最近總結一下了一下之前學過以及用到過得功能，整理了一個基于Ok+Rxjava實現斷點續傳下載的demo。下面先給大家展示一下使用效果吧。
說下我的大致思路吧:根據文件下載url按照自己定義的規則生成文件名，判斷本地同路徑下是否存在此文件，如果存在，文件大小與服務器上獲取的文件大小一致的情況下，則生成新的文件名重新下載；如果文件比服務器獲取的文件大小小，則執行斷點下載，從本地文件長度處開始下載。如果文件不存在，則從0字節開始下載。
DownloadSubscribe（被觀察者）中執行下載存入本地操作
核心還是：addHeader("RANGE", "bytes=" + downloadLength + "-" + contentLength)
DownLoadObserver（觀察者）通過onnext(DownloadInfo downloadInfo)方法回調下載進度
下面上主要代碼：
/**
* 開始下載
* @param url 下載請求的網址
* @param downFileCallback 用來回調的接口
*/
public void download(final String url, final DownFileCallback downFileCallback) {
if (url == null || downCalls.get(url) != null) {
return;
}
Observable.just(url)
.filter(new Predicate<String>() {
@Override
public boolean test(String s) throws Exception {
//過濾條件 若map中存在，則這次不下載
return !downCalls.containsKey(s);
}
})
.flatMap(new Function<String, ObservableSource<DownloadInfo>>() {
@Override
public ObservableSource<DownloadInfo> apply(String s) throws Exception {
//創建下載實體類
return Observable.just(createDownInfo(s));
}
})
.map(new Function<DownloadInfo, DownloadInfo>() {
@Override
public DownloadInfo apply(DownloadInfo s) throws Exception {
//根據本地是否存在此文件，來設置文件名及文件初始下載大小
return getRealFileName(s);
}
})
.flatMap(new Function<DownloadInfo, ObservableSource<DownloadInfo>>() {
@Override
public ObservableSource<DownloadInfo> apply(DownloadInfo downloadInfo) throws Exception {
//創建被觀察者
return Observable.create(new DownloadSubscribe(downloadInfo));
}
})//下載
.observeOn(AndroidSchedulers.mainThread())//在主線程回調
.subscribeOn(Schedulers.io())//在子線程執行
.subscribe(new DownLoadObserver() {//添加觀察者
@Override
public void onNext(DownloadInfo downloadInfo) {
super.onNext(downloadInfo);
downFileCallback.onProgress(downloadInfo.getTotal(), downloadInfo.getProgress());
}
@Override
public void onError(Throwable e) {
super.onError(e);
if (!(e instanceof SocketException)) {
downFileCallback.onFail(e.getMessage());
}
}
@Override
public void onComplete() {
downFileCallback.onSuccess(url);
}
});
}
/**
* 根據url暫停下載操作
* @param url
*/
public void cancel(String url) {
Call call = downCalls.get(url);
if (call != null) {
call.cancel();//取消
}
downCalls.remove(url);
}
/**
* 創建被觀察者DownloadSubscribe
*/
private class DownloadSubscribe implements ObservableOnSubscribe<DownloadInfo> {
private DownloadInfo downloadInfo;
public DownloadSubscribe(DownloadInfo downloadInfo) {
this.downloadInfo = downloadInfo;
}
@Override
public void subscribe(ObservableEmitter<DownloadInfo> e) throws Exception {
String url = downloadInfo.getUrl();
long downloadLength = downloadInfo.getProgress();//已經下載好的長度
long contentLength = downloadInfo.getTotal();//文件的總長度
//初始進度信息
e.onNext(downloadInfo);
Request request = new Request.Builder()
//斷點續傳的核心
.addHeader("RANGE", "bytes=" + downloadLength + "-" + contentLength)
.url(url)
.build();
Call call = mClient.newCall(request);
//根據下載url，把call存放在map中，取消的時候就可以通過call.cancle()來實現
downCalls.put(url, call);
Response response = call.execute();
File file = new File(getTemporaryPath(), downloadInfo.getFileName());
InputStream is = null;
FileOutputStream fileOutputStream = null;
try {
is = response.body().byteStream();
fileOutputStream = new FileOutputStream(file, true);
byte[] buffer = new byte[2048];//緩沖數組2kB
int len;
while ((len = is.read(buffer)) != -1) {
fileOutputStream.write(buffer, 0, len);
downloadLength += len;
downloadInfo.setProgress(downloadLength);
e.onNext(downloadInfo);
}
fileOutputStream.flush();
downCalls.remove(url);
} finally {
//關閉IO流
IOUtil.closeAll(is, fileOutputStream);
}
e.onComplete();//完成
}
}
/**
* 從服務器獲取文件長度
*
* @param downloadUrl
* @return
*/
private long getContentLength(String downloadUrl) {
Request request = new Request.Builder()
.url(downloadUrl)
.build();
try {
Response response = mClient.newCall(request).execute();
if (response != null && response.isSuccessful()) {
long contentLength = response.body().contentLength();
response.close();
return contentLength == 0 ? DownloadInfo.TOTAL_ERROR : contentLength;
}
} catch (IOException e) {
e.printStackTrace();
}
return DownloadInfo.TOTAL_ERROR;
}
從服務器獲取文件長度的時候注意一下，Android P之后，也就是api 28以上禁止明文網絡傳輸。需要在你的AndroidManifest中的application標簽中聲明"android:usesCleartextTraffic="true",允許應用進行明文傳輸。
使用方法：首先要獲取sd卡權限
DownloadManager.getInstance().downloadPath(本地存在地址).download(url1, new DownFileCallback() {
@Override
public void onProgress(long totalSize, long downSize) {
progress1.setMax((int) totalSize);
progress1.setProgress((int) downSize);
}
@Override
public void onSuccess(String url) {
Toast.makeText(MainActivity.this, url1 + "下載完成", Toast.LENGTH_SHORT).show();
}
@Override
public void onFail(String msg) {
Toast.makeText(MainActivity.this, url1 + "下載失敗", Toast.LENGTH_SHORT).show();
}
});
好了今天就到這里，希望能幫到大家，這對我來說也是一種加深印象的筆記，
下載地址demo
git地址：DownloadManager 歡迎star
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持服務器之家。
