ThrottledContentObserver.java

/*
 * Copyright 2014 Google Inc. All rights reserved.
 *
 * 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.google.samples.apps.iosched.util;

import android.database.ContentObserver;
import android.net.Uri;
import android.os.Handler;

/**
 * A ContentObserver that bundles multiple consecutive changes in a short time period into one.
 * This can be used in place of a regular ContentObserver to protect against getting
 * too many consecutive change events as a result of data changes. This observer will wait
 * a while before firing, so if multiple requests come in in quick succession, they will
 * cause it to fire only once.
 */
public class ThrottledContentObserver extends ContentObserver {
    Handler mMyHandler;
    Runnable mScheduledRun = null;
    private static final int THROTTLE_DELAY = 1000;
    Callbacks mCallback = null;

    public interface Callbacks {
        public void onThrottledContentObserverFired();
    }

    public ThrottledContentObserver(Callbacks callback) {
        super(null);
        mMyHandler = new Handler();
        mCallback = callback;
    }

    @Override
    public void onChange(boolean selfChange) {
        if (mScheduledRun != null) {
            mMyHandler.removeCallbacks(mScheduledRun);
        } else {
            mScheduledRun = new Runnable() {
                @Override
                public void run() {
                    if (mCallback != null) {
                        mCallback.onThrottledContentObserverFired();
                    }
                }
            };
        }
        mMyHandler.postDelayed(mScheduledRun, THROTTLE_DELAY);
    }

    public void cancelPendingCallback() {
        if (mScheduledRun != null) {
            mMyHandler.removeCallbacks(mScheduledRun);
        }
    }

    @Override
    public void onChange(boolean selfChange, Uri uri) {
        onChange(selfChange);
    }
}