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/*
* 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();
}
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