AS将SQLite中数据使用ViewHolder显示在ListView中出现数据重复问题
0
[已解决问题]
解决于 2020-04-10 17:00
public class DataStoreArrayAdapter extends ArrayAdapter<User> {
private ArrayList<User> users;
private Context context;
public DataStoreArrayAdapter(@NonNull Context context, int resource, @NonNull ArrayList<User> users) {
super(context, resource, users);
this.context = context;
this.users = users;
}
@Override
public int getCount() {
return users.size();
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
User user = users.get(position);
ViewHolder viewHolder;
String number = user.getNumber(), name = user.getName(), password = user.getPassword();
if(convertView == null){
convertView = LayoutInflater.from(this.context).inflate(R.layout.user_page, null);
viewHolder= new ViewHolder();
viewHolder.textView = convertView.findViewById(R.id.tv_show);
convertView.setTag(viewHolder);
} else{
viewHolder = (ViewHolder)convertView.getTag();
}
viewHolder.textView.setText("编号:" + number + " 用户名:" + name + " 密码:" + password);
return convertView;
}
private class ViewHolder{
private TextView textView;
}
}
public class DataStoreActivity extends AppCompatActivity implements View.OnClickListener{
private Button btnAdd, btnUpdate, btnDelete, btnDeleteAll, btnRefresh;
private EditText edTName, edTPassword, edTNumber;
private ListView listView;
private DataStoreDatabaseHelper helper;
private User user = new User();
private ArrayList<User> users = new ArrayList<>();
private DataStoreArrayAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_data_store);
btnAdd = findViewById(R.id.btn_add);
btnUpdate = findViewById(R.id.btn_update);
btnDelete = findViewById(R.id.btn_delete);
btnDeleteAll = findViewById(R.id.btn_delete_all);
btnRefresh = findViewById(R.id.btn_refresh);
edTName = findViewById(R.id.edt_name);
edTPassword = findViewById(R.id.edt_password);
edTNumber = findViewById(R.id.edt_number);
listView = findViewById(R.id.lv_show);
btnAdd.setOnClickListener(this);
btnUpdate.setOnClickListener(this);
btnDelete.setOnClickListener(this);
btnDeleteAll.setOnClickListener(this);
btnRefresh.setOnClickListener(this);
helper = new DataStoreDatabaseHelper(DataStoreActivity.this, "user.db", null, 1);
}
@Override
public void onClick(View v) {
SQLiteDatabase db = helper.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put("number", edTNumber.getText().toString());
cv.put("name", edTName.getText().toString());
cv.put("password", edTPassword.getText().toString());
switch (v.getId())
{
case R.id.btn_add:
Cursor cursor = db.query("user",new String[]{"number"},"number=?",new String[]{cv.get("number").toString()},null,null,null);
if(cursor.getCount() == 0){
db.insert("user", null, cv);
Toast.makeText(DataStoreActivity.this, "添加成功", Toast.LENGTH_LONG).show();
}else{
Toast.makeText(DataStoreActivity.this, "编号已存在", Toast.LENGTH_LONG).show();
}
cursor.close();
break;
case R.id.btn_update:
db.update("user", cv, "number=?", new String[]{cv.get("number").toString()});
Toast.makeText(DataStoreActivity.this, "修改成功", Toast.LENGTH_LONG).show();
break;
case R.id.btn_delete:
db.delete("user", "number=?", new String[]{cv.get("number").toString()});
Toast.makeText(DataStoreActivity.this, "删除成功", Toast.LENGTH_LONG).show();
break;
case R.id.btn_delete_all:
db.execSQL("delete from user");
Toast.makeText(DataStoreActivity.this, "全部删除", Toast.LENGTH_LONG).show();break;
case R.id.btn_refresh:
users.clear();
cursor = db.query("user",null,null,null,null,null,null);
//cursor = db.rawQuery("select * from user", null);
if(cursor != null && cursor.getCount() >=1){
while(cursor.moveToNext()){
user.setNumber(cursor.getString(1));
user.setName(cursor.getString(2));
user.setPassword(cursor.getString(3));
users.add(user);
}
}
cursor.close();
/*for(cursor.moveToFirst();!cursor.isAfterLast();cursor.moveToNext()){
user.setNumber(cursor.getString(1));
user.setName(cursor.getString(2));
user.setPassword(cursor.getString(3));
users.add(user);
}*/
adapter = new DataStoreArrayAdapter(DataStoreActivity.this, R.layout.user_page, users);
listView.setAdapter(adapter);
Toast.makeText(DataStoreActivity.this,"刷新成功",Toast.LENGTH_LONG).show();
break;
}
db.close();
}
}
第一条应该显示:编号:1用户名:1密码:1，但是这里重复显示了
最佳答案
1
while(cursor.moveToNext()){
user.setNumber(cursor.getString(1));//这里循环设置的同一个对象的值。
user.setName(cursor.getString(2));
user.setPassword(cursor.getString(3));
users.add(user);//同一个对象add了多次。
}
修改一下，在循环内部定义user变量，即每条记录，需要new一个User对象，加到users集合中。
while(cursor.moveToNext()){
User user = new User();//这里定义user对象
user.setNumber(cursor.getString(1));
user.setName(cursor.getString(2));
user.setPassword(cursor.getString(3));
users.add(user);
}
另外删除上面的user定义，定义在类级别没有用，且容易出错，在使用的时候声明为局部变量即可。
public class DataStoreActivity extends AppCompatActivity implements View.OnClickListener{
private Button btnAdd, btnUpdate, btnDelete, btnDeleteAll, btnRefresh;
private EditText edTName, edTPassword, edTNumber;
private ListView listView;
private DataStoreDatabaseHelper helper;
private User user = new User();//删除这一行，不要定义成对象或类级别的变量。
奖励园豆：5
非常感谢！！！
其他回答(1)
0
convertView=layoutInflater.inflate(R.layout.user_page,null);
改成这样看看，没发现其他地方问题
感谢回答！！！
