| /* |
| * Copyright (C) 2013 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 android.content.AsyncTaskLoader; |
| import android.content.Context; |
| import android.database.ContentObserver; |
| import android.os.CancellationSignal; |
| import android.os.OperationCanceledException; |
| |
| /** |
| * Loader that derives its data from a Uri. Watches for {@link ContentObserver} |
| * changes while started, manages {@link CancellationSignal}, and caches |
| * returned results. |
| */ |
| public abstract class UriDerivativeLoader<P, R> extends AsyncTaskLoader<R> { |
| final ForceLoadContentObserver mObserver; |
| |
| private final P mParam; |
| |
| private R mResult; |
| private CancellationSignal mCancellationSignal; |
| |
| @Override |
| public final R loadInBackground() { |
| synchronized (this) { |
| if (isLoadInBackgroundCanceled()) { |
| throw new OperationCanceledException(); |
| } |
| mCancellationSignal = new CancellationSignal(); |
| } |
| try { |
| return loadInBackground(mParam, mCancellationSignal); |
| } finally { |
| synchronized (this) { |
| mCancellationSignal = null; |
| } |
| } |
| } |
| |
| public abstract R loadInBackground(P param, CancellationSignal signal); |
| |
| @Override |
| public void cancelLoadInBackground() { |
| super.cancelLoadInBackground(); |
| |
| synchronized (this) { |
| if (mCancellationSignal != null) { |
| mCancellationSignal.cancel(); |
| } |
| } |
| } |
| |
| @Override |
| public void deliverResult(R result) { |
| if (isReset()) { |
| closeQuietly(result); |
| return; |
| } |
| R oldResult = mResult; |
| mResult = result; |
| |
| if (isStarted()) { |
| super.deliverResult(result); |
| } |
| |
| if (oldResult != null && oldResult != result) { |
| closeQuietly(oldResult); |
| } |
| } |
| |
| public UriDerivativeLoader(Context context, P param) { |
| super(context); |
| mObserver = new ForceLoadContentObserver(); |
| mParam = param; |
| } |
| |
| @Override |
| protected void onStartLoading() { |
| if (mResult != null) { |
| deliverResult(mResult); |
| } |
| if (takeContentChanged() || mResult == null) { |
| forceLoad(); |
| } |
| } |
| |
| @Override |
| protected void onStopLoading() { |
| cancelLoad(); |
| } |
| |
| @Override |
| public void onCanceled(R result) { |
| closeQuietly(result); |
| } |
| |
| @Override |
| protected void onReset() { |
| super.onReset(); |
| |
| // Ensure the loader is stopped |
| onStopLoading(); |
| |
| closeQuietly(mResult); |
| mResult = null; |
| |
| getContext().getContentResolver().unregisterContentObserver(mObserver); |
| } |
| |
| private void closeQuietly(R result) { |
| if (result instanceof AutoCloseable) { |
| try { |
| ((AutoCloseable) result).close(); |
| } catch (RuntimeException rethrown) { |
| throw rethrown; |
| } catch (Exception ignored) { |
| } |
| } |
| } |
| } |