| /* |
| * 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.app.Activity; |
| import android.os.AsyncTask; |
| |
| /** |
| * An {@link AsyncTask} that guards work with checks that a paired {@link Activity} |
| * is still alive. Instances of this class make no progress. |
| * |
| * <p>Use this type of task for greater safety when executing tasks that might complete |
| * after an Activity is destroyed. |
| * |
| * <p>Also useful as tasks can be static, limiting scope, but still have access to |
| * the owning class (by way the A template and the mActivity field). |
| * |
| * @template Owner Activity type. |
| * @template Input input type |
| * @template Output output type |
| */ |
| abstract class PairedTask<Owner extends Activity, Input, Output> |
| extends AsyncTask<Input, Void, Output> { |
| |
| protected final Owner mOwner; |
| |
| public PairedTask(Owner owner) { |
| mOwner = owner; |
| } |
| |
| /** 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 (mOwner.isDestroyed()) { |
| return; |
| } |
| prepare(); |
| } |
| |
| @Override |
| final protected Output doInBackground(Input... input) { |
| if (mOwner.isDestroyed()) { |
| return null; |
| } |
| return run(input); |
| } |
| |
| @Override |
| final protected void onPostExecute(Output result) { |
| if (mOwner.isDestroyed()) { |
| return; |
| } |
| finish(result); |
| } |
| } |