DownloadManager.class
在完成了编写网络请求、下载进度、线程等关键“零件”过后，我们现在要做的就是把这些零件通过一个核心骨架串联，方便调用。这有点类似Java的代理模式一样，需要一个或多个Class带负责这些组件的逻辑运行。现在，我们要编写一个完成这些职责的Class，这里就命名为DownloadManager.java：
/**
* Created by mid1529 on 2016/12/19.
* 下载管理方法
*/
public final class DownloadManager {
private static final String TAG = "DownloadManager";
public static final int HANDLER_DOWNLOAD_COMPLETED = 0x234123;
public static final int HANDLER_DOWNLOAD_FAILED = 0x12345234;
public static final int HANDLER_DOWNLOAD_PROGRESS = 0x2052344;
public static final int HANDLER_DOWNLOAD_CALL = 0x4234134;
@SuppressLint("StaticFieldLeak")
private static DownloadManager ourInstance = new DownloadManager();
private SQLiteDao mSQLiteDao = null;
private ArrayMap<Long, DownloadTask> mDownloadTaskQueue = null; //当前下载任务的集合
private ArrayMap<Long, Call> mDownloadTaskCallQueue = null;
private DownloadService.DownloadServiceBinder mDownloadServiceBinder = null;
private ServiceConnection mServiceConnection = null;
private Application mApplication = null;
private DownloadCallback mDownloadCallback = null;
private DownloadHandler mHandler = null;
private boolean mIsDeleteHistory = false;
private ExecutorService mCachedThreadPool = null;
public synchronized static DownloadManager getInstance() {
if (ourInstance == null) {
synchronized (DownloadManager.class) {
ourInstance = new DownloadManager();
}
}
return ourInstance;
}
private DownloadManager() {
mDownloadTaskQueue = new ArrayMap<>();
mDownloadTaskCallQueue = new ArrayMap<>();
}
/**
* 在Application中调用此方法初始化
* 只有调用这方法后才可以正常运行，否则会报错
*
* @param app Application
* @return DownloadManager实例
*/
public synchronized DownloadManager startService(Application app) {
if (mServiceConnection != null && mApplication != null)
return ourInstance;
mHandler = new DownloadHandler();
mCachedThreadPool = Executors.newCachedThreadPool();
mApplication = app;
Intent intent = new Intent(app, DownloadService.class);
mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
try {
mDownloadServiceBinder = (DownloadService.DownloadServiceBinder) iBinder;
mDownloadServiceBinder.setHandler(mHandler);
} catch (Exception e) {
e.printStackTrace();
onDestory();
}
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
onDestory();
}
};
app.startService(intent);
app.bindService(intent, mServiceConnection, Context.BIND_AUTO_CREATE);
mSQLiteDao = new SQLiteDao(app);
return ourInstance;
}
/**
* 添加到下载队列,阻塞线程，建议到子线程操作
* 如果任务已存在队列或者任务的url、filename不合法，也会添加错误
*
* @param task 下载任务
* @return 是否添加成功
*/
public boolean addTaskToQueue(DownloadTask task) {
if (!isDownloadTaskLegal(task)) //检测下载任务的参数是否合法
return false;
checkInited();
DownloadTask query = mSQLiteDao.queryTask(task);
task.setPause(false);
if (query == null) {//不存在表中，执行插入操作，加入下载列表
mSQLiteDao.insertDownloadTask(task);
query = mSQLiteDao.queryTask(task);
task.setTaskId(query.getTaskId());
mDownloadTaskQueue.put(query.getTaskId(), query);
mDownloadServiceBinder.startDownload(task);
} else {
task.setTaskId(query.getTaskId());
if (mDownloadTaskQueue.get(task.getTaskId()) == null) {
task.setPause(false);
mDownloadTaskQueue.put(task.getTaskId(), task);
mDownloadServiceBinder.startDownload(task);
}
}
return true;
}
/**
* 验证下载任务是否合法
*
* @param downloadTask 下载任务
* @return 是否合法
*/
@SuppressWarnings("RedundantIfStatement")
private boolean isDownloadTaskLegal(DownloadTask downloadTask) {
if (TextUtils.isEmpty(downloadTask.getFileName()))
return false;
if (TextUtils.isEmpty(downloadTask.getUrl()))
return false;
if (HttpUrl.parse(downloadTask.getUrl()) == null)
return false;
return true;
}
/**
* 暂停下载，并将下载任务从容器中移除
*
* @param task 下载的任务
*/
public void pauseDownload(DownloadTask task) {
task.setPause(true);
removeTaskFromQueue(task, false);
}
/**
* 从下载列表中移除下载任务
*
* @param downloadTask 下载任务
* @param isDeleteDbHistory 是否删除对应任务在数据库中的记录
*/
private void removeTaskFromQueue(final DownloadTask downloadTask, boolean isDeleteDbHistory) {
if (downloadTask.getTaskId() == null)
return;
DownloadTask task = mDownloadTaskQueue.get(downloadTask.getTaskId());
if (task != null) {
mDownloadTaskQueue.remove(task.getTaskId());
}
Call call = mDownloadTaskCallQueue.get(downloadTask.getTaskId());
if (call != null) {
call.cancel();
}
if (isDeleteDbHistory) { //不需要删除
//noinspection ConstantConditions
mCachedThreadPool.execute(new Runnable() {
@Override
public void run() {
mSQLiteDao.deleteDownloadTaskByKey(downloadTask.getTaskId());
}
});
}
}
private void addCallToQueue(Long taskId, Call call) {
mDownloadTaskCallQueue.put(taskId, call);
}
/**
* 停止下载服务，将会停止所有，且清空下载队列，但不会删除数据库中下载记录
*/
public void stopService() {
checkInited();
mDownloadTaskQueue.clear();
removeDownloadCallback();
if (mApplication == null)
return;
mApplication.stopService(new Intent(mApplication, DownloadService.class));
mApplication.unbindService(mServiceConnection);
}
/**
* 销毁
* 清空Handler中的消息
* 清空用到的容器
* 将对象置为null
* 尽量减少内存泄漏的可能
*/
private void onDestory() {
mHandler.removeCallbacksAndMessages(null);
mSQLiteDao = null;
mDownloadTaskQueue.clear(); //当前下载任务的集合
mDownloadTaskCallQueue.clear();
mDownloadServiceBinder = null;
mServiceConnection = null;
mCachedThreadPool.shutdown();
mCachedThreadPool = null;
mApplication = null;
}
/**
* 检查是否已经调用start()方法初始化，没有则直接抛异常
*/
private void checkInited() {
if (mDownloadServiceBinder == null) {
throw new NullPointerException("Do you remember invok \"DownloadManager.getInstance().start()\" in your Application.class? ");
}
}
/**
* @return 返回Dao
*/
public List<DownloadTask> getDownloadTask() {
checkInited();
return mSQLiteDao.queryAllTask();
}
/**
* 设置下载回调监听
*
* @param callback 回调
*/
public void setDownloadCallback(DownloadCallback callback) {
this.mDownloadCallback = callback;
}
/**
* 移除监听
*/
public void removeDownloadCallback() {
this.mDownloadCallback = null;
}
/**
* 更新下载任务到数据库
*
* @param downloadTask 下载任务
*/
private void updateDownloadTask(final DownloadTask downloadTask) {
mCachedThreadPool.execute(new Runnable() {
@Override
public void run() {
mSQLiteDao.updateDownloadTask(downloadTask);
}
});
}
/**
* 清空下载的信息
*
* @param downloadTask 下载任务
*/
private void cleanDownloadInfo(final DownloadTask downloadTask) {
mCachedThreadPool.execute(new Runnable() {
@Override
public void run() {
removeTaskFromQueue(downloadTask, mIsDeleteHistory);
}
});
}
/**
* 是否在下载失败或完成后，删除下载任务
*
* @return 是否删除
*/
public boolean isDeleteHistory() {
return mIsDeleteHistory;
}
/**
* 设置是否删除下载任务的记录
*
* @param deleteHistory 是否删除
*/
public void setDeleteHistory(boolean deleteHistory) {
mIsDeleteHistory = deleteHistory;
}
/**
* Handler负责处理进度传递消息等
*/
@SuppressWarnings("unchecked")
private static class DownloadHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case HANDLER_DOWNLOAD_PROGRESS:
getInstance().updateDownloadTask((DownloadTask) msg.obj);
getInstance().mDownloadCallback.onProgress((DownloadTask) msg.obj);
break;
case HANDLER_DOWNLOAD_COMPLETED:
getInstance().cleanDownloadInfo((DownloadTask) msg.obj);
getInstance().mDownloadCallback.onComplete((DownloadTask) msg.obj);
break;
case HANDLER_DOWNLOAD_FAILED:
getInstance().cleanDownloadInfo((DownloadTask) msg.obj);
getInstance().mDownloadCallback.onDownloadFaild((DownloadTask) msg.obj);
break;
case HANDLER_DOWNLOAD_CALL:
if (msg.obj instanceof ArrayMap) {
ArrayMap<Long, Call> map = (ArrayMap<Long, Call>) msg.obj;
if (map.size() != 0) {
getInstance().addCallToQueue(map.keyAt(0), map.get(map.keyAt(0)));
}
}
break;
}
}
}
}
典型的，因为一个App中只需要一个下载管理实例，所以我们控制只能用单例模式获取DownloadManager实例，然后进行通信。有兴趣的参考注释阅读。
总结
这个项目中，在提取网络Header中的数据时，采用正则表达式提取，比如Range，这种做法总感觉不科学，但不知道有什么方法获取到，这里就谦虚谦虚，谁能告知下科学方法。
整体思路就是这样，现在只是V0.2版本，很多地方不是很严谨，很多地方偷懒，过两天再改善吧。
流程图及整体Project周日会放到GitHub中，有兴趣的可以看看
到这里算是结束了这为期三天的水文，能静下来写点东西还真不容易，好好坚持吧。
Lolipop
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