餐厅添加注释所以我需要餐厅ID及其位置，因为我数据库中的便笺表是一个子表，该子表通过FK连接到餐厅表，并使用餐厅ID作为参考，我不知道为什么我会为adapter.getPosition获取NPE，请帮忙
MainActivity
public class MainActivity extends AppCompatActivity implements SwipeRefreshLayout.OnRefreshListener{
RecyclerView recyclerView;
RecyclerView.Adapter mAdapter;
RecyclerView.LayoutManager layoutManager;
SwipeRefreshLayout swipeRefreshLayout;
RestaurantAdapter adapter;
List<Restaurant> restaurants = new ArrayList<>();
String request_url = "https://localhost/api/all_fastfoods.php";
String post_url= "https://localhost/api/add_note.php";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
swipeRefreshLayout=findViewById(R.id.swipe_layout);
swipeRefreshLayout.setOnRefreshListener(this);
recyclerView = findViewById(R.id.recycleViewContainer);
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
restaurants = new ArrayList<>();
registerForContextMenu(recyclerView);
getData();
NukeSSLCerts.nuke();
}
private void getData() {
swipeRefreshLayout.setRefreshing(true);
sendRequest();
}
public void sendRequest(){
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.GET, request_url, null, new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
restaurants.clear();
for (int i = 0; i < response.length(); i++) {
Restaurant restaurant = new Restaurant();
try {
JSONObject jsonObject = response.getJSONObject(i);
restaurant.setId(jsonObject.getInt("restaurant_id"));
restaurant.setName(jsonObject.getString("restaurant_name"));
restaurant.setAddress(jsonObject.getString("restaurant_address"));
restaurant.setImage(jsonObject.getInt("restaurant_image_type"));
restaurant.setHasNote(jsonObject.getBoolean("restaurant_has_note"));
swipeRefreshLayout.setRefreshing(false);
} catch (JSONException e) {
swipeRefreshLayout.setRefreshing(false);
Log.i("Error",e.toString());
e.printStackTrace();
}
restaurants.add(restaurant);
}
mAdapter = new RestaurantAdapter(MainActivity.this, restaurants);
recyclerView.setAdapter(mAdapter);
swipeRefreshLayout.setRefreshing(false);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.i("Volley Error:", String.valueOf(error));
}
});
RequestQueue queue = Volley.newRequestQueue(getApplicationContext());
queue.add(jsonArrayRequest);
}
public boolean onContextItemSelected(MenuItem item) {
final Restaurant restaurant= new Restaurant();
if (item.getTitle().equals("Add Note")){
AlertDialog.Builder notepad = new AlertDialog.Builder(MainActivity.this);
LayoutInflater noteInflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
View notepadView = noteInflater.inflate(R.layout.notes,null,false);
notepad.setView(notepadView);
final AlertDialog notepadDialog = notepad.create();
notepadDialog.getWindow().getAttributes().windowAnimations = R.style.customdialog;
notepadDialog.show();
final EditText notepadedit = notepadView.findViewById(R.id.notepad);
final Button addnote = notepadView.findViewById(R.id.fab);
notepadedit.requestFocus();
addnote.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
JSONObject update = new JSONObject();
JSONObject postparams = new JSONObject();
try {
postparams.put("Content-Type", "application/json");
postparams.put("Accept", "application/json");
postparams.put("note_content",notepadedit.getText());
postparams.put("note_date_time",System.currentTimeMillis());
postparams.put("restaurant_id",restaurants.get(adapter.getPosition()).getId());
update.put("restaurant_has_note",true);
} catch (JSONException e) {
e.printStackTrace();
}
JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, post_url, postparams, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
Toast.makeText(getApplicationContext(), "SuccessFull", Toast.LENGTH_LONG).show();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.i("PostLog", String.valueOf(error));
}
}
RecyclerView适配器
public class RestaurantAdapter extends RecyclerView.Adapter<RestaurantAdapter.MyViewHolder> implements View.OnClickListener{
private Context context;
private List<Restaurant> restaurantList;
private int position;
public int getPosition() {return position;}
public void setPosition(int position) {this.position = position; }
public RestaurantAdapter(Context context,List <Restaurant> restaurantList){
this.context = context;
this.restaurantList = restaurantList;
}
@Override
public void onClick(View view){
}
public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnCreateContextMenuListener{
public TextView FastFoodName;
public TextView FastFoodAddress;
ImageView icon,noteIcon;
MyViewHolder(View itemView){
super(itemView);
icon = itemView.findViewById(R.id.type_ic);
FastFoodName = itemView.findViewById(R.id.listview_name);
FastFoodAddress = itemView.findViewById(R.id.listview_address);
noteIcon = itemView.findViewById(R.id.note_icon);
itemView.setOnCreateContextMenuListener(this);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) menuInfo;
menu.add(0, 1, 0, "Add Note");
menu.add(0, 2, 1, "All Notes");
}
}
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType){
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_layout,parent,false);
return new MyViewHolder(v);
}
@Override
public void onBindViewHolder(@NonNull final MyViewHolder holder, int position) {
holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
setPosition(holder.getAdapterPosition());
return false;
}
});
Restaurant restaurant = restaurantList.get(position);
holder.FastFoodName.setText(restaurant.getName());
holder.FastFoodAddress.setText(restaurant.getAddress());
switch (restaurant.getImage()){
case 1:
holder.icon.setImageResource(R.drawable.phoneorderr);
break;
case 2:
holder.icon.setImageResource(R.drawable.sitdownn);
break;
case 3:
holder.icon.setImageResource(R.drawable.takeaway);
break;
}
holder.noteIcon.setImageResource(R.drawable.notepadicon);
if(restaurant.isHasNote()){
holder.noteIcon.setVisibility(View.VISIBLE);
}else {
holder.noteIcon.setVisibility(View.INVISIBLE);
}
}
@Override
public int getItemCount() {
return restaurantList.size();
}
@Override
public long getItemId(int position) {
return position;
}
}
和我的模型课程
public class Restaurant implements Serializable {
private int id;
private String name;
private String address;
private int type;
private boolean hasNote = false;
private int image;
public Restaurant() {
}
public Restaurant(String name, String address,int type){
this.name = name;
this.address = address;
this.type = type;
}
public Restaurant(int id, String name, String address,int type){
this.id = id;
this.name = name;
this.address = address;
this.type = type;
}
public Restaurant(int id, String name, String address, int type,int image) {
this.id = id;
this.name = name;
this.address = address;
this.type = type;
this.image = image;
}
public int getId() { return id;}
public void setId (int id) { this.id = id;}
public String getName() {
return name;
}
public void setName(String name) { this.name = name;}
public boolean isHasNote(){
return hasNote;
}
public void setHasNote(boolean hasNote){
this.hasNote = hasNote;
}
public String getAddress() { return address;}
public void setAddress(String address) { this.address = address;}
public void setType(int type) {this.type = type;}
public int getType() {return type;}
public int getImage() {return image;}
public void setImage(int image) {this.image = image;}
}
答案 0 :(得分：1)
您尚未初始化adapter。在使用前尝试对其进行初始化。
public class MainActivity extends AppCompatActivity implements SwipeRefreshLayout.OnRefreshListener{
//remove this
//RecyclerView.Adapter mAdapter;
//User this everywhere
RestaurantAdapter adapter;
.....
public void sendRequest() {
....
adapter = new RestaurantAdapter(MainActivity.this, restaurants);
recyclerView.setAdapter(adapter);
....
}
}