Develop Reference

View data from SQLite database using ListView on Android

I am quite new to Android development. I managed to get data saved to SQLite database. Now, what I want is to view these data when I call viewData(). I have viewData() which shows data as a Toast as I made it as a sample. Now I need these data to show on a new activity using a ListView, but the number of data to show is depending on how many data is in the database at the moment, If user saved 10 items then I want all the 10 items to shown up. How can I do it?
I hope my question is clear.
Thanks in advance.

you could use ListView
declare it in your layout
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<ListView
android:id="#+id/list"
android:layout_height="wrap_content"
android:layout_width="match_parent">
</ListView>
</LinearLayout>
in yor activity declare a globar var:
ListView listView;
and onCreate
listView = (ListView) findViewById(R.id.list);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, android.R.id.text1, values);
// Assign adapter to ListView
listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v,
int position, long id){
// ListView Clicked item index
int itemPosition = position;
// ListView Clicked item value
String itemValue = (String) listView.getItemAtPosition(position);
}
});
datos can be an array that you can populate with data that you extract from your data base and that's the most simple way to show it. if you want to customizise your listView you can create a custom adapter, or in other way the newest element that replace listView is ReciclerView. I hope tihs help you

You can use a SimpleCursorAdapter:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ListView answerList=(ListView)findViewById(R.id.answerList);
Cursor mCursor = getData();
startManagingCursor(mCursor);
// now create a new list adapter bound to the cursor.
// SimpleListAdapter is designed for binding to a Cursor.
ListAdapter adapter = new SimpleCursorAdapter(this, // Context.
android.R.layout.two_line_list_item,
mCursor, // Pass in the cursor to bind to.
// Array of cursor columns to bind to.
new String[] {"_id", "answer"};
// Parallel array of which template objects to bind to those
// columns.
new int[] { android.R.id.text1,android.R.id.text2 });
// Bind to our new adapter.
answerList.setAdapter(adapter);
}
private Cursor getData() {
String sq = "Select _id, answer from foo";
Cursor c = db.rawQuery(sql);
return c;
}

I will try to give an in-depth answer to this.
Whenever you want to fetch and display a list of data from the database, you can use a ListView, GridView, Spinner, etc for it.
You can use a CursorAdapter which can make the job of querying and displaying data much more simple and easy.
Here is a basic visual representation of it,
Step 1
Firstly, you need to create a database. As mentioned in your question, it is clear that you know how to create a database and put some data into it. So I am not going into the depths of it.
Step 2
We need to define the layout to be used for the individual items in the ListView and save it as res/layout/item_todo.xml This is just a sample layout, you can design any kind of layout you want to.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<TextView
android:id="#+id/tvBody"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Study cursors"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="#+id/tvPriority"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:text="3"
android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>
Step 3
Now we need to define an adapter. Here we are using a CursorAdapter which converts a Cursor (that you provide) into Views (defined by your layout).
There are two methods, newView and bindView which we need to override. The newView is responsible for inflating newViews for the first time and the bindView is responsible for binding the data to the Views.
public class TodoCursorAdapter extends CursorAdapter {
public TodoCursorAdapter(Context context, Cursor cursor) {
super(context, cursor, 0);
}
// The newView method is used to inflate a new view and return it,
// you don't bind any data to the view at this point.
#Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
return LayoutInflater.from(context).inflate(R.layout.item_todo, parent, false);
}
// The bindView method is used to bind all data to a given view
// such as setting the text on a TextView.
#Override
public void bindView(View view, Context context, Cursor cursor) {
// Find fields to populate in inflated template
TextView tvBody = (TextView) view.findViewById(R.id.tvBody);
TextView tvPriority = (TextView) view.findViewById(R.id.tvPriority);
// Extract properties from cursor
String body = cursor.getString(cursor.getColumnIndexOrThrow("body"));
int priority = cursor.getInt(cursor.getColumnIndexOrThrow("priority"));
// Populate fields with extracted properties
tvBody.setText(body);
tvPriority.setText(String.valueOf(priority));
}
}
Step 4
Now as you can clearly see, that the constructor needs a Context and a Cursor. Now we need to query the database and retrieve the data into a Cursor and pass it to the adapter.
// TodoDatabaseHandler is a SQLiteOpenHelper class connecting to SQLite
TodoDatabaseHandler handler = new TodoDatabaseHandler(this);
// Get access to the underlying writeable database
SQLiteDatabase db = handler.getWritableDatabase();
// Query for items from the database and get a cursor back
Cursor todoCursor = db.rawQuery("SELECT * FROM todo_items", null);
Step 5
This is the last step where we need to instantiate the adapter and attach the ListView with the adapter to populate the data.
// Find ListView to populate
ListView lvItems = (ListView) findViewById(R.id.lvItems);
// Setup cursor adapter using cursor from last step
TodoCursorAdapter todoAdapter = new TodoCursorAdapter(this, todoCursor);
// Attach cursor adapter to the ListView
lvItems.setAdapter(todoAdapter);

Change Specific TextView Color in Listview

i Have Two Database
first one Contain All The Items, and the ListView Display it
and the second db contain the the Favorite item , [selected from the first database]
what i want is that when the listview display all the items
check if the item is already exist in Favoritelist then make that textview background RED for this item
i have this code that work fine
public static void ChangeMyFavoritesBG(){
for (int i = 0; i < Items.size(); i++) {
if(db.verification(Items.get(i).toString())){
try {
TextView favtextview = (TextView) listview.getChildAt(i-listview.getFirstVisiblePosition()).findViewById(R.id.item_name);
favtextview.setBackgroundResource(R.drawable.redcolor);
}catch (NullPointerException e) {
}}}}
db.verification check if item exist in favorites database
if true . then it should change the background of this item to red
this code work fine but only if i put it in button click
i need to make the code work automatically
but if i made it start automatically when the activity is loaded i get NullPointer Error
i guess because the function ChangeMyFavoritesBG(); work before the listview display items
any idea guys? and sorry for my bad english

Do this control inside the getView(int position, View convertView, ViewGroup parent) method of the Adapter used by the listView.

If your favorite is not currently visible in the ListView then getChildAt() will return null.
You are looping over all items in the list view and my guess is that it holds more items than can fit on the screen. When your favorite item is one of them then this fragment of your code
listview.getChildAt(i-listview.getFirstVisiblePosition())
will return null. And that will cause the NullPointerException when you call findViewById(R.id.item_name) on it.
Just add a check for null on the result of getChildAt(). If it is null then do nothing, if it is non-null then call the second part. This will protect against the exception when your favorite item is not on the screen, and will allow it to be colored red when your favorite is visible on the screen.
update
My apologies, I read to quickly and misunderstood your problem to be about the NullPointerException but you say that your code works fine when you call it from a button click handler but not when you call it automatically at start-up.
You are right, the ListView does not yet have any items loaded when you are still in onCreate(). You can add a delay before running you code. The following works for me:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
// initialize the ListView with data for the list items. (I'm using a string array in this
// example. You are loading it from a database table, but that is the same in principle.)
ListAdapter adapter = new ArrayAdapter<String>(this, R.layout.item_list, R.id.item_name, Items);
ListView listview = (ListView) findViewById(R.id.listview);
listview.setAdapter(adapter);
// ask the system to wait before setting the background color of the favorite item so that
// the ListView has time to load the items.
final int DELAY_IN_MILLISECONDS = 100;
listview.postDelayed(new Runnable() {
#Override
public void run() {
ChangeMyFavoritesBG();
}
}, DELAY_IN_MILLISECONDS);
}
As you can see in the above example, after initializing the ListView, you ask the system to wait 100 milliseconds before calling ChangeMyFavoritesBG(). Hopefully that is enough time to load the items from the database into the ListView. If it is not enough time then you can, of course, use a longer delay.
The alternative
The above should work, but to be honest I would not write it this way. The above code is very brittle because it depends on the timing of how long it takes to load the items. I recommend that you put your background coloring into a customized adapter.
Because you want the items displayed in a customized way -- you want them to have a red background when it is the favorite one -- you should use a customized adapter. Override the bindView() function to make the background red when it is the favorite one or give it a normal background when it is not the favorite.
I don't know how you currently get the items from the database into your ListView, but inheriting from SimpleCursorAdaptor would work pretty well.
public class FavoritesItemAdapter extends SimpleCursorAdapter {
public FavoritesItemAdapter(Context context, int layout, Cursor c, String[] from, int[] to, int flags) {
super(context, layout, c, from, to, flags);
}
#Override
public void bindView(View view, Context context, Cursor cursor) {
super.bindView(view, context, cursor);
// read the name from the database
int nameColumnIndex = cursor.getColumnIndexOrThrow("name");
String name = cursor.getString(nameColumnIndex);
// write the name to the TextView
TextView nameText = (TextView) view.findViewById(R.id.item_name);
nameText.setText(name);
// set the background to normal or to red, depending on if it is the favorite one or not
boolean isFavorite = db_verification(name);
if (isFavorite) {
nameText.setBackgroundResource(R.drawable.redcolor);
} else {
nameText.setBackgroundResource(android.R.color.transparent);
}
}
public boolean db_verification(String name) {
// this is a stub. You must use your own code here
return name.equals("the favorite one");
}
}
You can then throw away ChangeMyFavoritesBG() and initialize your ListView with the adapter in onCreate() like this.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
Cursor cursor = readItemsFromDatabase();
String[] from = new String[] { "name_column" }; // mapping from database column name ...
int[] to = new int[] { R.id.item_name }; // ... to View ID in the item's layout.
FavoritesItemAdapter adapter = new FavoritesItemAdapter(this, R.layout.item_list, cursor, from, to, 0);
ListView listview = (ListView) findViewById(R.id.listview);
listview.setAdapter(adapter);
}
Good luck!

What to use to put layout in activity Android?

I have an activity that uses setContentView to initiate a listview, and then I have an If-Else condition. In the If part of the statement I use a simpleAdapter to place a new layout in the listview and other data from a cursor. In the Else part, I just want to put a sentence in a label to provide some information. How can I do that? I tried parameters and textview but they didn't work. I tried to put another setcontentView but it can't work either.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_listview);
doMySearch() is a cursor that extracts data from database based on a keyword input by user.
public void onPostExecute() {
SimpleCursorAdapter adapter;
Int count = doMysearch().getCount;
If (count >= 1){
adapter=new SimpleCursorAdapter(this, R.layout.activity_results,
doMySearch(), new String[] {
DB.COL_NAME,
DB.COL_CITY },
new int[] { R.id.lblName, R.id.lblCity },
0);
setListAdapter(adapter);
}
Else {
}
I just want a sentence that says "No data found" for the Else part. Thanks.

It is not clear for me what you are asking but here we go.
There is empty view setting in ListView for empty lists, you have to add another empty view in your current layout. Then you will set the empty view layout in code like below:
//add to your layout
<LinearLayout
android:id="#+id/empty"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="There is no item" >
</TextView>
</LinearLayout>
//set empty view
ListView listView = (ListView) container.findViewById(R.id.list);
LinearLayout emptyView = (LinearLayout) container.findViewById(R.id.empty);
listView.setEmptyView(emptyView);

As far as I understand the label doesn't show up because of the listview, right?`
EDIT:
Okay I think I get it now.
To keep it simple you could hide your ListView with myList.setVisibility(View.GONE);
Then make a premade Label visible with myLabel.setVisibility(View.VISIBLE) that already holds your error-string.
The harder way you could make a StringArray, like this in (for example) the strings.xml
<string-array name="error">
<item>No results found</item>
</string-array>
Then, in your else-block you can do somethink like that:
ListView lv = (ListView) findViewById(R.id.myList);
String[] content = getResources().getStringArray(R.array.error);
ArrayAdapter<String> typeList = new ArrayAdapter<String>(this, R.layout.simple_list_item_custom, content);
lv.setAdapter(typeList);

Can't get custom ListAdapter to work

I have followed various "how to" examples to the letter (or so I thought), but I still can't get my custom ListAdapter to work. I have a dialog with a list view containing strings which are references to an array of objects (of class "Notam"). I want to set the colour of each list item according to an attribute of the referenced object.
(Before you read my code, I have a quirk that the braces must line up or I can't see where the blocks are. I don't like the convention of putting an opening brace at the end of the same line.)
This is the code for the custom class (just as a test I am trying to set the text colour of each item to magenta):
private class GotoAdapter extends ArrayAdapter<String>
{
private ArrayList<String> items;
public GotoAdapter(Context context, int textViewResourceId, ArrayList<String> items)
{
super(context, textViewResourceId, items);
this.items = items;
}
#Override
public View getView(int position, View convertView, ViewGroup parent)
{
View v = convertView;
if (v == null)
{
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.goto_row, null);
}
String s = items.get(position);
if (s != null)
{
TextView tt = (TextView) v.findViewById(R.id.text1);
if (tt != null)
{
String s1 = (String)tt.getText(); // this is always an empty string!
tt.setTextColor(0xFF00FF); // this has no effect!
}
}
return v;
}
}
String s has the displayed text as expected (except you can't see it on the screen) when using this derived class), but the text in the returned TextView is always an empty string, and setting the colour has no effect.
This is the code that displays the dialog when a "Goto" button is clicked in my main view:
mGotoButton.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
// The pre-loaded array gets round a problem which I read about somewhere else
// (the ArrayList gets cleared again below)
String[] array = {"one", "two", "three"};
ArrayList<String> lst = new ArrayList<String>();
lst.addAll(Arrays.asList(array));
// custom dialog
final Dialog dialog = new Dialog(context);
dialog.setContentView(R.layout.goto_dialog);
dialog.setTitle("Choose Notam");
// Create the list view and adapter
final ListView list = (ListView) dialog.findViewById(R.id.goto_list);
// If I replace this reference to my custom adapter...
final GotoAdapter adapter = new GotoAdapter
(mContext, R.layout.goto_row, lst);
// ... with this normal one, everything works!
// (but of course now I can't get access to the objects.)
// final ArrayAdapter<String> adapter = new ArrayAdapter<String>
// (mContext, R.layout.goto_row, lst);
list.setAdapter(adapter);
// Populate the adapter
adapter.clear(); // first clear the silly preset strings
// Notam is my object class.
// Spine.mNotamsDisplayed is a public static NotamArray.
// class NotamArray extends ArrayList<Notam>
// Spine is my main activity where I keep my global (app-wide) stuff.
for (Notam notam : Spine.mNotamsDisplayed)
{
// This gets the reference string from the Notam object.
// This is what goes into the list.
String s = notam.getReference();
adapter.add(s);
}
// Sort into alphabetical order
adapter.sort(new Comparator<String>()
{
public int compare(String arg0, String arg1)
{
return arg0.compareTo(arg1);
}
});
list.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
public void onItemClick(AdapterView<?> a, View v, int pos, long id)
{
String s;
int i;
s = (String)a.getItemAtPosition(pos);
// This static function returns the index in Spine.mNotamsDisplayed
// which is referenced by the reference string s.
// I have to do this because I lost the one-for-one correlation of page
// indexes with list view entries when I did the sort.
i = NotamArray.findNotamIndexByReference(Spine.mNotamsDisplayed, s);
if (i >= 0)
{
// This is what the Goto button and dialog is all about: this
// just moves my main view's pager to the page that was selected.
mPager.setCurrentItem(i);
}
dialog.dismiss();
}
});
dialog.show();
}
});
This is my xml for the dialog (goto_dialog.xml):
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<ListView
android:id="#+id/goto_list"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</RelativeLayout>
And this is my xml for the list view row (goto_row.xml):
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/text1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#00FF00"
android:gravity="center_vertical"
android:textAppearance="?android:attr/textAppearanceMedium"
android:padding="2dp"
android:textSize="20dp"
/>
(I set the text colour to green so I could see that this bit was working if I used the standard list view adapter. (Sure enough the text of every entry was green. However no text could be seen if I used my custom adapter, although it was there - I assume black on black.)
There must be someone out there who can spot what must be a trivial error I have made - please!

From what I read, it seems like you want to set the text color of every list item to match the color you have in your array.
I want to set the colour of each list item according to an attribute of the referenced object.
However, your initial array is set as
String[] array = {"one", "two", "three"};
So this will lead to problems later when you are dynamically setting the text color based on your array. But I'm sure you meant to change that later.
When you use a standard array adapter, it just shows the items in the array as a text, that's why:
if I used the standard list view adapter. (Sure enough the text of every entry was green. However no text could be seen if I used my custom adapter
To see if your custom adapter is working (changing color), you can just start off by adding one line to your TextView of goto_row.xml file:
android:text="Test String"
Now it will show "Test String" with different colors, and the
String s1 = (String)tt.getText();
above line will get "Test String"

I found the trivial error that I hinted at at the end of my question. It was this line in the custom adapter:
tt.setTextColor(0xFF00FF);
It seems that 0xFF00FF is not a valid colour value, which is why I saw nothing on the screen.
Changing that to:
tt.setTextColor(Color.rgb(255, 0, 255);
fixes the problem, and the default green colour is changed to magenta, and I can set the text to the value I want. So I can now set the individual row colours to what they need to be.
Thanks to #LukasKnuth and #tigerpenguin for pointing me in the right direction.

Adding new elements to the top of the ListView

I'm writing an IM client and I need to download (from filesystem or network) and show new elements at the top of ListView (it is history of messages -- older messages are at the top, newer -- at the bottom). I implemented my own Adapter for ListView but I can't add new elements at the beginning of the list and redraw it. (notifyDataSetChanged() isn't good for me, because indexes of messages in ListView changes and android can't redraw it normally).
How do other apps do something similar?
I don't create special code for it, I am simply creating new Adapter for my ListView:
messagesListView.setAdapter(new MessagesListAdapter(this));
And redefine getView() and getCount() method in MessagesListAdapter (extends ArrayAdapter now).
My XML for ListView is
<ListView
android:id="#+id/dialog_messages_list"
android:layout_height="fill_parent"
android:layout_width="fill_parent"
android:layout_marginTop="#dimen/title_height">
</ListView>
And my XML for one element (one message) is
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:id="#+id/dialogMessageText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""
android:background="#drawable/dialog_message_in"
/>
<TextView
android:id="#+id/dialogMessageDatetime"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text=""/>
</LinearLayout>
May be you need other code?
EDIT: I tried
messagesListView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList));
(new Thread() {
public void run() {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
arrayList.add(0, "qwer");
}
}).start();
But it also not seems good. I tried to call ((ArrayAdapter<String>)messagesListView.getAdapter()).notifyDataSetChanged(); in thread, but it makes exception.

I suggest reversing the order of the List to display the newest result first.
Run this example:
public class Example extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
String[] array = {"oldest", "older", "old", "new", "newer"};
List<String> list = new ArrayList<String>();
Collections.addAll(list, array);
Collections.reverse(list);
// When you want to add new Strings, put them at the beginning of list
list.add(0, "newest");
ListView listView = (ListView) findViewById(R.id.list);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, list);
listView.setAdapter(adapter);
}
}
You don't have to override anything in the ArrayAdapter or ListView this way.

you can programmatically add some views in the class associated with your list view. For example:
To add stuff to a layout and make new elements:
TextView tv = new TextView(getApplicationContext());
EditText edit = new EditText(getApplicationContext());
relative.addView(tv);
relative.addView(edit);
This is to manipulate an existing element in the xml layout:
final TextView tv = (TextView) v.findViewById(R.id.listItem);
tv.setText("This an item I am changing");
If you look at some of the related questions, they will give your more information on this. But you can also checkout other people's custom listviews and adapters online. This one is really nice: http://www.androidhive.info/2012/02/android-custom-listview-with-image-and-text/