如何将long或double int数据类型转换为字符串inffirebase datasNapshot

Question

我使用使用firebase数据库创建实时测验应用程序，但是当我从数据库中检索整数值时，它会向我显示错误。

com.google.firebase.database.DatabaseException: Failed to convert value of type java.lang.Long to String
    at com.google.android.gms.internal.zzepg.zzb(Unknown Source)
    at com.google.android.gms.internal.zzepg.zza(Unknown Source)
    at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
    at com.ejobbox.ejobbox.SimpleQuiz$6.onDataChange(SimpleQuiz.java:164)
    at com.google.android.gms.internal.zzejp.zza(Unknown Source)
    at com.google.android.gms.internal.zzelk.zza(Unknown Source)
    at com.google.android.gms.internal.zzelq.run(Unknown Source)
    at android.os.Handler.handleCallback(Handler.java:742)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:5523)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:739)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629)

在com.ejobbox.ejobbox.simplequiz $ 6.ondatAchange(simplequiz.java:164(

 DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
        DatabaseReference gOption1=mDatabase.child(mQuestionNumber+"/choice1");
        gOption1.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String Option1=String.valueOf(dataSnapshot.getValue(String.class).toString());
                mButtonChoice1.setText(Option1);
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });

在此应用程序中，我无法定义特定的数据类型，因为数据类型dataType字段值将是字符串或整数要在数据检索后要转换它，所以请让我知道如何执行此操作。

我有使用string.valueof((用于转换数据，但它不起作用，请帮助我如何将数据转换为字符串。

String Option1=String.valueOf(dataSnapshot.getValue(String.class).toString());  

simplequiz.java

package com.ejobbox.ejobbox;
import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
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;
public class SimpleQuiz extends AppCompatActivity {
    private TextView mScoreView;
    private TextView mQuestionView;
    private Button mButtonChoice1;
    private Button mButtonChoice2;
    private Button mButtonChoice3;
    private Button mButtonChoice4;
    private String mAnswer;
    private int mScore = 0;
    private int mQuestionNumber = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.simple_quiz);
        mScoreView = (TextView)findViewById(R.id.score);
        mQuestionView = (TextView)findViewById(R.id.question);
        mButtonChoice1 = (Button)findViewById(R.id.choice1);
        mButtonChoice2 = (Button)findViewById(R.id.choice2);
        mButtonChoice3 = (Button)findViewById(R.id.choice3);
        mButtonChoice4 = (Button)findViewById(R.id.choice4);
        updateQuestion();
        //Start of Button Listener for Button1
        mButtonChoice1.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view){
                //My logic for Button goes in here
                if (mButtonChoice1.getText().equals(mAnswer)){
                    mScore = mScore + 1;
                    updateScore(mScore);
                    updateQuestion();
                    //This line of code is optiona
                    Toast.makeText(SimpleQuiz.this, "correct", Toast.LENGTH_SHORT).show();
                    mButtonChoice1.setBackgroundColor(Color.parseColor("#29b200"));
                }else {
                    mButtonChoice1.setBackgroundColor(Color.parseColor("#c10000"));
                    Toast.makeText(SimpleQuiz.this, "wrong", Toast.LENGTH_SHORT).show();
                    updateQuestion();
                }
            }
        });
        //End of Button Listener for Button1
        //Start of Button Listener for Button2
        mButtonChoice2.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view){
                //My logic for Button goes in here
                if (mButtonChoice2.getText().equals(mAnswer)){
                    mScore = mScore + 1;
                    updateScore(mScore);
                    updateQuestion();
                    //This line of code is optiona
                    mButtonChoice2.setBackgroundColor(Color.parseColor("#29b200"));
                    Toast.makeText(SimpleQuiz.this, "correct", Toast.LENGTH_SHORT).show();
                }else {
                    mButtonChoice2.setBackgroundColor(Color.parseColor("#c10000"));
                    Toast.makeText(SimpleQuiz.this, "wrong", Toast.LENGTH_SHORT).show();
                    updateQuestion();
                }
            }
        });
        //End of Button Listener for Button2
        //Start of Button Listener for Button3
        mButtonChoice3.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view){
                //My logic for Button goes in here
                if (mButtonChoice3.getText().equals(mAnswer)){
                    mScore = mScore + 1;
                    updateScore(mScore);
                    updateQuestion();
                    //This line of code is optiona
                    mButtonChoice3.setBackgroundColor(Color.parseColor("#29b200"));
                    Toast.makeText(SimpleQuiz.this, "correct", Toast.LENGTH_SHORT).show();
                }else {
                    mButtonChoice3.setBackgroundColor(Color.parseColor("#c10000"));
                    Toast.makeText(SimpleQuiz.this, "wrong", Toast.LENGTH_SHORT).show();
                    updateQuestion();
                }
            }
        });
        //End of Button Listener for Button3
        mButtonChoice4.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view){
                //My logic for Button goes in here
                if (mButtonChoice4.getText().equals(mAnswer)){
                    mScore = mScore + 1;
                    updateScore(mScore);
                    updateQuestion();
                    //This line of code is optiona
                    mButtonChoice4.setBackgroundColor(Color.parseColor("#29b200"));
                    Toast.makeText(SimpleQuiz.this, "correct", Toast.LENGTH_SHORT).show();
                }else {
                    mButtonChoice1.setBackgroundColor(Color.parseColor("#c10000"));
                    Toast.makeText(SimpleQuiz.this, "wrong", Toast.LENGTH_SHORT).show();
                    updateQuestion();
                }
            }
        });
    }
    private void updateQuestion(){
        DatabaseReference mQuestion1 = FirebaseDatabase.getInstance().getReference();
        DatabaseReference gQuestion1=mQuestion1.child(mQuestionNumber+"/question");
        gQuestion1.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String question1=String.valueOf(dataSnapshot.getValue(String.class).toString());
                mQuestionView.setText(question1);
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });
        DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
        DatabaseReference gOption1=mDatabase.child(mQuestionNumber+"/choice1");
        gOption1.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String Option1=String.valueOf(dataSnapshot.getValue(String.class).toString());
                mButtonChoice1.setText(Option1);
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });

        DatabaseReference gOption2=mDatabase.child(mQuestionNumber+"/choice2");
        gOption2.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String Option2=String.valueOf(dataSnapshot.getValue(String.class).toString());
                mButtonChoice2.setText(Option2);
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });

        DatabaseReference gOption3=mDatabase.child(mQuestionNumber+"/choice3");
        gOption3.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String Option3=String.valueOf(dataSnapshot.getValue(String.class).toString());
                mButtonChoice3.setText(Option3);
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });

        DatabaseReference gOption4=mDatabase.child(mQuestionNumber+"/choice4");
        gOption4.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String Option4=String.valueOf(dataSnapshot.getValue(String.class).toString());
                mButtonChoice4.setText(Option4);
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });
        DatabaseReference mQAnswer=mDatabase.child(mQuestionNumber+"/answer");
        mQAnswer.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                mAnswer=String.valueOf(dataSnapshot.getValue(String.class));
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });
        mQuestionNumber++;
    }

    private void updateScore(int point) {
        mScoreView.setText("" + mScore);
    }
}

数据库结构

{
  "0" : {
    "answer" : "President",
    "choice1" : "PM",
    "choice2" : "AM",
    "choice3" : "President",
    "choice4" : "Vice President",
    "question" : "who is Ramnath kovind ?"
  },
  "1" : {
    "answer" : "Red",
    "choice1" : "Red",
    "choice2" : "Green",
    "choice3" : "Black",
    "choice4" : "Yellow",
    "question" : "Rose color is___?"
  },
  "2" : {
    "answer" : 3,
    "choice1" : 5,
    "choice2" : 4,
    "choice3" : 3,
    "choice4" : 2,
    "question" : "How many color in indian flage ?"
  },
  "UpdateVersion" : 1,
  "apkUrls" : "https://www.ejobbox.com"
}

Answer 1

要解决此问题，请更改此代码：

String Option1=String.valueOf(dataSnapshot.getValue(String.class).toString());

String Option1=String.valueOf(dataSnapshot.getValue(Long.class));

记住，dataSnapshot.getValue(Long.class)返回一个long，它是原始的，您无法在原始类型上调用toString()。

由于choice1拥有不同类型的对象，要解决问题，因此OP决定将所有值作为字符串。因此，而不是使用以下代码行：

ref.child("choice1").setValue(5);

我们应该使用：

use ref.child("choice1").setValue("5");

使用quotation marks，该值将作为字符串存储。最后，为使其正常工作，只需删除测试数据并添加新的数据。

Answer 2

可能是三种方法：

1st：这是一个非常简单的方法，但我不喜欢它。

String option1 = dataSnapshot.getValue() + ""; //it it works

第二：您需要检查每个数据类型的每个数据类型，并相应地转换它们。

if ((dataSnapshot.getValue()) instanceof Long )
{
    String Option1=String.valueOf(dataSnapshot.getValue(Long.class));
}
else if ((dataSnapshot.getValue()) instanceof Double )
{
    String Option1=String.valueOf(dataSnapshot.getValue(Double.class));
}
else if (...)
{
    //and so on
}

3rd：您可以将数据库中的每个数据作为字符串。怎么做？只需在每个数据之后添加任何字母即可。例如，

"choice1" : 5,
"choice2" : 4,
"choice3" : 3,
"choice4" : 2,

将成为

"choice1" : 5L,
"choice2" : 4L,
"choice3" : 3L,
"choice4" : 2L,

以这种方式，每个数据都将为"字符串"类型。然后使用

String Option1 = String.valueOf(dataSnapshot.getValue(String.class));
int indexno = Option1.indexOf("L");
Option1 = Option1.substring(0,indexno); //this line will remove "L" from the string