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.Future; 19 import java.util.concurrent.TimeUnit; 20 import java.util.concurrent.ExecutionException; 21 import java.util.concurrent.TimeoutException; 22 import java.io.IOException; 23 24 /** 25 * A <tt>AccountManagerFuture</tt> represents the result of an asynchronous 26 * {@link AccountManager} call. Methods are provided to check if the computation is 27 * complete, to wait for its completion, and to retrieve the result of 28 * the computation. The result can only be retrieved using method 29 * <tt>get</tt> when the computation has completed, blocking if 30 * necessary until it is ready. Cancellation is performed by the 31 * <tt>cancel</tt> method. Additional methods are provided to 32 * determine if the task completed normally or was cancelled. Once a 33 * computation has completed, the computation cannot be cancelled. 34 * If you would like to use a <tt>Future</tt> for the sake 35 * of cancellability but not provide a usable result, you can 36 * declare types of the form <tt>Future<?></tt> and 37 * return <tt>null</tt> as a result of the underlying task. 38 */ 39 public interface AccountManagerFuture<V> { 40 /** 41 * Attempts to cancel execution of this task. This attempt will 42 * fail if the task has already completed, has already been cancelled, 43 * or could not be cancelled for some other reason. If successful, 44 * and this task has not started when <tt>cancel</tt> is called, 45 * this task should never run. If the task has already started, 46 * then the <tt>mayInterruptIfRunning</tt> parameter determines 47 * whether the thread executing this task should be interrupted in 48 * an attempt to stop the task. 49 * 50 * <p>After this method returns, subsequent calls to {@link #isDone} will 51 * always return <tt>true</tt>. Subsequent calls to {@link #isCancelled} 52 * will always return <tt>true</tt> if this method returned <tt>true</tt>. 53 * 54 * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this 55 * task should be interrupted; otherwise, in-progress tasks are allowed 56 * to complete 57 * @return <tt>false</tt> if the task could not be cancelled, 58 * typically because it has already completed normally; 59 * <tt>true</tt> otherwise 60 */ 61 boolean cancel(boolean mayInterruptIfRunning); 62 63 /** 64 * Returns <tt>true</tt> if this task was cancelled before it completed 65 * normally. 66 * 67 * @return <tt>true</tt> if this task was cancelled before it completed 68 */ 69 boolean isCancelled(); 70 71 /** 72 * Returns <tt>true</tt> if this task completed. 73 * 74 * Completion may be due to normal termination, an exception, or 75 * cancellation -- in all of these cases, this method will return 76 * <tt>true</tt>. 77 * 78 * @return <tt>true</tt> if this task completed 79 */ 80 boolean isDone(); 81 82 /** 83 * Accessor for the future result the {@link AccountManagerFuture} represents. This 84 * call will block until the result is available. In order to check if the result is 85 * available without blocking, one may call {@link #isDone()} and {@link #isCancelled()}. 86 * If the request that generated this result fails or is canceled then an exception 87 * will be thrown rather than the call returning normally. 88 * @return the actual result 89 * @throws android.accounts.OperationCanceledException if the request was canceled for any 90 * reason 91 * @throws android.accounts.AuthenticatorException if there was an error communicating with 92 * the authenticator or if the authenticator returned an invalid response 93 * @throws java.io.IOException if the authenticator returned an error response that indicates 94 * that it encountered an IOException while communicating with the authentication server 95 */ 96 V getResult() throws OperationCanceledException, IOException, AuthenticatorException; 97 98 /** 99 * Accessor for the future result the {@link AccountManagerFuture} represents. This 100 * call will block until the result is available. In order to check if the result is 101 * available without blocking, one may call {@link #isDone()} and {@link #isCancelled()}. 102 * If the request that generated this result fails or is canceled then an exception 103 * will be thrown rather than the call returning normally. If a timeout is specified then 104 * the request will automatically be canceled if it does not complete in that amount of time. 105 * @param timeout the maximum time to wait 106 * @param unit the time unit of the timeout argument. This must not be null. 107 * @return the actual result 108 * @throws android.accounts.OperationCanceledException if the request was canceled for any 109 * reason 110 * @throws android.accounts.AuthenticatorException if there was an error communicating with 111 * the authenticator or if the authenticator returned an invalid response 112 * @throws java.io.IOException if the authenticator returned an error response that indicates 113 * that it encountered an IOException while communicating with the authentication server 114 */ 115 V getResult(long timeout, TimeUnit unit) 116 throws OperationCanceledException, IOException, AuthenticatorException; 117 }
