1 page.title=Remembering Your User 2 parent.title=Remembering and Authenticating Users 3 parent.link=index.html 4 5 trainingnavtop=true 6 next.title=Authenticating to OAuth2 Services 7 next.link=authenticate.html 8 9 @jd:body 10 11 12 <div id="tb-wrapper"> 13 <div id="tb"> 14 <h2>This lesson teaches you to</h2> 15 <ol> 16 <li><a href="#ForYou">Determine if AccountManager is for You</a></li> 17 <li><a href="#TaskTwo">Decide What Type of Account to Use</a></li> 18 <li><a href="#GetPermission">Request GET_ACCOUNT permission</a></li> 19 <li><a href="#TaskFive">Query AccountManager for a List of Accounts</a></li> 20 <li><a href="#IdentifyUser">Use the Account Object to Personalize Your App</a></li> 21 <li><a href="#IdIsEnough">Decide Whether an Account Name is Enough</a></li> 22 </ol> 23 </div> 24 </div> 25 26 27 <p>Everyone likes it when you remember their name. One of the simplest, most 28 effective things you can do to make your app more lovable is to remember who 29 your user is—especially when the user upgrades to a new device or starts carrying 30 a tablet as well as a phone. But how do you know who your user is? And how do 31 you recognize them on a new device?</p> 32 33 <p>For many applications, the answer is the {@link android.accounts.AccountManager} APIs. With the 34 user's permission, you can use Account Manager to fetch the account names 35 that the user has stored on their device.</p> 36 37 <p>Integration with the user's accounts allows you to do a variety of things such as:</p> 38 <ul> 39 <li>Auto-fill forms with the user's email address.</li> 40 <li>Retrieve an ID that is tied to a user, not the device.</li> 41 </ul> 42 43 44 <h2 id="ForYou">Determine if AccountManager is for You</h2> 45 46 <p>Applications typically try to remember the user using one of three techniques:</p> 47 <ol type="a"> 48 <li>Ask the user to type in a username </li> 49 <li>Retrieve a unique device ID to remember the device</li> 50 <li>Retrieve a built-in account from {@link android.accounts.AccountManager}</li> 51 </ol> 52 53 <p>Option (a) is problematic. First, asking the user to type something before 54 entering your app will automatically make your app less appealing. Second, 55 there's no guarantee that the username chosen will be unique. </p> 56 57 <p>Option (b) is less onerous for the user, but it's 58 <a href="http://android-developers.blogspot.com/2011/03/identifying-app-installations.html">tricky 59 to get right</a>. More 60 importantly, it only allows you to remember the user on one device. Imagine the 61 frustration of someone who upgrades to a shiny new device, only to find that 62 your app no longer remembers them.</p> 63 64 <p>Option (c) is the preferred technique. Account Manager allows you to get 65 information about the accounts that are stored on the user's device. As we'll 66 see in this lesson, using Account Manager lets you remember your user, no matter 67 how many devices the user may own, by adding just a couple of extra taps to your 68 UI.</p> 69 70 71 <h2 id="TaskTwo">Decide What Type of Account to Use</h2> 72 73 <p>Android devices can store multiple accounts from many different providers. 74 When you query {@link android.accounts.AccountManager} for account names, you can choose to filter 75 by 76 account type. The account type is a string that uniquely identifies the entity 77 that issued the account. For instance, Google accounts have type "com.google," 78 while Twitter uses "com.twitter.android.auth.login."</p> 79 80 81 <h2 id="GetPermission">Request GET_ACCOUNT permission</h2> 82 83 <p>In order to get a list of accounts on the device, your app needs the {@link 84 android.Manifest.permission#GET_ACCOUNTS} 85 permission. Add a <a href="{@docRoot}guide/topics/manifest/uses-permission-element.html">{@code 86 <uses-permission>}</a> tag in your manifest file to request 87 this permission:</p> 88 89 <pre> 90 <manifest ... > 91 <uses-permission android:name="android.permission.GET_ACCOUNTS" /> 92 ... 93 </manifest> 94 </pre> 95 96 97 <h2 id="TaskFive">Query AccountManager for a List of Accounts</h2> 98 99 <p>Once you decide what account type you're interested in, you need to query for accounts of that 100 type. Get an instance of {@link android.accounts.AccountManager} by calling {@link 101 android.accounts.AccountManager#get(android.content.Context) AccountManager.get()}. Then use that 102 instance to call {@link android.accounts.AccountManager#getAccountsByType(java.lang.String) 103 getAccountsByType()}.</p> 104 105 <pre> 106 AccountManager am = AccountManager.get(this); // "this" references the current Context 107 108 Account[] accounts = am.getAccountsByType("com.google"); 109 </pre> 110 111 <p>This returns an array of {@link android.accounts.Account} objects. If there's more than one 112 {@link android.accounts.Account} in 113 the array, you should present a dialog asking the user to select one.</p> 114 115 116 <h2 id="IdentifyUser">Use the Account Object to Personalize Your App</h2> 117 118 <p>The {@link android.accounts.Account} object contains an account name, which for Google accounts 119 is an 120 email address. You can use this information in several different ways, such as: 121 <ul> 122 <li> As suggestions in forms, so the user doesn't need to input account information by 123 hand.</li> 124 <li> As a key into your own online database of usage and personalization information.</li> 125 </ul> 126 </p> 127 128 129 <h2 id="IdIsEnough">Decide Whether an Account Name is Enough</h2> 130 131 <p>An account name is a good way to remember the user, but the {@link android.accounts.Account} 132 object by 133 itself doesn't protect your data or give you access to anything besides the user's account name. If your app 134 needs to allow the user to go online to access private data, you'll need something stronger: authentication. 135 The next lesson explains how to authenticate to existing online services. The lesson after that 136 deals with writing a custom authenticator so that you can install your own 137 account types.</p> 138
