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What is a NullPointerException, and how do I fix it?（12个答案）
昨天关门了。
这是一个通过Android Studio使用Firebase的Crud函数的简单示例，我在更新过程中发现了几个障碍，以及更新时出现的错误。
java.lang.NullPointerException:无法为child（）中的参数'pathString'传递null
有简单的解决方案来克服这个问题吗？下面是更新活动的完整代码。

import static android.text.TextUtils.isEmpty;
    import android.annotation.SuppressLint;
    import android.app.DatePickerDialog;
    import android.os.Bundle;
    import android.text.TextUtils;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.RadioButton;
    import android.widget.RadioGroup;
    import android.widget.Spinner;
    import android.widget.Toast;
    import androidx.appcompat.app.AppCompatActivity;
    
    //import com.bumptech.glide.Glide;
    import com.google.android.gms.tasks.OnSuccessListener;
    import com.google.firebase.database.DatabaseReference;
    import com.google.firebase.database.FirebaseDatabase;
    
    import java.text.SimpleDateFormat;
    
    public class UpdateLaundry extends AppCompatActivity {
    //deklarasi variable
    private EditText namaBaru, tempatBaru;
    private Spinner jenisBaru;
    private RadioButton ktgBaru, new_Rb1, new_Rb2, new_Rb3;
    private Button update;
    private DatabaseReference database;
    private RadioGroup rgkategoriBaru;
    private String cekNama, cekTempat, cekJenis, cekKategori;

    @SuppressLint("WrongViewCast")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_updatelaundry);

        namaBaru = findViewById(R.id.new_nama);
        tempatBaru = findViewById(R.id.new_lokasi);
        jenisBaru = findViewById(R.id.newspinner_jenis);
        update = findViewById(R.id.btn_update);
        new_Rb1 = findViewById(R.id.new_rb1);
        new_Rb2 = findViewById(R.id.new_rb2);
        new_Rb3 = findViewById(R.id.new_rb3);
        rgkategoriBaru = findViewById(R.id.new_rg_ktg);

        final String getKategori = getIntent().getExtras().getString("dataKategori");

        if (getKategori.equals("Cuci")) {
            new_Rb1.setChecked(true);
        } else if (getKategori.equals("Setrika")) {
            new_Rb2.setChecked(true);
        } else if (getKategori.equals("Cuci dan Setrika")) {
            new_Rb3.setChecked(true);
        }

        database= FirebaseDatabase.getInstance().getReference();
        getData();

        update.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                int pilihKtgBaru = rgkategoriBaru.getCheckedRadioButtonId();
                ktgBaru = findViewById(pilihKtgBaru);
                cekNama = namaBaru.getText().toString();
                cekTempat = tempatBaru.getText().toString();
                cekJenis = jenisBaru.getSelectedItem().toString();

//mengubah data databse menggunakan data yang baru di inputkan
                if (isEmpty(cekNama) || isEmpty(cekTempat)) {
                    Toast.makeText(UpdateLaundry.this, "Data tidak boleh kosong", Toast.LENGTH_SHORT).show();
                } else {
                                    /*Processing Update Data
                                    Reload setter recomended to get new data from user*/

                    Laundry setLaundry = new Laundry();
                    setLaundry.setNama(namaBaru.getText().toString());
                    setLaundry.setJenis(jenisBaru.getSelectedItem().toString());
                    setLaundry.setTempat(tempatBaru.getText().toString());
                    setLaundry.setKategori(ktgBaru.getText().toString());
                    updateLaundry(setLaundry);

                }
            }
        });
    }

    private boolean isEmpty(String s){
        return TextUtils.isEmpty(s);
    }

    //mengambil data dari database ke form update
    private void getData() {

        final String getNama = getIntent().getExtras().getString("dataNama");
        final String getTempat = getIntent().getExtras().getString("dataTempat");
        final String getKategori = getIntent().getExtras().getString("dataKategori");
        final String getJenis = getIntent().getExtras().getString("dataJenis");

        namaBaru.setText(getNama);
        tempatBaru.setText(getTempat);

    }
    private void updateLaundry(Laundry ldry) {

        String getKey = getIntent().getExtras().getString("getPrimaryKey");
        database.child("Admin")
                .child("Laundry")
                .child(getKey)
                .setValue(ldry)
                .addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        namaBaru.setText("");
                        tempatBaru.setText("");

                        Toast.makeText(UpdateLaundry.this, "Data Berhasil diubah", Toast.LENGTH_SHORT).show();
                        finish();
                    }
                });
    }