1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.email; 18 19 import com.android.emailcommon.Logging; 20 21 import android.util.Log; 22 23 import java.util.concurrent.atomic.AtomicBoolean; 24 25 /** 26 * Base class for a task that runs at most one instance at any given moment. 27 * 28 * Call {@link #run} to start the task. If the task is already running on another thread, it'll do 29 * nothing. 30 */ 31 public abstract class SingleRunningTask<Param> { 32 private final AtomicBoolean mIsRunning = new AtomicBoolean(false); 33 private final String mLogTaskName; 34 35 public SingleRunningTask(String logTaskName) { 36 mLogTaskName = logTaskName; 37 } 38 39 /** 40 * Calls {@link #runInternal} if it's not running already. 41 */ 42 public final void run(Param param) { 43 if (mIsRunning.compareAndSet(false, true)) { 44 Log.i(Logging.LOG_TAG, mLogTaskName + ": start"); 45 try { 46 runInternal(param); 47 } finally { 48 Log.i(Logging.LOG_TAG, mLogTaskName + ": done"); 49 mIsRunning.set(false); 50 } 51 } else { 52 // Already running -- do nothing. 53 Log.i(Logging.LOG_TAG, mLogTaskName + ": already running"); 54 } 55 } 56 57 /** 58 * The actual task must be implemented by subclasses. 59 */ 60 protected abstract void runInternal(Param param); 61 62 /* package */ boolean isRunningForTest() { 63 return mIsRunning.get(); 64 } 65 } 66
