NullPointerException 从 Firebase 数据库中检索数据

Question

我正在尝试从 Firebase 数据库中检索 9 个布尔变量和一个 int 变量，但是每次我运行我的应用程序时，它都会给我一个空指针异常它来自一个 Android 应用程序，我设置了一个模型页面，我设置了 getter 和 setter 方法，但它一直在检索空指针 exeption 这是模型public class ButtonInformation {    private boolean Button1=false;    private boolean Button2=false;    private boolean Button3=false;    private boolean Button4=false;    private boolean Button5=false;    private boolean Button6=false;    private boolean Button7=false;    private boolean Button8=false;    private boolean Button9=false;    private int ApeOmaggio=0;    public ButtonInformation(){    }    public ButtonInformation(boolean button1, boolean button2, boolean button3, boolean button4, boolean button5, boolean button6, boolean button7, boolean button8, boolean button9, int apeOmaggio) {        Button1 = button1;        Button2 = button2;        Button3 = button3;        Button4 = button4;        Button5 = button5;        Button6 = button6;        Button7 = button7;        Button8 = button8;        Button9 = button9;        ApeOmaggio = apeOmaggio;    }    public boolean getButton1(){        return Button1;    }    public void setButton1(boolean Button1){        this.Button1 = Button1;    }    public boolean getButton2(){        return Button2;    }    public void setButton2(boolean Button2){        this.Button2 = Button2;    }    public boolean getButton3(){        return Button3;    }    public void setButton3(boolean Button3){        this.Button3 = Button3;    }    public boolean getButton4(){        return Button4;    }    public void setButton4(boolean Button4){        this.Button4 = Button4;    }    public boolean getButton5(){        return Button5;    }    public void setButton5(boolean Button5){        this.Button5 = Button5;    }    public boolean getButton6(){        return Button6;    }    public void setButton6(boolean Button6){        this.Button6 = Button6;    }    public boolean getButton7(){        return Button7;    }

Answer 1

您可以直接将您的模型类与 Firebase 响应数据进行映射。您不必手动设置模型类中的每个数据。

如果您的数据将从 Firebase 中成功检索，则此代码将起作用，请尝试以下代码。

@Override

    protected void onCreate(@Nullable Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_clienti);

        Utente=findViewById(R.id.tvUtente);

        ApeOmaggio = findViewById(R.id.tvOmaggio);

        bInfo= new ButtonInformation();

        img1=findViewById(R.id.img1);

        img2=findViewById(R.id.img2);

        img3=findViewById(R.id.img3);

        img4=findViewById(R.id.img4);

        img5=findViewById(R.id.img5);

        img6=findViewById(R.id.img6);

        img7=findViewById(R.id.img7);

        img8=findViewById(R.id.img8);

        img9=findViewById(R.id.img9);

        mAuth=FirebaseAuth.getInstance();

        mFirebaseDatabase = FirebaseDatabase.getInstance();

        user = mAuth.getCurrentUser();

        utenteLog = user.getDisplayName();

        mail = user.getEmail();

        mailNoSpace=mail.replaceAll("\\.","");

        Utente.setText(utenteLog);

        myRef=mFirebaseDatabase.getReference(mailNoSpace);

        myRef.addValueEventListener(new ValueEventListener()

        {

            @Override

            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

            ButtonInformation buttonInformation = dataSnapshot.getValue(ButtonInformation.class);

                showData(buttonInformation);

            }

            @Override

            public void onCancelled(@NonNull DatabaseError databaseError) {

            }

        });

    }

    private void showData(ButtonInformation buttonInformation) {

        

            if (buttonInformation.getButton1()==true){

                img1.setImageResource(R.drawable.berry_icon);

            }else{

                img1.setImageResource(R.drawable.radio_button);

            }

            if (buttonInformation.getButton2()==true){

                img2.setImageResource(R.drawable.berry_icon);

            }else{

                img2.setImageResource(R.drawable.radio_button);

            }

            if (buttonInformation.getButton3()==true){

                img3.setImageResource(R.drawable.berry_icon);

            }else{

                img3.setImageResource(R.drawable.radio_button);

            }

            if (buttonInformation.getButton4()==true){

                img4.setImageResource(R.drawable.berry_icon);

            }else{

                img4.setImageResource(R.drawable.radio_button);

            }

            if (buttonInformation.getButton5()==true){

                img5.setImageResource(R.drawable.berry_icon);

            }else{

                img5.setImageResource(R.drawable.radio_button);

            }

            if (buttonInformation.getButton6()==true){

                img6.setImageResource(R.drawable.berry_icon);

            }else{

                img6.setImageResource(R.drawable.radio_button);

            }

            if (buttonInformation.getButton7()==true){

                img7.setImageResource(R.drawable.berry_icon);

            }else{

                img7.setImageResource(R.drawable.radio_button);

            }

            if (buttonInformation.getButton8()==true){

                img8.setImageResource(R.drawable.berry_icon);

            }else{

                img8.setImageResource(R.drawable.radio_button);

            }

            if (buttonInformation.getButton9()==true){

                img9.setImageResource(R.drawable.berry_icon);

            }else{

                img9.setImageResource(R.drawable.radio_button);

            }

            ApeOmaggio.setText(Integer.toString(bInfo.getApeOmaggio()));

    }

Answer 2

在访问 firebase 之前使用 if not null 条件。或者，如果您已将子属性更改为您的 firebase 项目，请检查树。