我正在制作一个FragmentActivity，它使用viewPager显示三个片段和两个来自SQLite数据库的访问数据。
我关注的片段是ContactList模块，它只显示数据库myDatabase3中表mainTable的两个字段。
现在，我通过长按和项目时出现的AlertDialog添加了编辑和删除功能。问题出在哪里，是删除部分。我之前遇到的问题是，一旦我从数据库中删除了一条记录，ListView就没有更新。我尝试了以下方法，但它没有用。
dataAdapter.notifyDataSetChanged();
listView.invalidateViews();
所以我决定通过另一个确认删除操作的AlertDialog以及当用户点击是时删除记录并重新启动当前的FragmentActivity来解决方法，从而刷新列表（当然我必须更改onBackPressed方法） FragmentActivity.java用于启动主要活动，但也是如此。一切顺利，但只是第一次。第二次在调试模式下启动应用程序时，ListView会在上一次会话结束时打开数据集，然后当我尝试删除记录时，记录不会从列表中消失！当然没有异常，并且该行从数据库中删除，但它会弄乱索引，因为我可以从ContactAdd.java模块添加新记录，它们也会出现在列表中，但是由于存在未删除的行索引都搞砸了，导致运行时异常。我尝试了4个不同的数据库名称，每次，我第一次使用数据库时一切正常，但在后续发布时，问题再次发生。 这是相关的代码：
ContactList.java
public class ContactList extends Fragment{
private SimpleCursorAdapter dataAdapter;
private ContactsAdapter dbHelper;
private ListView listView;
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ViewGroup rootView = (ViewGroup) inflater.inflate(
R.layout.fragment_item_list, container, false);
dbHelper = new ContactsAdapter(this.getActivity());
dbHelper.open();
Cursor cursor = dbHelper.getAllFriends();
String[] columns = new String[] {
ContactsAdapter.KEY_NAME, ContactsAdapter.KEY_Phone
};
int[] to = new int[] {
R.id.name, R.id.phonenumber
};
dataAdapter = new SimpleCursorAdapter(
this.getActivity(), R.layout.contact_row,
cursor,
columns,
to,
0);
listView = (ListView) rootView.findViewById(R.id.list);
listView.setAdapter(dataAdapter);
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Pick an action");
builder.setItems(new String[]{"Edit", "Delete", "Activate Call Forwarding"}, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (which == 0) {
Intent i = new Intent(getActivity(), ContactEdit.class);
i.putExtra("RowID", position);
startActivity(i);
} else if (which == 1) {
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(getActivity());
alertDialogBuilder.setMessage("Are you sure you want to delete the record?");
alertDialogBuilder.setPositiveButton("yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface arg0, int arg1) {
dbHelper.removeFriend(position);
dataAdapter.notifyDataSetChanged();
listView.invalidateViews();
/*Intent i = new Intent(getActivity(), FirstSplashScreen.class);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(i);*/
}
});
alertDialogBuilder.setNegativeButton("No", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(getActivity(), "You clicked no button", Toast.LENGTH_LONG).show();
}
});
AlertDialog alertDialog = alertDialogBuilder.create();
alertDialog.show();
}
}
});
AlertDialog alertDialog = builder.create();
alertDialog.show();
return true;
}
});
return rootView;
}
}
ContactsAdapter.java
public class ContactsAdapter {
private static final String DATABASE_NAME ="myDatabase4.db";
private static final String DATABASE_TABLE ="mainTable1";
private static final int DATABASE_VERSION = 1;
public static final String KEY_ID="_id";
public static final String KEY_NAME="name";
public static final int NAME_COLUMN = 1;
public static final String KEY_Phone="mobile";
public static final int Mobile_COLUMN = 2;
public static final String KEY_Home="home";
public static final int Home_COLUMN = 3;
public static final String KEY_Address="address";
public static final int Address_COLUMN = 4;
private SQLiteDatabase db;
private final Context context;
private MyDatabaseHelper dbHelper;
public ContactsAdapter(Context _context){
context = _context;
dbHelper = new MyDatabaseHelper(context, DATABASE_NAME, null,DATABASE_VERSION);
}
public ContactsAdapter open() throws SQLException {
try {
db = dbHelper.getWritableDatabase();
}
catch(SQLException ex){
db=dbHelper.getReadableDatabase();
}
return this;
}
public void close() {
db.close();
}
public void addFriend(String name, String address, String mobile, String home)
{
ContentValues values=new ContentValues(4);
values.put("name", name);
values.put("address", address);
values.put("mobile", mobile);
values.put("home", home);
db.insert(DATABASE_TABLE, null, values);
}
public Cursor getFriend(int id) throws SQLException
{id+=1;
Cursor res = db.query(true, DATABASE_TABLE,
new String[] {KEY_ID, KEY_NAME, KEY_Address,KEY_Phone,KEY_Home},
KEY_ID + "=" + id, null, null, null,
null, null);
if ((res.getCount() == 0) || !res.moveToFirst()) {
throw new SQLException("No item found for row: " +
id);
}
return res;
}
public Cursor getAllFriends() {
Cursor res = db.query(DATABASE_TABLE, new String[] {KEY_ID, KEY_NAME, KEY_Address,KEY_Phone,KEY_Home}, null, null, null, null, null);
if(res!=null){
res.moveToFirst();
}
return res;
}
public boolean removeFriend(long _rowIndex) {
_rowIndex+=1;
return db.delete(DATABASE_TABLE, KEY_ID + "=" + _rowIndex, null) > 0;
}
}
MyDatabaseHelper
public class MyDatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_TABLE ="mainTable1";
public static final String KEY_ID="_id";
public static final String KEY_NAME="name";
public static final int NAME_COLUMN = 1;
public static final String KEY_Phone="mobile";
public static final int Mobile_COLUMN = 2;
public static final String KEY_Home="home";
public static final int Home_COLUMN = 3;
public static final String KEY_Address="address";
public static final int Address_COLUMN = 4;
private static final String DATABASE_CREATE = "create table " +
DATABASE_TABLE + " (" + KEY_ID +" integer primary key autoincrement, " +KEY_NAME + " text not null,"+KEY_Address+" text ,"+KEY_Phone+" text not null,"+KEY_Home+" text);";
public MyDatabaseHelper(Context context, String name,
SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase database) {
database.execSQL(DATABASE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+DATABASE_TABLE+";");
onCreate(db);
}
}
请在这里帮忙。
答案 0 :(得分：0)
我认为问题是removeFriend方法，因为你正在删除带有（_rowIndex + = 1）行的索引，这可能是不正确的，这就是为什么你得到错误并且列表没有正确地重新加载;您可以使用光标获取KEY_ID并尝试使用KEY_ID删除行：并提出一些建议为了更好地优化代码，您可以使用BaseAdapter和POJO类。