尝试调用虚方法 'long android.database.sqlite.SQLite

Question

我正在开发 android 项目并获取空对象引用数据库助手类package com.example.smartpmr;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DataBaseHelper extends SQLiteOpenHelper {    // DATABASE NAME    private static final String DATABASE_NAME = "PMR";    // DATABASE VERSION    private static final int DATABASE_VERSION = 1;    // PATIENT TABLE    private static final String TABLE_PATIENT = "tblPatient";    // DOCTOR TABLE    private static final String TABLE_DOCTOR = "tblDoctor";    // PRESCRIPTION TABLE    private static final String TABLE_PRESCRIPTION = "tblPrescription";    // MEDICINE TABLE    private static final String TABLE_MEDICINES = "tblMedicines";    // PATIENT TABLE COLUMNS    public static final String PATIENT_ID = "PATIENT_ID";    public static final String PATIENT_NAME = "PATIENT_NAME";    public static final String PATIENT_EMAIL = "PATIENT_EMAIL";    public static final String PATIENT_PASSWORD = "PATIENT_PASSWORD";    public static final String PATIENT_AGE = "PATIENT_AGE";    public static final String PATIENT_CONTACT = "PATIENT_CONTACT";    public static final String PATIENT_ADDRESS = "PATIENT_ADDRESS";    // DOCTOR TABLE COLUMS    public static final String DOCTOR_ID = "DOCTOR_ID";    public static final String DOCTOR_NAME = "DOCTOR_NAME";    public static final String DOCTOR_EMAIL = "DOCTOR_EMAIL";    public static final String DOCTOR_PASSWORD = "DOCTOR_PASSWORD";    public static final String DOCTOR_CONTACT = "DOCTOR_CONTACT";

Answer 1

您没有db在方法中初始化insertPrescription()并且saveMedicine()（就像您在其他方法中正确执行的那样）：

db = this.getWritableDatabase();

所以db当你使用它时它是空的。