Adding Recent Query Suggestions

When using the Android search dialog or search widget, you can provide search suggestions based on recent search queries. For example, if a user previously searched for "puppies," then that query appears as a suggestion once he or she begins typing the same query. Figure 1 shows an example of a search dialog with recent query suggestions.

Before you begin, you need to implement the search dialog or a search widget for basic searches in your application. If you haven't, see Creating a Search Interface.

The Basics

Figure 1. Screenshot of a search dialog with recent query suggestions.

Recent query suggestions are simply saved searches. When the user selects one of the suggestions, your searchable activity receives a ACTION_SEARCH intent with the suggestion as the search query, which your searchable activity already handles (as described in Creating a Search Interface).

To provide recent queries suggestions, you need to:

• Implement a searchable activity, as described in Creating a Search Interface.
• Create a content provider that extends SearchRecentSuggestionsProvider and declare it in your application manifest.
• Modify the searchable configuration with information about the content provider that provides search suggestions.
• Save queries to your content provider each time a search is executed.

Just as the Android system displays the search dialog, it also displays the search suggestions below the dialog or search widget. All you need to do is provide a source from which the system can retrieve suggestions.

When the system identifies that your activity is searchable and provides search suggestions, the following procedure takes place as soon as the user begins typing a query:

1. The system takes the search query text (whatever has been typed so far) and performs a query to the content provider that contains your suggestions.
2. Your content provider returns a Cursor that points to all suggestions that match the search query text.
3. The system displays the list of suggestions provided by the Cursor.

Once the recent query suggestions are displayed, the following might happen:

• If the user types another key, or changes the query in any way, the aforementioned steps are repeated and the suggestion list is updated.
• If the user executes the search, the suggestions are ignored and the search is delivered to your searchable activity using the normal ACTION_SEARCH intent.
• If the user selects a suggestion, an ACTION_SEARCH intent is delivered to your searchable activity using the suggested text as the query.

The SearchRecentSuggestionsProvider class that you extend for your content provider automatically does the work described above, so there's actually very little code to write.

Creating a Content Provider

The content provider that you need for recent query suggestions must be an implementation of SearchRecentSuggestionsProvider. This class does practically everything for you. All you have to do is write a class constructor that executes one line of code.

For example, here's a complete implementation of a content provider for recent query suggestions:

public class MySuggestionProvider extends SearchRecentSuggestionsProvider {
    public final static String AUTHORITY = "com.example.MySuggestionProvider";
    public final static int MODE = DATABASE_MODE_QUERIES;

    public MySuggestionProvider() {
        setupSuggestions(AUTHORITY, MODE);
    }
}

The call to setupSuggestions() passes the name of the search authority and a database mode. The search authority can be any unique string, but the best practice is to use a fully qualified name for your content provider (package name followed by the provider's class name; for example, "com.example.MySuggestionProvider"). The database mode must include DATABASE_MODE_QUERIES and can optionally include DATABASE_MODE_2LINES, which adds another column to the suggestions table that allows you to provide a second line of text with each suggestion. For example, if you want to provide two lines in each suggestion:

public final static int MODE = DATABASE_MODE_QUERIES | DATABASE_MODE_2LINES;

Now declare the content provider in your application manifest with the same authority string used in your SearchRecentSuggestionsProvider class (and in the searchable configuration). For example:

<application>
    <provider android:name=".MySuggestionProvider"
              android:authorities="com.example.MySuggestionProvider" />
    ...
</application>

Modifying the Searchable Configuration

To configure the system to use your suggestions provider, you need to add the android:searchSuggestAuthority and android:searchSuggestSelection attributes to the <searchable> element in your searchable configuration file. For example:

<?xml version="1.0" encoding="utf-8"?>
<searchable xmlns:android="http://schemas.android.com/apk/res/android"
    android:label="@string/app_label"
    android:hint="@string/search_hint"
    android:searchSuggestAuthority="com.example.MySuggestionProvider"
    android:searchSuggestSelection=" ?" >
</searchable>

The value for android:searchSuggestAuthority should be a fully qualified name for your content provider that exactly matches the authority used in the content provider (the AUTHORITY string in the above example).

The value for android:searchSuggestSelection must be a single question mark, preceded by a space (" ?"), which is simply a placeholder for the SQLite selection argument (which is automatically replaced by the query text entered by the user).

Saving Queries

To populate your collection of recent queries, add each query received by your searchable activity to your SearchRecentSuggestionsProvider. To do this, create an instance of SearchRecentSuggestions and call saveRecentQuery() each time your searchable activity receives a query. For example, here's how you can save the query during your activity's onCreate() method:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    Intent intent  = getIntent();

    if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
        String query = intent.getStringExtra(SearchManager.QUERY);
        SearchRecentSuggestions suggestions = new SearchRecentSuggestions(this,
                MySuggestionProvider.AUTHORITY, MySuggestionProvider.MODE);
        suggestions.saveRecentQuery(query, null);
    }
}

The SearchRecentSuggestionsProvider constructor requires the same authority and database mode declared by your content provider.

The saveRecentQuery() method takes the search query string as the first parameter and, optionally, a second string to include as the second line of the suggestion (or null). The second parameter is only used if you've enabled two-line mode for the search suggestions with DATABASE_MODE_2LINES. If you have enabled two-line mode, then the query text is also matched against this second line when the system looks for matching suggestions.

Clearing the Suggestion Data

To protect the user's privacy, you should always provide a way for the user to clear the recent query suggestions. To clear the query history, call clearHistory(). For example:

SearchRecentSuggestions suggestions = new SearchRecentSuggestions(this,
        HelloSuggestionProvider.AUTHORITY, HelloSuggestionProvider.MODE);
suggestions.clearHistory();

Execute this from your choice of a "Clear Search History" menu item, preference item, or button. You should also provide a confirmation dialog to verify that the user wants to delete their search history.