Develop Reference

How to open my app documents directory with Android File Manager

I've been trying to figure out a way to open the Android File Manager directly in my app's Documents directory so the user can select a JSON file among several without requiring the user to go search for the file path /storage/emulated/0/Android/data/com.company.app/files/Documents/. So far, I can make the "go find it yourself" tactic work, but not the "take the user to the directory for them" approach. Here's what I've tried:
// this is the "go find it yourself" approach that I've used:
String filename = this.getResources().getString(R.string.ExportImportFileNameString);
File directory = this.getExternalFilesDir(Environment.DIRECTORY_DOCUMENTS);
Uri dirPathUri = Uri.fromFile(directory);
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("*/*");
Intent.createChooser(intent, "Open in...");
intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, directory);
startActivityForResult(intent, IMPORT_REQUEST);
When my onActivityComplete handler is called for IMPORT_REQUEST I see the returned data looks like dat=content://com.lge.filemanager.FileProvider/storage/emulated/0/Android/data/com.company.app/files/Documents/SelectedFile.json flg=0x1 }
I've tried to invoke two different combinations of intent.setDataAndType instead of intent.setTypefollowing and that fails to let me select anything:
// This setDataAndType setup does not allow the user to open File Manager, nor navigate to the app Documents:
intent.setDataAndType(dirPath2, "application/json");
// This allows opening of File Manager but returns immediately without allowing the user to select a file, and returns a null data pointer:
intent.setDataAndType(dirPath2, "*/*");
Note that I've tried creating the intent object with ACTION_OPEN_DOCUMENT, ACTION_GET_CONTENT, and ACTION_VIEW with the similar result.
If I only have one file, I know I can have the app simply open a stream reader for a known file name as such:
File directory = this.getExternalFilesDir(Environment.DIRECTORY_DOCUMENTS);
File importFile = new File(directory, filename);
try
{
fis = new FileInputStream (importFile);
InputStreamReader inputStreamReader =
new InputStreamReader(fis, StandardCharsets.UTF_8);
...
However, that doesn't allow me the flexibility that I desire to allow a user to select from multiple files. Can anyone illuminate what's going on here and how to correct the situation.

Based on Commonsware feedback, here's what I have for the solution to this question:
//--------------
// Get the documents location for this app
File directory = this.getExternalFilesDir(Environment.DIRECTORY_DOCUMENTS);
File desiredFilePath = new File(directory.toString());
try{
// read all pathnames for files and directory
File[] allFilesInDirectory = desiredFilePath.listFiles();
// prepare array to place all path strings into
ArrayList<String> filesInDirectoryArray = new ArrayList<String>();
// retrieve each pathname file array
// but someone could simply use the "path" object instead
for(File path:allFilesInDirectory){
if (path != null){
// put all file paths into string array
filesInDirectoryArray.add(path.getPath());
// could discriminate based on file extension, if so desired
}
}
// send file path array for processing
ProcessDocuments(filesInDirectoryArray);
}catch(SecurityException e){
e.printStackTrace();
}

Open image from external public directory through intent

Recently I am developing a file sharing application and I created a GridView, where the downloaded files are being shown. From this View, I would like to be able to open the default application through an intent, to open the whole file. Currently I am testing the app with only image files. All the files are downloaded to the external public directory this way:
File externalFolder = new File(Environment.getExternalStorageDirectory(), "My application");
if(!externalFolder.exists()){
externalFolder.mkdir();
}
...
File folder = new File(externalFolder, "Images");
if(!folder.exists()){
folder.mkdir();
}
...
String filename = folder.getAbsolutePath() + "/" + fileToDownload.getName() + "." + fileToDownload.getExtension();
FileOutputStream fos = new FileOutputStream(filename);
When the file is downloaded, I scan it with MediaScannerConnection.scanFile. The scan is successful, the picture is visible among other files in Photos app.
After the file is downloaded, I am able to extract a thumbnail in the adapter of the GridView, so I surely have a valid path to the file.
And where the fun begins: I tried to set an onClickListener to the GridView items in the adapter to be able to open the picture in Photos app this way:
listItem.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(Intent.ACTION_VIEW);
if(new File(current.getPath()).exists()){
Log.e("path", "valid");
}else{
Log.e("path", "invalid");
}
Log.e("path", Uri.parse("content://"+current.getPath()).toString());
intent.setDataAndType(Uri.parse("content://"+current.getPath()), "image/*");
getContext().startActivity(intent);
}
});
The Intent is created successfully, I get the following in the log:
E/path: valid
E/path: content:///storage/emulated/0/My application/Images/best_picture_ever.jpeg
I have the option to choose among apps to open. When I select the app, it fails to open the image, like when it does not exist. All the 5 applications.
I tested this on my device with Oreo, and on two emulated devices with Nougat and Lollipop, all of them behaves the same way.
What am I doing wrong?

What am I doing wrong?
You are not creating a valid Uri. You cannot put content:// in front of arbitrary things and have a useful Uri, any more than you can put https:// in front of arbitrary things and have a usable URL.
Use FileProvider to serve up this file.

List downloaded files in Android using Spinner

My app involves downloading a few csv files and then choosing one of them to perform some functions. After the user downloads the required files, a spinner must display the files that have been downloaded. On selecting the required file, it must link to another activity where the path of the file chosen is the FileName. Is this possible using a spinner and how do I go about it?
File selected = new File("/storage/emulated/0/Download/");
String item_ext = "";
try {
item_ext = selected.getName().substring(selected.getName().lastIndexOf("."));
} catch (StringIndexOutOfBoundsException e) {
item_ext = "";
}
if(item_ext.equalsIgnoreCase(".csv")) {
Intent txtIntent = new Intent();
txtIntent.setAction(android.content.Intent.ACTION_VIEW);
txtIntent.setDataAndType(Uri.fromFile(selected), "text/csv");
Toast.makeText(MainActivity.this, "Success", Toast.LENGTH_SHORT).show();
try {
startActivity(txtIntent);
} catch(ActivityNotFoundException e) {
txtIntent.setType("text/*");
startActivity(txtIntent);
}
}

Since my application requirement mainly dealt with downloaded files, I linked the app to Downloads folder. By clicking on the file of interest, the path for the file was obtained. This link helped to get the absolute path and was suitably modified for the purpose.

android-where to store lots of images and how to move them while installing

I'm writing an android app that contains about 500 images .
there are somethings that make me worry, I don't want to use internet.
1-the application size will be very big , is there anyway to moving images to sd card while installing? some devices may don't have this amount of space on the phone .
2-should I make 3 images for hdpi , ldpi and mdpi ?

You can put you image in asset folder. If you want to transfer image from assets to SD Card then you can't do like this.
But you can do by one way. You put your image on server and at 1st time when you will open app you can download it and save it in SD Card and then access from there.

Yes, it will be big. No, you can't remove them from your package.
No, you can make only hdpi images. Android will scale them automatically (which may slow down a bit the app).
Suggestion - use internet. Since the user has internet to download your app, he can wait to download the resources on first start. Also it give you the ability to add/remove files via online configuration. Just imagine if you have to add 1 image and upload new version - this means that the user will have to download the same huge package again.

I had a similar requirement - include a bunch of images in the app, but in my case, the image had to be accessible by any user or app, not just the app that unpacked them. I stored them in the res/raw folder and copied them to user space on start up:
private void loadCopyResources() {
// copy resources to space any activity can use
String sourceName;
String resourceName;
String fileName;
int resource;
String typeName = sourceSink.Types.photo.toString();
for (sourceSink.Sources source: sourceSink.Sources.values() ){
for (int i = 0; i< photoFileCount; i++) {
sourceName = source.toString();
resourceName = sourceName + "_" + typeName + (i+1); // i.e. dropbox_photo2
fileName = resourceName + ".jpg"; // files requires extension
resource = getResources().getIdentifier(resourceName, "raw", "com.example.myapp");
createExternalStoragePublicFile(typeName,fileName, resource); // copy it over
}
}
}
void createExternalStoragePublicFile(String fType, String fname, int res ) {
// Create a path where we will place our picture in the user's
// public pictures directory. Note that you should be careful about
// what you place here, since the user often manages these files. For
// pictures and other media owned by the application, consider
// Context.getExternalMediaDir().
File path = null;
if (((fType.equals(sourceSink.Types.photo.toString())) || (fType.equals(sourceSink.Types.file.toString())) ) ){
path = Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES);
}
if (fType.equals(sourceSink.Types.music.toString())) {
path = Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_MUSIC);
}
if (fType.equals(sourceSink.Types.video.toString())) {
path = Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_MOVIES);
}
File file = new File(path, "/" + fname);
try {
// Make sure the Pictures directory exists.
path.mkdirs();
// Very simple code to copy a picture from the application's
// resource into the external file. Note that this code does
// no error checking, and assumes the picture is small (does not
// try to copy it in chunks). Note that if external storage is
// not currently mounted this will silently fail.
InputStream is = getResources().openRawResource(res);
OutputStream os = new FileOutputStream(file);
byte[] data = new byte[is.available()];
is.read(data);
os.write(data);
is.close();
os.close();
scanMedia(file);
} catch (IOException e) {
// Unable to create file, likely because external storage is
// not currently mounted.
Log.w("ExternalStorage", "Error writing " + file, e);
}
}
sourceSink, which I didn't include, is just a list of file names and file types I needed copied.

Android How to use and create temporary folder

I develop an app which collects some data from internet. Then save it to a temporary folder. To build this app I need to create and access a folder ( just for the purpose of app, not for the user). How can I do it?

this code is to create folder:
File direct = new File(Environment.getExternalStorageDirectory() + "/New Folder");
if(!direct.exists())
{
(direct.mkdir()) //directory is created;
}
try it may help you

File mFile;
onCreate()
mFile= new File(Environment.getExternalStorageDirectory()+"/temp/";
mFile.mkdir();
onDestroy();
mFile.delete();

try out this...
private void makeFolder(){
File root = new File(Environment.getExternalStorageDirectory()
+ File.separator + getString(R.string.folder_name));
boolean mainfolderexist = root.exists();
if (!mainfolderexist) {
try {
if (Environment.getExternalStorageDirectory().canWrite()) {
root.mkdirs();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
All The best

You should really check this other SO answer: https://stackoverflow.com/a/6485850/65716
Aside from the fact that you have to completely manage your use of the space, etc, caching on external storage requires more permission for your app.
See http://developer.android.com/reference/android/content/Context.html#getCacheDir()
"Apps require no extra permissions to read or write to the returned path, since this path lives in their private storage."

For app use only, I would recommend to use Context.getDir() for retrieving the directory if the files is used by our app only and don`t want to be visible to users by file browsers.
// No need to check if exist, created automatically.
File tempRoot = context.getDir("temp", Context.MODE_PRIVATE);
// do something