Content Provider methods all implemented except delete

PetProvider.java

package com.example.android.pets.data;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.Log;
import android.widget.Toast;

import static com.example.android.pets.data.PetContract.PetEntry.CONTENT_AUTHORITY;
import static com.example.android.pets.data.PetContract.PetEntry.PATH_PETS;
import static com.example.android.pets.data.PetDbHelper.LOG_TAG;

/**
 * Created by Navjot on 11/15/2017.
 */

public class PetProvider extends ContentProvider
{

    public  static  final int PETS = 100;
    public static  final  int PET_ID=200;
    public static UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    private PetDbHelper petDbHelper;
    static
    {
        sUriMatcher.addURI(CONTENT_AUTHORITY,PATH_PETS,PETS);
        sUriMatcher.addURI(CONTENT_AUTHORITY,PATH_PETS+"/#",PET_ID);
    }
    @Override
    public boolean onCreate()
    {
        petDbHelper = new PetDbHelper(getContext());
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        SQLiteDatabase db = petDbHelper.getReadableDatabase();
        Cursor cursor = null ;
        int match = sUriMatcher.match(uri);
        switch(match){
            case PETS:
                //FULL Table
                cursor = db.query(PetContract.PetEntry.Table_Name,projection,null,null,null,null,null);
                break;
            case PET_ID:
                selection = PetContract.PetEntry._ID+ "=?";
                selectionArgs = new String[]{String.valueOf(ContentUris.parseId(uri))}; //last segment to number
                cursor = db.query(PetContract.PetEntry.Table_Name,projection,selection,selectionArgs,null,null,sortOrder);
                break;
                default:
                    throw  new IllegalArgumentException("Cannot qyery unknown uri"+uri);
        }
        return cursor;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values)
    {

        int match = sUriMatcher.match(uri);
        switch (match){
            case PETS:
            {
                 return insertPet(uri,values);
            }
            default:
            {
                throw new IllegalArgumentException("Insertion not supported"+uri);
            }
        }

       // db.insert(PetContract.PetEntry.Table_Name,null,values);
       // db.insert(PetContract.PetEntry.Table_Name,null,values);

    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        return 0;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs)
    {
        int match = sUriMatcher.match(uri);
        switch (match)
        {
            case PETS:
             return  updatePet(uri,values,selection,selectionArgs);
            case PET_ID:
             selection = PetContract.PetEntry._ID+"=?";
             selectionArgs = new String[]{ String.valueOf(ContentUris.parseId(uri))};
              return updatePet(uri,values,selection,selectionArgs);
            default:
             throw new IllegalArgumentException("Error");
        }
        //return 0;
    }
    private  Uri insertPet(Uri uri,ContentValues contentValues)
    {
        SQLiteDatabase db = petDbHelper.getWritableDatabase();
        long id = db.insert(PetContract.PetEntry.Table_Name,null,contentValues);
         if(id==-1)
         {
             Log.e(LOG_TAG,"Failed to insert row for "+uri);
             return  null;
         }

               return ContentUris.withAppendedId(uri,id);
    }
    private  int updatePet(Uri uri,ContentValues contentValues,String selection,String[] selectionArgs)
    {
        SQLiteDatabase db =petDbHelper.getWritableDatabase();
        int resultRows = db.update(PetContract.PetEntry.Table_Name,contentValues,selection,selectionArgs);
         Uri uri1;
        if(resultRows>0)
        {
            uri1 = ContentUris.withAppendedId(uri,resultRows);

           // Toast.makeText(this,"Updated uri is "+uri1, Toast.LENGTH_LONG).show();
            Log.e(LOG_TAG,uri1.toString());
        }
        return resultRows;
    }
}