Android RecyclerView适配器列表<;E>;得到0
我是android开发的新手。我遇到了一个问题,我创建了一个简单的应用程序,其中我在MainActivity中有RecyclerView。我尝试拖放位置。但当我从MainActivity移动到CompleteList_activity,再次移动到MainActivity并尝试拖放时,我得到了ArrayOutOfBound错误,因为列表值为0 public void positionchange(int-fromPosition,int-toPosition)方法 主要活动:Android RecyclerView适配器列表<;E>;得到0,android,android-recyclerview,drag-and-drop,Android,Android Recyclerview,Drag And Drop,我是android开发的新手。我遇到了一个问题,我创建了一个简单的应用程序,其中我在MainActivity中有RecyclerView。我尝试拖放位置。但当我从MainActivity移动到CompleteList_activity,再次移动到MainActivity并尝试拖放时,我得到了ArrayOutOfBound错误,因为列表值为0 public void positionchange(int-fromPosition,int-toPosition)方法 主要活动: package co
package com.example.marmeto.todolist;
import android.content.Intent;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.helper.ItemTouchHelper;
import android.view.View;
import android.widget.ImageButton;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
DBHelper db;
ImageButton btn_addtodolist,btn_completelist;
List<Model> todolist = new ArrayList<>();
List<Model> adapterList = new ArrayList<>();
private RecyclerView recyclerView;
private RecyclerView.LayoutManager layoutManager;
private ToDoList_Adapter adapter;
public static final int NEW_WORD_ACTIVITY_REQUEST_CODE = 1;
Model mToDOItemList = new Model();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
db = new DBHelper(this);
recyclerView = (RecyclerView)findViewById(R.id.recyclerview);
recyclerView.setHasFixedSize(true);
layoutManager = new LinearLayoutManager(getApplicationContext());
recyclerView.setLayoutManager(layoutManager);
btn_addtodolist = (ImageButton) findViewById(R.id.btn_addtodolist);
btn_completelist = (ImageButton)findViewById(R.id.btn_completedlist);
btn_addtodolist.setOnClickListener(this);
btn_completelist.setOnClickListener(this);
getValue();
}
void getValue(){
todolist.clear();
todolist = db.getUserDetail();
Collections.sort(todolist, new Comparator<Model>() {
@Override public int compare(Model p1, Model p2) {
return p1.getPosition()- p2.getPosition(); // Ascending
}
});
adapter = new ToDoList_Adapter(todolist,getApplicationContext());
ItemTouchHelper.SimpleCallback callback=new SwipItem(adapter);
ItemTouchHelper helper=new ItemTouchHelper(callback);
helper.attachToRecyclerView(recyclerView);
recyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
@Override
protected void onResume() {
super.onResume();
}
@Override
protected void onPause() {
super.onPause();
}
@Override
public void onClick(View v) {
if (v.getId() == R.id.btn_addtodolist) {
Intent intent = new Intent(getApplicationContext(), AddToDoList_Activity.class);
startActivity(intent);
} else {
Intent intent = new Intent(getApplicationContext(),CompletedActivity.class);
startActivity(intent);
}
}
}
package com.example.marmeto.todolist;
导入android.content.Intent;
导入android.support.v4.app.Fragment;
导入android.support.v4.app.FragmentTransaction;
导入android.support.v7.app.AppActivity;
导入android.os.Bundle;
导入android.support.v7.widget.LinearLayoutManager;
导入android.support.v7.widget.RecyclerView;
导入android.support.v7.widget.helper.ItemTouchHelper;
导入android.view.view;
导入android.widget.ImageButton;
导入android.widget.Toast;
导入java.util.ArrayList;
导入java.util.Collections;
导入java.util.Comparator;
导入java.util.List;
公共类MainActivity扩展AppCompatActivity实现View.OnClickListener{
dbdb;
图像按钮btn_添加到列表,btn_完成列表;
List todolist=new ArrayList();
List adapterList=新建ArrayList();
私人回收站;
private RecyclerView.LayoutManager LayoutManager;
私有ToDoList_适配器;
公共静态最终int NEW\u WORD\u ACTIVITY\u REQUEST\u CODE=1;
模型mToDOItemList=新模型();
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
db=新的DBHelper(此);
recyclerView=(recyclerView)findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
layoutManager=新的LinearLayoutManager(getApplicationContext());
recyclerView.setLayoutManager(layoutManager);
btn_addtodolist=(ImageButton)findViewById(R.id.btn_addtodolist);
btn_completelist=(ImageButton)findViewById(R.id.btn_completelist);
btn_addtodolist.setOnClickListener(此);
btn_completelist.setOnClickListener(此);
getValue();
}
void getValue(){
todolist.clear();
todolist=db.getUserDetail();
Collections.sort(todolist,newcomparator(){
@覆盖公共整数比较(p1型、p2型){
返回p1.getPosition()-p2.getPosition();//升序
}
});
adapter=newtodolist_适配器(ToDoList,getApplicationContext());
ItemTouchHelper.SimpleCallback回调=新的SwipItem(适配器);
ItemTouchHelper=新的ItemTouchHelper(回调);
helper.attachToRecyclerView(recyclerView);
recyclerView.setAdapter(适配器);
adapter.notifyDataSetChanged();
}
@凌驾
受保护的void onResume(){
super.onResume();
}
@凌驾
受保护的void onPause(){
super.onPause();
}
@凌驾
公共void onClick(视图v){
if(v.getId()==R.id.btn\u addtodolist){
Intent Intent=new Intent(getApplicationContext(),AddToDoList\u Activity.class);
星触觉(意向);
}否则{
Intent Intent=新的Intent(getApplicationContext(),CompletedActivity.class);
星触觉(意向);
}
}
}
适配器类:
package com.example.marmeto.todolist;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.util.Collections;import java.util.List;
public class ToDoList_Adapter extends RecyclerView.Adapter<ToDoList_Adapter.ViewHolder> {
List<Model> items;
private Context context;
public ToDoList_Adapter(List<Model> items, Context context) {
this.items = items;
this.context = context;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.todolist_adapter, parent, false);
ViewHolder viewHolder = new ViewHolder(v);
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder holder, final int position) {
final Model itemlist = items.get(position);
holder.todoText.setText(itemlist.getPosition()+" "+itemlist.getTitle());
}
@Override
public int getItemCount() {
return items.size();
}
public void positionchange(int fromPosition, int toPosition)
{
try {
Collections.swap(items,fromPosition,toPosition);
DBHelper db = new DBHelper(context);
db.updateList(items);
}catch (Exception e)
{
e.printStackTrace();
}
this.notifyItemMoved(fromPosition,toPosition);
}
public void deletePlanet(int pos)
{
//GET ID
try {
Model p = items.get(pos);
int id = p.getId();
//DELETE FROM DB
DBHelper db = new DBHelper(context);
if (db.delete(id)) {
items.remove(pos);
db.updateList(items);
} else {
Toast.makeText(context, "Unable To Delete", Toast.LENGTH_SHORT).show();
}
this.notifyItemRemoved(pos);
}catch (Exception e){
e.printStackTrace();
}
}
class ViewHolder extends RecyclerView.ViewHolder {
public TextView todoText;
public Button btn_done;
public ViewHolder(final View itemView) {
super(itemView);
todoText = (TextView)itemView.findViewById(R.id.todoItem_text);
btn_done = (Button)itemView.findViewById(R.id.btn_done);
btn_done.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DBHelper db = new DBHelper(context);
try {
Model p = items.get(getAdapterPosition());
db.updateData(p.getId());
items.remove(getAdapterPosition());
db.updateList(items);
}catch (Exception e){
e.printStackTrace();
}
notifyItemRemoved(getAdapterPosition());
}
});
}
}
}
package com.example.marmeto.todolist;
导入android.content.Context;
导入android.support.annotation.NonNull;
导入android.support.v7.widget.RecyclerView;
导入android.util.Log;
导入android.view.LayoutInflater;
导入android.view.view;
导入android.view.ViewGroup;
导入android.widget.Button;
导入android.widget.TextView;
导入android.widget.Toast;
导入java.util.Collections;导入java.util.List;
公共类ToDoList_适配器扩展了RecyclerView.Adapter{
清单项目;
私人语境;
公共ToDoList_适配器(列表项、上下文){
这个项目=项目;
this.context=上下文;
}
@凌驾
public ViewHolder onCreateViewHolder(视图组父级,int-viewType){
视图v=LayoutInflater.from(parent.getContext())
.充气(R.layout.todolist_适配器,父级,错误);
视窗夹持器视窗夹持器=新视窗夹持器(v);
返回视图持有者;
}
@凌驾
公共无效onBindViewHolder(ViewHolder,最终int位置){
最终模型itemlist=items.get(位置);
holder.todoText.setText(itemlist.getPosition()+“”+itemlist.getTitle());
}
@凌驾
public int getItemCount(){
返回items.size();
}
公共无效位置更改(int-fromPosition、int-toPosition)
{
试一试{
集合。交换(项目、起始位置、位置);
DBHelper db=新的DBHelper(上下文);
数据库更新列表(项目);
}捕获(例外e)
{
e、 printStackTrace();
}
此.notifyItemMoved(从位置、位置);
}
公共区域(内部位置)
{
//取得身份证
试一试{
模型p=项目获取(pos);
int id=p.getId();
//从数据库中删除
DBHelper db=新的DBHelper(上下文);
如果(数据库删除(id)){
项目。移除(pos);
数据库更新列表(项目);
}否则{
Toast.makeText(上下文,“无法删除”,Toast.LENGTH_SHORT.show();
}
此项已删除(pos);
}捕获(例外e){
e、 printStackTrace();
}
}
类ViewHolder扩展了RecyclerView.ViewHolder{
公共文本视图到文本;
公共按钮btn_完成;
公共视图持有者(最终视图项视图){
超级(项目视图);
todoText=(TextView)itemView.findViewBy