add resume mechanism for download request

android-networking/src/main/java/com/androidnetworking/common/ANConstants.java

@@ -33,4 +33,6 @@ public final class ANConstants {
     public static final String USER_AGENT = "User-Agent";
     public static final String SUCCESS = "success";
     public static final String OPTIONS = "OPTIONS";
+    public static final String RANGE = "Range";
+    public static final String ACCEPT_ENCODING = "Accept-Encoding";
 }

android-networking/src/main/java/com/androidnetworking/common/ANRequest.java

@@ -139,6 +139,7 @@ public class ANRequest<T extends ANRequest> {
     private Executor mExecutor = null;
     private OkHttpClient mOkHttpClient = null;
     private String mUserAgent = null;
+    private boolean mResumeAllowed = false;
     private Type mType = null;
 
     public ANRequest(GetRequestBuilder builder) {
@@ -200,6 +201,7 @@ public ANRequest(DownloadBuilder builder) {
         this.mExecutor = builder.mExecutor;
         this.mOkHttpClient = builder.mOkHttpClient;
         this.mUserAgent = builder.mUserAgent;
+        this.mResumeAllowed = builder.mResumeAllowed;
     }
 
     public ANRequest(MultiPartBuilder builder) {
@@ -465,6 +467,10 @@ public String getUserAgent() {
         return mUserAgent;
     }
 
+    public boolean getResumeAllowed() {
+        return mResumeAllowed;
+    }
+
     public Type getType() {
         return mType;
     }
@@ -1443,6 +1449,7 @@ public static class DownloadBuilder<T extends DownloadBuilder> implements Reques
         private Executor mExecutor;
         private OkHttpClient mOkHttpClient;
         private String mUserAgent;
+        private boolean mResumeAllowed;
 
         public DownloadBuilder(String url, String dirPath, String fileName) {
             this.mUrl = url;
@@ -1600,6 +1607,11 @@ public T setUserAgent(String userAgent) {
             return (T) this;
         }
 
+        public T allowResume(boolean resumeAllowed) {
+            mResumeAllowed = resumeAllowed;
+            return (T) this;
+        }
+
         public T setPercentageThresholdForCancelling(int percentageThresholdForCancelling) {
             mPercentageThresholdForCancelling = percentageThresholdForCancelling;
             return (T) this;

android-networking/src/main/java/com/androidnetworking/internal/InternalNetworking.java

@@ -205,9 +205,11 @@ public Response intercept(Chain chain) throws IOException {
             }
         } catch (IOException ioe) {
             try {
-                File destinationFile = new File(request.getDirPath() + File.separator + request.getFileName());
-                if (destinationFile.exists()) {
-                    destinationFile.delete();
+                if (!request.getResumeAllowed()) {
+                    File destinationFile = new File(request.getDirPath() + File.separator + request.getFileName());
+                    if (destinationFile.exists()) {
+                        destinationFile.delete();
+                    }
                 }
             } catch (Exception e) {
                 e.printStackTrace();
@@ -276,12 +278,28 @@ public static void addHeadersToRequestBuilder(Request.Builder builder, ANRequest
             request.setUserAgent(sUserAgent);
             builder.addHeader(ANConstants.USER_AGENT, sUserAgent);
         }
+        if (request.getResumeAllowed()) {
+            File destinationFile = new File(request.getDirPath() + File.separator + request.getFileName());
+            if (destinationFile.exists()) {
+                long fileLength = destinationFile.length();
+                builder.addHeader(ANConstants.ACCEPT_ENCODING, "identity");
+                builder.addHeader(ANConstants.RANGE, "bytes=" + fileLength + "-");
+            }
+        }
         Headers requestHeaders = request.getHeaders();
         if (requestHeaders != null) {
             builder.headers(requestHeaders);
             if (request.getUserAgent() != null && !requestHeaders.names().contains(ANConstants.USER_AGENT)) {
                 builder.addHeader(ANConstants.USER_AGENT, request.getUserAgent());
             }
+            if (request.getResumeAllowed() && !requestHeaders.names().contains(ANConstants.RANGE)) {
+                File destinationFile = new File(request.getDirPath() + File.separator + request.getFileName());
+                if (destinationFile.exists()) {
+                    long fileLength = destinationFile.length();
+                    builder.addHeader(ANConstants.ACCEPT_ENCODING, "identity");
+                    builder.addHeader(ANConstants.RANGE, "bytes=" + fileLength + "-");
+                }
+            }
         }
     }
 

android-networking/src/main/java/com/androidnetworking/utils/Utils.java

@@ -172,7 +172,7 @@ public static int findBestSampleSize(int actualWidth, int actualHeight,
     public static void saveFile(Response response, String dirPath,
                                 String fileName) throws IOException {
         InputStream is = null;
-        byte[] buf = new byte[2048];
+        byte[] buf = new byte[8192];
         int len;
         FileOutputStream fos = null;
         try {
@@ -182,11 +182,15 @@ public static void saveFile(Response response, String dirPath,
                 dir.mkdirs();
             }
             File file = new File(dir, fileName);
-            fos = new FileOutputStream(file);
+            int code = response.code();
+            if ((code == 206 || code == 416) && file.exists()) {
+                fos = new FileOutputStream(file, true);
+            } else {
+                fos = new FileOutputStream(file);
+            }
             while ((len = is.read(buf)) != -1) {
                 fos.write(buf, 0, len);
             }
-            fos.flush();
         } finally {
             try {
                 if (is != null) is.close();