本篇主要介紹文件的斷點續傳下載。
原文來自:http://blog.csdn.net/KevinsCSDN/article/details/51934274
1.Gradle引入依賴:
compile 'com.squareup.okhttp3:okhttp:3.6.0'
compile 'io.reactivex:rxjava:1.1.6'
compile 'io.reactivex:rxandroid:1.2.1'
2.定義能夠實現Progress進度條顯示功能的ResponseBody:
/**
* Created by BeautifulSoup on 2017/2/24.
*/
public class DownLoadResponse extends ResponseBody {
private final ResponseBody responseBody;
private final UpdateProgressListener progressListener;
private BufferedSource bufferedSource;
public DownLoadResponse (ResponseBody responseBody,UpdateProgressListener progressListener) {
this.responseBody = responseBody;
this.progressListener = progressListener;
if(progressListener!=null){
progressListener.onPreExecute(contentLength());
}
}
@Override
public MediaType contentType() {
return responseBody.contentType();
}
@Override
public long contentLength() {
return responseBody.contentLength();
}
@Override
public BufferedSource source() {
if (bufferedSource == null) {
bufferedSource = Okio.buffer(source(responseBody.source()));
}
return bufferedSource;
}
public interface UpdateProgressListener {
void onPreExecute(long contentLength);
void update(long totalBytes, boolean done);
}
private Source source(Source source) {
return new ForwardingSource(source) {
long totalBytes = 0L;
@Override
public long read(Buffer sink, long byteCount) throws IOException {
long bytesRead = super.read(sink, byteCount);
totalBytes += bytesRead != -1 ? bytesRead : 0;
if (null != progressListener) {
progressListener.update(totalBytes, bytesRead == -1);
}
return bytesRead;
}
};
}
}
3.定義帶有進度響應的工具類:
public static final String TAG = "ProgressDownloader";
private ProgressListener progressListener;
private String url;
private OkHttpClient client;
private File destination;
private Call call;
public ProgressDownloader(String url, File destination, ProgressListener progressListener) {
this.url = url;
this.destination = destination;
this.progressListener = progressListener;
//在下載、暫停後的繼續下載中可複用同一個client對象
client = getProgressClient();
}
//每次下載需要新建新的Call對象
private Call newCall(long startPoints) {
Request request = new Request.Builder()
.url(url)
.header("RANGE", "bytes=" + startPoints + "-")//斷點續傳要用到的,指示下載的區間
.build();
return client.newCall(request);
}
public OkHttpClient getProgressClient() {
// 攔截器,用上ProgressResponseBody
Interceptor interceptor = new Interceptor() {
@Override
public Response intercept(Chain chain) throws IOException {
Response originalResponse = chain.proceed(chain.request());
return originalResponse.newBuilder()
.body(new ProgressResponseBody(originalResponse.body(), progressListener))
.build();
}
};
return new OkHttpClient.Builder()
.addNetworkInterceptor(interceptor)
.build();
}
// startsPoint指定開始下載的點
public void download(final long startsPoint) {
call = newCall(startsPoint);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
}
@Override
public void onResponse(Call call, Response response) throws IOException {
save(response, startsPoint);
}
});
}
public void pause() {
if(call!=null){
call.cancel();
}
}
private void save(Response response, long startsPoint) {
ResponseBody body = response.body();
InputStream in = body.byteStream();
FileChannel channelOut = null;
// 隨機訪問文件,可以指定斷點續傳的起始位置
RandomAccessFile randomAccessFile = null;
try {
randomAccessFile = new RandomAccessFile(destination, "rwd");
//Chanel NIO中的用法,由於RandomAccessFile沒有使用緩存策略,直接使用會使得下載速度變慢,親測緩存下載3.3秒的文件,用普通的RandomAccessFile需要20多秒。
channelOut = randomAccessFile.getChannel();
// 內存映射,直接使用RandomAccessFile,是用其seek方法指定下載的起始位置,使用緩存下載,在這裏指定下載位置。
MappedByteBuffer mappedBuffer = channelOut.map(FileChannel.MapMode.READ_WRITE, startsPoint, body.contentLength());
byte[] buffer = new byte[1024];
int len;
while ((len = in.read(buffer)) != -1) {
mappedBuffer.put(buffer, 0, len);
}
} catch (IOException e) {
e.printStackTrace();
}finally {
try {
in.close();
if (channelOut != null) {
channelOut.close();
}
if (randomAccessFile != null) {
randomAccessFile.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
4.測試代碼:
private File file;
private long totalBytes;
private long contentLength;
private long breakPoints;
private ProgressDownLoader downloader;
public static final String PACKAGE_URL = "http://10.0.2.2:8088/filedownload/download.txt";
private ProgressBar progressBar;
public void downLoadFile(View view){
// 新下載前清空斷點信息
breakPoints = 0L;
file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "aaaa.txt");
downloader = new ProgressDownLoader(PACKAGE_URL, file, this);
downloader.download(0L);
}
public void downPauseFile(View view){
downloader.pause();
Toast.makeText(this, "下載暫停", Toast.LENGTH_SHORT).show();
// 存儲此時的totalBytes,即斷點位置。
breakPoints = totalBytes;
}
public void CountinueDownLoadFile(View view){
downloader.download(breakPoints);
}
@Override
public void onPreExecute(long contentLength) {
// 文件總長只需記錄一次,要注意斷點續傳後的contentLength只是剩餘部分的長度
if (this.contentLength == 0L) {
this.contentLength = contentLength;
progressBar.setMax((int) (contentLength / 1024));
}
}
@Override
public void update(long totalBytes, boolean done) {
// 注意加上斷點的長度
this.totalBytes = totalBytes + breakPoints;
progressBar.setProgress((int) (totalBytes + breakPoints) / 1024);
if (done) {
// 切換到主線程
Observable
.empty()
.observeOn(AndroidSchedulers.mainThread())
.doOnCompleted(new Action0() {
@Override
public void call() {
Toast.makeText(MainActivity.this, "下載完成", Toast.LENGTH_SHORT).show();
}
})
.subscribe();
}
}