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Diffstat (limited to 'docs/html/guide/topics/data/data-storage.jd')
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1 files changed, 70 insertions, 37 deletions
diff --git a/docs/html/guide/topics/data/data-storage.jd b/docs/html/guide/topics/data/data-storage.jd index 2b3491c..0a1ee02 100644 --- a/docs/html/guide/topics/data/data-storage.jd +++ b/docs/html/guide/topics/data/data-storage.jd @@ -1,16 +1,45 @@ page.title=Data Storage @jd:body + +<div id="qv-wrapper"> +<div id="qv"> + + <h2>Storage quickview</h2> + <ul> + <li>Fast, lightweight storage through system preferences</li> + <li>File storage to device internal or removable flash</li> + <li>Arbitrary and structured storage in databases</li> + <li>Support for network-based storage</li> + </ul> + + <h2>In this document</h2> + <ol> + <li><a href="#pref">Preferences</a></li> + <li><a href="#files">Files</a></li> + <li><a href="#db">Databases</a></li> + <li><a href="#netw">Network</a></li> + </ol> + + <h2>See also</h2> + <ol> + <li><a href="#pref">Content Providers and Content Resolvers</a></li> + </ol> + +</div> +</div> + <p> A typical desktop operating system provides a common file system that any application can use to store files that can be read by other applications (perhaps with some access control settings). Android uses a different system: On Android, all application data (including files) are private to that application. +</p> <p> However, Android also provides a standard way for an application to expose -its private data to other applications — through a content providers. +its private data to other applications — through content providers. A content provider is an optional component of an application that exposes read/write access to the application's data, subject to whatever restrictions it might impose. @@ -19,23 +48,19 @@ data, and a standard mechanism for reading the returned data. Android supplies a number of content providers for standard data types, such as image, audio, and video files and personal contact information. For more information on using content providers, see a separate document, -<a href="{@docRoot}devel/data/contentproviders.html">Content Providers</a>. +<a href="{@docRoot}guide/topics/providers/content-providers.html">Content Providers</a>. +</p> <p> Whether or not you want to export your application's data to others, you need a way to store it. Android provides the following four mechanisms -for storing and retrieving data: - -<dl> -<dd><a href="#pref">Preferences</a> -<dd><a href="#files">Files</a> -<dd><a href="#db">Databases</a> -<dd><a href="#netw">Network</a> -</dl> - -<dl> -<dt><a name="pref"></a><b>Preferences</b></dt> -<dd>A lightweight mechanism to store and retrieve key-value pairs of primitive +for storing and retrieving data: <a href="#pref">Preferences</a>, +<a href="#files">Files</a>, <a href="#db">Databases</a>, and <a href="#netw">Network</a>. +</p> + + +<h2 id="pref">Preferences</h2> +<p>Preferences is a lightweight mechanism to store and retrieve key-value pairs of primitive data types. It is typically used to store application preferences, such as a default greeting or a text font to be loaded whenever the application is started. Call <code>{@link android.content.Context#getSharedPreferences(java.lang.String,int) @@ -44,11 +69,13 @@ your set of preferences if you want to share them with other components in the s application, or use <code>{@link android.app.Activity#getPreferences(int) Activity.getPreferences()}</code> with no name to keep them private to the calling activity. You cannot share preferences across applications (except by using a -content provider). +content provider). +</p> <p> Here is an example of setting user preferences for silent keypress mode for a calculator: +</p> <pre> import android.app.Activity; @@ -84,12 +111,13 @@ public static final String PREFS_NAME = "MyPrefsFile"; editor.commit(); } } -</pre></dd> +</pre> -<p> -<dt><a name="files"></a><b>Files</b></dt> -<dd>You can store files directly on the mobile device or on a removable + +<h2 id="files">Files</h2> +<p>You can store files directly on the mobile device or on a removable storage medium. By default, other applications cannot access these files. +</p> <p> To read data from a file, call {@link android.content.Context#openFileInput @@ -100,6 +128,7 @@ Context.openFileOutput()} with the name and path. It returns a {@link java.io.FileOutputStream} object. Calling these methods with name and path strings from another application will not work; you can only access local files. +</p> <p> If you have a static file to package with your application at compile time, @@ -108,11 +137,12 @@ and then open it with {@link android.content.res.Resources#openRawResource(int) Resources.openRawResource (R.raw.<em>myDataFile</em>)}. It returns an {@link java.io.InputStream} object that you can use to read from the file. -</dd> +</p> -<dt><a name="db"></a><b>Databases</b></dt> -<dd>The Android API contains support for creating and using SQLite databases. +<h2 id="db">Databases</h2> +<p>The Android API contains support for creating and using SQLite databases. Each database is private to the application that creates it. +</p> <p> The {@link android.database.sqlite.SQLiteDatabase} object represents a database @@ -120,6 +150,7 @@ and has methods for interacting with it — making queries and managing the data. To create the database, call <code>{@link android.database.sqlite.SQLiteDatabase#create SQLiteDatabase.create()}</code> and also subclass {@link android.database.sqlite.SQLiteOpenHelper}. +</p> <p> As part of its support for the SQLite database system, Android exposes @@ -128,16 +159,19 @@ wrapped into useful objects. For example, Android defines a data type for contact information; it consists of many fields including a first and last name (strings), an address and phone numbers (also strings), a photo (bitmap image), and much other information describing a person. +</p> <p> Android ships with the sqlite3 database tool, which enables you to browse table contents, run SQL commands, and perform other useful functions on SQLite -databases. See <a href="{@docRoot}reference/adb.html#sqlite">Examine databases +databases. See <a href="{@docRoot}guide/developing/tools/adb.html#sqlite">Examine databases (sqlite3)</a> to learn how to run this program. +</p> <p> All databases, SQLite and others, are stored on the device in <code>/data/data/<em>package_name</em>/databases</code>. +</p> <p> Discussion of how many tables to create, what fields they contain, and how @@ -146,21 +180,20 @@ impose any limitations beyond the standard SQLite concepts. We do recommend including an autoincrement value key field that can be used as a unique ID to quickly find a record. This is not required for private data, but if you implement a content provider, you must include such a unique ID field. See the -<a href="{@docRoot}devel/data/contentproviders.html">Content Providers</a> +<a href="{@docRoot}guide/topics/providers/content-providers.html">Content Providers</a> document for more information on this field and the NotePadProvider class in the NotePad sample code for an example of creating and populating a new database. Any databases you create will be accessible by name to any other -class in the application, but not outside the application.</p> -</dd> - -<dt><a name="netw"></a><b>Network</b></dt> -<dd>You can also use the network to store and retrieve data (when it's available). -To do network operations, use the classes in the following packages: -<dl> - <dd><code>{@link java.net java.net.*}</code></dd> - <dd><code>{@link android.net android.net.*}</code></dd> -</dl> -</dd> - -</dl> +class in the application, but not outside the application. +</p> + + +<h2 id="netw">Network</h2> +<p>You can also use the network to store and retrieve data (when it's available). +To do network operations, use the classes in the following packages:</p> + +<ul class="no-style"> + <li><code>{@link java.net java.net.*}</code></li> + <li><code>{@link android.net android.net.*}</code></li> +</ul> |