空指針異常插入

Question

package com.omkarsoft.ImagePortofolio; 

import java.util.ArrayList; 

import com.omkarsoft.ImagePortofolio.dataBaseHelper; 

import android.content.ContentValues; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 

public class sqlQueries { 
    dataBaseHelper database; 
    SQLiteDatabase db ; 
    UrlList urllist ; 

    public sqlQueries(dataBaseHelper dbh , SQLiteDatabase db ) 
    { 
     database = dbh; 
     this.db = db; 
    } 

     public sqlQueries() { 
      System.out.println("no are sqlqueries constructor"); 
    } 

    public void insertIntoCompanyTable(String companyname ) { 

       db = database.getWritableDatabase(); // this works fine here 
      ContentValues values = new ContentValues(); 
      values.put(dataBaseHelper.COMPANY_NAME, companyname); 
      System.out.println(values); 
      db.insert(dataBaseHelper.COMPANY_LIST, null, values); 
      } 

    public int getCompanyID(String companyName) 
    { 
     int id = 0 ; 
     Cursor c = null; 

      try { 
      db = database.getReadableDatabase(); // this works fine here 
       String query = "SELECT company_id FROM company_list WHERE company_name = '"+ companyName +"'"; 
       c = db.rawQuery(query,null); 
      } catch (Exception e) { 
       System.out.println("In getCompanyID : " +e); 
      } 

     if (c != null) { 
      if (c.moveToFirst()) { 
       id = c.getInt(c.getColumnIndex("company_id")); 
      } 
     } 
     return id; 
    } 

    public int getCompanies(String comp) { 
     int id = 0; 
     Cursor c = null; 
     ArrayList<String> names = new ArrayList<String>(); 

     try { 
      db = database.getReadableDatabase(); // this works fine here 
      String query = "SELECT * FROM company_list "; 
      c = db.rawQuery(query, null); 
     } catch (Exception e) { 
      System.out.println(e); 
     } 

      if (c != null) { 

       if (c.getCount() == 0) 
        id = 1; 
       else { 
        if (c.moveToFirst()) { 

         do { 
          String name = c.getString(c.getColumnIndex("company_name")); 
          names.add(name); 
         } while (c.moveToNext()); 
        } 

        if(names.contains(comp)) 
         id = 0; 
         else 
         id = 1 ; 
       } 
      } 

     return id; 
    } 

     public void insertIntoImageTable(int companyid , String productname , String productdesc , byte[] bmp) 
     { 
      try 
      { 
         db = database.getWritableDatabase(); // blows here i get a NPE 
       ContentValues values = new ContentValues(); 
       values.put(dataBaseHelper.COMPANY_ID, companyid);   
       values.put(dataBaseHelper.PRODUCT_NAME, productname); 
       values.put(dataBaseHelper.PRODUCT_DESCRIPTION, productdesc); 
       values.put(dataBaseHelper.PRODUCT_IMAGE, bmp); 
       System.out.println(values); 
       db.insertOrThrow(dataBaseHelper.IMAGE_DATA, null, values); 
       System.out.println(values); 
      } 
      catch(Exception e) 
      { 
       e.printStackTrace(); 
      } 
     } 
} 

Answer 1

剛剛嘗試logcat的各項參數，放在db.insert與String.valueOf();然後你會看到它的參數是null。

Answer 2

您需要先打開數據庫才能寫入第一個數據，如

SQLiteDatabase db = tdHelper.getWritableDatabase(); 

和tdHelper被的

private static class TweetDBOpenHelper extends SQLiteOpenHelper