在我們的開發過程中，經常會用到下載功能,也經常伴有顯示下載進度的需求，什麼下載文件啊，更新版本啊等等吧，今天給大家介紹一個帶進度更新下載的開源框架—-android-downloader（下載地址），並跟大家一起看一下它的源碼，熟悉一下它的實現過程。
一、涉及到的類及作用。
1. DownloadTask.java
封裝單個下載任務包含的信息，包括要下載文件的名稱、文件的下載地址、要下載到本地的路徑、開始結束時間、文件類型、文件大小、下載監聽（DownloadListener）等等，還有就是當前下載任務的開始，停止等方法。
2.DownloadListener.java
下載任務回調類，包括onAdd（DownloadTask task）、onDelete(DownloadTask task)、onStop(DownloadTask task)、onStart()、onProgressUpdate(Integer... values)、onSuccess(DownloadTask task)、onCancelled()、onError(Throwable thr)、onFinish()方法。
3.AsycDownloadTask.java
真正實現下載的類，繼承自AsyncTask類。
4.DownloadException.java
繼承自Exception類的自定義錯誤提示類。
5.DownloadStatus.java
下載中的各種狀態，包括STATUS_PENDING、STATUS_RUUUING、STATUS_STOPPED、STATUS_FINISHED、STATUS_FAILED、STATUS_DETELED幾種狀態。
6.DownloadType.java
下載文件的類型，包括Type_unknown、type_text、type_image、type_music、type_video、type_app幾種類型。
7.Isql.java、ISqlmpl.java、DatabaseConfigUtil.java、DatabaseHelper.java
OrmLite數據庫操作相關類，保存下載任務信息，這裏先不講，知道有這麼回事就行了，還是主要將下載更新相關實現。
二、源碼分析。
至於怎麼用大家可以網上去查一下，可以結合Listview一起用，我在這裏只跟大家分析一下它的實現過程，，實現過程明白了，用起來也就得心應手了。很簡單，大致的過程就是我們需要自己去new一個DownloadListener並實現裏邊的方法（在這裏實現具體的更新操作），實例化DownLoadManager對象，當要建立下載任務時，每一個下載任務創建一個DownLoadTask對象並賦值（name、path、url等等），將當前對象與DownloadListener對象一起添加到DownLoadMagager中如下代碼：
DownloadTask task = new DownloadTask(KnowledgeDocListActivity.this);
task.setUrl(Settings.DOMAINNAME + docEntity.getUrl());
task.setName(docEntity.getDocName());
task.setPath(Settings.WORDFILE + docEntity.getDocName());
task.setId(docEntity.getId());
mDownloadManager.add(task, listener);
/**
* Add Task
*
* @param task DownloadTask
* @return
*/
public void add(DownloadTask task, DownloadListener listener) {
Log.i("Add Task");
//判斷task的可用性；
if (task == null || !task.isValid()) {
OnResult(POST_MESSAGE.ERROR, task, listener, DownloadException.DOWNLOAD_TASK_NOT_VALID);
return;
}
if (task.getContext() == null) {
//如果我們沒有對task的Context屬性賦值，在這裏賦值；
//可以通過上邊代碼得知，在new DownloadTask(KnowledgeDocListActivity.this)的時候將Context傳過來的；
task.setContext(context);
}
ISql iSql = new ISqlImpl(context);
DownloadTask temptask = null;
try {
//根據傳入的task到OrmLite數據庫查找；
temptask = iSql.queryDownloadTask(task);
if (temptask == null || !temptask.isValid() || !temptask.isComplete()) {
//判斷task的name、path、url屬性是否都存在；
if (task.isComplete()) {
iSql.addDownloadTask(task);
//發送添加task事件；
OnResult(POST_MESSAGE.ADD, task, listener, -1);
Log.i("The Task is stored in the sqlite.");
} else {
//如果沒有name等屬性，開啓異步任務去網上獲取，這裏只是獲取，沒有下載；
task.start(context, listener, true);
}
} else {
//數據庫中已經存在這個下載任務；
task.setDownloadTask(temptask);
OnResult(POST_MESSAGE.ADD, task, listener, -1);
Log.i("The Task is already stored in the sqlite.");
}
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* deal with the result
*
* @param message POST_MESSAGE
* @param listener DownloadListener
* @param code code
*/
@SuppressWarnings("rawtypes")
private void OnResult(final POST_MESSAGE message, final DownloadTask task, final DownloadListener listener, final Integer code) {
if (context == null || !(context instanceof Activity)) {
Log.w("The context is null or invalid!");
return;
}
((Activity) context).runOnUiThread(new Runnable() {
public void run() {
if (listener == null) {
return;
}
switch (message) {
case ADD:
listener.onAdd(task);
break;
case DELETE:
listener.onDelete(task);
break;
case START:
listener.onStart();
break;
case FINISH:
listener.onFinish();
break;
case STOP:
listener.onStop(task);
break;
case ERROR:
listener.onError(new DownloadException(code));
break;
}
}
});
}可見他是通過message不同的狀態，調用了DownloadListener的不同方法,正好，也看一下我們這個最終操作UI的類吧：
private DownloadListener listener = new DownloadListener<Integer, DownloadTask>() {
@Override
public void onAdd(DownloadTask downloadTask) {
super.onAdd(downloadTask);
LogUtils.d("onAdd()");
mDownloadTasklist.add(downloadTask);
LogUtils.d("" + downloadTask);
mDocListAdapter.notifyDataSetChanged();
}
@Override
public void onDelete(DownloadTask downloadTask) {
super.onDelete(downloadTask);
LogUtils.d("onDelete()");
}
@Override
public void onStop(DownloadTask downloadTask) {
super.onStop(downloadTask);
LogUtils.d("onStop()");
}
/**
* Runs on the UI thread before doInBackground(Params...).
*/
@Override
public void onStart() {
super.onStart();
UIUtils.makeToast(KnowledgeDocListActivity.this, getResources().getString(R.string.start_download), AppMsg.STYLE_ALERT).show();
}
/**
* Runs on the UI thread after publishProgress(Progress...) is invoked. The
* specified values are the values passed to publishProgress(Progress...).
*
* @param values The values indicating progress.
*/
@Override
public void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
mDocListAdapter.notifyDataSetChanged();
LogUtils.d("onProgressUpdate");
}
/**
* Runs on the UI thread after doInBackground(Params...). The specified
* result is the value returned by doInBackground(Params...). This method
* won't be invoked if the task was cancelled.
*
* @param downloadTask The result of the operation computed by
* doInBackground(Params...).
*/
@Override
public void onSuccess(DownloadTask downloadTask) {
super.onSuccess(downloadTask);
LogUtils.d("異步URL:" + downloadTask.getUrl());
for (int i = 0; i < mDocList.size(); i++) {
LogUtils.d("docListURL:" + i + ":" + mDocList.get(i).getUrl());
if (downloadTask.getUrl().contains(mDocList.get(i).getUrl())) {
mDocList.get(i).setIsLocalHave(true);
break;
}
}
UIUtils.makeToast(KnowledgeDocListActivity.this, getResources().getString(R.string.download_success), AppMsg.STYLE_ALERT).show();
mDocListAdapter.notifyDataSetChanged();
LogUtils.d("onSuccess()");
}
/**
* Applications should preferably override onCancelled(Object). This method
* is invoked by the default implementation of onCancelled(Object). Runs on
* the UI thread after cancel(boolean) is invoked and
* doInBackground(Object[]) has finished.
*/
@Override
public void onCancelled() {
super.onCancelled();
LogUtils.d("onCancelled()");
}
@Override
public void onError(Throwable thr) {
super.onError(thr);
LogUtils.d("onError()：" + thr.getMessage());
UIUtils.makeToast(KnowledgeDocListActivity.this, getResources().getString(R.string.down_fail), AppMsg.STYLE_ALERT).show();
}
/**
* Runs on the UI thread after doInBackground(Params...) when the task is
* finished or cancelled.
*/
@Override
public void onFinish() {
super.onFinish();
LogUtils.d("onFinish()");
}
};
/**
* url, name and path is not empty.
*
* @return true is valid,otherwise not.
*/
public boolean isComplete() {
return !TextUtils.isEmpty(url) && !TextUtils.isEmpty(name) && !TextUtils.isEmpty(path);
}
/**
* Start the Task
*
* @param context Context
* @param listener DownloadListener
*/
@SuppressWarnings({
"rawtypes", "unchecked"
})
protected void start(Context context, DownloadListener listener, boolean isOnlyGetHead) {
//Get context,which will be used to communicate with sqlite.
if (this.context == null && context != null) {
this.context = context;
}
if (task != null) {
task.cancel(false);
}
<span style="white-space:pre"> </span>//AsycDownloadTask是繼承了AsyncTask的一個類，
<span style="white-space:pre"> </span>//所以在這裏他開啓了異步去獲取信息；
task = new AsycDownloadTask(listener, isOnlyGetHead);
task.execute(this);
}
/**
* TODO if error occurs,carry it out. if (listener != null) {
* listener.onError(new Throwable()); }
*/
protected DownloadTask doInBackground(DownloadTask... tasks) {
if (tasks.length <= 0) {
Log.e("There is no DownloadTask.");
return null;
}
DownloadTask task = tasks[0];
if (task == null || !task.isValid()) {
//發送task異常錯誤信息；
SendError(task, DownloadException.DOWNLOAD_TASK_NOT_VALID);
Log.e("The task is not valid,or the url of the task is not valid.");
return null;
}
String path = task.getPath();
File file = new File(path);
InputStream in = null;
RandomAccessFile out = null;
HttpURLConnection connection = null;
try {
long range = file.length();
long size = task.getSize();
long curSize = range;
String filename = task.getName();
String contentType = task.getMimeType();
//本地文件信息與數據庫保存task信息一致，說明下載了這個任務；
if (task.getStatus() == DownloadStatus.STATUS_FINISHED && size == range) {
Log.i("The DownloadTask has already been downloaded.");
return task;
}
<span style="white-space:pre"> </span> //根據url獲取網絡文件相關信息；
String urlString = task.getUrl();
String cookies = null;
while (true) {
URL url = new URL(urlString);
connection = (HttpURLConnection) url.openConnection();
connection.setRequestProperty("User-Agent", "Snowdream Mobile");
connection.setRequestProperty("Connection", "Keep-Alive");
if (cookies != null && cookies != "") {
connection.setRequestProperty("Cookie", cookies);
}
connection.setRequestMethod("GET");
if (range > 0) {
connection.setRequestProperty("Range", "bytes=" + range +
"-");
}
//http auto redirection
//see: http://www.mkyong.com/java/java-httpurlconnection-follow-redirect-example/
boolean redirect = false;
boolean success = false;
// normally, 3xx is redirect
int status = connection.getResponseCode();
Log.i("HTTP STATUS CODE: " + status);
switch (status) {
case HttpURLConnection.HTTP_OK:
case HttpURLConnection.HTTP_PARTIAL:
success = true;
String transfer_encoding = connection.getHeaderField("Transfer-Encoding");
if (!TextUtils.isEmpty(transfer_encoding)
&& transfer_encoding.equalsIgnoreCase("chunked")) {
mode = MODE_TRUNKED;
Log.i("HTTP MODE: TRUNKED");
} else {
mode = MODE_DEFAULT;
Log.i("HTTP MODE: DEFAULT");
}
String accept_ranges = connection.getHeaderField("Accept-Ranges");
if (!TextUtils.isEmpty(accept_ranges)
&& accept_ranges.equalsIgnoreCase("bytes")) {
Log.i("Accept-Ranges: bytes");
} else {
range = 0;
Log.i("Accept-Ranges: none");
}
break;
case HttpURLConnection.HTTP_MOVED_TEMP:
case HttpURLConnection.HTTP_MOVED_PERM:
case HttpURLConnection.HTTP_SEE_OTHER:
redirect = true;
// get redirect url from "location" header field
urlString = connection.getHeaderField("Location");
// get the cookie if need, for login
cookies = connection.getHeaderField("Set-Cookie");
Log.i("Redirect Url : " + urlString);
break;
default:
success = false;
break;
}
if (!redirect) {
if (!success) {
SendError(task, DownloadException.DOWNLOAD_TASK_FAILED);
Log.e("Http Connection error. ");
return null;
}
Log.i("Successed to establish the http connection.Ready to download...");
break;
}
}
if (range == 0) {
//set the whole file size
size = connection.getContentLength();
//賦值文件大小字段；
task.setSize(size);
if (contentType != connection.getContentType()) {
contentType = connection.getContentType();
//賦值類型；
task.setMimeType(contentType);
}
//auto get filename
if (TextUtils.isEmpty(filename)) {
String disposition = connection.getHeaderField("Content-Disposition");
if (disposition != null) {
// extracts file name from header field
final String FILENAME = "filename=";
final int startIdx = disposition.indexOf(FILENAME);
final int endIdx = disposition.indexOf(';', startIdx);
filename = disposition.substring(startIdx + FILENAME.length(), endIdx > 0 ? endIdx : disposition.length());
} else {
// extracts file name from URL
filename = urlString.substring(urlString.lastIndexOf("/") + 1,
urlString.length());
}
//賦值文件名稱；
task.setName(filename);
}
//auto get filepath
if (TextUtils.isEmpty(path)) {
path = STORE_PATH + filename;
file = new File(path);
<span style="white-space:pre"> </span>//賦值path；
task.setPath(path);
}
task.setStartTime(System.currentTimeMillis());
<span style="white-space:pre"> </span>//下載任務添加到數據庫；
SaveDownloadTask(task, task.getStatus());
Log.i("The Task is stored in the sqlite.");
<span style="white-space:pre"> </span>//如果是隻獲取信息，不下載文件，則發送調用DownLoadLisener的add方法，
<span style="white-space:pre"> </span>//並不進行後續下載操作；
if (isOnlyGetHead) {
SendAdd(task);
return null;
}
}
File dir = file.getParentFile();
if (!dir.exists() && !dir.mkdirs()) {
SendError(task, DownloadException.DOWNLOAD_TASK_FAILED);
Log.e("The directory of the file can not be created!");
return null;
}
task.setStatus(DownloadStatus.STATUS_RUNNING);
SaveDownloadTask(task, task.getStatus());
Log.i("DownloadTask " + task);
out = new RandomAccessFile(file, "rw");
out.seek(range);
in = new BufferedInputStream(connection.getInputStream());
byte[] buffer = new byte[1024];
int nRead = 0;
int progress = -1;
boolean isFinishDownloading = true;
//下載操作；
while ((nRead = in.read(buffer, 0, 1024)) > 0) {
out.write(buffer, 0, nRead);
curSize += nRead;
if (size != 0) {
progress = (int) ((curSize * 100) / size);
}
//這裏更新了進度條，注意注意... ...
publishProgress(progress);
Log.i("cur size:" + (curSize) + " total size:" + (size) + " cur progress:" + (progress));
if (isCancelled()) {
task.setStatus(DownloadStatus.STATUS_STOPPED);
isFinishDownloading = false;
break;
}
if (task.getStatus() != DownloadStatus.STATUS_RUNNING) {
isFinishDownloading = false;
break;
}
}
if (!isFinishDownloading) {
Log.w("The DownloadTask has not been completely downloaded.");
SaveDownloadTask(task, task.getStatus());
return null;
}
//when the mode is MODE_TRUNKED,set the latest size.
if (size == 0 && curSize != 0) {
task.setSize(curSize);
}
range = file.length();
size = task.getSize();
Log.i("range: " + range + " size: " + size);
if (range != 0 && range == size) {
Log.i("The DownloadTask has been successfully downloaded.");
task.setFinishTime(System.currentTimeMillis());
SaveDownloadTask(task, DownloadStatus.STATUS_FINISHED);
return task;
} else {
Log.i("The DownloadTask failed to downloaded.");
SendError(task, DownloadException.DOWNLOAD_TASK_FAILED);
return null;
}
} catch (MalformedURLException e) {
SendError(task, DownloadException.DOWNLOAD_TASK_FAILED);
e.printStackTrace();
} catch (ProtocolException e) {
SendError(task, DownloadException.DOWNLOAD_TASK_FAILED);
e.printStackTrace();
} catch (FileNotFoundException e) {
SendError(task, DownloadException.DOWNLOAD_TASK_FAILED);
e.printStackTrace();
} catch (IOException e) {
SendError(task, DownloadException.DOWNLOAD_TASK_FAILED);
e.printStackTrace();
} finally {
try {
if (in != null) {
in.close();
}
if (out != null) {
out.close();
}
} catch (IOException e) {
e.printStackTrace();
}
if (connection != null) {
connection.disconnect();
}
}
return null;
}
private void SendError(DownloadTask task, Integer code) {
Log.e("Errors happen while downloading.");
SaveDownloadTask(task, DownloadStatus.STATUS_FAILED);
<span style="white-space:pre"> </span>//調用了當前類裏邊的一個sHandler對象；
sHandler.obtainMessage(
MESSAGE_POST_ERROR,
new AsyncTaskResult(this, task,
code)).sendToTarget();
}
private void SendAdd(DownloadTask task) {
sHandler.obtainMessage(
MESSAGE_POST_ADD,
new AsyncTaskResult(this, task,
-1)).sendToTarget();
}
private static class InternalHandler extends Handler {
@Override
public void handleMessage(Message msg) {
AsyncTaskResult result = (AsyncTaskResult) msg.obj;
if (result == null || result.mTask == null || result.mTask.isCancelled()) {
Log.i("The asyncTask is not valid or cancelled!");
return;
}
switch (msg.what) {
case MESSAGE_POST_ERROR:
<span style="white-space:pre"> </span>//調用當前類的OnError方法；
((AsycDownloadTask) result.mTask).OnError(result.mDownloadTask, result.mData);
break;
case MESSAGE_POST_ADD:
//調用當前類的OnAdd方法；
((AsycDownloadTask) result.mTask).OnAdd(result.mDownloadTask);
break;
default:
break;
}
}
}
/**
* throw error
*
* @param task task
* @param code The code of the exception
*/
private void OnError(DownloadTask task, Integer code) {
if (listener != null) {
listener.onError(new DownloadException(code));
}
}
/**
* inform Add
*
* @param task task
*/
private void OnAdd(DownloadTask task) {
if (listener != null && listener instanceof DownloadListener) {
((DownloadListener) listener).onAdd(task);
}
}publishProgress(progress);
protected final void publishProgress(Progress... values) {
if (!isCancelled()) {
getHandler().obtainMessage(MESSAGE_POST_PROGRESS,
new AsyncTaskResult<Progress>(this, values)).sendToTarget();
}
}
private static Handler getHandler() {
synchronized (AsyncTask.class) {
if (sHandler == null) {
sHandler = new InternalHandler();
}
return sHandler;
}
}
public InternalHandler() {
super(Looper.getMainLooper());
}
private static class InternalHandler extends Handler {
public InternalHandler() {
super(Looper.getMainLooper());
}
@SuppressWarnings({"unchecked", "RawUseOfParameterizedType"})
@Override
public void handleMessage(Message msg) {
AsyncTaskResult<?> result = (AsyncTaskResult<?>) msg.obj;
switch (msg.what) {
case MESSAGE_POST_RESULT:
// There is only one result
result.mTask.finish(result.mData[0]);
break;
case MESSAGE_POST_PROGRESS:
//最終在這裏調用了更新操作；
result.mTask.onProgressUpdate(result.mData);
break;
}
}
}
**
* Start Task
*
* @param task
* @param listener
* @return
*/
@SuppressWarnings("rawtypes")
public boolean start(DownloadTask task, DownloadListener listener) {
Log.i("Start Task");
boolean ret = false;
if (task == null) {
OnResult(POST_MESSAGE.ERROR, task, listener, DownloadException.DOWNLOAD_TASK_NOT_VALID);
return ret;
}
if (task.getContext() == null) {
task.setContext(context);
}
ISql iSql = new ISqlImpl(context);
DownloadTask temptask = null;
try {
temptask = iSql.queryDownloadTask(task);
if (temptask == null) {
add(task, listener);
} else if (!temptask.equals(task)) {
task.setDownloadTask(temptask);
}
switch (task.getStatus()) {
case DownloadStatus.STATUS_RUNNING:
OnResult(POST_MESSAGE.START, task, listener, -1);
OnResult(POST_MESSAGE.FINISH, task, listener, -1);
Log.i("The Task is already Running.");
break;
default:
if (listener != null) {
//這裏就跟添加task時一樣了，注意最後一個參數；
task.start(context, listener, false);
}
break;
}
ret = true;
} catch (SQLException e) {
e.printStackTrace();
}
return ret;
}剛剛創建了132079212，希望能共同學習，非誠勿擾！
