Lesson four

app/src/main/AndroidManifest.xml

@@ -29,14 +29,17 @@
  </activity>
  <activity
  android:name=".EditorActivity"
- android:label="@string/editor_activity_title_new_pet"
  android:theme="@style/EditorTheme"
  android:parentActivityName=".CatalogActivity" >
  <!-- Parent activity meta-data to support 4.0 and lower -->
  <meta-data
  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

@@ -15,28 +15,36 @@
  */
 package com.example.android.pets;
 
+import android.app.LoaderManager;
+import android.content.ContentUris;
 import android.content.ContentValues;
+import android.content.CursorLoader;
 import android.content.Intent;
+import android.content.Loader;
 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;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
-import android.widget.TextView;
+import android.widget.AdapterView;
+import android.widget.ListView;
 
 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 {
+public class CatalogActivity extends AppCompatActivity implements
+ LoaderManager.LoaderCallbacks<Cursor> {
 
- /** Database helper that will provide us access to the database */
- private PetDbHelper mDbHelper;
+ /** Identifier for the pet data loader */
+ private static final int PET_LOADER = 0;
+
+ /** Adapter for the ListView */
+ PetCursorAdapter mCursorAdapter;
 
  @Override
  protected void onCreate(Bundle savedInstanceState) {
@@ -53,98 +61,48 @@ public void onClick(View view) {
  }
  });
 
- // To access our database, we instantiate our subclass of SQLiteOpenHelper
- // and pass the context, which is the current activity.
- mDbHelper = new PetDbHelper(this);
- }
+ // Find the ListView which will be populated with the pet data
+ ListView petListView = (ListView) findViewById(R.id.list);
 
- @Override
- protected void onStart() {
- super.onStart();
- displayDatabaseInfo();
- }
+ // Find and set empty view on the ListView, so that it only shows when the list has 0 items.
+ View emptyView = findViewById(R.id.empty_view);
+ petListView.setEmptyView(emptyView);
 
- /**
- * Temporary helper method to display information in the onscreen TextView about the state of
- * the pets database.
- */
- private void displayDatabaseInfo() {
- // Create and/or open a database to read from it
- SQLiteDatabase db = mDbHelper.getReadableDatabase();
+ // Setup an Adapter to create a list item for each row of pet data in the Cursor.
+ // There is no pet data yet (until the loader finishes) so pass in null for the Cursor.
+ mCursorAdapter = new PetCursorAdapter(this, null);
+ petListView.setAdapter(mCursorAdapter);
 
- // Define a projection that specifies which columns from the database
- // you will actually use after this query.
- String[] projection = {
- PetEntry._ID,
- PetEntry.COLUMN_PET_NAME,
- PetEntry.COLUMN_PET_BREED,
- 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
-
- TextView displayView = (TextView) findViewById(R.id.text_view_pet);
-
- try {
- // Create a header in the Text View that looks like this:
- //
- // The pets table contains <number of rows in Cursor> pets.
- // _id - name - breed - gender - weight
- //
- // In the while loop below, iterate through the rows of the cursor and display
- // the information from each column in this order.
- displayView.setText("The pets table contains " + cursor.getCount() + " pets.\n\n");
- displayView.append(PetEntry._ID + " - " +
- PetEntry.COLUMN_PET_NAME + " - " +
- PetEntry.COLUMN_PET_BREED + " - " +
- PetEntry.COLUMN_PET_GENDER + " - " +
- PetEntry.COLUMN_PET_WEIGHT + "\n");
-
- // Figure out the index of each column
- int idColumnIndex = cursor.getColumnIndex(PetEntry._ID);
- int nameColumnIndex = cursor.getColumnIndex(PetEntry.COLUMN_PET_NAME);
- int breedColumnIndex = cursor.getColumnIndex(PetEntry.COLUMN_PET_BREED);
- int genderColumnIndex = cursor.getColumnIndex(PetEntry.COLUMN_PET_GENDER);
- int weightColumnIndex = cursor.getColumnIndex(PetEntry.COLUMN_PET_WEIGHT);
-
- // Iterate through all the returned rows in the cursor
- while (cursor.moveToNext()) {
- // Use that index to extract the String or Int value of the word
- // at the current row the cursor is on.
- int currentID = cursor.getInt(idColumnIndex);
- String currentName = cursor.getString(nameColumnIndex);
- String currentBreed = cursor.getString(breedColumnIndex);
- int currentGender = cursor.getInt(genderColumnIndex);
- int currentWeight = cursor.getInt(weightColumnIndex);
- // Display the values from each column of the current row in the cursor in the TextView
- displayView.append(("\n" + currentID + " - " +
- currentName + " - " +
- currentBreed + " - " +
- currentGender + " - " +
- currentWeight));
+ // Setup the item click listener
+ petListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
+ @Override
+ public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
+ // Create new intent to go to {@link EditorActivity}
+ Intent intent = new Intent(CatalogActivity.this, EditorActivity.class);
+
+ // Form the content URI that represents the specific pet that was clicked on,
+ // by appending the "id" (passed as input to this method) onto the
+ // {@link PetEntry#CONTENT_URI}.
+ // For example, the URI would be "content://com.example.android.pets/pets/2"
+ // if the pet with ID 2 was clicked on.
+ Uri currentPetUri = ContentUris.withAppendedId(PetEntry.CONTENT_URI, id);
+
+ // Set the URI on the data field of the intent
+ intent.setData(currentPetUri);
+
+ // Launch the {@link EditorActivity} to display the data for the current pet.
+ startActivity(intent);
  }
- } finally {
- // Always close the cursor when you're done reading from it. This releases all its
- // resources and makes it invalid.
- cursor.close();
- }
+ });
+
+ // Kick off the loader
+ getLoaderManager().initLoader(PET_LOADER, null, this);
  }
 
  /**
  * 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 +111,11 @@ 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
@@ -178,7 +133,6 @@ public boolean onOptionsItemSelected(MenuItem item) {
  // Respond to a click on the "Insert dummy data" menu option
  case R.id.action_insert_dummy_data:
  insertPet();
- displayDatabaseInfo();
  return true;
  // Respond to a click on the "Delete all entries" menu option
  case R.id.action_delete_all_entries:
@@ -187,4 +141,33 @@ public boolean onOptionsItemSelected(MenuItem item) {
  }
  return super.onOptionsItemSelected(item);
  }
+
+ @Override
+ public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
+ // Define a projection that specifies the columns from the table we care about.
+ String[] projection = {
+ PetEntry._ID,
+ PetEntry.COLUMN_PET_NAME,
+ PetEntry.COLUMN_PET_BREED };
+
+ // This loader will execute the ContentProvider's query method on a background thread
+ return new CursorLoader(this, // Parent activity context
+ PetEntry.CONTENT_URI, // Provider content URI to query
+ projection, // Columns to include in the resulting Cursor
+ null, // No selection clause
+ null, // No selection arguments
+ null); // Default sort order
+ }
+
+ @Override
+ public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
+ // Update {@link PetCursorAdapter} with this new cursor containing updated pet data
+ mCursorAdapter.swapCursor(data);
+ }
+
+ @Override
+ public void onLoaderReset(Loader<Cursor> loader) {
+ // Callback called when the data needs to be deleted
+ mCursorAdapter.swapCursor(null);
+ }
 }