怎么在非activity使用数据库
private SQLiteDatabase db=dbHeler.getReadableDatabase();这句报了下面这些错误
Unable to start activity ComponentInfo{com.example.qw.weathery/com.example.qw.weathery.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
@键盘舞者113 ,application的实例怎么给额。不懂额。
public class MyApplication extends Application{
private static Context mContext; @Override
public void onCreate() {
super.onCreate();
mContext = getApplicationContext();
} public static Context getInstance() {
return mContext;
}
}
你还是把Android基础教程过一遍吧,基础没打好,到处有问题