我正在尝试删除存储在SQLite数据库中的项目，并且正在列表视图中显示。
给我带来麻烦的动作是在OnItemLongClickListener（）中。错误
构造函数DatabaseHandler（new AdapterView.OnItemLongClickListener（）{}）未定义
与此行DatabaseHandler db = new DatabaseHandler(this);
我认为问题出在DatabaseHandler的构造函数上，如何在onItemLongClickListener（）中使用它？
MainActivity
public class MainActivity extends FragmentActivity implements OnClickListener {
ListView listView;
int lastIndex = -1;
ArrayList<Event> lstEvents = new ArrayList<Event>();
// detail view
TextView tvTitle, tvTime, tvDate;
ImageView ivPic;
View vw_master;
boolean _isBack = true;
ImageButton add;
String title;
String date;
String time;
int resId;
static final int PICK_CONTACT_REQUEST = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
// // get detail controls
tvTitle = (TextView) findViewById(R.id.textViewTitle);
tvDate = (TextView) findViewById(R.id.textViewDate);
tvTime = (TextView) findViewById(R.id.textViewTime);
ivPic = (ImageView) findViewById(R.id.imageView1);
add = (ImageButton) findViewById(R.id.add);
add.setOnClickListener(this);
// ///////////////////////////////LISTVIEW////////////////////////////////////////
// Create the adapter to convert the array to views
EventAdapter adapter = new EventAdapter(this, lstEvents);
// attach adapter to a list view
listView = (ListView) findViewById(R.id.listViewFragment);
listView.setAdapter(adapter);
listView.setOnItemLongClickListener(new OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> arg0, View arg1,
int arg2, long arg3) {
// TODO Auto-generated method stub
DatabaseHandler db = new DatabaseHandler(this);
Event event = db.getEvent(arg2);
List<Event> events = db.deleteEvent(event);
return false;
}
});
// ///////////////////////////////LISTVIEW////////////////////////////////////////
// /////////////////////////////DATABASE/////////////////////////////////////////////
DatabaseHandler db = new DatabaseHandler(this);
// /////////////////////////////DATABASE/////////////////////////////////////////////
List<Event> events = db.getAllContacts();
adapter.addAll(events);
adapter.notifyDataSetChanged();
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.add:
Intent intent = new Intent(this, CreateActivity.class);
startActivityForResult(intent, 100);
break;
}
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// /////////////////////////////DATABASE/////////////////////////////////////////////
DatabaseHandler db = new DatabaseHandler(this);
// /////////////////////////////DATABASE/////////////////////////////////////////////
// Create the adapter to convert the array to views
EventAdapter adapter = new EventAdapter(this, lstEvents);
// attach adapter to a list view
listView = (ListView) findViewById(R.id.listViewFragment);
listView.setAdapter(adapter);
if (requestCode == 100) {
if (resultCode == RESULT_OK) {
Bundle b = data.getExtras();
title = b.getString("TITLE");
time = b.getString("TIME");
date = b.getString("DATE");
Bitmap bitmap = b.getParcelable("BITMAP");
/////CONVERTING A BITMAP TO A BYTE[]
byte[] image = null;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);
image = bos.toByteArray();
/////////
// /////////////////////////////DATABASE/////////////////////////////////////////////
/**
* CRUD OPERATIONS
*/
Log.e("Insert: ", "Inserting ..");
db.addEvent(new Event(0, title, time, date, image));
// Reading all contacts
Log.e("Reading: ", "Reading all contacts..");
// List<Event> events = db.getAllContacts();
List<Event> events = db.getAllContacts();
adapter.addAll(events);
adapter.notifyDataSetChanged();
// logging all events
for (Event ev : events) {
String log = "Id: " + ev.get_Id() + " ,Title: "
+ ev.get_title() + " ,Date: " + ev.get_date()
+ " ,RESOURCEID: " + ev.get_image();
// Writing Contacts to log
Log.e("Name: ", log);
}
// /////////////////////////////DATABASE/////////////////////////////////////////////
}
}
}
}
数据库处理器
public class DatabaseHandler extends SQLiteOpenHelper {
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "scheduleManager";
// Contacts table name
private static final String TABLE_EVENTS = "events";
// Contacts Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_TITLE = "title";
private static final String KEY_TIME = "time";
private static final String KEY_DATE = "date";
private static final String KEY_IMAGE = "image";
public DatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
String CREATE_EVENTS_TABLE = "CREATE TABLE " + TABLE_EVENTS + "("
+ KEY_ID + " INTEGER," + KEY_TITLE + " TEXT,"
+ KEY_TIME + " TEXT," + KEY_DATE + " TEXT," + KEY_IMAGE + " BLOB" + ")";
db.execSQL(CREATE_EVENTS_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_EVENTS);
// Create tables again
onCreate(db);
}
/**
* All CRUD(Create, Read, Update, Delete) Operations
*/
//adding an event (NEEDS TO ADD DRAWABLE)
public void addEvent(Event event) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_ID, event.get_Id()); //Event ID
values.put(KEY_TITLE, event.get_title()); // Event Title
values.put(KEY_TIME, event.get_time()); // Event Time
values.put(KEY_DATE, event.get_date()); // Event Date
values.put(KEY_IMAGE, event.get_image()); // Event RESOURCEID
// Inserting Row
db.insert(TABLE_EVENTS, null, values);
db.close(); // Closing database connection
}
// Getting single contact
public Event getEvent(int id) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_EVENTS, new String[] { KEY_ID,
KEY_TITLE, KEY_TIME, KEY_DATE, KEY_IMAGE }, KEY_ID + "=?",
new String[] { String.valueOf(id) }, null, null, null, null);
if (cursor != null)
cursor.moveToFirst();
Event event = new Event(Integer.parseInt(cursor.getString(0)),
cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getBlob(4));
// return contact
return event;
}
// Getting All Contacts
public List<Event> getAllContacts() {
List<Event> eventList = new ArrayList<Event>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_EVENTS;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
Event event = new Event();
event.set_Id(Integer.parseInt(cursor.getString(0)));
event.set_title(cursor.getString(1));
event.set_time(cursor.getString(2));
event.set_date(cursor.getString(3));
event.set_image(cursor.getBlob(4));
eventList.add(event);
} while (cursor.moveToNext());
}
// return contact list
return eventList;
}
// Getting event Count
public int getEventsCount() {
String countQuery = "SELECT * FROM " + TABLE_EVENTS;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(countQuery, null);
cursor.close();
// return count
return cursor.getCount();
}
// Updating single contact
public int updateEvent(Event event) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_TITLE, event.get_title());
values.put(KEY_TIME, event.get_time());
values.put(KEY_DATE, event.get_date());
// updating row
return db.update(TABLE_EVENTS, values, KEY_ID + " = ?",
new String[] { String.valueOf(event.get_Id()) });
}
// Deleting single contact
public void deleteEvent(Event event) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_EVENTS, KEY_ID + " = ?",
new String[] { String.valueOf(event.get_Id()) });
db.close();
}
}
答案 0 :(得分：2)
更改您的
DatabaseHandler db = new DatabaseHandler(this);
这一个
DatabaseHandler db = new DatabaseHandler(getActivity());
数据库处理程序需要上下文，在listView.setOnItemLongClickListener内部使用时，this与类this不同，因此在onClickListener中使用时应使用getActivity()。
其他可能的解决方案，而不是getActivity()
MainActivity.this MainActivity.getActivity() 答案 1 :(得分：1)
记住任何onclick或ontouch或onitemlongclick等...监听器的类型有自己的上下文。对我来说，你可以定义一个全局变量上下文上下文，你可以在你的oncreate中初始化它作为context = this（它应该在任何onclick或onitemlongclick等之外......它应该在oncreate的主要内容）现在你可以使用这个上下文在你的整个班级中，在longclick，Toast，构造函数......等等......
在执行任何数据库活动之前，您还没有使用db.open（）打开与db的连接... THX
答案 2 :(得分：1)
更改 - ＆gt; DatabaseHandler db = new DatabaseHandler(this);
到DatabaseHandler db = new DatabaseHandler(MainActivity.this);