Home | History | Annotate | Download | only in concurrent 
      1 /*
      2  * Copyright (C) 2017 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.dialer.common.concurrent;
     18 
     19 import android.app.Fragment;
     20 import android.app.FragmentManager;
     21 import android.content.Context;
     22 import android.os.Bundle;
     23 import android.support.annotation.MainThread;
     24 import android.support.annotation.NonNull;
     25 import android.support.annotation.Nullable;
     26 import com.android.dialer.common.Assert;
     27 import com.android.dialer.common.LogUtil;
     28 import com.android.dialer.common.concurrent.DialerExecutor.FailureListener;
     29 import com.android.dialer.common.concurrent.DialerExecutor.SuccessListener;
     30 import com.google.common.util.concurrent.FutureCallback;
     31 import com.google.common.util.concurrent.Futures;
     32 import com.google.common.util.concurrent.ListenableFuture;
     33 
     34 /**
     35  * A headless fragment for use in UI components that interact with ListenableFutures.
     36  *
     37  * <p>Callbacks are only executed if the UI component is still alive.
     38  *
     39  * <p>Example usage: <code><pre>
     40  * public class MyActivity extends Activity {
     41  *
     42  *   private UiListener&lt;MyOutputType&gt uiListener;
     43  *
     44  *   public void onCreate(Bundle bundle) {
     45  *     super.onCreate(bundle);
     46  *
     47  *     // Must be called in onCreate!
     48  *     uiListener = DialerExecutorComponent.get(context).createUiListener(fragmentManager, taskId);
     49  *   }
     50  *
     51  *   private void onSuccess(MyOutputType output) { ... }
     52  *   private void onFailure(Throwable throwable) { ... }
     53  *
     54  *   private void userDidSomething() {
     55  *     ListenableFuture&lt;MyOutputType&gt; future = callSomeMethodReturningListenableFuture(input);
     56  *     uiListener.listen(this, future, this::onSuccess, this::onFailure);
     57  *   }
     58  * }
     59  * </pre></code>
     60  */
     61 public class UiListener<OutputT> extends Fragment {
     62 
     63   private CallbackWrapper<OutputT> callbackWrapper;
     64 
     65   @MainThread
     66   static <OutputT> UiListener<OutputT> create(FragmentManager fragmentManager, String taskId) {
     67     @SuppressWarnings("unchecked")
     68     UiListener<OutputT> uiListener =
     69         (UiListener<OutputT>) fragmentManager.findFragmentByTag(taskId);
     70 
     71     if (uiListener == null) {
     72       LogUtil.i("UiListener.create", "creating new UiListener for " + taskId);
     73       uiListener = new UiListener<>();
     74       // When launching an activity with the screen off, its onSaveInstanceState() is called before
     75       // its fragments are created, which means we can't use commit() and need to use
     76       // commitAllowingStateLoss(). This is not a problem for UiListener which saves no state.
     77       fragmentManager.beginTransaction().add(uiListener, taskId).commitAllowingStateLoss();
     78     }
     79     return uiListener;
     80   }
     81 
     82   /**
     83    * Adds the specified listeners to the provided future.
     84    *
     85    * <p>The listeners are not called if the UI component this {@link UiListener} is declared in is
     86    * dead.
     87    */
     88   @MainThread
     89   public void listen(
     90       Context context,
     91       @NonNull ListenableFuture<OutputT> future,
     92       @NonNull SuccessListener<OutputT> successListener,
     93       @NonNull FailureListener failureListener) {
     94     callbackWrapper =
     95         new CallbackWrapper<>(Assert.isNotNull(successListener), Assert.isNotNull(failureListener));
     96     Futures.addCallback(
     97         Assert.isNotNull(future),
     98         callbackWrapper,
     99         DialerExecutorComponent.get(context).uiExecutor());
    100   }
    101 
    102   private static class CallbackWrapper<OutputT> implements FutureCallback<OutputT> {
    103     private SuccessListener<OutputT> successListener;
    104     private FailureListener failureListener;
    105 
    106     private CallbackWrapper(
    107         SuccessListener<OutputT> successListener, FailureListener failureListener) {
    108       this.successListener = successListener;
    109       this.failureListener = failureListener;
    110     }
    111 
    112     @Override
    113     public void onSuccess(@Nullable OutputT output) {
    114       if (successListener == null) {
    115         LogUtil.i("UiListener.runTask", "task succeeded but UI is dead");
    116       } else {
    117         successListener.onSuccess(output);
    118       }
    119     }
    120 
    121     @Override
    122     public void onFailure(Throwable throwable) {
    123       LogUtil.e("UiListener.runTask", "task failed", throwable);
    124       if (failureListener == null) {
    125         LogUtil.i("UiListener.runTask", "task failed but UI is dead");
    126       } else {
    127         failureListener.onFailure(throwable);
    128       }
    129     }
    130   }
    131 
    132   @Override
    133   public void onCreate(Bundle savedInstanceState) {
    134     super.onCreate(savedInstanceState);
    135     setRetainInstance(true);
    136     // Note: We use commitAllowingStateLoss when attaching the fragment so it may not be safe to
    137     // read savedInstanceState in all situations. (But it's not anticipated that this fragment
    138     // should need to rely on saved state.)
    139   }
    140 
    141   @Override
    142   public void onDetach() {
    143     super.onDetach();
    144     LogUtil.enterBlock("UiListener.onDetach");
    145     if (callbackWrapper != null) {
    146       callbackWrapper.successListener = null;
    147       callbackWrapper.failureListener = null;
    148     }
    149   }
    150 }
    151