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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.app.Fragment;
import android.app.FragmentManager;
import android.os.Bundle;
import android.support.annotation.MainThread;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import com.android.dialer.common.Assert;
import com.android.dialer.common.LogUtil;
import com.android.dialer.common.concurrent.DialerExecutor.FailureListener;
import com.android.dialer.common.concurrent.DialerExecutor.SuccessListener;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.concurrent.Executor;
/**
* A headless fragment for use in UI components that interact with ListenableFutures.
*
* <p>Callbacks are only executed if the UI component is still alive.
*
* <p>Example usage: <code><pre>
* public class MyActivity extends Activity {
*
* private UiListener<MyOutputType> uiListener;
*
* public void onCreate(Bundle bundle) {
* super.onCreate(bundle);
*
* // Must be called in onCreate!
* uiListener = DialerExecutorComponent.get(context).createUiListener(fragmentManager, taskId);
* }
*
* private void onSuccess(MyOutputType output) { ... }
* private void onFailure(Throwable throwable) { ... }
*
* private void userDidSomething() {
* ListenableFuture<MyOutputType> future = callSomeMethodReturningListenableFuture(input);
* uiListener.listen(future, this::onSuccess, this::onFailure);
* }
* }
* </pre></code>
*/
public class UiListener<OutputT> extends Fragment {
private Executor uiThreadExecutor;
private CallbackWrapper<OutputT> callbackWrapper;
@MainThread
static <OutputT> UiListener<OutputT> create(
Executor uiThreadExecutor, FragmentManager fragmentManager, String taskId) {
@SuppressWarnings("unchecked")
UiListener<OutputT> uiListener =
(UiListener<OutputT>) fragmentManager.findFragmentByTag(taskId);
if (uiListener == null) {
LogUtil.i("UiListener.create", "creating new UiListener for " + taskId);
uiListener = new UiListener<>();
uiListener.uiThreadExecutor = uiThreadExecutor;
fragmentManager.beginTransaction().add(uiListener, taskId).commit();
}
return uiListener;
}
/**
* Adds the specified listeners to the provided future.
*
* <p>The listeners are not called if the UI component this {@link UiListener} is declared in is
* dead.
*/
@MainThread
public void listen(
@NonNull ListenableFuture<OutputT> future,
@NonNull SuccessListener<OutputT> successListener,
@NonNull FailureListener failureListener) {
callbackWrapper =
new CallbackWrapper<>(Assert.isNotNull(successListener), Assert.isNotNull(failureListener));
Futures.addCallback(Assert.isNotNull(future), callbackWrapper, uiThreadExecutor);
}
private static class CallbackWrapper<OutputT> implements FutureCallback<OutputT> {
private SuccessListener<OutputT> successListener;
private FailureListener failureListener;
private CallbackWrapper(
SuccessListener<OutputT> successListener, FailureListener failureListener) {
this.successListener = successListener;
this.failureListener = failureListener;
}
@Override
public void onSuccess(@Nullable OutputT output) {
if (successListener == null) {
LogUtil.i("UiListener.runTask", "task succeeded but UI is dead");
} else {
successListener.onSuccess(output);
}
}
@Override
public void onFailure(Throwable throwable) {
LogUtil.e("UiListener.runTask", "task failed", throwable);
if (failureListener == null) {
LogUtil.i("UiListener.runTask", "task failed but UI is dead");
} else {
failureListener.onFailure(throwable);
}
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
@Override
public void onDetach() {
super.onDetach();
LogUtil.enterBlock("UiListener.onDetach");
if (callbackWrapper != null) {
callbackWrapper.successListener = null;
callbackWrapper.failureListener = null;
}
}
}
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