Lesson three

app/src/main/AndroidManifest.xml

@@ -37,6 +37,10 @@
                 android:name="android.support.PARENT_ACTIVITY"
                 android:value=".CatalogActivity" />
         </activity>
+        <provider
+            android:name=".data.PetProvider"
+            android:authorities="com.example.android.pets"
+            android:exported="false" />
     </application>
 
 </manifest>

app/src/main/java/com/example/android/pets/CatalogActivity.java

@@ -18,7 +18,7 @@
 import android.content.ContentValues;
 import android.content.Intent;
 import android.database.Cursor;
-import android.database.sqlite.SQLiteDatabase;
+import android.net.Uri;
 import android.os.Bundle;
 import android.support.design.widget.FloatingActionButton;
 import android.support.v7.app.AppCompatActivity;
@@ -28,16 +28,12 @@
 import android.widget.TextView;
 
 import com.example.android.pets.data.PetContract.PetEntry;
-import com.example.android.pets.data.PetDbHelper;
 
 /**
  * Displays list of pets that were entered and stored in the app.
  */
 public class CatalogActivity extends AppCompatActivity {
 
-    /** Database helper that will provide us access to the database */
-    private PetDbHelper mDbHelper;
-
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -52,10 +48,6 @@ public void onClick(View view) {
                 startActivity(intent);
             }
         });
-
-        // To access our database, we instantiate our subclass of SQLiteOpenHelper
-        // and pass the context, which is the current activity.
-        mDbHelper = new PetDbHelper(this);
     }
 
     @Override
@@ -69,9 +61,6 @@ protected void onStart() {
      * the pets database.
      */
     private void displayDatabaseInfo() {
-        // Create and/or open a database to read from it
-        SQLiteDatabase db = mDbHelper.getReadableDatabase();
-
         // Define a projection that specifies which columns from the database
         // you will actually use after this query.
         String[] projection = {
@@ -81,15 +70,14 @@ private void displayDatabaseInfo() {
                 PetEntry.COLUMN_PET_GENDER,
                 PetEntry.COLUMN_PET_WEIGHT };
 
-        // Perform a query on the pets table
-        Cursor cursor = db.query(
-                PetEntry.TABLE_NAME,   // The table to query
-                projection,            // The columns to return
-                null,                  // The columns for the WHERE clause
-                null,                  // The values for the WHERE clause
-                null,                  // Don't group the rows
-                null,                  // Don't filter by row groups
-                null);                   // The sort order
+        // Perform a query on the provider using the ContentResolver.
+        // Use the {@link PetEntry#CONTENT_URI} to access the pet data.
+        Cursor cursor = getContentResolver().query(
+                PetEntry.CONTENT_URI,   // The content URI of the words table
+                projection,             // The columns to return for each row
+                null,                   // Selection criteria
+                null,                   // Selection criteria
+                null);                  // The sort order for the returned rows
 
         TextView displayView = (TextView) findViewById(R.id.text_view_pet);
 
@@ -142,9 +130,6 @@ private void displayDatabaseInfo() {
      * Helper method to insert hardcoded pet data into the database. For debugging purposes only.
      */
     private void insertPet() {
-        // Gets the database in write mode
-        SQLiteDatabase db = mDbHelper.getWritableDatabase();
-
         // Create a ContentValues object where column names are the keys,
         // and Toto's pet attributes are the values.
         ContentValues values = new ContentValues();
@@ -153,14 +138,11 @@ private void insertPet() {
         values.put(PetEntry.COLUMN_PET_GENDER, PetEntry.GENDER_MALE);
         values.put(PetEntry.COLUMN_PET_WEIGHT, 7);
 
-        // Insert a new row for Toto in the database, returning the ID of that new row.
-        // The first argument for db.insert() is the pets table name.
-        // The second argument provides the name of a column in which the framework
-        // can insert NULL in the event that the ContentValues is empty (if
-        // this is set to "null", then the framework will not insert a row when
-        // there are no values).
-        // The third argument is the ContentValues object containing the info for Toto.
-        long newRowId = db.insert(PetEntry.TABLE_NAME, null, values);
+        // Insert a new row for Toto into the provider using the ContentResolver.
+        // Use the {@link PetEntry#CONTENT_URI} to indicate that we want to insert
+        // into the pets database table.
+        // Receive the new content URI that will allow us to access Toto's data in the future.
+        Uri newUri = getContentResolver().insert(PetEntry.CONTENT_URI, values);
     }
 
     @Override

app/src/main/java/com/example/android/pets/EditorActivity.java

@@ -16,7 +16,7 @@
 package com.example.android.pets;
 
 import android.content.ContentValues;
-import android.database.sqlite.SQLiteDatabase;
+import android.net.Uri;
 import android.os.Bundle;
 import android.support.v4.app.NavUtils;
 import android.support.v7.app.AppCompatActivity;
@@ -31,7 +31,6 @@
 import android.widget.Toast;
 
 import com.example.android.pets.data.PetContract.PetEntry;
-import com.example.android.pets.data.PetDbHelper;
 
 /**
  * Allows user to create a new pet or edit an existing one.
@@ -121,12 +120,6 @@ private void insertPet() {
         String weightString = mWeightEditText.getText().toString().trim();
         int weight = Integer.parseInt(weightString);
 
-        // Create database helper
-        PetDbHelper mDbHelper = new PetDbHelper(this);
-
-        // Gets the database in write mode
-        SQLiteDatabase db = mDbHelper.getWritableDatabase();
-
         // Create a ContentValues object where column names are the keys,
         // and pet attributes from the editor are the values.
         ContentValues values = new ContentValues();
@@ -135,16 +128,18 @@ private void insertPet() {
         values.put(PetEntry.COLUMN_PET_GENDER, mGender);
         values.put(PetEntry.COLUMN_PET_WEIGHT, weight);
 
-        // Insert a new row for pet in the database, returning the ID of that new row.
-        long newRowId = db.insert(PetEntry.TABLE_NAME, null, values);
+        // Insert a new pet into the provider, returning the content URI for the new pet.
+        Uri newUri = getContentResolver().insert(PetEntry.CONTENT_URI, values);
 
         // Show a toast message depending on whether or not the insertion was successful
-        if (newRowId == -1) {
-            // If the row ID is -1, then there was an error with insertion.
-            Toast.makeText(this, "Error with saving pet", Toast.LENGTH_SHORT).show();
+        if (newUri == null) {
+            // If the new content URI is null, then there was an error with insertion.
+            Toast.makeText(this, getString(R.string.editor_insert_pet_failed),
+                    Toast.LENGTH_SHORT).show();
         } else {
-            // Otherwise, the insertion was successful and we can display a toast with the row ID.
-            Toast.makeText(this, "Pet saved with row id: " + newRowId, Toast.LENGTH_SHORT).show();
+            // Otherwise, the insertion was successful and we can display a toast.
+            Toast.makeText(this, getString(R.string.editor_insert_pet_successful),
+                    Toast.LENGTH_SHORT).show();
         }
     }
 

app/src/main/java/com/example/android/pets/data/PetContract.java

@@ -15,6 +15,8 @@
  */
 package com.example.android.pets.data;
 
+import android.net.Uri;
+import android.content.ContentResolver;
 import android.provider.BaseColumns;
 
 /**
@@ -26,12 +28,49 @@ public final class PetContract {
     // give it an empty constructor.
     private PetContract() {}
 
+    /**
+     * The "Content authority" is a name for the entire content provider, similar to the
+     * relationship between a domain name and its website.  A convenient string to use for the
+     * content authority is the package name for the app, which is guaranteed to be unique on the
+     * device.
+     */
+    public static final String CONTENT_AUTHORITY = "com.example.android.pets";
+
+    /**
+     * Use CONTENT_AUTHORITY to create the base of all URI's which apps will use to contact
+     * the content provider.
+     */
+    public static final Uri BASE_CONTENT_URI = Uri.parse("content://" + CONTENT_AUTHORITY);
+
+    /**
+     * Possible path (appended to base content URI for possible URI's)
+     * For instance, content://com.example.android.pets/pets/ is a valid path for
+     * looking at pet data. content://com.example.android.pets/staff/ will fail,
+     * as the ContentProvider hasn't been given any information on what to do with "staff".
+     */
+    public static final String PATH_PETS = "pets";
+
     /**
      * Inner class that defines constant values for the pets database table.
      * Each entry in the table represents a single pet.
      */
     public static final class PetEntry implements BaseColumns {
 
+        /** The content URI to access the pet data in the provider */
+        public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, PATH_PETS);
+
+        /**
+         * The MIME type of the {@link #CONTENT_URI} for a list of pets.
+         */
+        public static final String CONTENT_LIST_TYPE =
+                ContentResolver.CURSOR_DIR_BASE_TYPE + "/" + CONTENT_AUTHORITY + "/" + PATH_PETS;
+
+        /**
+         * The MIME type of the {@link #CONTENT_URI} for a single pet.
+         */
+        public static final String CONTENT_ITEM_TYPE =
+                ContentResolver.CURSOR_ITEM_BASE_TYPE + "/" + CONTENT_AUTHORITY + "/" + PATH_PETS;
+
         /** Name of database table for pets */
         public final static String TABLE_NAME = "pets";
 
@@ -79,6 +118,17 @@ public static final class PetEntry implements BaseColumns {
         public static final int GENDER_UNKNOWN = 0;
         public static final int GENDER_MALE = 1;
         public static final int GENDER_FEMALE = 2;
+
+        /**
+         * Returns whether or not the given gender is {@link #GENDER_UNKNOWN}, {@link #GENDER_MALE},
+         * or {@link #GENDER_FEMALE}.
+         */
+        public static boolean isValidGender(int gender) {
+            if (gender == GENDER_UNKNOWN || gender == GENDER_MALE || gender == GENDER_FEMALE) {
+                return true;
+            }
+            return false;
+        }
     }
 
 }