1 /* 2 * Copyright (C) 2017 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 17 package com.android.dialer.common.concurrent; 18 19 import android.os.AsyncTask; 20 import android.support.annotation.NonNull; 21 import android.support.annotation.Nullable; 22 import com.android.dialer.common.concurrent.FallibleAsyncTask.FallibleTaskResult; 23 import com.google.auto.value.AutoValue; 24 25 /** 26 * A task that runs work in the background, passing Throwables from {@link 27 * #doInBackground(Object[])} to {@link #onPostExecute(Object)} through a {@link 28 * FallibleTaskResult}. 29 * 30 * @paramthe type of the parameters sent to the task upon execution 31 * @param the type of the progress units published during the background computation 32 * @param the type of the result of the background computation 33 */ 34 public abstract class FallibleAsyncTask<ParamsT, ProgressT, ResultT> 35 extends AsyncTask<ParamsT, ProgressT, FallibleTaskResult<ResultT>> { 36 37 @Override 38 protected final FallibleTaskResult<ResultT> doInBackground(ParamsT... params) { 39 try { 40 return FallibleTaskResult.createSuccessResult(doInBackgroundFallible(params)); 41 } catch (Throwable t) { 42 return FallibleTaskResult.createFailureResult(t); 43 } 44 } 45 46 /** Performs background work that may result in a Throwable. */ 47 @Nullable 48 protected abstract ResultT doInBackgroundFallible(ParamsT... params) throws Throwable; 49 50 /** 51 * Holds the result of processing from {@link #doInBackground(Object[])}. 52 * 53 * @param the type of the result of the background computation 54 */ 55 @AutoValue 56 public abstract static class FallibleTaskResult<ResultT> { 57 58 /** Creates an instance of FallibleTaskResult for the given throwable. */ 59 private static <ResultT> FallibleTaskResult<ResultT> createFailureResult(@NonNull Throwable t) { 60 return new AutoValue_FallibleAsyncTask_FallibleTaskResult<>(t, null); 61 } 62 63 /** Creates an instance of FallibleTaskResult for the given result. */ 64 private static <ResultT> FallibleTaskResult<ResultT> createSuccessResult( 65 @Nullable ResultT result) { 66 return new AutoValue_FallibleAsyncTask_FallibleTaskResult<>(null, result); 67 } 68 69 /** 70 * Returns the Throwable thrown in {@link #doInBackground(Object[])}, or {@code null} if 71 * background work completed without throwing. 72 */ 73 @Nullable 74 public abstract Throwable getThrowable(); 75 76 /** 77 * Returns the result of {@link #doInBackground(Object[])}, which may be {@code null}, or {@code 78 * null} if the background work threw a Throwable. 79 * 80 * <p>Use {@link #isFailure()} to determine if a {@code null} return is the result of a 81 * Throwable from the background work. 82 */ 83 @Nullable 84 public abstract ResultT getResult(); 85 86 /** 87 * Returns {@code true} if this object is the result of background work that threw a Throwable. 88 */ 89 public boolean isFailure() { 90 //noinspection ThrowableResultOfMethodCallIgnored 91 return getThrowable() != null; 92 } 93 } 94 } 95
