Unit - 6 Acting as a Content Provider

Lesson Plan: Unit - 06
Subject: P15A2AAD - Android Application Development
Topic of Study: Acting as a Content Provider
Grade/Level: Master of Computer Applications
Objective: Acting as a Content Provider and Implementation with its methods 
Time Allotment: 55 Minutes
  • Acting as a Content Provider
    • The ContentProvider class is the central component of a content provider. 
    • To create a content provider we have to
      • Create sub class for ContentProvider.
      • Define content URI
      • Implement all the unimplemented methods. insert(), update(), query(), delete(), getType().
      • Declare the content provider in AndroidManifest.xml
    • ContentProvider is an abstract class you have to implement the six abstract methods.
      • Exa.
  • Example
    • Step 01:
    • Step 02:
    • Step 03:  com.example.exacontentprovider.MyContentProvider
package com.example.exacontentprovider;

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.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.text.TextUtils;

import java.sql.SQLException;
import java.util.HashMap;

public class MyContentProvider extends ContentProvider {
    static final String PROVIDER_NAME = "ampics.cp";
    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 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);
        }
    }

    public MyContentProvider() {
    }

    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // Implement this to handle requests to delete one or more rows.        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 String getType(Uri uri) {
        // TODO: Implement this to handle requests for the MIME type of the data        // at the given 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);
        }
    }

    @Override    public Uri insert(Uri uri, ContentValues values) {
        // TODO: Implement this to handle requests to insert a new row.        /**         * 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;
        }
        return  null;
    }
    @Override    public boolean onCreate() {
        // TODO: Implement this to initialize your content provider on startup.        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 Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        // TODO: Implement this to handle query requests from clients.
            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:
            }

            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 update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        // TODO: Implement this to handle requests to update one or more rows.            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;
    }
}
    • Step 04:
      • Design of Blueprint
      • Design of Component Tree
    • Step 05: Code of XML (layout/activity_main.xml)
xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context=".MainActivity">

    <EditText        android:id="@+id/editText"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:ems="10"        android:inputType="textPersonName" />

    <EditText        android:id="@+id/editText2"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:ems="10"        android:inputType="textPersonName" />

    <Button        android:id="@+id/button"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:onClick="addrecord"        android:text="Add" />

    <Button        android:id="@+id/button2"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:onClick="readRecord"        android:text="Read" />
</LinearLayout>
    • Step 06:  Java code of com.example.exacontentprovider.MainActivity
package com.example.exacontentprovider;

import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    EditText ed1,ed2;
    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ed1 = findViewById(R.id.editText);
        ed2 = findViewById(R.id.editText2);
    }

    public void addrecord(View view) {
        // Add a new student record        ContentValues values = new ContentValues();
        values.put(MyContentProvider.NAME, ed1.getText().toString());

        values.put(MyContentProvider.GRADE, ed2.getText().toString());

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

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

    public void readRecord(View view) {
        // Retrieve student records        String URL = MyContentProvider.URL;

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

        if (c.moveToFirst()) {
            do{
                Toast.makeText(this,
                        c.getString(c.getColumnIndex(MyContentProvider._ID)) +
                                ", " +  c.getString(c.getColumnIndex(MyContentProvider.NAME)) +
                                ", " + c.getString(c.getColumnIndex(MyContentProvider.GRADE)),
                        Toast.LENGTH_SHORT).show();
            } while (c.moveToNext());
        }
    }
}
    • Step 07: Run your Project.
Tags:

Thanks a lot for query or your valuable suggestions related to the topic.

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