1 /* 2 * Copyright (C) 2009 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 package android.accounts; 17 18 import java.util.concurrent.TimeUnit; 19 import java.io.IOException; 20 21 /** 22 * A <tt>AccountManagerFuture</tt> represents the result of an asynchronous 23 * {@link AccountManager} call. Methods are provided to check if the computation is 24 * complete, to wait for its completion, and to retrieve the result of 25 * the computation. The result can only be retrieved using method 26 * <tt>get</tt> when the computation has completed, blocking if 27 * necessary until it is ready. Cancellation is performed by the 28 * <tt>cancel</tt> method. Additional methods are provided to 29 * determine if the task completed normally or was cancelled. Once a 30 * computation has completed, the computation cannot be cancelled. 31 * If you would like to use a <tt>Future</tt> for the sake 32 * of cancellability but not provide a usable result, you can 33 * declare types of the form <tt>Future<?></tt> and 34 * return <tt>null</tt> as a result of the underlying task. 35 */ 36 public interface AccountManagerFuture<V> { 37 /** 38 * Attempts to cancel execution of this task. This attempt will 39 * fail if the task has already completed, has already been cancelled, 40 * or could not be cancelled for some other reason. If successful, 41 * and this task has not started when <tt>cancel</tt> is called, 42 * this task should never run. If the task has already started, 43 * then the <tt>mayInterruptIfRunning</tt> parameter determines 44 * whether the thread executing this task should be interrupted in 45 * an attempt to stop the task. 46 * 47 * <p>After this method returns, subsequent calls to {@link #isDone} will 48 * always return <tt>true</tt>. Subsequent calls to {@link #isCancelled} 49 * will always return <tt>true</tt> if this method returned <tt>true</tt>. 50 * 51 * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this 52 * task should be interrupted; otherwise, in-progress tasks are allowed 53 * to complete 54 * @return <tt>false</tt> if the task could not be cancelled, 55 * typically because it has already completed normally; 56 * <tt>true</tt> otherwise 57 */ 58 boolean cancel(boolean mayInterruptIfRunning); 59 60 /** 61 * Returns <tt>true</tt> if this task was cancelled before it completed 62 * normally. 63 * 64 * @return <tt>true</tt> if this task was cancelled before it completed 65 */ 66 boolean isCancelled(); 67 68 /** 69 * Returns <tt>true</tt> if this task completed. 70 * 71 * Completion may be due to normal termination, an exception, or 72 * cancellation -- in all of these cases, this method will return 73 * <tt>true</tt>. 74 * 75 * @return <tt>true</tt> if this task completed 76 */ 77 boolean isDone(); 78 79 /** 80 * Accessor for the future result the {@link AccountManagerFuture} represents. This 81 * call will block until the result is available. In order to check if the result is 82 * available without blocking, one may call {@link #isDone()} and {@link #isCancelled()}. 83 * If the request that generated this result fails or is canceled then an exception 84 * will be thrown rather than the call returning normally. 85 * @return the actual result 86 * @throws android.accounts.OperationCanceledException if the request was canceled for any 87 * reason (including if it is forbidden 88 * by policy to modify an account (of that type)) 89 * @throws android.accounts.AuthenticatorException if there was an error communicating with 90 * the authenticator or if the authenticator returned an invalid response 91 * @throws java.io.IOException if the authenticator returned an error response that indicates 92 * that it encountered an IOException while communicating with the authentication server 93 */ 94 V getResult() throws OperationCanceledException, IOException, AuthenticatorException; 95 96 /** 97 * Accessor for the future result the {@link AccountManagerFuture} represents. This 98 * call will block until the result is available. In order to check if the result is 99 * available without blocking, one may call {@link #isDone()} and {@link #isCancelled()}. 100 * If the request that generated this result fails or is canceled then an exception 101 * will be thrown rather than the call returning normally. If a timeout is specified then 102 * the request will automatically be canceled if it does not complete in that amount of time. 103 * @param timeout the maximum time to wait 104 * @param unit the time unit of the timeout argument. This must not be null. 105 * @return the actual result 106 * @throws android.accounts.OperationCanceledException if the request was canceled for any 107 * reason 108 * @throws android.accounts.AuthenticatorException if there was an error communicating with 109 * the authenticator or if the authenticator returned an invalid response 110 * @throws java.io.IOException if the authenticator returned an error response that indicates 111 * that it encountered an IOException while communicating with the authentication server 112 */ 113 V getResult(long timeout, TimeUnit unit) 114 throws OperationCanceledException, IOException, AuthenticatorException; 115 }
