【发布时间】：2015-12-17 12:42:18
【问题描述】：
我正在尝试构建事件列表器。我正在从一些站点获取事件，然后记录到数据库然后显示。
这是我从 main 激活按钮时调用的 updatedb 类：
public class UpdateDB {
private String TAG = "Chic";
EventRetriever eventRetriever;
private Activity mActivity;
public UpdateDB(Activity activity){
Log.e(TAG,"UpdateDB constructor");
this.mActivity = activity;
eventRetriever = new EventRetriever(mActivity);
eventRetriever.execute();
Log.e(TAG,"UpdateDB constructor async executed");
currentDate = Calendar.getInstance(); //Get the current date
lastUpdateTime=currentDate;//if succesful methodu olması lazım
Log.e(TAG,"DB updated");
}
这是更新数据库的内部：
class EventRetriever extends AsyncTask<Void,Void,List<Event>> {
Event evnt;
private List<Event> evnts;
DBHandler dbhandler ;
public EventRetriever(Activity activity){
super();
Log.e(TAG,"EventRetriever constructor");
mActivity = activity;
}
protected void onPreExecute() {
super.onPreExecute();
Log.e(TAG,"onPreExecute()");
dialog = ProgressDialog.show(mActivity,"LUTFEN BEKLEYINIZ...","ETKINLIKLER VERITABANINA KAYIT ICIN HAZIRLANIYOR...", true);
}
protected List<Event> doInBackground(Void ... params) {
Log.e(TAG,"doinbackground");
//taking each event and then putting into events arraylist
evnts.add(evnt);
Log.e(TAG,"doinbackground sonu");
return evnts;
}//end of doinbackground
@Override
protected void onPostExecute(List<Event> events) {
super.onPostExecute(events);
Log.e(TAG,"onPostExecute()");
if (dialog.isShowing()) {
dialog.dismiss();
}
Log.e(TAG,"ITU db ekleme");
dbhandler = new DBHandler(mContext);
for(Event e:events) {
dbhandler.addEvent(e);
}
Log.e(TAG,"endof onPostExecute()");
}//endof onpostexecute
}//end of asyntask
这是事件类的构造函数和getter setter
public Event(String nme,String loc,String typ,String lnk,String sDate,String eDate,String desc) {
this.description = desc;
this.link = lnk;
this.type = typ;
this.location = loc;
this.startDate = sDate;
this.endDate = eDate;
this.name = nme;
}
这是我的数据库助手类。我在这里进行所有操作
public class DBHandler extends SQLiteOpenHelper {
private String TAG = "Chic";
SQLiteDatabase db;
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 2;
// Database Name
private static final String DATABASE_NAME = "eventsManager";
// events table name
private static final String TABLE_EVENTS = "events";
// EVents Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_NAME = "name";
private static final String KEY_LOCATION = "location";
private static final String KEY_TYPE = "type";
private static final String KEY_START_TIME = "start_time";
private static final String KEY_END_TIME = "end time";
private static final String KEY_DESCRIPTION = "description";
private static final String KEY_LINK = "link";
public DBHandler(Context context) {//, Activity mActivity
super(context, DATABASE_NAME, null, DATABASE_VERSION);
Log.e(TAG,"db handler construct");
}
public void onCreate(SQLiteDatabase db) {
Log.e(TAG,"db handleroncreta");
String CREATE_EVENTS_TABLE = "CREATE TABLE If not exists " + TABLE_EVENTS + "("
+ KEY_ID + " INTEGER PRIMARY KEY autoincrement," + KEY_NAME + " TEXT not null,"
+ KEY_LOCATION + " TEXT not null," + KEY_TYPE + " TEXT not null,"
+ KEY_LINK + " TEXT not null,"
+ KEY_START_TIME + " TEXT not null,"
+ KEY_END_TIME + " TEXT not null,"//bu belki null olabilir
+ KEY_DESCRIPTION + " TEXT not null"//bu da null olabilir
+ ")";
db.execSQL(CREATE_EVENTS_TABLE);
}
public void addEvent(Event e) {
Log.e(TAG,"db handler addevent");
SQLiteDatabase db = this.getWritableDatabase();
//db.execSQL("DROP TABLE IF EXISTS "+TABLE_EVENTS);
ContentValues values = new ContentValues();
alues.put(KEY_NAME, e.getName()); // event Name
values.put(KEY_LOCATION, e.getLocation());
values.put(KEY_TYPE, e.getType());
values.put(KEY_LINK, e.getLink());
values.put(KEY_START_TIME, e.getStartDate()); // Event start
values.put(KEY_END_TIME, e.getEndDate());
values.put(KEY_DESCRIPTION, e.getDescription());
// Inserting Rows
db.insert(TABLE_EVENTS, null, values);
db.close(); // Closing database connection
}
public void open() throws SQLException {
Log.e(TAG,"db handler open");
db = this.getWritableDatabase();
}
}//endof class
我没有使用光标。我使用价值观。
我也有这个方法在事件中：
public void addEvents(List<Event> events) {
Log.e(TAG,"db handler addevents: "+events.get(0).getDescription());
open();
//db.execSQL("DROP TABLE IF EXISTS "+TABLE_EVENTS);
for(Event e:events) {
Log.e(TAG,"ekleniyor: "+e.getName());
ContentValues values = new ContentValues();
values.put(KEY_NAME, e.getName()); // event Name
values.put(KEY_LOCATION, e.getLocation());
values.put(KEY_TYPE, e.getType());
values.put(KEY_LINK, e.getLink());
values.put(KEY_START_TIME, e.getStartDate()); // Event start
values.put(KEY_END_TIME, e.getEndDate());
values.put(KEY_DESCRIPTION, e.getDescription());
// Inserting Rows
db.insert(TABLE_EVENTS, null, values);
}//for sonu
db.close(); // Closing database connection
Log.e(TAG,"db handler addevents sonu");
}*/
我使用它来将事件作为数组发送。现在我一一发送，但错误仍然相同。还有一个问题，哪个好？
我也尝试在 doitbackground 中再次发送错误。
对于我发布的那些代码，错误是：
AndroidRuntime: FATAL EXCEPTION: main
Process: cu PID: 28765
java.lang.NullPointerException
Kat android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
at . .DBHandler.addEvent(DBHandler.java:99)
at . .EventRetriever.onPostExecute(UpdateDB.java:401)
at . .EventRetriever.onPostExecute(UpdateDB.java:73)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5584)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
at dalvik.system.NativeStart.main(Native Method)
从主要，当我这样做时
Event evt =new Event("name","name","name","name","name","name","name");
Event evtt =new Event("name","name","name","name","name","name","name");
List<Event> e = new ArrayList();
e.add(evt); e.add(evtt);
DBHandler d = new DBHandler(this);
d.addEvents(e);
它没有错误地写入数据库。所以它也不能为空。我正在检查值。
【问题讨论】：
标签： android sqlite android-asynctask