Android Content Providers Example

admin November 25, 2015 Android Leave a comment 637 Views

A content provider component supplies data from one application to others on request. Such requests are handled by the methods of the ContentResolver class. A content provider can use different ways to store its data and the data can be stored in a database, in files, or even over a network.

sometimes it is required to share data across applications. This is where content providers become very useful.

A content provider is implemented as a subclass of ContentProvider class and must implement a standard set of APIs that enable other applications to perform transactions.

public class My Application extends ContentProvider {

}

Content URIs

To query a content provider, you specify the query string in the form of a URI which has following format:

Example

This example will explain you how to create your own ContentProvider. So let’s follow the following steps:

1) MainActivity.java

package com.example.My Application;

import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContentValues;
import android.content.CursorLoader;
import android.database.Cursor;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

public void onClickAddName(View view) {
// Add a new student record
ContentValues values = new ContentValues();

values.put(StudentsProvider.NAME,
((EditText)findViewById(R.id.editText2)).getText().toString());

values.put(StudentsProvider.GRADE,
((EditText)findViewById(R.id.editText3)).getText().toString());

Uri uri = getContentResolver().insert(
StudentsProvider.CONTENT_URI, values);

Toast.makeText(getBaseContext(),
uri.toString(), Toast.LENGTH_LONG).show();
}

public void onClickRetrieveStudents(View view) {

// Retrieve student records
String URL = “content://com.example.provider.College/students”;

Uri students = Uri.parse(URL);
Cursor c = managedQuery(students, null, null, null, “name”);

if (c.moveToFirst()) {
do{
Toast.makeText(this,
c.getString(c.getColumnIndex(StudentsProvider._ID)) +
“, ” + c.getString(c.getColumnIndex( StudentsProvider.NAME)) +
“, ” + c.getString(c.getColumnIndex( StudentsProvider.GRADE)),
Toast.LENGTH_SHORT).show();
} while (c.moveToNext());
}
}
}

2) StudentsProvider.java

package com.example.My Application;

import java.util.HashMap;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;

import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;

import android.net.Uri;
import android.text.TextUtils;

public class StudentsProvider extends ContentProvider {

static final String PROVIDER_NAME = “com.example.provider.College”;
static final String URL = “content://” + PROVIDER_NAME + “/students”;
static final Uri CONTENT_URI = Uri.parse(URL);

static final String _ID = “_id”;
static final String NAME = “name”;
static final String GRADE = “grade”;

private static HashMap<String, String> STUDENTS_PROJECTION_MAP;

static final int STUDENTS = 1;
static final int STUDENT_ID = 2;

static final UriMatcher uriMatcher;
static{
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(PROVIDER_NAME, “students”, STUDENTS);
uriMatcher.addURI(PROVIDER_NAME, “students/#”, STUDENT_ID);
}

/**
* Database specific constant declarations
*/
private SQLiteDatabase db;
static final String DATABASE_NAME = “College”;
static final String STUDENTS_TABLE_NAME = “students”;
static final int DATABASE_VERSION = 1;
static final String CREATE_DB_TABLE =
” CREATE TABLE ” + STUDENTS_TABLE_NAME +
” (_id INTEGER PRIMARY KEY AUTOINCREMENT, ” +
” name TEXT NOT NULL, ” +
” grade TEXT NOT NULL);”;

/**
* Helper class that actually creates and manages
* the provider’s underlying data repository.
*/
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context){
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(CREATE_DB_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL(“DROP TABLE IF EXISTS ” + STUDENTS_TABLE_NAME);
onCreate(db);
}
}

@Override
public boolean onCreate() {
Context context = getContext();
DatabaseHelper dbHelper = new DatabaseHelper(context);

/**
* Create a write able database which will trigger its
* creation if it doesn’t already exist.
*/
db = dbHelper.getWritableDatabase();
return (db == null)? false:true;
}

@Override
public Uri insert(Uri uri, ContentValues values) {
/**
* Add a new student record
*/
long rowID = db.insert( STUDENTS_TABLE_NAME, “”, values);

/**
* If record is added successfully
*/

if (rowID > 0)
{
Uri _uri = ContentUris.withAppendedId(CONTENT_URI, rowID);
getContext().getContentResolver().notifyChange(_uri, null);
return _uri;
}
throw new SQLException(“Failed to add a record into ” + uri);
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
qb.setTables(STUDENTS_TABLE_NAME);

switch (uriMatcher.match(uri)) {
case STUDENTS:
qb.setProjectionMap(STUDENTS_PROJECTION_MAP);
break;

case STUDENT_ID:
qb.appendWhere( _ID + “=” + uri.getPathSegments().get(1));
break;

default:
throw new IllegalArgumentException(“Unknown URI ” + uri);
}

if (sortOrder == null || sortOrder == “”){
/**
* By default sort on student names
*/
sortOrder = NAME;
}
Cursor c = qb.query(db, projection, selection, selectionArgs,null, null, sortOrder);

/**
* register to watch a content URI for changes
*/
c.setNotificationUri(getContext().getContentResolver(), uri);
return c;
}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
int count = 0;

switch (uriMatcher.match(uri)){
case STUDENTS:
count = db.delete(STUDENTS_TABLE_NAME, selection, selectionArgs);
break;

case STUDENT_ID:
String id = uri.getPathSegments().get(1);
count = db.delete( STUDENTS_TABLE_NAME, _ID + ” = ” + id +
(!TextUtils.isEmpty(selection) ? ” AND (” + selection + ‘)’ : “”), selectionArgs);
break;

default:
throw new IllegalArgumentException(“Unknown URI ” + uri);
}

getContext().getContentResolver().notifyChange(uri, null);
return count;
}

@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
int count = 0;

switch (uriMatcher.match(uri)){
case STUDENTS:
count = db.update(STUDENTS_TABLE_NAME, values, selection, selectionArgs);
break;

case STUDENT_ID:
count = db.update(STUDENTS_TABLE_NAME, values, _ID + ” = ” + uri.getPathSegments().get(1) +
(!TextUtils.isEmpty(selection) ? ” AND (” +selection + ‘)’ : “”), selectionArgs);
break;

default:
throw new IllegalArgumentException(“Unknown URI ” + uri );
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}

@Override
public String getType(Uri uri) {
switch (uriMatcher.match(uri)){
/**
* Get all student records
*/
case STUDENTS:
return “vnd.android.cursor.dir/vnd.example.students”;

/**
* Get a particular student
*/
case STUDENT_ID:
return “vnd.android.cursor.item/vnd.example.students”;

default:
throw new IllegalArgumentException(“Unsupported URI: ” + uri);
}
}
}

3) AndroidManifest.xml

Here we have added <provider…/> tag to include our content provider:

<?xml version=”1.0″ encoding=”utf-8″?>
<manifest xmlns:android=”http://schemas.android.com/apk/res/android”
package=”com.example.My Application”
android:versionCode=”1″
android:versionName=”1.0″ >

<uses-sdk
android:minSdkVersion=”8″
android:targetSdkVersion=”22″ />

<intent-filter>
<action android:name=”android.intent.action.MAIN” />
<category android:name=”android.intent.category.LAUNCHER” />
</intent-filter>

</activity>

</application>
</manifest>

4) activity_main.xml

</RelativeLayout>

Preview :

W2class Tutorials for Android, Java, Php, Html

Android Content Providers Example

Content URIs

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