Integration ContentResolver#refresh into RefreshLayout.

Bug: 32873048
Change-Id: Ifbe114f3c91c6b48cde482ebc3874e8a7f3fb2f5
diff --git a/src/com/android/documentsui/RefreshTask.java b/src/com/android/documentsui/RefreshTask.java
new file mode 100644
index 0000000..2521976
--- /dev/null
+++ b/src/com/android/documentsui/RefreshTask.java
@@ -0,0 +1,103 @@
+/*
+ * 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 static com.android.documentsui.base.Shared.DEBUG;
+
+import android.annotation.Nullable;
+import android.app.Activity;
+import android.app.Fragment;
+import android.content.ContentProviderClient;
+import android.content.ContentResolver;
+import android.content.Context;
+import android.net.Uri;
+import android.os.CancellationSignal;
+import android.util.Log;
+
+import com.android.documentsui.TimeoutTask;
+import com.android.documentsui.base.CheckedTask;
+import com.android.documentsui.base.State;
+import com.android.documentsui.dirlist.Model;
+
+import java.util.function.Consumer;
+
+/**
+ * A {@link CheckedTask} that calls
+ * {@link ContentResolver#refresh(Uri, android.os.Bundle, android.os.CancellationSignal)} on the
+ * current directory, and then calls the supplied callback with the refresh return value.
+ */
+public class RefreshTask extends TimeoutTask<Void, Boolean> {
+
+    private final static String TAG = "RefreshTask";
+
+    private final Context mContext;
+    private final State mState;
+    private final Consumer<Boolean> mCallback;
+    private final CancellationSignal mSignal;
+
+
+    public RefreshTask(State state, Activity activity, Consumer<Boolean> callback) {
+        this(state, activity, activity::isDestroyed, callback);
+    }
+
+    public RefreshTask(State state, Fragment fragment, Consumer<Boolean> callback) {
+        this(state, fragment.getContext(), fragment::isDetached, callback);
+    }
+
+    public RefreshTask(State state, Context context, Check check, Consumer<Boolean> callback) {
+        super(check);
+        mContext = context.getApplicationContext();
+        mState = state;
+        mCallback = callback;
+        mSignal = new CancellationSignal();
+    }
+
+    @Override
+    public @Nullable Boolean run(Void... params) {
+        final Uri uri = mState.stack.peek().derivedUri;
+        final ContentResolver resolver = mContext.getContentResolver();
+        final String authority = uri.getAuthority();
+        boolean refreshed = false;
+        ContentProviderClient client = null;
+        try {
+            client = DocumentsApplication.acquireUnstableProviderOrThrow(resolver, authority);
+            refreshed = client.refresh(uri, null, mSignal);
+        } catch (Exception e) {
+            Log.w(TAG, "Failed to refresh", e);
+        } finally {
+            ContentProviderClient.releaseQuietly(client);
+        }
+        return refreshed;
+    }
+
+    @Override
+    protected void onTimeout() {
+        mSignal.cancel();
+    }
+
+    @Override
+    public void finish(Boolean refreshed) {
+        if (DEBUG) {
+            if (refreshed) {
+                Log.v(TAG, "Provider has new content and has refreshed");
+            } else {
+                Log.v(TAG, "Provider has no new content and did not refresh");
+            }
+        }
+        mCallback.accept(refreshed);
+    }
+}