Develop Reference

Android: Quickest way to filter lists as user types a query

Good day all, I have a list of Objects (Let's call them ContactObject for simplicity). This object contains 2 Strings, Name and Email.
This list of objects will number somewhere around 2000 in size. The goal here is to filter that list as the user types letters and display it on the screen (IE in a recyclerview) if they match. Ideally, It would filter where the objects with a not-null name would be above an object with a null name.
As of right now, the steps I am taking are:
1) Create 2 lists to start and get the String the user is typing to compare to
List<ContactObject> nameContactList = new ArrayList<>();
List<ContactObject> emailContactList = new ArrayList<>();
String compareTo; //Passed in as an argument
2) Loop though the master list of ContactObjects via an enhanced for loop
3) Get the name and email Strings
String name = contactObject.getName();
String email = contactObject.getEmail();
4) If the name matches, add it to the list. Intentionally skip this loop if the name is not null and it gets added to the list to prevent doubling.
if(name != null){
if(name.toLowerCase().contains(compareTo)){
nameContactList.add(contactObject);
continue;
}
}
if(email != null){
if(email.toLowerCase().contains(compareTo)){
emailContactList.add(contactObject);
}
}
5) Outside of the for loop now as the object lists are build, use a comparator to sort the ones with names (I do not care about sorting the ones with emails at the moment)
Collections.sort(nameContactList, new Comparator<ContactObject>() {
public int compare(ContactObject v1, ContactObject v2) {
String fName1, fName2;
try {
fName1 = v1.getName();
fName2 = v2.getName();
return fName1.compareTo(fName2);
} catch (Exception e) {
return -1;
}
}
});
6) Loop through the built lists (one sorted) and then add them to the master list that will be used to set into the adapter for the recyclerview:
for(ContactObject contactObject: nameContactList){
masterList.add(contactObject);
}
for(ContactObject contactObject: emailContactList){
masterList.add(contactObject);
}
7) And then we are all done.
Herein lies the problem, this code works just fine, but it is quite slow. When I am filtering through the list of 2000 in size, it can take 1-3 seconds each time the user types a letter.
My goal here is to emulate apps that allow you to search the contact list of the phone, but seem to always to it quicker than I am able to replicate.
Does anyone have any recommendations as to how I can speed this process up at all?
Is there some hidden Android secret I don't know of that only allows you to query a small section of the contacts in quicker succession?

How to check if an Array contains specific term - Android

I currently have a statement which reads
if(Arrays.asList(results).contains("Word"));
and I want to add at least several more terms to the .contains parameter however I am under the impression that it is bad programming practice to have a large number of terms on one line..
My question is, is there a more suitable way to store all the values I want to have in the .contains parameters?
Thanks

You can use intersection of two lists:
String[] terms = {"Word", "Foo", "Bar"};
List<String> resultList = Arrays.asList(results);
resultList.retainAll(Arrays.asList(terms))
if(resultList.size() > 0)
{
/// Do something
}
To improve performance though, it's better to use the intersection of two HashSets:
String[] terms = {"Word", "Foo", "Bar"};
Set<String> termSet = new HashSet<String>(Arrays.asList(terms));
Set<String> resultsSet = new HashSet<String>(Arrays.asList(results));
resultsSet.retainAll(termSet);
if(resultsSet.size() > 0)
{
/// Do something
}
As a side note, the above code checks whether ANY of the terms appear in results. To check that ALL the terms appear in results, you simply make sure the intersection is the same size as your term list:
resultsSet.retainAll(termSet);
if(resultSet.size() == termSet.size())

You can utilize Android's java.util.Collections
class to help you with this. In particular, disjoint will be useful:
Returns whether the specified collections have no elements in common.
Here's a code sample that should get you started.
In your Activity or wherever you are checking to see if your results contain a word that you are looking for:
String[] results = {"dog", "cat"};
String[] wordsWeAreLookingFor = {"foo", "dog"};
boolean foundWordInResults = this.checkIfArrayContainsAnyStringsInAnotherArray(results, wordsWeAreLookingFor);
Log.d("MyActivity", "foundWordInResults:" + foundWordInResults);
Also in your the same class, or perhaps a utility class:
private boolean checkIfArrayContainsAnyStringsInAnotherArray(String[] results, String[] wordsWeAreLookingFor) {
List<String> resultsList = Arrays.asList(results);
List<String> wordsWeAreLookingForList = Arrays.asList(wordsWeAreLookingFor);
return !Collections.disjoint(resultsList, wordsWeAreLookingForList);
}
Note that this particular code sample will have contain true in foundWordInResults since "dog" is in both results and wordsWeAreLookingFor.

Why don't you just store your results in a HashSet? With a HashSet, you can benefit from hashing of the keys, and it will make your assertion much faster.
Arrays.asList(results).contains("Word") creates a temporary List object each time just to do linear search, it is not efficient use of memory and it's slow.
There's HashSet.containsAll(Collection collection) method you can use to do what you want, but again, it's not efficient use of memory if you want to create a temporary List of the parameters just to do an assertion.
I suggest the following:
HashSet hashSet = ....
public assertSomething(String[] params) {
for(String s : params) {
if(hashSet.contains(s)) {
// do something
break;
}
}
}

Android: loading from SQLite Database

So I'm still building a Database to support a project of mine. There are two different things to be saved: first, attribute values of some player objects and second, simple values stored in a java class.
ATM my problem lies in the process of loading values of a player object and writing it in the respective class.
Now let's see some code:
Following you see the method I want to use for saving the values in the database.
That works fine atm, but I just realized I'm still passing the contentValues object an extra value for the 'ID' , which I did set - and planned to keep that way - as autoincrement.
Any Idea how to work this in accordingly?
public void savePlayer(Player player[]) {
for (int i = 0; i <= 3; i++) {
playerValues.put("ID", i);
playerValues.put("Name", player[i].getName());
playerValues.put("HP", player[i].getHp());
playerValues.put("Satisfaction", player[i].getsatisfaction());
playerValues.put("Hygiene", player[i].isHygieneInt());
playerValues.put("IsAlive", player[i].isAliveInt());
}
db.insert("playertable", null, playerValues);
}
Okay, hold on to your hats because this might look a bit like spaghetti - the load-method:
public void loadPlayer() {
String[] namecolumn = { "Name" };
String[] intcolumn = { "ID, HP, Satisfaction, Hygiene, IsAlive" };
String[] namesToString = new String[4];
for (int j = 0; j <= 3; j++) {
Cursor playerCursorName = db.query("playertable", namecolumn, "ID="
+ j, null, null, null, null);
namesToString = cursorToString(playerCursorName);
Resource.playerArray[j].setName(namesToString[j]);
}
for (int i = 0; i < 3; i++) {
int[] restToInt;
Cursor playerCursorInt = db.query("playertable", intcolumn, "ID="
+ i, null, null, null, null);
restToInt = cursorToInt(playerCursorInt, 4);
Resource.playerArray[i].setHp(restToInt[i]);
Resource.playerArray[i].setsatisfaction(restToInt[i]);
Resource.playerArray[i].setHygieneInt(restToInt[i]);
Resource.playerArray[i].setAliveInt(restToInt[i]);
}
}
Yeah, I know this looks pretty ugly but let me explain it:
Because there are 4 player objects I planned on iterating through the database entries by using the ID as identifier to get exactly one row at a time and writing the name and the other values of this object in the java class where I want to manage them within my project.
Note: same problem with autoincrement here than in the save method
In addition, I get a CursorIndexOutOfBoundsException when calling loadPlayer because
Index -1 is being requested - isn't that the result of an operation on the database resulting in an error?
Yeah that's pretty much it, I'll provide you with additional code if requested, hope someone can help me

You are using Cursors in a slightly odd way here.
The point of a Cursor is to ask SQLite to do the hard work of fetching data for you, and your job is simply to use the cursor to iterate through the returned values.
Firstly, I would change the query here to ask for all values in the table (and perhaps put some condition to constrain what you get back), to make sure your cursor then contains all your values.
Then, I would loop through the cursor's values by using a while loop, (with cursor.moveToPosition(-1) before the loop) moving along the cursor by using cursor.moveToNext().
See the API for more information:
http://developer.android.com/reference/android/database/Cursor.html
With regard to the autoincrement problem, as far as I can remember you can leave out the ID and use db.insert() without that field and the database will provide an ID for you.
You shouldn't have the same issue in your load method because it doesn't make sense to autoincrement when loading, you just get back what's in the database.

can't get the text from an autocomplete

I have to create an app in android with a database.In that database I have a predefined list of products.
Now,the thing is that my ap has to offer to the user the posibility to introduce in that list some other products which are not in the list.
To this end, I've created an autocomplete text view in which I introduce a new product and I take the text fro autocomplete and I have to write it in the database
Now,my problem is that when I display the products that I've introduced in the database,the toast text that I use to display what I have in the database it shows me nothing next to "product......".
Now,that may be because when I try to get the text from the autocomplete I get nothing in return?
This is how I read from autocomplete:
mItem = (AutoCompleteTextView) findViewById(R.id.todo_edit_item);
String nou=mItem.getText().toString();
And then I compare nou(which is what I wrote in the autocomplete) with what I have predefnied in the list,so if it is a new product(which was not in the list already) the I add it in the database:
for(int i = 0; i < l; i++)
{
if (nou!=fruits[i])
t=true;
else t=false;
}
if (t==true)
{
db.insertTitle(nou);
fruits=db.getAllfromDB("Fruits","fruit");
l=l+1;
}
Anyone any ideas of what I'm doing wrong in here cause I can't figure out.I'lll be here for further details.Thank u in advance:)

You compare strings using != instead of using !nou.equals(fruits[i]). also you compare to all elements in array each time, since you so t is always the value of the comparison to the last element in the array whether a match was found or not.
It should be written like that:
t = true;
for(int i = 0; i < l; i++)
{
if (nou.equals(fruits[i]))
{
t=false;
break;
}
}
if (t==true)
{
db.insertTitle(nou);
fruits=db.getAllfromDB("Fruits","fruit");
l=l+1;
}

How to efficiently manage search suggestion using Android QSB?

I try to make a dictionary using Quick Search Box in Android. As shown in the SearchableDictionary tutorial, it loads all (999 definitions)data and uses them as matches to the input text to get the search suggestion. in my case, I have 26963 rows of data that need to be suggest while user input a word on QSB. therefore, I want to grab the char data one by one from the QSB, so that it will be efficiently load necessary suggestion. how can i do this?
here's the code i use...
bringit(200);
if (Intent.ACTION_VIEW.equals(intent.getAction())) {
// from click on search results
//Dictionary.getInstance().ensureLoaded(getResources());
String word = intent.getDataString();
//if(word.length() > 3){bringit(10);}
Dictionary.Word theWord = Dictionary.getMatches(word).get(0);
launchWord(theWord);
finish();
} else if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
String query = intent.getStringExtra(SearchManager.QUERY);
//SearchManager.
//String bb =
mTextView.setText(getString(R.string.search_results, query));
WordAdapter wordAdapter = new WordAdapter(Dictionary.getMatches(query));
//letsCount(query);
mList.setAdapter(wordAdapter);
mList.setOnItemClickListener(wordAdapter);
}
Log.d("dict", intent.toString());
if (intent.getExtras() != null) {
Log.d("dict", intent.getExtras().keySet().toString());
}
}
private void letsCount(String query) {
// TODO Auto-generated method stub
for(int i=0; i<query.length(); i++){
definite[i] = query.charAt(i);
}
}
public void bringit(int sum) {
// TODO Auto-generated method stub
String[] ss = new String[10];
Log.d("dict", "loading words");
for(int i=1; i<=sum; i++){
KamusDbAdapter a = new KamusDbAdapter(getApplicationContext());
a.open();
Cursor x = a.quick(String.valueOf(i));startManagingCursor(x);
if(x.moveToFirst()){
ss[0] = x.getString(1);
ss[1] = x.getString(2);
}
Dictionary.addWord(ss[0].trim(), ss[1].trim());
Log.v("Debug",ss[0]+" "+ss[1]);
//onStop();
}
}
I use SQLite to collect data. and the other code is just same as the tutorial...

Retrieving a cursor is generally slow. You only want to retrieve one cursor which contains all the matching results.
You should perform the searching using SQL rather than fetching everything. A FULL_TEXT search is usually fastest for text matching, it is however slightly more complicated to implement than a simple LIKE, but I highly recommend you give it a try.
So you want to execute an SQL statement like:
SELECT * FROM my_table WHERE subject_column MATCH 'something'
See SQLite FTS Extension for more information. You can also use wild-cards to match part of a word.
In terms of search suggestions there is really no point returning more than around ~100 results since generally no users ever bother to scroll down that far, so you can further speed things up by adding a LIMIT 0, 100 to the end of your SQL statement.
If possible only start getting cursors once the user has entered more than X number of characters (usually 3 but in you're case this may not be appropriate). That way you're not performing searches that could potentially match thousands of items.
You seem to be leaving lots of cursors open until the application closes them even though you don't actually need them anymore: instead of calling startManagingCursor just make sure to call x.close() after your if (x.moveToFirst()) { ... } - this will free up memory faster.
On an unrelated note: please don't name your variables and methods things like ss or bringIt() as it makes code hard to read -- what is ss and what does bringIt() bring exactly?

You could have a look at the full text search extension in SQL Lite. Idea is to have a SQL query that fetches only the matching results, not all the results and then filter.
There is also a sample for the Android SDK: com/example/android/searchabledict/DictionaryDatabase