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/*
* Copyright (C) 2016 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.documentsui;
import android.os.AsyncTask;
/**
* An {@link AsyncTask} that guards work with checks that a paired {@link Check}
* has not yet given signals to stop progress.
*
* <p>Use this type of task for greater safety when executing tasks that might complete
* after the owner of the task has explicitly given a signal to stop progress.
*
* <p>Also useful as tasks can be static, limiting scope, but still have access to
* signal from the owning class.
*
* @template Input input type
* @template Output output type
*/
abstract class CheckedTask<Input, Output>
extends AsyncTask<Input, Void, Output> {
private Check mCheck;
public CheckedTask(Check check) {
mCheck = check;
}
/** Called prior to run being executed. Analogous to {@link AsyncTask#onPreExecute} */
void prepare() {}
/** Analogous to {@link AsyncTask#doInBackground} */
abstract Output run(Input... input);
/** Analogous to {@link AsyncTask#onPostExecute} */
abstract void finish(Output output);
@Override
final protected void onPreExecute() {
if (mCheck.stop()) {
return;
}
prepare();
}
@Override
final protected Output doInBackground(Input... input) {
if (mCheck.stop()) {
return null;
}
return run(input);
}
@Override
final protected void onPostExecute(Output result) {
if (mCheck.stop()) {
return;
}
finish(result);
}
@FunctionalInterface
interface Check {
boolean stop();
}
}
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