Using the Android Search Dialog
When the user invokes search, a search dialog appears at the top of the screen with your application icon to the left of the search box. When the user executes the search, your application receives the query so it can search your application's data.
The Android search framework manages the search dialog for your application. You never need to draw it or worry about where it is, and your Activity is not interrupted when the search dialog appears. The Search Manager (SearchManager) is the component that does this work for you. It manages the life of the search dialog and sends your application the user's search query.
When the user executes a search, the Search Manager creates an Intent to pass the search query to the Activity that you've declared to handle searches. Basically, all you need is an Activity that receives the search Intent, performs the search, and presents the results. Specifically, you need the following:
A searchable configuration
An XML file that configures the search dialog and includes settings for features such as voice search, search suggestion, and the hint text.
A searchable Activity
The Activity that receives the search query, then searches your data and displays the search results.
A mechanism by which the user can invoke search
The device search key invokes the search dialog, by default. However, a dedicated search key is not guaranteed on all devices, so provide another means by which the user can invoke a search, such as a search button in the Options Menu or elsewhere in the Activity UI.
The searchable configuration is an XML file that defines several settings for the search dialog in your application. This file is traditionally named searchable.xml and must be saved in the res/xml/ project directory.
The file must consist of the
android:hint="@string/search_hint" >
The android:label attribute is the only required attribute and points to a string resource, which should be the same as the application name. This label isn't actually visible to the user until you enable suggestions for Quick Search Box, at which point, this label is visible in the list of Searchable items in the system Settings.
Though it's not required, we recommend that you always include the android:hint attribute, which provides a hint string in the search dialog's text box before the user enters their query. The hint is important because it provides important clues to users about what they can search.
Tip: For consistency among other Android applications, you should format the string for android:hint as "Search
The
Declaring a searchable Activity
If you don't have one already, create an Activity that performs searches and present search results. To set up this Activity as your searchable Activity:
1. Declare the Activity to accept the ACTION_SEARCH Intent, in an
2. Apply the searchable configuration, in a
For example:
...
The
Note: The
The search dialog is not, by default, available from every Activity of your application. Rather, the search dialog is presented to users only when they invoke search from a searchable context of your application. A searchable context is any Activity for which you have declared searchable meta-data in the manifest file. For example, the searchable Activity itself (declared in the manifest snippet above) is a searchable context because it includes meta-data that defines the searchable configuration. Any other Activity in your application is not a searchable context, by default, and thus, does not reveal the search dialog. However, you probably do want the search dialog available from your other activities (and to launch the searchable Activity when the user executes a search). You can do exactly that.
If you want all of your activities to provide the search dialog, add another
...
The
You can also control which activities provide search at a more granular level. To specify only an individual Activity as a searchable context, place the
Performing a search
Once you have declared your searchable Activity, performing a search for the user involves three steps:
1. Receiving the query
2. Searching your data
3. Presenting the results
Traditionally, your search results should be presented in a ListView, so you might want your searchable Activity to extend ListActivity, which provides easy access to ListView APIs. (See the List View Tutorial for a simple ListActivity sample.)
Receiving the query
When a user executes a search from the search dialog, the Search Manager sends the ACTION_SEARCH Intent to your searchable Activity. This Intent carries the search query in the QUERYstring extra. You must check for this Intent when the Activity starts and extract the string. For example, here's how you can get the query when your Activity starts:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.search);
Intent intent = getIntent();
if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
String query = intent.getStringExtra(SearchManager.QUERY);
doMySearch(query);
}
}
The QUERY string is always included with the ACTION_SEARCH Intent. In this example, the query is retrieved and passed to a local doMySearch() method where the actual search operation is done.
Searching your data
The process of storing and searching your data is unique to your application. You can store and search your data in many ways, but this guide does not show you how to store your data and search it. Storing and searching your data is something you should carefully consider in terms of your needs and your data. However, here are some tips you might be able to apply:
• If your data is stored in a SQLite database on the device, performing a full-text search (using FTS3, rather than a LIKE query) can provide a more robust search across text data and can produce results significantly faster. See sqlite.org for information about FTS3 and the SQLiteDatabase class for information about SQLite on Android. Also look at the Searchable Dictionary sample application to see a complete SQLite implementation that performs searches with FTS3.
• If your data is stored online, then the perceived search performance might be inhibited by the user's data connection. You might want to display a spinning progress wheel until your search returns. See android.net for a reference of network APIs and Creating a Progress Dialog to see how you can display a progress wheel.
About Adapters
An Adapter binds individual items from a set of data into individual View objects. When the Adapter is applied to a ListView, the Views are injected as individual items of the list. Adapter is simply an interface, so implementations such asCursorAdapter (for binding data from a Cursor) are needed. If none of the existing implementations work for your data, then you should implement your own from BaseAdapter. Install the SDK Samples package for API Level 4 to see the original version of the Searchable Dictionary, which creates a custom BaseAdapter.
Regardless of where your data lives and how you search it, we recommend that you return search results to your searchable Activity with an Adapter. This way, you can easily present all the search results in a ListView. If your data comes from a SQLite database query, then you can apply your results to a ListView using a CursorAdapter. If your data comes in some other type of format, then you can create an extension of the BaseAdapter.
Presenting the results
Presenting your search results is mostly a UI detail that is not handled by the search APIs. However, one option is to create your searchable Activity to extend ListActivity and call setListAdapter(ListAdapter), passing it an Adapter that is bound to your data. This injects all the results into the Activity ListView.
For more help presenting your results, see the ListActivity documentation.
Also see the Searchable Dictionary sample for an a complete demonstration of how to search an SQLite database and use an Adapterto provide results in a ListView.
Invoking the Search Dialog
Once you have a searchable Activity, invoking the search dialog is easy. Many Android devices provide a dedicated SEARCH key, which reveals the search dialog when the user presses it from a searchable context of your application. However, you should not assume that a SEARCH key is available on the user's device and should always provide a search button in your UI that invokes search.
To invoke search from your Activity, call onSearchRequested().
For instance, you should provide a menu item in your Options Menu or a button in your UI to invoke search with this method. The search_icons.zip file includes icons for medium and high density screens, which you can use for your search menu item or button (low density screens automatically scale-down the hdpi image by one half).
You can also enable "type-to-search" functionality, which reveals the search dialog when the user starts typing on the keyboard and the keystrokes are inserted into the search dialog. You can enable type-to-search in your Activity by calling setDefaultKeyMode(DEFAULT_KEYS_SEARCH_LOCAL) during your Activity's onCreate() method.
The impact of the search dialog on your Activity lifecycle
The search dialog is a Dialog that floats at the top of the screen. It does not cause any change in the Activity stack, so when the search dialog appears, no lifecycle methods for the currently open Activity (such as onPause()) are called. Your Activity just loses input focus as it is given to the search dialog.
If you want to be notified when search is invoked, override the onSearchRequested() method. When the system calls this method, you can do any work you want to when your Activity looses input focus to the search dialog (such as pause animations). Unless you are passing search context data (discussed below), you should end the method by calling the super class implementation. For example:
@Override
public boolean onSearchRequested() {
pauseSomeStuff();
return super.onSearchRequested();
}
If the user cancels search by pressing the BACK key, the Activity in which search was invoked re-gains input focus. You can register to be notified when the search dialog is closed withsetOnDismissListener() and/or setOnCancelListener(). You should need to register only the OnDismissListener, because it is called every time the search dialog closes. TheOnCancelListener only pertains to events in which the user explicitly exited the search dialog, so it is not called when a search is executed (in which case, the search dialog naturally disappears).
If the current Activity is not the searchable Activity, then the normal Activity lifecycle events are triggered once the user executes a search (the current Activity receives onPause() and so forth, as described in Application Fundamentals). If, however, the current Activity is the searchable Activity, then one of two things happens:
a. By default, the searchable Activity receives the ACTION_SEARCH Intent with a call to onCreate() and a new instance of the Activity is brought to the top of the Activity stack. There are now two instances of your searchable Activity in the Activity stack (so pressing the BACK key goes back to the previous instance of the searchable Activity, rather than exiting the searchable Activity).
b. If you set android:launchMode to "singleTop", then the searchable Activity receives the ACTION_SEARCH Intent with a call to onNewIntent(Intent), passing the new ACTION_SEARCHIntent here. For example, here's how you might handle this case, in which the searchable Activity's launch mode is "singleTop":
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.search);
handleIntent(getIntent());
}
@Override
protected void onNewIntent(Intent intent) {
setIntent(intent);
handleIntent(intent);
}
private void handleIntent(Intent intent) {
if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
String query = intent.getStringExtra(SearchManager.QUERY);
doMySearch(query);
}
}
Compared to the example code in the section about Performing a Search, all the code to handle the search Intent is now in the handleIntent() method, so that both onCreate() andonNewIntent() can execute it.
When the system calls onNewIntent(Intent), the Activity has not been restarted, so the getIntent() method returns the same Intent that was received with onCreate(). This is why you should call setIntent(Intent) inside onNewIntent(Intent) (so that the Intent saved by the Activity is updated in case you call getIntent() in the future).
The second scenario using "singleTop" launch mode is usually ideal, because chances are good that once a search is done, the user will perform additional searches and it's a bad experience if your application creates multiple instances of the searchable Activity. So, we recommend that you set your searchable Activity to "singleTop" launch mode in the application manifest. For example:
Passing Search Context Data
To refine your search criteria from the current Activity instead of depending only on the user's search query, you can provide additional data in the Intent that the Search Manager sends to your searchable Activity. In a simple case, you can make your refinements inside the searchable Activity, for every search made, but if your search criteria varies from one searchable context to another, then you can pass whatever data is necessary to refine your search in the APP_DATA Bundle, which is included in the ACTION_SEARCH Intent.
To pass this kind of data to your searchable Activity, override onSearchRequested() method for the Activity in which search can be invoked. For example:
@Override
public boolean onSearchRequested() {
Bundle appData = new Bundle();
appData.putBoolean(MySearchableActivity.JARGON, true);
startSearch(null, false, appData, false);
return true;
}
Returning "true" indicates that you have successfully handled this callback event. Then in your searchable Activity, you can extract the data placed inside appdata from the APP_DATA Bundle to refine the search. For example:
Bundle appData = getIntent().getBundleExtra(SearchManager.APP_DATA);
if (appData != null) {
boolean jargon = appData.getBoolean(MySearchableActivity.JARGON);
}
No comments:
Post a Comment