当我按下微调器时，我看到了我的数据，但是当我尝试 select 时，它没有设置数据？
When i press my spinner i see my data, but when i try to select it, it doesn't set the data?
我正在尝试制作一个从实时 Firebase 数据库获取数据的微调器。我在我的日志语句中很好地提取了数据，当我按下下拉菜单时，我也看到了我的数据。但是当我尝试 select 微调器中的某些内容时，它不会设置数据。此外，当我尝试调用我的 getSelectedItem() 方法时，它给我错误 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
在我写的日志中没有空值，因此我很困惑为什么我会收到这种错误
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import com.example.bankapp.BankAccount;
import com.example.bankapp.R;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
public class TransferOwnAccount extends AppCompatActivity {
private Spinner accountFrom, accountTo;
private EditText transferAmount;
private FirebaseDatabase database;
ArrayList<BankAccount> accounts = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_transfer_own_account);
init();
loadAccounts();
}
public void transferMoney(View view) {
Log.d("grinern", "olool"+accountFrom.getSelectedItem().toString());
}
public void loadAccounts() {
Intent getIntent = getIntent();
String userCPR = getIntent.getStringExtra("CPR");
DatabaseReference dbref = database.getReference("usersbankaccounts/" + userCPR);
dbref.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot data : dataSnapshot.getChildren()) {
DatabaseReference bankaccounts = database.getReference("bankaccounts/" + data.getKey());
Log.d("grinern", data.getKey());
bankaccounts.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
BankAccount bankAccount = dataSnapshot.getValue(BankAccount.class);
accounts.add(bankAccount);
Log.d("grinern", ""+accounts);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
Log.d("grinern", ""+accounts);
ArrayAdapter<BankAccount> adapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_spinner_dropdown_item, accounts);
accountFrom.setAdapter(adapter);
accountTo.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
public void init() {
this.accountFrom = findViewById(R.id.transferFromSpinner);
this.accountTo = findViewById(R.id.transferToSpinner);
this.transferAmount = findViewById(R.id.transferAmount);
this.database = FirebaseDatabase.getInstance();
}
}
它应该 select 无论我在我的下拉微调器中按下什么，并在我的日志中打印它，这是在我的 transferMoney() 方法中调用的
下面是我的布局文件：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/background"
tools:context=".TransferOwnAccount">
<Button
android:id="@+id/transferButton"
style="@style/Widget.AppCompat.Button.ButtonBar.AlertDialog"
android:layout_width="100dp"
android:layout_height="48dp"
android:layout_marginTop="80dp"
android:layout_marginBottom="8dp"
android:background="@drawable/contrast_background"
android:text="@string/transfer"
android:textColor="#FFFFFF"
android:typeface="serif"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.501"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferToSpinner"
app:layout_constraintVertical_bias="0.006"
tools:targetApi="lollipop" />
<TextView
android:id="@+id/transferToTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="56dp"
android:text="@string/transfer_to"
android:textColor="#FFFFFF"
android:textSize="18sp"
app:fontFamily="serif"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferFromSpinner" />
<TextView
android:id="@+id/transferFromTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="44dp"
android:text="@string/transfer_from"
android:textColor="#FFFFFF"
android:textSize="18sp"
app:fontFamily="serif"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferAmount" />
<TextView
android:id="@+id/transferTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="44dp"
android:text="@string/transfer_money"
android:textColor="#F9FAF9"
android:textSize="24sp"
app:fontFamily="serif"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<EditText
android:id="@+id/transferAmount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="99dp"
android:autofillHints=""
android:ems="10"
android:hint="@string/choose_amount"
android:inputType="textPersonName"
android:text="@string/choose_amount"
android:textColor="#FFFFFF"
android:typeface="serif"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferTitle"
tools:targetApi="o" />
<Spinner
android:id="@+id/transferFromSpinner"
android:layout_width="288dp"
android:layout_height="32dp"
android:layout_marginTop="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.504"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferFromTitle" />
<Spinner
android:id="@+id/transferToSpinner"
android:layout_width="288dp"
android:layout_height="32dp"
android:layout_marginTop="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferToTitle" />
</android.support.constraint.ConstraintLayout>
下面是来自我的 Firebase 数据库的 JSON。
{
"bankaccounts" : {
"126" : {
"accNumber" : "126",
"balance" : 0,
"title" : "Default"
},
"127" : {
"accNumber" : "127",
"balance" : 0,
"title" : "Budget"
},
"128" : {
"accNumber" : "128",
"balance" : 0,
"title" : "Pension"
}
},
"nextNumber" : "128",
"users" : {
"1111111111" : {
"address" : "qwe",
"cpr" : "1111111111",
"email" : "qwe",
"firstname" : "qwe",
"lastname" : "qwe",
"password" : "111111",
"phonenumber" : "793"
}
},
"usersbankaccounts" : {
"1111111111" : {
"126" : "Default Account",
"127" : "Budget Account",
"128" : "Pension Account"
}
}
}
您需要将您的 bankaccounts arraylist 更改为静态（以确保即使状态发生变化也是一样的）
然后我将适配器作为一个字段移动并在 init 方法中对其进行了初始化，检查我提供的代码：
package com.example.bankapp;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import com.example.bankapp.BankAccount;
import com.example.bankapp.R;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
public class TransferOwnAccount extends AppCompatActivity {
private Spinner accountFrom, accountTo;
private EditText transferAmount;
private FirebaseDatabase database;
static ArrayList<BankAccount> accounts = new ArrayList<>();
ArrayAdapter<BankAccount> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_transfer_own_account);
init();
loadAccounts();
}
public void transferMoney(View view) {
Log.d("test", "olool" + accountFrom.getSelectedItem().toString());
}
public void loadAccounts() {
Intent getIntent = getIntent();
String userCPR = getIntent.getStringExtra("CPR");
DatabaseReference dbref = database.getReference("usersbankaccounts/" + userCPR);
dbref.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot data : dataSnapshot.getChildren()) {
DatabaseReference bankaccounts = database.getReference("bankaccounts/" + data.getKey());
Log.d("test", data.getKey());
bankaccounts.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
BankAccount bankAccount = dataSnapshot.getValue(BankAccount.class);
accounts.add(bankAccount);
adapter.notifyDataSetChanged();
Log.d("test", "" + accounts);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
Log.d("test", "" + accounts);
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
public void init() {
this.adapter = new ArrayAdapter<>(this, android.R.layout.simple_dropdown_item_1line, accounts);
this.accountFrom = findViewById(R.id.transferFromSpinner);
this.accountTo = findViewById(R.id.transferToSpinner);
this.transferAmount = findViewById(R.id.transferAmount);
this.database = FirebaseDatabase.getInstance();
this.accountFrom.setAdapter(adapter);
this.accountTo.setAdapter(adapter);
}
}
然后您需要确保您的银行账户中有一个 toString() 方法
@Override
public String toString() {
return title + "--- " +accNumber + " " + balance ;
}
这应该可以解决问题:)
我正在尝试制作一个从实时 Firebase 数据库获取数据的微调器。我在我的日志语句中很好地提取了数据，当我按下下拉菜单时，我也看到了我的数据。但是当我尝试 select 微调器中的某些内容时，它不会设置数据。此外，当我尝试调用我的 getSelectedItem() 方法时，它给我错误 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
在我写的日志中没有空值，因此我很困惑为什么我会收到这种错误
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import com.example.bankapp.BankAccount;
import com.example.bankapp.R;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
public class TransferOwnAccount extends AppCompatActivity {
private Spinner accountFrom, accountTo;
private EditText transferAmount;
private FirebaseDatabase database;
ArrayList<BankAccount> accounts = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_transfer_own_account);
init();
loadAccounts();
}
public void transferMoney(View view) {
Log.d("grinern", "olool"+accountFrom.getSelectedItem().toString());
}
public void loadAccounts() {
Intent getIntent = getIntent();
String userCPR = getIntent.getStringExtra("CPR");
DatabaseReference dbref = database.getReference("usersbankaccounts/" + userCPR);
dbref.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot data : dataSnapshot.getChildren()) {
DatabaseReference bankaccounts = database.getReference("bankaccounts/" + data.getKey());
Log.d("grinern", data.getKey());
bankaccounts.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
BankAccount bankAccount = dataSnapshot.getValue(BankAccount.class);
accounts.add(bankAccount);
Log.d("grinern", ""+accounts);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
Log.d("grinern", ""+accounts);
ArrayAdapter<BankAccount> adapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_spinner_dropdown_item, accounts);
accountFrom.setAdapter(adapter);
accountTo.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
public void init() {
this.accountFrom = findViewById(R.id.transferFromSpinner);
this.accountTo = findViewById(R.id.transferToSpinner);
this.transferAmount = findViewById(R.id.transferAmount);
this.database = FirebaseDatabase.getInstance();
}
}
它应该 select 无论我在我的下拉微调器中按下什么，并在我的日志中打印它，这是在我的 transferMoney() 方法中调用的
下面是我的布局文件：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/background"
tools:context=".TransferOwnAccount">
<Button
android:id="@+id/transferButton"
style="@style/Widget.AppCompat.Button.ButtonBar.AlertDialog"
android:layout_width="100dp"
android:layout_height="48dp"
android:layout_marginTop="80dp"
android:layout_marginBottom="8dp"
android:background="@drawable/contrast_background"
android:text="@string/transfer"
android:textColor="#FFFFFF"
android:typeface="serif"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.501"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferToSpinner"
app:layout_constraintVertical_bias="0.006"
tools:targetApi="lollipop" />
<TextView
android:id="@+id/transferToTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="56dp"
android:text="@string/transfer_to"
android:textColor="#FFFFFF"
android:textSize="18sp"
app:fontFamily="serif"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferFromSpinner" />
<TextView
android:id="@+id/transferFromTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="44dp"
android:text="@string/transfer_from"
android:textColor="#FFFFFF"
android:textSize="18sp"
app:fontFamily="serif"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferAmount" />
<TextView
android:id="@+id/transferTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="44dp"
android:text="@string/transfer_money"
android:textColor="#F9FAF9"
android:textSize="24sp"
app:fontFamily="serif"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<EditText
android:id="@+id/transferAmount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="99dp"
android:autofillHints=""
android:ems="10"
android:hint="@string/choose_amount"
android:inputType="textPersonName"
android:text="@string/choose_amount"
android:textColor="#FFFFFF"
android:typeface="serif"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferTitle"
tools:targetApi="o" />
<Spinner
android:id="@+id/transferFromSpinner"
android:layout_width="288dp"
android:layout_height="32dp"
android:layout_marginTop="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.504"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferFromTitle" />
<Spinner
android:id="@+id/transferToSpinner"
android:layout_width="288dp"
android:layout_height="32dp"
android:layout_marginTop="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/transferToTitle" />
</android.support.constraint.ConstraintLayout>
下面是来自我的 Firebase 数据库的 JSON。
{
"bankaccounts" : {
"126" : {
"accNumber" : "126",
"balance" : 0,
"title" : "Default"
},
"127" : {
"accNumber" : "127",
"balance" : 0,
"title" : "Budget"
},
"128" : {
"accNumber" : "128",
"balance" : 0,
"title" : "Pension"
}
},
"nextNumber" : "128",
"users" : {
"1111111111" : {
"address" : "qwe",
"cpr" : "1111111111",
"email" : "qwe",
"firstname" : "qwe",
"lastname" : "qwe",
"password" : "111111",
"phonenumber" : "793"
}
},
"usersbankaccounts" : {
"1111111111" : {
"126" : "Default Account",
"127" : "Budget Account",
"128" : "Pension Account"
}
}
}
您需要将您的 bankaccounts arraylist 更改为静态（以确保即使状态发生变化也是一样的）
然后我将适配器作为一个字段移动并在 init 方法中对其进行了初始化，检查我提供的代码：
package com.example.bankapp;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import com.example.bankapp.BankAccount;
import com.example.bankapp.R;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
public class TransferOwnAccount extends AppCompatActivity {
private Spinner accountFrom, accountTo;
private EditText transferAmount;
private FirebaseDatabase database;
static ArrayList<BankAccount> accounts = new ArrayList<>();
ArrayAdapter<BankAccount> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_transfer_own_account);
init();
loadAccounts();
}
public void transferMoney(View view) {
Log.d("test", "olool" + accountFrom.getSelectedItem().toString());
}
public void loadAccounts() {
Intent getIntent = getIntent();
String userCPR = getIntent.getStringExtra("CPR");
DatabaseReference dbref = database.getReference("usersbankaccounts/" + userCPR);
dbref.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot data : dataSnapshot.getChildren()) {
DatabaseReference bankaccounts = database.getReference("bankaccounts/" + data.getKey());
Log.d("test", data.getKey());
bankaccounts.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
BankAccount bankAccount = dataSnapshot.getValue(BankAccount.class);
accounts.add(bankAccount);
adapter.notifyDataSetChanged();
Log.d("test", "" + accounts);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
Log.d("test", "" + accounts);
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
public void init() {
this.adapter = new ArrayAdapter<>(this, android.R.layout.simple_dropdown_item_1line, accounts);
this.accountFrom = findViewById(R.id.transferFromSpinner);
this.accountTo = findViewById(R.id.transferToSpinner);
this.transferAmount = findViewById(R.id.transferAmount);
this.database = FirebaseDatabase.getInstance();
this.accountFrom.setAdapter(adapter);
this.accountTo.setAdapter(adapter);
}
}
然后您需要确保您的银行账户中有一个 toString() 方法
@Override
public String toString() {
return title + "--- " +accNumber + " " + balance ;
}
这应该可以解决问题:)