Caching exisiting files

Question

I have the following code:

file = new File(getRealPathFromURI(uri));

How am I able to store this in the cache with a name so I can then access it later on?

I know there are methods such as File outputDir = context.getCacheDir(); File outputFile = File.createTempFile("prefix", "extension", outputDir);

But I don't understand how I can store this file in the cache with a specific name so then at a further date I can do file = new File(getActivity().getCacheDir(), "storedFileName"); in other activitys.

Any guidance would be great, thanks.

EDIT: Here is my main activity where I get a pic from the gallery and it is returned as a uri in the onActivityResult:

@Override
protected void onActivityResult(int requestCode, int resultCode,
        Intent imageReturnedIntent) {
    super.onActivityResult(requestCode, resultCode, imageReturnedIntent);

    switch (requestCode) {
    case SELECT_PHOTO:
        if (resultCode == RESULT_OK) {
            Uri selectedImage = imageReturnedIntent.getData();

            Intent i = new Intent(getApplicationContext(),
                    sliding_menu.class);


            File file = new File(selectedImage.getPath());

              ObjectOutput out;
                try {
                    String filenameOffer="Image";

                    out = new ObjectOutputStream(new FileOutputStream(new File
                            (getCacheDir(),"")+filenameOffer));
                    out.writeObject(file);
                    out.close();
                } catch (Exception e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } 
            startActivity(i);

        }
    }
}

As you can see, I am trying to make the Uri of the selected image, then make it into a file.

Then I am trying to store the file in the cache so I can then further retrieve it throughout my application.

Here is the next activity where I am trying to access the file:

try {
            String filename="Image";

            ObjectInputStream in = new ObjectInputStream(new FileInputStream(new File(new File(
                    getActivity().getCacheDir(),"")+filename)));
            String res =  (String) in.readObject();



            Picasso.with(getActivity().getApplication()).load((res))
            .into(mImageView);

        } catch (Exception e) {


        }

But the image isn't loading. What can I change to make this work?

Answer 1

Example with a .png file

Save File:( InputStream = from internet )

    final Bitmap bitmap = BitmapFactory.decodeStream(inputStream);


    ByteArrayOutputStream bytes = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG, 80, bytes);

    File f = new File(Environment.getExternalStorageDirectory() + File.separator + "MyApp/" + fileName );

    if (!f.exists())
    {
        f.getParentFile().mkdirs();
        f.createNewFile();
    }

    FileOutputStream fo = new FileOutputStream(f);
    fo.write(bytes.toByteArray());
    fo.close();

Read File:

 File path = new File(Environment.getExternalStorageDirectory(),"MyApp/" + fileName);

        if(path.exists())
        {
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inPreferredConfig = Bitmap.Config.ARGB_8888;
            Bitmap bitmap = BitmapFactory.decodeFile(path.getAbsolutePath(), options);
        }

Answer 2

To store your data on cache file you can use,

Suppose response is string which you want to store in cache.

           ObjectOutput out;
            try {
                String filenameOffer="cacheFileSearch.srl";

                out = new ObjectOutputStream(new FileOutputStream(new File
                        (getActivity().getCacheDir(),"")+filenameOffer));
                out.writeObject( response );
                out.close();
            } catch (Exception e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            } 

And for getting data back from cache file,

    try {
        String filename="cacheFileSearch.srl";

        ObjectInputStream in = new ObjectInputStream(new FileInputStream(new File(new File(
                getActivity().getCacheDir(),"")+filename)));
        String res =  (String) in.readObject();

    } catch (Exception e) {
        AppConstant.isLoadFirstTime=true;
    }

And for deleting file, you can use

        String filename="cacheFileSearch.srl";

        try {
            ObjectInputStream in = new ObjectInputStream(new FileInputStream(new File(new File(
                    getActivity().getCacheDir(),"")+filename)));
            File dir = getActivity().getCacheDir();
            if (dir.isDirectory()) {
                if (new File(new File(dir, "")+filename).delete()) {
                }

            } 
            in.close();

        } catch (Exception e) {

        }