如何使用RecyclerView Adapter
我只是想使用RecyclerView来创建一个列表，其中每个列表项都将包含一个复选框按钮。因此，当用户单击复选框时，它将替换表格列的值，例如列国家/地区获取值“ A”，而未选中则将国家/地区列的值从“ A”替换为“ B”或其他任何值。
有人可以帮我吗？关于使用Recyclable在SQLite数据库中添加数据以及其他类似方法的任何建议都将非常有帮助。
下面我添加了我的代码供您参考，并提前致谢。
我的DatabaseHelper类
package com.hfad.ressql;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.hfad.ressql.DatabaseContractor.*;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;
public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "workers.db";
private static final int DATABASE_VERSION =7;
SQLiteDatabase db;
public DatabaseHelper( Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
this.db=db;
final String SQL_CREATE_TBALE="CREATE TABLE " + EmployeeDetails.TABLE_NAME + "(" + EmployeeDetails._ID +" INTEGER PRIMARY KEY AUTOINCREMENT, "+
EmployeeDetails.COLUMN_FIRSTNAME+" TEXT, "+EmployeeDetails.COLUMN_LASTNAME+" TEXT, "+EmployeeDetails.COLUMN_COUNTRY+" TEXT)";
db.execSQL(SQL_CREATE_TBALE);
fillquestion();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + EmployeeDetails.TABLE_NAME);
onCreate(db);
}
public void fillquestion(){
DataModel o4 = new DataModel("Earth","Soil","B");
IntertData(o4);
DataModel o5 = new DataModel("Sun","Light","B");
IntertData(o5);
DataModel o6 = new DataModel("Moon","Rock","B");
IntertData(o6);
}
public void IntertData (DataModel data){
ContentValues contentValues = new ContentValues();
contentValues.put(EmployeeDetails.COLUMN_FIRSTNAME, data.getFirstName());
contentValues.put(EmployeeDetails.COLUMN_LASTNAME, data.getLastName());
contentValues.put(EmployeeDetails.COLUMN_COUNTRY, data.country);
db.insert(EmployeeDetails.TABLE_NAME,null,contentValues);
}
public List<DataModel> object1() {
ArrayList<DataModel> details = new ArrayList<DataModel>();
db = getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + EmployeeDetails.TABLE_NAME, null );
if (cursor.moveToFirst()) {
do {
DataModel object2 = new DataModel();
object2.setFirstName(cursor.getString(cursor.getColumnIndex(EmployeeDetails.COLUMN_FIRSTNAME)));
object2.setLastName(cursor.getString(cursor.getColumnIndex(EmployeeDetails.COLUMN_LASTNAME)));
object2.setCountry(cursor.getString(cursor.getColumnIndex(EmployeeDetails.COLUMN_COUNTRY)));
details.add(object2);
} while (cursor.moveToNext());
}
cursor.close();
return details;
}
}
这是我的DataModel类
package com.hfad.ressql;
public class DataModel {
public String FirstName;
public String LastName;
public String country;
public DataModel() {
}
public DataModel(String firstName, String lastName, String country) {
this.FirstName = firstName;
this.LastName = lastName;
this.country = country;
}
public String getFirstName() {
return FirstName;
}
public void setFirstName(String firstName) {
FirstName = firstName;
}
public String getLastName() {
return LastName;
}
public void setLastName(String lastName) {
LastName = lastName;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
}
数据库构造器
public final class DatabaseContractor {
private DatabaseContractor (){}
public static class EmployeeDetails implements BaseColumns {
public static final String TABLE_NAME="employy";
public static final String COLUMN_FIRSTNAME="First_Name";
public static final String COLUMN_LASTNAME="Last_Name";
public static final String COLUMN_COUNTRY="Country";
public static final String COLUMN_FAVO="mfav";
}
}
回收站适配器
我在这里努力解决问题。我所需要的是，如果我单击复选框，则将在数据库中更新一个给定的值，同时将选中该复选框，直到用户取消选中它为止。当用户取消选中它时，数据库将用新值替换以前的值。实际上，我只是试图在表列中包含值，以便可以将其用作收藏夹或书签列表。
public class RecycAdapter extends
RecyclerView.Adapter<RecycAdapter.ViewHolder> {
List<DataModel> dotamodeldataArraylist;
Context context;
SQLiteDatabase db;
DatabaseHelper helper;
ContentValues contentValues;
Cursor cursor;
public RecycAdapter(List<DataModel> dotamodeldataArraylist,Context context) {
this.dotamodeldataArraylist=dotamodeldataArraylist;
this.context=context;
}
@Override
public ViewHolder onCreateViewHolder( ViewGroup parent, int ViewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.itemlist,parent,false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(final RecycAdapter.ViewHolder holder, final int position) {
DataModel obj3= dotamodeldataArraylist.get(position);
holder.Fnam.setText(obj3.getFirstName());
holder.Lname.setText(obj3.getLastName());
holder.Country.setText(obj3.getCountry());
holder.fav.();
holder.fav.setChecked(fav);
final int currentPosition = position;
final boolean fav = 0==0;
holder.fav.setChecked(fav);
final int currentPosition = position;
holder.fav.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(holder.fav.isChecked()){
try {
contentValues = new ContentValues();
contentValues.put(DatabaseContractor.EmployeeDetails.COLUMN_COUNTRY, "B");
db.update("DRINK", contentValues, "id_=?", new String[]{Integer.toString(currentPosition)});
} catch (SQLException e){
Toast.makeText(context,"error" + position , Toast.LENGTH_LONG).show();
}
Toast.makeText(context,"checked " + position , Toast.LENGTH_LONG).show();
} if(!holder.fav.isChecked()){
Toast.makeText(context,"not checked" + position , Toast.LENGTH_LONG).show();
}
}
});
}
@Override
public int getItemCount() {
return dotamodeldataArraylist.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView Fnam,Lname,Country;
CheckBox fav;
RelativeLayout relativeLayout;
public ViewHolder(View itemView) {
super(itemView);
Fnam = itemView.findViewById(R.id.name1);
Lname = itemView.findViewById(R.id.city1);
Country = itemView.findViewById(R.id.country1);
fav=itemView.findViewById(R.id.chk);
relativeLayout = (RelativeLayout) itemView.findViewById(R.id.layout);
}
}
}
查看课程
查看所有课程
public class Viewall extends AppCompatActivity {
RecyclerView recyclerView;
DatabaseHelper databaseHelper;
RecycAdapter recycAdapter;
List<DataModel> dotamodeldataArraylist;
Context context;
Button show;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.viewall);
show = findViewById(R.id.view);
recyclerView=findViewById(R.id.recycle);
databaseHelper =new DatabaseHelper(this);
dotamodeldataArraylist = new ArrayList<DataModel>();
dotamodeldataArraylist=databaseHelper.object1();
recycAdapter =new RecycAdapter(dotamodeldataArraylist,this);
RecyclerView.LayoutManager reLayoutManager =new
LinearLayoutManager(getApplicationContext());
recyclerView.setLayoutManager(reLayoutManager);
recyclerView.setItemAnimator(new DefaultItemAnimator());
recyclerView.setAdapter(recycAdapter);
2 个答案:
答案 0 :(得分：1)
我相信以下内容可以满足您的要求。
代码有很多问题。主要问题之一是您希望该职位与 id （也就是您的 _id 列）相关。
列表中第一项的位置为 0 ，除非您强制/专门设置值为0，即 rowid 列的别名（您的 _id 列是rowid列的别名），分配的第一个值将是1，然后可能是2，然后可能是3 ...........
因此，最佳位置比ID少1。
如果删除了一行，则除最后一行外，位置将减少一个，直到通过已删除的行为止，然后位置将比该行ID小2。删除次数更多，位置和ID之间的关联更加复杂。我想有人可以提出一个简单的转换方法，但简单的方法是确保DataModel具有相应的 _id 列。
因此应更改 DataModel.java 使其包含ID的成员/变量，因此使用了以下内容：-
public class DataModel {
public String FirstName;
public String LastName;
public String country;
public long id; //<<<<<<<<<< ADDED also added gettter and setter
public DataModel() {
}
public DataModel(String firstName, String lastName, String country) {
this(firstName,lastName,country,-1);
}
//<<<<<<<<<< ADDED so ID can be set
public DataModel(String firstName, String lastName, String country, long id) {
this.FirstName = firstName;
this.LastName = lastName;
this.country = country;
this.id = id;
}
public String getFirstName() {
return FirstName;
}
public void setFirstName(String firstName) {
FirstName = firstName;
}
public String getLastName() {
return LastName;
}
public void setLastName(String lastName) {
LastName = lastName;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public void setId(long id) {
this.id = id;
}
public long getId() {
return id;
}
}
- 查看评论以了解变化
由于需要从数据库中提取ID，因此在 DatabaseHelper.java 中更改了object1方法（还进行了其他一些更改），使用了以下内容：-
public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "workers.db";
private static final int DATABASE_VERSION =7;
SQLiteDatabase db;
public DatabaseHelper( Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
db = this.getWritableDatabase();
}
@Override
public void onCreate(SQLiteDatabase db) {
this.db=db; //<<<<<<< WRONG PLACE as onCreate only ever runs when there is no database
final String SQL_CREATE_TBALE="CREATE TABLE " + DatabaseContractor.EmployeeDetails.TABLE_NAME + "(" + DatabaseContractor.EmployeeDetails._ID +" INTEGER PRIMARY KEY AUTOINCREMENT, "+
DatabaseContractor.EmployeeDetails.COLUMN_FIRSTNAME+" TEXT, "+ DatabaseContractor.EmployeeDetails.COLUMN_LASTNAME+" TEXT, "+ DatabaseContractor.EmployeeDetails.COLUMN_COUNTRY+" TEXT)";
db.execSQL(SQL_CREATE_TBALE);
fillquestion();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + DatabaseContractor.EmployeeDetails.TABLE_NAME);
onCreate(db);
}
public void fillquestion(){
IntertData(new DataModel("Earth","Soil","B"));
IntertData(new DataModel("Sun","Light","B"));
IntertData(new DataModel("Moon","Rock","B"));
}
public void IntertData (DataModel data){
ContentValues contentValues = new ContentValues();
contentValues.put(DatabaseContractor.EmployeeDetails.COLUMN_FIRSTNAME,data.getFirstName());
contentValues.put(DatabaseContractor.EmployeeDetails.COLUMN_LASTNAME,data.getLastName());
contentValues.put(DatabaseContractor.EmployeeDetails.COLUMN_COUNTRY,data.country);
db.insert(DatabaseContractor.EmployeeDetails.TABLE_NAME,null,contentValues);
}
public List<DataModel> object1() {
ArrayList<DataModel> details = new ArrayList<>();
//db = getReadableDatabase(); db has already been set when database was instantiated/constructed
Cursor cursor = db.rawQuery("SELECT * FROM " + DatabaseContractor.EmployeeDetails.TABLE_NAME, null );
while (cursor.moveToNext()) {
details.add(new DataModel(
cursor.getString(cursor.getColumnIndex(DatabaseContractor.EmployeeDetails.COLUMN_FIRSTNAME)),
cursor.getString(cursor.getColumnIndex(DatabaseContractor.EmployeeDetails.COLUMN_LASTNAME)),
cursor.getString(cursor.getColumnIndex(DatabaseContractor.EmployeeDetails.COLUMN_COUNTRY)),
cursor.getLong(cursor.getColumnIndex(DatabaseContractor.EmployeeDetails._ID)) //<<<<<<<<< Added so id is available
));
}
cursor.close();
return details;
}
}
对RecycAdapter.java进行了相当广泛的更改，使用了以下内容：-
public class RecycAdapter extends RecyclerView.Adapter<RecycAdapter.ViewHolder> {
List<DataModel> dotamodeldataArraylist;
Context context;
SQLiteDatabase db;
DatabaseHelper helper;
ContentValues contentValues;
public RecycAdapter(List<DataModel> dotamodeldataArraylist,Context context) {
this.dotamodeldataArraylist=dotamodeldataArraylist;
this.context=context;
helper = new DatabaseHelper(context);
db = helper.getWritableDatabase();
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int ViewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.itemlist,parent,false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(final RecycAdapter.ViewHolder holder, final int position) {
//DataModel obj3= dotamodeldataArraylist.get(position); //<<<<<<<<<< NOT NEEDED
holder.Fnam.setText(dotamodeldataArraylist.get(position).getFirstName());
holder.Lname.setText(dotamodeldataArraylist.get(position).getLastName());
holder.Country.setText(dotamodeldataArraylist.get(position).getCountry());
holder.fav.setChecked(false); //<<<<<<<<< not stored so initially set to false
holder.fav.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String newcountry = "B";
if(holder.fav.isChecked()){
if (dotamodeldataArraylist.get(position).getCountry().equals("B")) {
newcountry = "A";
}
contentValues = new ContentValues();
contentValues.put(DatabaseContractor.EmployeeDetails.COLUMN_COUNTRY, newcountry);
if (db.update(
DatabaseContractor.EmployeeDetails.TABLE_NAME,
contentValues,
DatabaseContractor.EmployeeDetails._ID +"=?",
new String[]{String.valueOf(dotamodeldataArraylist.get(position).getId())}
) > 0) {
dotamodeldataArraylist.get(position).setCountry(newcountry);
notifyItemChanged(position);
Toast.makeText(context,
"checked and updated " +
position+ dotamodeldataArraylist.get(position).getFirstName() +
" ID is " + String.valueOf(dotamodeldataArraylist.get(position).getId()),
Toast.LENGTH_LONG
).show();
} else {
Toast.makeText(context,"error" + position , Toast.LENGTH_LONG).show();
}
} else {
Toast.makeText(context,"not checked" + position , Toast.LENGTH_LONG).show();
}
}
});
}
@Override
public int getItemCount() {
return dotamodeldataArraylist.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView Fnam,Lname,Country;
CheckBox fav;
public ViewHolder(View itemView) {
super(itemView);
Fnam = itemView.findViewById(R.id.name1);
Lname = itemView.findViewById(R.id.city1);
Country = itemView.findViewById(R.id.country1);
fav = itemView.findViewById(R.id.chk);
}
}
}
最后对Viewall.java进行了一些小的更改，使用了以下内容：-
public class Viewall extends AppCompatActivity {
RecyclerView recyclerView;
DatabaseHelper databaseHelper;
RecycAdapter recycAdapter;
List<DataModel> dotamodeldataArraylist;
Button show;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.viewall);
show = findViewById(R.id.view);
recyclerView = findViewById(R.id.recycle);
databaseHelper = new DatabaseHelper(this);
dotamodeldataArraylist = databaseHelper.object1();
recycAdapter = new RecycAdapter(dotamodeldataArraylist, this);
RecyclerView.LayoutManager reLayoutManager = new
LinearLayoutManager(this);
recyclerView.setLayoutManager(reLayoutManager);
recyclerView.setItemAnimator(new DefaultItemAnimator());
recyclerView.setAdapter(recycAdapter);
}
}
结果
请注意，布局可能有所不同，但是您的布局应该可以工作并相应地更改显示方式
首次运行时：-
点击 Sun
的复选框后 
再次单击并返回到B国，依此类推。
- 请注意，复选框未翻转，这对于正确显示更改的数据（国家/地区）而言是个问题，因为notifyItemChanged会重新使用列表，因此将复选框设置为false。您需要将复选框的值存储在某个地方（总之，您应该以这种方式使用复选框）。
关闭应用程序并重新启动将保留所做的更改，从而确认已对数据库进行了更改。
答案 1 :(得分：0)
在@MiKe的代码之上，我刚刚在onClickListener内的RecyclerAdapter中进行了一些更改以保存复选框状态，并在dataModel类中将 isChecked作为布尔值添加了。现在它可以正常工作了。
holder.chkbox.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Values = new ContentValues();
Values.put(DatabaseContractor.EmployeeDetails.COLUMN_FAVORITE,holder.chkbox.isChecked());
try{ db.update(DatabaseContractor.EmployeeDetails.TABLE_NAME,
Values,
DatabaseContractor.EmployeeDetails._ID + "=?",
new String[]{String.valueOf(dotamodeldataArraylist.get(position).getId())});
} catch (SQLException e){
Toast.makeText(context,"Error"+position,Toast.LENGTH_LONG).show();
}
}
});
再次感谢麦克，您的指导方针很棒。现在，我可以将复选框状态直接保存在sqlite数据库中。
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