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/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License
*/
package com.android.dialer.common.concurrent;
import android.os.AsyncTask;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import com.android.dialer.common.concurrent.FallibleAsyncTask.FallibleTaskResult;
import com.google.auto.value.AutoValue;
/**
* A task that runs work in the background, passing Throwables from {@link
* #doInBackground(Object[])} to {@link #onPostExecute(Object)} through a {@link
* FallibleTaskResult}.
*
* @param <ParamsT> the type of the parameters sent to the task upon execution
* @param <ProgressT> the type of the progress units published during the background computation
* @param <ResultT> the type of the result of the background computation
*/
public abstract class FallibleAsyncTask<ParamsT, ProgressT, ResultT>
extends AsyncTask<ParamsT, ProgressT, FallibleTaskResult<ResultT>> {
@Override
protected final FallibleTaskResult<ResultT> doInBackground(ParamsT... params) {
try {
return FallibleTaskResult.createSuccessResult(doInBackgroundFallible(params));
} catch (Throwable t) {
return FallibleTaskResult.createFailureResult(t);
}
}
/** Performs background work that may result in a Throwable. */
@Nullable
protected abstract ResultT doInBackgroundFallible(ParamsT... params) throws Throwable;
/**
* Holds the result of processing from {@link #doInBackground(Object[])}.
*
* @param <ResultT> the type of the result of the background computation
*/
@AutoValue
public abstract static class FallibleTaskResult<ResultT> {
/** Creates an instance of FallibleTaskResult for the given throwable. */
private static <ResultT> FallibleTaskResult<ResultT> createFailureResult(@NonNull Throwable t) {
return new AutoValue_FallibleAsyncTask_FallibleTaskResult<>(t, null);
}
/** Creates an instance of FallibleTaskResult for the given result. */
private static <ResultT> FallibleTaskResult<ResultT> createSuccessResult(
@Nullable ResultT result) {
return new AutoValue_FallibleAsyncTask_FallibleTaskResult<>(null, result);
}
/**
* Returns the Throwable thrown in {@link #doInBackground(Object[])}, or {@code null} if
* background work completed without throwing.
*/
@Nullable
public abstract Throwable getThrowable();
/**
* Returns the result of {@link #doInBackground(Object[])}, which may be {@code null}, or {@code
* null} if the background work threw a Throwable.
*
* <p>Use {@link #isFailure()} to determine if a {@code null} return is the result of a
* Throwable from the background work.
*/
@Nullable
public abstract ResultT getResult();
/**
* Returns {@code true} if this object is the result of background work that threw a Throwable.
*/
public boolean isFailure() {
//noinspection ThrowableResultOfMethodCallIgnored
return getThrowable() != null;
}
}
}
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