Develop Reference

extracting frames from a mp4.file

i want to open a .mp4 file, so that i can access each frame.
I tried to do it using javacv, but it didnt work.(see code below)
Does anyone know why it didnt work or how else i could achieve my goal?
i tried to call
string path = Environment.getExternalStorageDirectory().getAbsolutePath()
+ File.separator + "Test";
opencv_videoio.VideoCapture cap = new opencv_videoio.VideoCapture(path + File.separator + "test.mp4");
but then cap.isOpend() returns false. I have set the permission WRITE_EXTERNAL_STORAGE(which includes READ)

Different value for 'get/setDestination' Directory

Tested in Emulator
At first I make a directory in this form :
File root = android.os.Environment.getExternalStorageDirectory();
File dir = new File(root.getAbsolutePath() + "/" + "SubFolderName");
if (!dir.exists()) {
dir.mkdirs();
That make directory in this path : /storage/emulated/0/SubFolderName
Now, I need to use this path for downloaded file, so add this code:
DownloadManager.Request request = new DownloadManager.Request(uri);
request.setDestinationInExternalPublicDir(root.getAbsolutePath() + "/" + "SubFolderName","FileName");
That return this path: /storage/emulated/0/storage/emulated/0/SubFolderName/
Too try before this:
request.setDestinationInExternalFilesDir(getActivity(), root.getAbsolutePath() + "/" + "SubFolderName","FileName");
This section are repeated : storage/emulated/0
I check my codes but there-are not mistake.

You are not specifying which directory in external storage.
There are several directories you can use depending on what you are storing e.g "Downloads", "Video"
You can use the downloads directory like this for example:
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).mkdirs();
Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_DOWNLOADS + "/" + "SubFolderName/" + mTedListModel.get(position).getTitle()).mkdirs();
And then set your destination with the request manager as
.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, + "SubFolderName/" + mTedListModel.get(position).getTitle());

You are using setDestinationInExternalPublicDir(), as i can read here it is already adding the external root dir so you only need to especify the directory type,subpath and file name.
Example:
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOCUMENTS,"SubFolderName/FileName");
Hope im not wrong.

android download manager - download file into previously created directory

I want to save the downloaded file into a custom folder previously created as :
String trainingDirectory = "swimmer" + File.separator + "trainings";
String trainingsPath = Environment.getExternalStorageDirectory().toString() + File.separator + trainingDirectory;
File trainingSubdirectory = new File(getFilesDir() + File.separator + trainingsPath );
trainingSubdirectory.mkdirs();
to store the downloaded file into this directory, I tried to follow the solution given : Set custom folder Android Download Manager
writing
request.setDestinationInExternalPublicDir ( "/trainings", "mydownloadedfile.mp4");
In this case , the download manager is creating a new 'training' directory , not using the one I created previously...
I tried also to use
request.setDestinationInExternalPublicDir ( "/swimmer/trainings", "mydownloadedfile.mp4");
but in this case an error is raised ( a path with separators is not accepted..)
where am I wrong ?

Use this:
String directoryPath = Environment.getExternalStorageDirectory() + "/swimmer/trainings/"
// ...
request.setDestinationUri(Uri.fromFile(new File(directoryPath + "fileName.ext")));

Android: How to access a file in the SD Card

I'm trying to access the image on the SD card using below code but I"m getting File not found exception. Can someone tell me a correct way to acess the file???
new File("/mnt/sdcard/splah2.jpg")

Try like this:
String SD_CARD_PATH = Environment.getExternalStorageDirectory().toString();
new File(SD_CARD_PATH + "/" + "splah2.jpg");

Try running: new File(Environment.getExternalStorageDirectory() + "/splah2.jpg")

try this,
File f=new File("/sdcard/splah2.jpg");

The code below has worked for me.
String mRelativeFolderPath = "/DCIM/Camera/"; // i.e. SDCard/DCIM/Camera
String mBaseFolderPath = Environment.getExternalStorageDirectory().getAbsolutePath() + mRelativeFolderPath;
String filePath = mBaseFolderPath + "test.jpg";
File handle = new File(filePath);
Shash

try
new File("/sdcard/splah2.jpg")
or
new File(Environment.getExternalStorageDirectory() + "/" + "splah2.jpg")
both are same if SD card is install because,
Environment.getExternalStorageDirectory() returns "/sdcard"

file.isDirectory() always false in android with the path

ANSWER:
Needed the call to getExternalFilesDir(p); like so:
String p = thepathblah;
File path=context.getExternalFilesDir(p);
EDIT EDIT:
While I knew the Environment.DIRECTORY_PICTURES was returning just Pictures/ I figured this worked because in android I assumed the file pointer was already pointing to your application space (sorta like in c#). So in this:
String p = Environment.DIRECTORY_PICTURES + "/" + s.getClient().getFirstName()+s.getClient().getLastName() +
"/" + s.getPackage().getName() +
(mSession.getSessionDate().getMonth()+1) +
mSession.getSessionDate().getDate() +
(mSession.getSessionDate().getYear()+1900);
I thought was getting the full path, in fact I was writing a file out to this with no issues. It turns out though to delete individual files (and load them) I needed a fuller path which ended up being:
String p = Environment.DIRECTORY_PICTURES + "/" + s.getClient().getFirstName()+s.getClient().getLastName() +
"/" + s.getPackage().getName() +
(mSession.getSessionDate().getMonth()+1) +
mSession.getSessionDate().getDate() +
(mSession.getSessionDate().getYear()+1900);
File dir = new File("/sdcard/Android/data/com.software.oursoftware/files/"+p);
Not sure if I can take it that the above link is valid for all Honeycomb devices or not, specifically the /sdcard/Android/data/packagespace/files/
Is this safe to use this or do I have to do something more dynamic for honeycomb devices???
EDIT: This is my little test function code to just write something to a folder...
String p = Environment.DIRECTORY_PICTURES + "/" + s.getClient().getFirstName()+s.getClient().getLastName() + "/" + s.getPackage().getName() + (mSession.getSessionDate().getMonth()+1) + mSession.getSessionDate().getDate() + (mSession.getSessionDate().getYear()+1900);
File path = mContext.getExternalFilesDir(p);
File file = new File(path, "DemoPicture.jpg");
try {
// 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(R.drawable.ic_contact_picture);
OutputStream os = new FileOutputStream(file);
byte[] data = new byte[is.available()];
is.read(data);
os.write(data);
is.close();
os.close();
// Tell the media scanner about the new file so that it is
// immediately available to the user.
MediaScannerConnection.scanFile(mContext,
new String[] { file.toString() }, null,
new MediaScannerConnection.OnScanCompletedListener() {
public void onScanCompleted(String arg0, Uri arg1) {
Log.i("ExternalStorage", "Scanned " + arg0 + ":");
Log.i("ExternalStorage", "-> uri=" + arg1);
}
});
} catch (IOException e) {
// Unable to create file, likely because external storage is
// not currently mounted.
Log.w("ExternalStorage", "Error writing " + file, e);
}
Then the way I try to delete this folder:
String p = Environment.DIRECTORY_PICTURES + "/" + firstName+lastName +"/" + pName+pDate;
File dir=new File(p);
deleteRecursive(dir);
results in
Pictures/ShaneThomas/Portrait882011/
Which can write a file, tested that, but if I try to say:
void deleteRecursive(File dir)
{
Log.d("DeleteRecursive", "DELETEPREVIOUS TOP" + dir.getPath());
if (dir.isDirectory())
{
String[] children = dir.list();
for (int i = 0; i < children.length; i++)
{
File temp = new File(dir, children[i]);
if(temp.isDirectory())
{
Log.d("DeleteRecursive", "Recursive Call" + temp.getPath());
deleteRecursive(temp);
}
else
{
Log.d("DeleteRecursive", "Delete File" + temp.getPath());
boolean b = temp.delete();
if(b == false)
{
Log.d("DeleteRecursive", "DELETE FAIL");
}
}
}
dir.delete();
}
}
The dir.isDirectory is always false!? I got this delete file/directories code off stack overflow but am puzzled as to why its not working?
and I do have this set:
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

There are several reasons for File.isDirectory() to return false:
The path points to file (obviously), and not to directory.
The path is invalid (i.e. there is no such file/directory exists).
There is not enough permissions granted to your application to determine whether path points to directory.
In general, if isDirectory() returns true, you've got path that points to directory. But if isDirectory() returns false, then it might be or might not be a directory.
In your particular case, the path most likely does not exist. You need to call dir.mkdirs() to create all directories in the path. But since you need that to only recursively delete them, then there is no point in calling dir.mkdirs() just to remove that directory after that.

I think you want to add
dir.mkdirs() right after File dir=new File(p). mkdirs() is the method responsible for actually creating a directory, not new File().

Ok it's answered, but sometimes the issue fires because of sample reasone:permission :
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
if you forgot this permission you will always get false result.