1 files changed, 143 insertions, 0 deletions
diff --git a/java/com/android/dialer/common/concurrent/UiListener.java b/java/com/android/dialer/common/concurrent/UiListener.java
new file mode 100644
index 000000000..11302d299
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+++ b/java/com/android/dialer/common/concurrent/UiListener.java
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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&lt;MyOutputType&gt 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&lt;MyOutputType&gt; 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;
+    }
+  }
+}