项目代码链接：https://github.com/baiyazi/AndroidDownloadUtils，可自取。
并进行了粗略的封装，本篇目的：使用的时候调用方便，继续封装一下。
最终调用接口案例：
String url1 = "http://vjs.zencdn.net/v/oceans.mp4";
DownLoader downloader = new DownLoader.Builder(getApplicationContext())
.url(url1)
.cacheDirName("Images")
.suffix(Downloader.FileSuffix.MP4)
.method("GET")
.timeout(3000)
.build();
downloader.download(new DownLoader.DownloadListener() {
@Override
public void onSuccess(File file) {
}
@Override
public void onError(String msg) {
Log.e("TAG", "onError: ");
}
});
最终下载在SD卡的/data/package name/cache/Images/中：
当然，我在类中将线程池的核心线程数、最大线程数目这里直接写死了的，即：
private static final int corePoolSize = Runtime.getRuntime().availableProcessors() + 1;
private static final int maximumPoolSize = Runtime.getRuntime().availableProcessors() * 2 + 1;
如果需要采用建造者模式来定制核心线程数和最大线程数目，可以在Builder中提供对应的设置方法即可，这里我就不做了。
对于支持的文件类型，简单的使用枚举来定义设置：
// 支持的文件类型后缀
public enum FileSuffix{
EXE("exe"),
ZIP("zip"),
JPEG("jpeg"),
PNG("png"),
GIF("gif"),
MP4("mp4"),
MP3("mp3"),
PDF("pdf");
private String value; // 实际值
FileSuffix(String value) {
this.value = value;
}
public String getValue(){
return this.value;
}
}
其余没什么变化。
新版DownLoader.java代码：
public class DownLoader {
private static final String TAG = "Downloader";
private String url;
private int connectionTimeout;
private String method;
private Context context;
private String cachePath = "imgs";
private static final int corePoolSize = Runtime.getRuntime().availableProcessors() + 1;
private static final int maximumPoolSize = Runtime.getRuntime().availableProcessors() * 2 + 1;
private HttpURLConnection connection = null;
private FileSuffix suffix;
private DownLoader(){
}
public DownLoader(Context context){
connectionTimeout = 500; // 500毫秒
method = "GET";
this.context = context;
}
public DownLoader url(String url){
this.url = url;
return this;
}
// 支持的文件类型后缀
public enum FileSuffix{
EXE("exe"),
ZIP("zip"),
JPEG("jpeg"),
PNG("png"),
GIF("gif"),
MP4("mp4"),
MP3("mp3"),
PDF("pdf");
private String value; // 实际值
FileSuffix(String value) {
this.value = value;
}
public String getValue(){
return this.value;
}
}
/**
* 指明下载文件后缀
* @param fileSuffix
* @return
*/
public DownLoader fileSuffix(FileSuffix fileSuffix){
this.suffix = fileSuffix;
return this;
}
public DownLoader(Builder builder){
this.url = builder.url;
this.connectionTimeout = builder.connectionTimeout;
this.method = builder.method;
this.context = builder.context;
this.cachePath = builder.cachePath;
this.suffix = builder.suffix;
}
public static class Builder{
private String url;
private int connectionTimeout;
private String method;
private String cachePath = "imgs";
private Context context;
private FileSuffix suffix;
public Builder(Context context){
this.context = context;
}
public Builder url(String url){
this.url = url;
return this;
}
public Builder timeout(int ms){
this.connectionTimeout = ms;
return this;
}
public Builder suffix(FileSuffix suffix){
this.suffix = suffix;
return this;
}
public Builder method(String method) {
if (!(method.toUpperCase().equals("GET") || method.toUpperCase().equals("POST"))) {
throw new AssertionError("Assertion failed");
}
this.method = method;
return this;
}
public Builder cacheDirName(String cacheDirName){
this.cachePath = cacheDirName;
return this;
}
public DownLoader build(){
return new DownLoader(this);
}
}
public interface DownloadListener{
void onSuccess(File file);
void onError(String msg);
}
private static class DownloadThread extends Thread{
private long startPos;
private long endPos;
private RandomAccessFile randomAccessFile;
private File file;
private String url;
private int connectionTimeout = 5 * 1000; // 5秒钟
private String method = "GET";
private long maxFileSize;
private DownloadListener listener;
public DownloadThread(String url, long startPos, long endPos, long maxFileSize, File file) {
this.startPos = startPos;
this.endPos = endPos;
this.url = url;
this.file = file;
this.maxFileSize = maxFileSize;
}
public void setDownloadListener(DownloadListener listener){
this.listener = listener;
}
@Override
public void run() {
Log.e(TAG, "=========> " + Thread.currentThread().getName());
HttpURLConnection connection = null;
URL url_c = null;
try{
randomAccessFile = new RandomAccessFile(this.file, "rwd");
randomAccessFile.seek(this.startPos);
url_c = new URL(url);
connection = (HttpURLConnection) url_c.openConnection();
connection.setConnectTimeout(this.connectionTimeout);
connection.setRequestMethod(this.method);
connection.setRequestProperty("Charset", "UTF-8");
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("Range", "bytes=" + startPos +"-" + endPos);
Log.e(TAG, "Range: bytes=" + startPos +"-" + endPos);
InputStream inputStream = connection.getInputStream();
Log.e(TAG, "connection.getContentLength() == " + connection.getContentLength());
int contentLength = connection.getContentLength();
if(contentLength < 0) {
Log.e(TAG, "Download fail!");
return;
}
try {
if (connection.getResponseCode() == 206) {
byte[] buffer = new byte[2048];
int len = -1;
while ((len = inputStream.read(buffer)) != -1) {
randomAccessFile.write(buffer, 0, len);
}
}
} catch (IOException e) {
e.printStackTrace();
}finally {
try{
if(inputStream != null) inputStream.close();
}catch (IOException e){
e.printStackTrace();
}
}
}catch (IOException e){
Log.e(TAG, "Download bitmap failed.", e);
if(listener!=null) listener.onError(e.getLocalizedMessage());
e.printStackTrace();
}finally {
if(connection != null) connection.disconnect();
// todo 通知下载完毕
if(this.endPos == this.maxFileSize){
Log.e(TAG, "Download bitmap success.");
if(listener!=null) listener.onSuccess(this.file);
}
}
}
}
private static final ThreadFactory mThreadFactory = new ThreadFactory(){
private final AtomicInteger mCount = new AtomicInteger(1);
@Override
public Thread newThread(Runnable r) {
return new Thread(r, "Thread#" + mCount.getAndIncrement());
}
};
private Executor executor = new ThreadPoolExecutor(corePoolSize,
maximumPoolSize,
10L,
TimeUnit.SECONDS,
new LinkedBlockingDeque<>(),
mThreadFactory);
public void download(DownloadListener listener){
new Thread(new Runnable() {
@Override
public void run() {
File path = buildPath(cachePath);
try{
URL url1 = new URL(url);
connection = (HttpURLConnection) url1.openConnection();
connection.setConnectTimeout(connectionTimeout);
connection.setRequestMethod(method);
connection.setRequestProperty("Charset", "UTF-8");
connection.setRequestProperty("accept", "*/*");
connection.connect();
int contentLength = connection.getContentLength();
if(contentLength < 0) {
Log.e(TAG, "Download fail!");
return;
}
// TODO 分为多个线程，进行执行
int step = contentLength / maximumPoolSize;
Log.d(TAG, "maximumPoolSize: " + maximumPoolSize +" , step:" + step);
Log.d(TAG, "contentLength: " + contentLength);
if(suffix == null){
throw new RuntimeException("You must set the download file suffix before.");
}
File file = new File(path, Utils.hashKeyFromUrl(url) + "." + suffix.getValue());
if(contentLength == file.length()){
Log.e(TAG, "Nothing changed!"); // already downlaod.
if(listener != null) listener.onSuccess(file);
return;
}
// 否则就下载
for (int i = 0; i < maximumPoolSize; i++) {
if(i != maximumPoolSize - 1) {
DownloadThread downloadThread = new DownloadThread(url, i * step, (i + 1) * step, contentLength, file);
executor.execute(downloadThread);
}else{
DownloadThread downloadThread = new DownloadThread(url, i * step, contentLength, contentLength, file);
if(listener != null) downloadThread.setDownloadListener(listener);
executor.execute(downloadThread);
}
}
}catch (IOException e){
Log.e(TAG, "Download bitmap failed.", e);
if(listener != null) listener.onError(e.getLocalizedMessage());
e.printStackTrace();
}finally {
if(connection != null) connection.disconnect();
}
}
}).start();
}
private File buildPath(String filePath) {
// 是否有SD卡
boolean flag = Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);
// 如果有SD卡就存在外存，否则就位于这个应用的data/package name/cache目录下
final String cachePath;
if(flag) cachePath = context.getExternalCacheDir().getPath();
else cachePath = context.getCacheDir().getPath();
File directory = new File(cachePath + File.separator + filePath);
// 目录不存在就创建
if(!directory.exists()) directory.mkdirs();
return directory;
}
}