05 content providers - Android
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This document discusses how to retrieve and display data from a content provider using a content resolver and cursor adapter. It explains that a content provider manages access to a central data repository and exposes data through a uniform interface. It then provides steps to query the provider, retrieve the cursor, use a cursor adapter to bind it to a list view, and populate the view with the data.
![Since our activity consists of a list, we can extend the class
public class MyActivity extends ListActivity
ListActivity to make life easier.
{
ListView lv;
Cursor Cursor1; lv is used to manage the Listview, note that since the layout contains only one listview,
the extend ListActivity is enough for the connection.
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState); A projection is the specific columns of the
setContentView(R.layout.main); table that we want to query.
String [] projection = new String[] { Phone.DISPLAY_NAME,
Phone.NUMBER,
Phone._ID getContentResolver() – returns a ContentResolver object
}; from the activity class that can be used to query the
content databases with
Cursor1 = getContentResolver().query( query(projection, selection, selectionargs, sortorder)
Phone.CONTENT_URI,
projection,
null,
null, Phone.CONTENT_URI :
Phone.DISPLAY_NAME + " ASC"); (android.provider.ContactsContract.CommonDataKinds.Phone)
Points to the contact database location
startManagingCursor(Cursor1);](https://image.slidesharecdn.com/05-contentproviders-120924011649-phpapp01/85/05-content-providers-Android-12-320.jpg)
![startManagingCursor(Cursor1); From and to are used to convert between the
result of the query in the cursor to the textview’s
String[] from = { in a list layout
Phone.DISPLAY_NAME,
Phone.NUMBER,
SimpleCursorAdapter maps columns
Phone._ID}; from a cursor to TextViews or
ImageViews defined in an XML file.
int[] to = {android.R.id.text1, android.R.id.text2}; Cursor1, from, to are the respective data
args
SimpleCursorAdapter listadapter = new SimpleCursorAdapter(this,
android.R.layout.simple_list_item_2,
Cursor1, from, to );
setListAdapter(listadapter);
android.R.layout.simple_list_item_2 is an inbuilt
lv = getListView(); layout with 2 textviews for a list.
A custom XML layout in res/layout can be inserted
} // onCreate ends here
here too with the id names of the textveiws replaced
in the to variable.](https://image.slidesharecdn.com/05-contentproviders-120924011649-phpapp01/85/05-content-providers-Android-13-320.jpg)
![[…]
Get the cursor object and
cursor = managedQuery(EXTERNAL_CONTENT_URI, perform the query on it
proj, selection, arg, sort);
Find the listview view from
list = (ListView) findViewById(R.id.List01); the view
list.setAdapter(new N_Adapter(getApplicationContext(), cursor));
[..]
Use this function to bind the listview to an adaptor of
class N_Adapter..
The function is taking a constructor to this class as
arguments](https://image.slidesharecdn.com/05-contentproviders-120924011649-phpapp01/85/05-content-providers-Android-14-320.jpg)
![body = new String[c.getCount()];
number = new String[c.getCount()];
if(c.moveToFirst()){
for(int i=0;i<c.getCount();i++){
body[i]= c.getString(c.getColumnIndexOrThrow("body")).toString();
number[i]=c.getString(c.getColumnIndexOrThrow("address")).toString();
c.moveToNext();
}
}
c.close();](https://image.slidesharecdn.com/05-contentproviders-120924011649-phpapp01/85/05-content-providers-Android-22-320.jpg)
05 content providers - Android
- 2. » Content providers allow programs access to data which is present on the device. » A content provider manages access to a central repository of data. » They encapsulate the data from tables, and provide mechanisms for defining data security and unified usage. » Content providers are the standard interface that connects data in one process with code running in another process.
- 3. Content Provider Intended Data Browser Browser bookmarks, browser history, etc. CallLog Missed calls, call details, etc. Contacts Contact details MediaStore Media files such as audio, video and images Settings Device settings and preferences
- 4. » Irrespective of how the data is stored, Content Providers give a uniform interface to access the data. » Data is exposed as a simple table with rows and columns where row is a record and column is a particular data type with a specific meaning. » Each record is identified by a unique _ID field which is the key to the record. » Each content provider exposes a unique URI that identifies its data set uniquely. URI == table-name
- 5. » First we need to create a layout and activity class. » In our layout we need to create a ListView. » Create a cursor to query the phone database for the contacts.. » Use an adaptor to send the results to the view for displaying
- 6. » An application accesses the data from a content provider with a ContentResolver client object. » The ContentResolver methods provide the basic "CRUD" (create, retrieve, update, and delete) functions of persi // Queries the user dictionary and returns results mCursor = getContentResolver().query( UserDictionary.Words.CONTENT_URI, // The content URI of the words table mProjection, // The columns to return for each row mSelectionClause // Selection statement mSelectionArgs, // Selection criteria mSortOrder); // The sort order for the returned rows
- 7. » A content URI is a URI that identifies data in a provider. » Content URIs include the symbolic name of the entire provider (its authority) and a name that points to a table (a path). » content://user_dictionary/words
- 8. » To retrieve data from a provider, your application needs "read access permission" for the provider in androidmanifest.xml. » Construct the query ˃ A "projection" defines the columns that will be returned for each row ˃ Do a query and return a cursor object which holds the result returned from the database » Read the result with the cursor implementation ˃ you can iterate over the rows in the results ˃ determine the data type of each column ˃ get the data out of a column ˃ And more!
- 9. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <ListView android:id="@android:id/list" android:layout_width="fill_parent" android:layout_height="fill_parent"/> </LinearLayout> This would create a listView of id list in the layout.
- 10. » Cursor is an interface that provides random read-write access to the result of a database query from a content provider. » A cursor is a collection of rows » All field access methods are based on column number. You have to convert column name to a column number first » Random means (you can move forward and backwards) » You can also find size / traverse result set easily. Cursor cur; for(cur.moveToFirst();!cur.isAfterLast();cur.moveToNext()) { //access methods }
- 11. » Since a Cursor is a "list" of rows, a good way to display the contents of a Cursor is to link it to a ListView via an adaptor. // Creates a new SimpleCursorAdapter mCursorAdapter = new SimpleCursorAdapter( getApplicationContext(), // The application's Context object R.layout.wordlistrow, // A layout in XML for one row in the ListView mCursor, // The result from the query mWordListColumns, // A string array of column names in the cursor mWordListItems, // An integer array of view IDs in the row layout 0); // Flags (usually none are needed) // Sets the adapter for the ListView mWordList.setAdapter(mCursorAdapter);
- 12. Since our activity consists of a list, we can extend the class public class MyActivity extends ListActivity ListActivity to make life easier. { ListView lv; Cursor Cursor1; lv is used to manage the Listview, note that since the layout contains only one listview, the extend ListActivity is enough for the connection. @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); A projection is the specific columns of the setContentView(R.layout.main); table that we want to query. String [] projection = new String[] { Phone.DISPLAY_NAME, Phone.NUMBER, Phone._ID getContentResolver() – returns a ContentResolver object }; from the activity class that can be used to query the content databases with Cursor1 = getContentResolver().query( query(projection, selection, selectionargs, sortorder) Phone.CONTENT_URI, projection, null, null, Phone.CONTENT_URI : Phone.DISPLAY_NAME + " ASC"); (android.provider.ContactsContract.CommonDataKinds.Phone) Points to the contact database location startManagingCursor(Cursor1);
- 13. startManagingCursor(Cursor1); From and to are used to convert between the result of the query in the cursor to the textview’s String[] from = { in a list layout Phone.DISPLAY_NAME, Phone.NUMBER, SimpleCursorAdapter maps columns Phone._ID}; from a cursor to TextViews or ImageViews defined in an XML file. int[] to = {android.R.id.text1, android.R.id.text2}; Cursor1, from, to are the respective data args SimpleCursorAdapter listadapter = new SimpleCursorAdapter(this, android.R.layout.simple_list_item_2, Cursor1, from, to ); setListAdapter(listadapter); android.R.layout.simple_list_item_2 is an inbuilt lv = getListView(); layout with 2 textviews for a list. A custom XML layout in res/layout can be inserted } // onCreate ends here here too with the id names of the textveiws replaced in the to variable.
- 14. […] Get the cursor object and cursor = managedQuery(EXTERNAL_CONTENT_URI, perform the query on it proj, selection, arg, sort); Find the listview view from list = (ListView) findViewById(R.id.List01); the view list.setAdapter(new N_Adapter(getApplicationContext(), cursor)); [..] Use this function to bind the listview to an adaptor of class N_Adapter.. The function is taking a constructor to this class as arguments
- 15. public class N_Adapter extends BaseAdapter { This class extends BaseAdapter which is the base private Context mContext; class for all adapter implementations Cursor cursor; public N_Adapter(Context c,Cursor m) { This constructor takes in the arguments passed to it mContext = c; and returns the object to the setadapter method. cursor = m; } public int getCount() { return count; } public Object getItem(int position) { return position; These functions are required for the adapter to work } properly within the android subsystem public long getItemId(int position) { return position; }
- 16. This function performs the binding between the public View getView(int position, View convertView, ViewGroup parent) { cursor and the listview. TextView tv; View row; The view row is used to hold the xml file to place the LayoutInflater inflater = getLayoutInflater(); listview’s contents in. if (convertView == null) { convertView is in case the inflated view is being row = inflater.inflate(android.R.layout.item, null); passed in as arguments, in this case – we don’t } else want to inflate again.. row = convertView; android.R.layout.item -> xml file for the list elements tv = (TextView) row.findViewById(R.id.TextView01); cursor.moveToPosition(position); music_column_index = cursor .getColumnIndexOrThrow(People.DISPLAY_NAME); id = cursor.getString(music_column_index); Cursor is a class member initialized by the tv.setText(id); argument to the constructor, these lines extract return row; the data required and pass it to the textView } element in the listview XML file. }
- 17. » Create a large text white background contacts list. » Attach an on click event to each list item and open a new activity that shows that contact’s details » Make an application that allows you to enter a phrase and searches through the SMS messages for all sms’s containing that text.
- 18. » Make a edittext view in a layout and load it in activity. » Make a button and bind an onclickhandler() to it » When the button is clicked, load sms from the content provider and search the contents for all messages containing that word. » Display all messages (one by one or in a listview as per your choice)
- 19. » <uses-permission android:name="android.permission.READ_SMS"></uses-permission> » <uses-permission android:name="android.permission.READ_CONTACTS"></uses- permission> » URI for sms content providers is as follows » Inbox = "content://sms/inbox" » Failed = "content://sms/failed" » Queued = "content://sms/queued" » Sent = "content://sms/sent" » Draft = "content://sms/draft" » Outbox = "content://sms/outbox" » Undelivered = "content://sms/undelivered" » All = "content://sms/all" » Conversations = "content://sms/conversations"
- 20. » addressCol= mCurSms.getColumnIndex("address"); » personCol= mCurSms.getColumnIndex("person"); » dateCol = mCurSms.getColumnIndex("date"); » protocolCol= mCurSms.getColumnIndex("protocol"); » readCol = mCurSms.getColumnIndex("read"); » statusCol = mCurSms.getColumnIndex("status"); » typeCol = mCurSms.getColumnIndex("type"); » subjectCol = mCurSms.getColumnIndex("subject"); » bodyCol = mCurSms.getColumnIndex("body");
- 21. » Uri uri = Uri.parse("content://sms/inbox"); » Cursor c= getContentResolver().query(uri, null, null ,null,null); » startManagingCursor(c)
- 22. body = new String[c.getCount()]; number = new String[c.getCount()]; if(c.moveToFirst()){ for(int i=0;i<c.getCount();i++){ body[i]= c.getString(c.getColumnIndexOrThrow("body")).toString(); number[i]=c.getString(c.getColumnIndexOrThrow("address")).toString(); c.moveToNext(); } } c.close();
- 23. » Understand the application and do proper research online! » This example has some concepts that you have to figure out on your own. » Use documentation, books provided and other online resources to code the application. » Ask help in online forums also!