1 /* 2 * Copyright (C) 2016 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.documentsui.base; 18 19 import android.os.AsyncTask; 20 21 /** 22 * An {@link AsyncTask} that guards work with checks that a paired {@link Check} 23 * has not yet given signals to stop progress. 24 * 25 * <p>Use this type of task for greater safety when executing tasks that might complete 26 * after the owner of the task has explicitly given a signal to stop progress. 27 * 28 * <p>Also useful as tasks can be static, limiting scope, but still have access to 29 * signal from the owning class. 30 * 31 * @template Input input type 32 * @template Output output type 33 */ 34 public abstract class CheckedTask<Input, Output> 35 extends AsyncTask<Input, Void, Output> { 36 37 private Check mCheck; 38 CheckedTask(Check check)39 public CheckedTask(Check check) { 40 mCheck = check; 41 } 42 43 /** Called prior to run being executed. Analogous to {@link AsyncTask#onPreExecute} */ prepare()44 protected void prepare() {} 45 46 /** Analogous to {@link AsyncTask#doInBackground} */ run(Input... input)47 protected abstract Output run(Input... input); 48 49 /** Analogous to {@link AsyncTask#onPostExecute} */ finish(Output output)50 protected abstract void finish(Output output); 51 52 @Override onPreExecute()53 protected final void onPreExecute() { 54 if (mCheck.stop()) { 55 return; 56 } 57 prepare(); 58 } 59 60 @Override doInBackground(Input... input)61 protected final Output doInBackground(Input... input) { 62 if (mCheck.stop()) { 63 return null; 64 } 65 return run(input); 66 } 67 68 @Override onPostExecute(Output result)69 protected final void onPostExecute(Output result) { 70 if (mCheck.stop()) { 71 return; 72 } 73 finish(result); 74 } 75 76 @FunctionalInterface 77 public interface Check { stop()78 boolean stop(); 79 } 80 } 81