Exporting larger files
lazarus / 43-Android

----------------------------------------------------------------------
Guser979 · 2025-07-08 21:55

In my app, I tried to export a 400 MB file using "savebytestouri," and
the file was 0 bytes. When the file was 200 MB, it was written
normally. This is due to the limitation of the array used:
TDynArrayOfJByte.

Solution:
1) Create an additional "AppendBytesToUri" method.
2) Use a function in your app that dynamically adjusts the array size
until the entire file is written to user-accessible storage.



1)
Add code in “androidwidget.pas”:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
AppendBytesToUri(_bytes: TDynArrayOfJByte; _toTreeUri:
jObject);procedure jForm_AppendBytesToUri(env: PJNIEnv; _jform:
JObject; _bytes: TDynArrayOfJByte; _toUri: jObject);  procedure
 AppendBytesToUri(_bytes: TDynArrayOfJByte; _toTreeUri:
jObject);begin  //in designing component state: set value here...  if
FInitialized then     jForm_AppendBytesToUri(FjEnv, FjObject, _bytes
,_toTreeUri);end; procedure jForm_AppendBytesToUri(env: PJNIEnv;
_jform: JObject; _bytes: TDynArrayOfJByte; _toUri: jObject);var 
jParams: array[0..1] of jValue;  jMethod: jMethodID = nil;  jCls:
jClass = nil;  byteArray: jByteArray;  len: SizeInt;label 
_exceptionOcurred;begin  jCls := env^.GetObjectClass(env, _jform);  if
jCls = nil then goto _exceptionOcurred;   jMethod :=
env^.GetMethodID(env, jCls, 'AppendBytesToUri',
'([BLandroid/net/Uri;)V');  if jMethod = nil then goto
_exceptionOcurred;   len := Length(_bytes);  byteArray :=
env^.NewByteArray(env, len);  env^.SetByteArrayRegion(env, byteArray,
0 , len, @_bytes[0]);   jParams[0].l := byteArray;  jParams[1].l :=
_toUri;   env^.CallVoidMethodA(env, _jform, jMethod, @jParams); 
env^.DeleteLocalRef(env, jParams[0].l);  env^.DeleteLocalRef(env,
jCls);    _exceptionOcurred: jni_ExceptionOccurred(env);end;   
Add code in “jForm.java”:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i public void
AppendBytesToUri(byte[] _bytes, Uri _toTreeUri) {    OutputStream out
= null;    try {        out =
controls.activity.getContentResolver().openOutputStream(_toTreeUri,
"wa"); //   append mode        out.write(_bytes);        out.flush(); 
  } catch (FileNotFoundException e) {        e.printStackTrace();    }
catch (IOException e) {        e.printStackTrace();    } finally {   
   try {            if (out != null) out.close();        } catch
(IOException e) {            e.printStackTrace();        }    }}     
   


2)
Usage example:



Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  //In this
 example  the app registers several photos that need to be exported.
   // procedure export(arqname:string);// procedure
AndroidModule1ActivityResult(Sender: TObject;requestCode: integer;
resultCode: TAndroidResult; intentData: jObject);// function
 StreamFileSmart(const FilePath: string; const Uri: jObject): Boolean;
    //  var  zipnam :string; //Global var    // call export//
zipnam:='fotos.zip' ; export (zipnam);     // Here a .zip file
 (zipnam) is created with all the photos registered in the app and we
invoke the file creation to obtain the uri procedure
TAndroidModule1.export(arqname:string);       var zip: TZipper;i:
Integer;relativefn,tmp: String;     begin      L := TStringList.Create
;FindAllFiles(L,GetEnvironmentDirectoryPath(dirDCIM), '*.jpg', true); 
                 zip := TZipper.Create;     try    zip.Filename :=
arqname;     try       for i:=0 to  L.Count-1    do begin            
             if L[i] ='' then break;                         
relativefn :=
CreateRelativePath(L[i],GetEnvironmentDirectoryPath(dirDownloads));  
       zip.Entries.AddFileEntry ( SysToUTF8(L[i]),extractfilename(
l[i] ));      end;     finally      L.Free;    end;     zip.SaveToFile
(GetEnvironmentDirectoryPath(dirDownloads)+'/'+arqname);     Self.Requ
estCreateFile(Self.GetEnvironmentDirectoryPath(dirDownloads),'applicat
ion/zip',arqname, 114);     finally    zip.Free;  end; end;          
               // This is where we get the .zip file's uri and call
the function to write the content. procedure
TAndroidModule1.AndroidModule1ActivityResult(Sender: TObject; 
requestCode: integer; resultCode: TAndroidResult; intentData:
jObject);   begin        treeUri:=
IntentManager1.GetDataUri(intentData);     if requestCode = 114 then
 //create file     begin       Self.CopyFile(Self.GetEnvironmentDirect
oryPath(dirDatabase)+'/'+zipnam,Self.GetEnvironmentDirectoryPath(dirDo
wnloads)+'/'+zipnam );                                            Stre
amFileSmart(GetEnvironmentDirectoryPath(dirDownloads)+'/'+zipnam,treeU
ri);        end;    end;  // Here's the function that uses
AppendBytesToUri for any file size. It sends a maximum of 200 MB and
adjusts the array size if necessary.function
 TAndroidModule1.StreamFileSmart(const FilePath: string; const Uri:
jObject): Boolean;const  MAX_CHUNK = 200 * 1024 * 1024; var  fs:
TFileStream;  buffer: array of byte;  jBuffer: TDynArrayOfJByte; 
bytesRead, chunkSize: Integer;begin  Result := False;   if not
FileExists(FilePath) then Exit;   try    fs :=
TFileStream.Create(FilePath, fmOpenRead or fmShareDenyWrite);    try 
   if fs.Size <= MAX_CHUNK then        chunkSize := fs.Size      else 
      chunkSize := MAX_CHUNK;       SetLength(buffer, chunkSize);    
SetLength(jBuffer, chunkSize);       repeat        bytesRead :=
fs.Read(buffer[0], chunkSize);        if bytesRead > 0 then       
begin                     Move(buffer[0], jBuffer[0], bytesRead);    
    SetLength(jBuffer, bytesRead);                   AppendBytesToUri(
jBuffer, Uri);        end;      until bytesRead < chunkSize;      
Result := True;    finally      fs.Free;    end;  except    on E:
Exception do    begin      //  log error ou message             Result
:= False;    end;  end;end;                     


// Credits : jmpessoa, neuro , ChatGpt