android - NullPointerException openOrCreateDatabase Android

Question

我在打开数据库时在我的 EhActivity 类中遇到 NullPointerException

 public class EHActivity extends Activity {
ArrayList<String>ques= new ArrayList<String>();
 ArrayList<String>ans=new ArrayList<String>();
 SQLiteDatabase db2;

  public ArrayList<String> getQues()
  {
   db2=openOrCreateDatabase("interview.db", MODE_PRIVATE, null);
   db2.execSQL("create table eh (qid int primary key,ques varchar,ans char)");
       db2.execSQL("insert into subject values(1,'What is an exception?','A1 '))");
   db2.execSQL("insert into subject values(2,'What is error?','A2 '))");
       Cursor c=db2.rawQuery("select * from eh",null);
   while(c.moveToNext())
   {
    ques.add(c.getString(1));
   }
   return ques;
  }
 }

日志猫 View 是:

03-21 14:06:15.910: E/AndroidRuntime(955): java.lang.NullPointerException 03-21 14:06:15.910: E/AndroidRuntime(955): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203) 03-21 14:06:15.910: E/AndroidRuntime(955): at interview.android.EHActivity.getQues(EHActivity.java:19)

Answer 1

尽量不要发送 null..openOrCreateDatabase 对此有另一种方法..

db2=openOrCreateDatabase("interview.db", MODE_PRIVATE);

或

openDatabase("interview.db", MODE_PRIVATE, SQLiteDatabase.CREATE_IF_NECESSARY)