| /* |
| * Copyright (C) 2012 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.os.Looper; |
| import android.os.Message; |
| import android.os.SystemClock; |
| |
| /** |
| * Class to queue tasks. This delay the specified task by the specified time, up to the maximum |
| * duration from the time that the first request was received |
| */ |
| public abstract class DelayedTaskHandler extends Handler { |
| private final int mDelayMs; |
| |
| private static final long UNSET_TIME = -1; |
| |
| /** |
| * Tracks the time when a task was queued, when there had been no pending task. |
| */ |
| private long mLastTaskExecuteTime = UNSET_TIME; |
| |
| public DelayedTaskHandler(Looper looper, int defaultDelayMs) { |
| super(looper); |
| mDelayMs = defaultDelayMs; |
| } |
| |
| /** |
| * Schedule the task to be run after the default delay. |
| */ |
| public void scheduleTask() { |
| final long currentTime = SystemClock.elapsedRealtime(); |
| removeMessages(0); |
| if (mLastTaskExecuteTime == UNSET_TIME || |
| ((mLastTaskExecuteTime + mDelayMs) < currentTime)) { |
| // If this is the first task that has been queued or if the last task ran more than |
| // long enough ago that we don't want to delay this task, run it now |
| sendEmptyMessage(0); |
| } else { |
| // Otherwise delay this task for the specify delay duration |
| sendEmptyMessageDelayed(0, mDelayMs); |
| } |
| } |
| |
| @Override |
| public void dispatchMessage(Message msg) { |
| onTaskExecution(); |
| performTask(); |
| } |
| |
| /** |
| * Called when the task managed by this handler is executed. This method can also be called |
| * to indicate that the task has been started externally. |
| * |
| * This updates the handler's internal timestamp. |
| */ |
| public void onTaskExecution() { |
| mLastTaskExecuteTime = SystemClock.elapsedRealtime(); |
| } |
| |
| /** |
| * Method to perform the needed task. |
| */ |
| protected abstract void performTask(); |
| } |