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/*
* Copyright (C) 2010 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.mail.utils;
import android.os.Handler;
import android.util.Log;
import java.util.Timer;
import java.util.TimerTask;
/**
* This class used to "throttle" a flow of events.
*
* When {@link #onEvent()} is called, it calls the callback in a certain timeout later.
* Initially {@link #mMinTimeout} is used as the timeout, but if it gets multiple {@link #onEvent}
* calls in a certain amount of time, it extends the timeout, until it reaches {@link #mMaxTimeout}.
*
* This class is primarily used to throttle content changed events.
*/
public class Throttle {
public static final boolean DEBUG = false; // Don't submit with true
public static final int DEFAULT_MIN_TIMEOUT = 150;
public static final int DEFAULT_MAX_TIMEOUT = 2500;
// exposed for testing
public static final int TIMEOUT_EXTEND_INTERVAL = 500;
private static final String LOG_TAG = LogTag.getLogTag();
private static Timer TIMER = new Timer();
private final Clock mClock;
private final Timer mTimer;
/** Name of the instance. Only for logging. */
private final String mName;
/** Handler for UI thread. */
private final Handler mHandler;
/** Callback to be called */
private final Runnable mCallback;
/** Minimum (default) timeout, in milliseconds. */
private final int mMinTimeout;
/** Max timeout, in milliseconds. */
private final int mMaxTimeout;
/** Current timeout, in milliseconds. */
private int mTimeout;
/** When {@link #onEvent()} was last called. */
private long mLastEventTime;
private MyTimerTask mRunningTimerTask;
/** Constructor with default timeout */
public Throttle(String name, Runnable callback, Handler handler) {
this(name, callback, handler, DEFAULT_MIN_TIMEOUT, DEFAULT_MAX_TIMEOUT);
}
/** Constructor that takes custom timeout */
public Throttle(String name, Runnable callback, Handler handler,int minTimeout,
int maxTimeout) {
this(name, callback, handler, minTimeout, maxTimeout, Clock.INSTANCE, TIMER);
}
/** Constructor for tests */
// exposed for testing
public Throttle(String name, Runnable callback, Handler handler,int minTimeout,
int maxTimeout, Clock clock, Timer timer) {
if (maxTimeout < minTimeout) {
throw new IllegalArgumentException();
}
mName = name;
mCallback = callback;
mClock = clock;
mTimer = timer;
mHandler = handler;
mMinTimeout = minTimeout;
mMaxTimeout = maxTimeout;
mTimeout = mMinTimeout;
}
private void debugLog(String message) {
Log.d(LOG_TAG, "Throttle: [" + mName + "] " + message);
}
private boolean isCallbackScheduled() {
return mRunningTimerTask != null;
}
public void cancelScheduledCallback() {
if (mRunningTimerTask != null) {
if (DEBUG) debugLog("Canceling scheduled callback");
mRunningTimerTask.cancel();
mRunningTimerTask = null;
}
}
// exposed for testing
public void updateTimeout() {
final long now = mClock.getTime();
if ((now - mLastEventTime) <= TIMEOUT_EXTEND_INTERVAL) {
mTimeout *= 2;
if (mTimeout >= mMaxTimeout) {
mTimeout = mMaxTimeout;
}
if (DEBUG) debugLog("Timeout extended " + mTimeout);
} else {
mTimeout = mMinTimeout;
if (DEBUG) debugLog("Timeout reset to " + mTimeout);
}
mLastEventTime = now;
}
public void onEvent() {
if (DEBUG) debugLog("onEvent");
updateTimeout();
if (isCallbackScheduled()) {
if (DEBUG) debugLog(" callback already scheduled");
} else {
if (DEBUG) debugLog(" scheduling callback");
mRunningTimerTask = new MyTimerTask();
mTimer.schedule(mRunningTimerTask, mTimeout);
}
}
/**
* Timer task called on timeout,
*/
private class MyTimerTask extends TimerTask {
private boolean mCanceled;
@Override
public void run() {
mHandler.post(new HandlerRunnable());
}
@Override
public boolean cancel() {
mCanceled = true;
return super.cancel();
}
private class HandlerRunnable implements Runnable {
@Override
public void run() {
mRunningTimerTask = null;
if (!mCanceled) { // This check has to be done on the UI thread.
if (DEBUG) debugLog("Kicking callback");
mCallback.run();
}
}
}
}
// exposed for testing
public int getTimeoutForTest() {
return mTimeout;
}
// exposed for testing
public long getLastEventTimeForTest() {
return mLastEventTime;
}
}
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