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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.support.annotation.MainThread;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.annotation.WorkerThread;
import java.util.concurrent.ExecutorService;
/**
* Provides a consistent interface for doing background work in either UI or non-UI contexts.
*
* <p>You may create an executor from a UI component (activity or fragment) or a non-UI component.
* Using this class provides a number of benefits:
*
* <ul>
* <li>Ensures that UI tasks keep running across configuration changes by using a headless
* fragment.
* <li>Forces exceptions to crash the application, unless the user implements their own onFailure
* method.
* <li>Checks for dead UI components which can be encountered if a UI task runs longer than its
* UI. If a dead UI component is encountered, onSuccess/onFailure are not called (because they
* can't be) but a message is logged.
* <li>Helps prevent memory leaks in UI tasks by ensuring that callbacks are nulled out when the
* headless fragment is detached.
* <li>UI and non-UI threads are shared across the application and run at reasonable priorities
* </ul>
*
* <p>Executors accept a single input and output parameter which should be immutable data objects.
* If you don't require an input or output, use Void and null as needed.
*
* <p>You may optionally specify onSuccess and onFailure listeners; the default behavior on success
* is a no-op and the default behavior on failure is to crash the application.
*
* <p>To use an executor from a UI component, you must create it in your onCreate method and then
* use it from anywhere:
*
* <pre><code>
*
* public class MyActivity extends Activity {
*
* private final DialerExecutor<MyInputType> myExecutor;
*
* public void onCreate(Bundle state) {
* super.onCreate(bundle);
*
* // Must be called in onCreate; don't use non-static or anonymous inner classes for worker!
* myExecutor = DialerExecutorComponent.get(context).dialerExecutorFactory()
* .createUiTaskBuilder(fragmentManager, taskId, worker)
* .onSuccess(this::onSuccess) // Lambdas, anonymous, or non-static inner classes all fine
* .onFailure(this::onFailure) // Lambdas, anonymous, or non-static inner classes all fine
* .build();
* );
* }
*
* private static class MyWorker implements Worker<MyInputType, MyOutputType> {
* MyOutputType doInBackground(MyInputType input) { ... }
* }
* private void onSuccess(MyOutputType output) { ... }
* private void onFailure(Throwable throwable) { ... }
*
* private void userDidSomething() { myExecutor.executeParallel(input); }
* }
* </code></pre>
*
* <p>Usage for non-UI tasks is the same, except that tasks can be created from anywhere instead of
* in onCreate. Non-UI tasks use low-priority threads separate from the UI task threads so as not to
* compete with more critical UI tasks.
*
* <pre><code>
*
* public class MyManager {
*
* private final DialerExecutor<MyInputType> myExecutor;
*
* public void init() {
* // Don't use non-static or anonymous inner classes for worker!
* myExecutor = DialerExecutorComponent.get(context).dialerExecutorFactory()
* .createNonUiTaskBuilder(worker)
* .onSuccess(this::onSuccess) // Lambdas, anonymous, or non-static inner classes all fine
* .onFailure(this::onFailure) // Lambdas, anonymous, or non-static inner classes all fine
* .build();
* );
* }
*
* private static class MyWorker implements Worker<MyInputType, MyOutputType> {
* MyOutputType doInBackground(MyInputType input) { ... }
* }
* private void onSuccess(MyOutputType output) { ... }
* private void onFailure(Throwable throwable) { ... }
*
* private void userDidSomething() { myExecutor.executeParallel(input); }
* }
* </code></pre>
*
* Note that non-UI tasks are intended to be relatively quick; for example reading/writing shared
* preferences or doing simple database work. If you submit long running non-UI tasks you may
* saturate the shared application threads and block other tasks. Also, this class does not create
* any wakelocks, so a long running task could be killed if the device goes to sleep while your task
* is still running. If you have to do long running or periodic work, consider using a job
* scheduler.
*/
public interface DialerExecutor<InputT> {
/** Functional interface for doing work in the background. */
interface Worker<InputT, OutputT> {
@WorkerThread
@Nullable
OutputT doInBackground(@Nullable InputT input) throws Throwable;
}
/** Functional interface for handling the result of background work. */
interface SuccessListener<OutputT> {
@MainThread
void onSuccess(@Nullable OutputT output);
}
/** Functional interface for handling an error produced while performing background work. */
interface FailureListener {
@MainThread
void onFailure(@NonNull Throwable throwable);
}
/** Builder for {@link DialerExecutor}. */
interface Builder<InputT, OutputT> {
/**
* Optional. Default is no-op.
*
* @param successListener a function executed on the main thread upon task success. There are no
* restraints on this as it is executed on the main thread, so lambdas, anonymous, or inner
* classes of your activity or fragment are all fine.
*/
@NonNull
Builder<InputT, OutputT> onSuccess(@NonNull SuccessListener<OutputT> successListener);
/**
* Optional. If this is not set and your worker throws an exception, the application will crash.
*
* @param failureListener a function executed on the main thread upon task failure. There are no
* restraints on this as it is executed on the main thread, so lambdas, anonymous, or inner
* classes of your activity or fragment are all fine.
*/
@NonNull
Builder<InputT, OutputT> onFailure(@NonNull FailureListener failureListener);
/**
* Builds the {@link DialerExecutor} which can be used to execute your task (repeatedly with
* differing inputs if desired).
*/
@NonNull
DialerExecutor<InputT> build();
}
/** Executes the task such that repeated executions for this executor are serialized. */
@MainThread
void executeSerial(@Nullable InputT input);
/**
* Executes the task after waiting {@code waitMillis}. If called while the previous invocation is
* still waiting to be started, the original invocation is cancelled.
*
* <p>This is useful for tasks which might get scheduled many times in very quick succession, but
* it is only the last one that actually needs to be executed.
*/
@MainThread
void executeSerialWithWait(@Nullable InputT input, long waitMillis);
/**
* Executes the task on a thread pool shared across the application. Multiple calls using this
* method may result in tasks being executed in parallel.
*/
@MainThread
void executeParallel(@Nullable InputT input);
/**
* Executes the task on a custom executor service. This should rarely be used; instead prefer
* {@link #executeSerial(Object)} or {@link #executeParallel(Object)}.
*/
@MainThread
void executeOnCustomExecutorService(
@NonNull ExecutorService executorService, @Nullable InputT input);
}
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