适配器未填充RecyclerView

Question

嘿，我有一个当前的应用程序，它从用户那里获取密码信息并将其存储到SQLiteDatabase中。我的问题是，我无法用这些数据填充我的RecyclerView。我可以看到数据库中有条目。

我的适配器的代码。

public class DataAdapter extends RecyclerView.Adapter<DataAdapter.DataHolder> {
protected ArrayList<PasswordResults> passwords;
class DataHolder extends RecyclerView.ViewHolder {
public TextView id_tv;
public TextView name_tv;
public TextView website_tv;
public TextView desc_tv;
// public Button view_btn; (IGNORE)
public TextView username_tv;
public TextView password_tv;
DataHolder(View v) {
super(v);
id_tv = (TextView) v.findViewById(R.id.tv_id);
name_tv = (TextView) v.findViewById(R.id.tv_name);
website_tv = (TextView) v.findViewById(R.id.tv_website);
desc_tv = (TextView) v.findViewById(R.id.tv_desc);
username_tv = (TextView) v.findViewById(R.id.tv_username);
password_tv = (TextView) v.findViewById(R.id.tv_password);
}
}
DataAdapter(ArrayList<PasswordResults> inData){
passwords = inData;
}
@Override
public DataAdapter.DataHolder onCreateViewHolder(ViewGroup parent, int type){
View v = (View) LayoutInflater.from(parent.getContext()).inflate(R.layout.password_rows, parent, false);
DataHolder passwordHolder = new DataHolder(v);
return passwordHolder;
}
@Override
public void onBindViewHolder(DataHolder holder, int position){
PasswordResults passwordResults = passwords.get(position);
// set values to text views.
holder.id_tv.setText(String.valueOf(position+1));
String name = passwordResults.entryName;
holder.name_tv.setText(name);
String website = passwordResults.website;
holder.website_tv.setText(website);
String desc = passwordResults.description;
holder.desc_tv.setText(desc);
String username = passwordResults.username;
holder.username_tv.setText(username);
String password = passwordResults.password;
holder.password_tv.setText(password);
}
@Override
public int getItemCount(){
return passwords.size();
}
}

这是我的数据库类的代码

public class Database extends SQLiteOpenHelper {
// version, database name, and table name.
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_NAME = "DB_Passwords";
protected static final String TABLE_NAME = "passwords";
public ArrayList<PasswordResults> passwords;
// creating names for columns.
public final static String COLUMN_ID = "_id";
public final static String COLUMN_NAME = "entryName";
public final static String COLUMN_WEBSITE = "website";
public final static String COLUMN_USERNAME = "username";
public final static String COLUMN_PASSWORD = "password";
public final static String COLUMN_DESC = "description";
// creating table string.
public static final String CREATE_TABLE = "create table if not exists "+TABLE_NAME+" ("
+ COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "
+ COLUMN_NAME +" VARCHAR(100), "
+ COLUMN_WEBSITE +" VARCHAR(100), "
+ COLUMN_USERNAME +" VARCHAR(100), "
+ COLUMN_PASSWORD +" VARCHAR(100), "
+ COLUMN_DESC +" TEXT)";
// db helper
public Database(Context c){
super(c, DATABASE_NAME, null, DATABASE_VERSION);
}
// create table when the app is loaded.
@Override
public void onCreate(SQLiteDatabase db){
db.execSQL(CREATE_TABLE);
}
// handle upgrades
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// drop and create new.
db.execSQL("DROP TABLE "+TABLE_NAME);
onCreate(db);
}
public void addPassword(String n, String w, String u, String p, String d) {
// get database.
SQLiteDatabase db = getWritableDatabase();
try {
// add scores.
ContentValues values = new ContentValues();
values.put(COLUMN_NAME, n);
values.put(COLUMN_WEBSITE, w);
values.put(COLUMN_USERNAME, u);
values.put(COLUMN_PASSWORD, p);
values.put(COLUMN_DESC, d);
// insert will handle null values. closing.
db.insert(TABLE_NAME, "", values);
db.close();
} catch (Exception e) {
e.getLocalizedMessage();
}
}
public void removePassword(String id){
// get database.
SQLiteDatabase db = getWritableDatabase();
// delete database then close or print error.
try {
db.delete(TABLE_NAME, "id="+id, null);
db.close();
} catch(Exception e) {
e.getLocalizedMessage();
}
}
public void updatePassword(String id, String n, String w, String u, String p, String d) {
// get database.
SQLiteDatabase db = getWritableDatabase();
//update database then close or print error.
try {
ContentValues values = new ContentValues();
values.put(COLUMN_ID, id);
values.put(COLUMN_NAME, n);
values.put(COLUMN_WEBSITE, w);
values.put(COLUMN_USERNAME, u);
values.put(COLUMN_PASSWORD, p);
values.put(COLUMN_DESC, d);
db.update(TABLE_NAME, values, "_id="+id, null);
db.close();
} catch (Exception e) {
e.getLocalizedMessage();
}
}
public ArrayList<PasswordResults> getPasswords() {
// get database, password array, and select statement.
passwords = new ArrayList<>();
String refQuery = "Select "+COLUMN_NAME+", "+COLUMN_WEBSITE+", "+COLUMN_USERNAME+", "+COLUMN_PASSWORD+", "+COLUMN_DESC+" FROM "+TABLE_NAME;
SQLiteDatabase db = getWritableDatabase();
// link to database
Cursor cursor = db.rawQuery(refQuery, null);
if(cursor.moveToFirst()) {
do {
PasswordResults passwordResults = new PasswordResults();
passwordResults.entryName = cursor.getString(0);
passwordResults.website = cursor.getString(1);
passwordResults.username = cursor.getString(2);
passwordResults.password = cursor.getString(3);
passwordResults.description = cursor.getString(4);
} while(cursor.moveToNext());
}
db.close();
return passwords;
}
public ArrayList<PasswordResults> getSelectedPassword(String id) {
// get database, password array, and select statement.
passwords = new ArrayList<>();
String refQuery = "Select * from "+TABLE_NAME+" WHERE "+COLUMN_ID+" = "+id;
SQLiteDatabase db = getWritableDatabase();
// link to database
Cursor cursor = db.rawQuery(refQuery, null);
if(cursor.moveToFirst()) {
do {
PasswordResults passwordResults = new PasswordResults();
passwordResults.id = cursor.getInt(0);
passwordResults.entryName = cursor.getString(1);
passwordResults.website = cursor.getString(2);
passwordResults.username = cursor.getString(3);
passwordResults.password = cursor.getString(4);
passwordResults.description = cursor.getString(5);
} while(cursor.moveToNext());
}
db.close();
return passwords;
}
}

这是我的班级持有的结果

public class PasswordResults {
public int id;
public String entryName;
public String website;
public String username;
public String password;
public String description;
}

Answer 1

在getPasswords((和getSelectedPasswords

passwords = new ArrayList<>(); 

但是您返回密码时从未向其中添加passwordResults。在getSelectedPasswords((中，下面的代码：

if(cursor.moveToFirst()) {
do {
PasswordResults passwordResults = new PasswordResults();
passwordResults.id = cursor.getInt(0);
passwordResults.entryName = cursor.getString(1);
passwordResults.website = cursor.getString(2);
passwordResults.username = cursor.getString(3);
passwordResults.password = cursor.getString(4);
passwordResults.description = cursor.getString(5);
} while(cursor.moveToNext());
}
db.close();
return passwords;

应更改为：

if(cursor.moveToFirst()) {
do {
PasswordResults passwordResults = new PasswordResults();
passwordResults.id = cursor.getInt(0);
passwordResults.entryName = cursor.getString(1);
passwordResults.website = cursor.getString(2);
passwordResults.username = cursor.getString(3);
passwordResults.password = cursor.getString(4);
passwordResults.description = cursor.getString(5);
passwords.add(passwordResults); //This line is missing!
} while(cursor.moveToNext());
}
db.close();
return passwords;

同样必须添加到getPasswords((方法中。

Answer 2

我没有足够的声誉发表评论，但这可能会有所帮助。一旦你填写了你的ArrayList，你打电话了吗？

adapter.notifyDataSetChanged();

如果没有，您必须这样做。如果是，请确保您的回收器视图中肯定没有填充数据，并且您的布局xml文件没有问题。因为通常情况下，如果您的recyclerView布局文件设计不正确，即使recyclerView及其适配器在java代码中做得很好，您也无法看到它。