how to save my image loaded from firebase storage through picasso in cache of my app

Question

I am new to android development I followed some tutorials for loading image through Picasso , but I have 1 problem like I when ever I load image from firebase storage through Picasso the image is appears but when I close my app and open app the image is gone and I need to upload and retrieve it again. my friend suggested me to store the image in cache , so please help me in doing this. Here is my code I implemented to load image from firebase storage.

import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.provider.MediaStore;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.OnProgressListener;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.UploadTask;
import com.squareup.picasso.Picasso;

import java.io.IOException;

import static android.R.attr.bitmap;

public class ProfilePhotoUI extends AppCompatActivity implements View.OnClickListener /*  implementing click listener */ {
    //a constant to track the file chooser intent
    private static final int PICK_IMAGE_REQUEST = 234;

    //Buttons
    private Button buttonChoose;
    private Button buttonUpload;

    //ImageView
    private ImageView imageView;

    //a Uri object to store file path
    private Uri filePath;

    //firebase storage reference
    private StorageReference storageReference;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_profile_photo_ui);

        //getting views from layout
        buttonChoose = (Button) findViewById(R.id.buttonChoose);
        buttonUpload = (Button) findViewById(R.id.buttonUpload);

        imageView = (ImageView) findViewById(R.id.imageView);

        //attaching listener
        buttonChoose.setOnClickListener(this);
        buttonUpload.setOnClickListener(this);

        //getting firebase storage reference
        storageReference = FirebaseStorage.getInstance().getReference();
    }

    //method to show file chooser
    private void showFileChooser() {
        Intent intent = new Intent();
        intent.setType("image/*");
        intent.setAction(Intent.ACTION_GET_CONTENT);
        startActivityForResult(Intent.createChooser(intent, "Select Picture"), PICK_IMAGE_REQUEST);
    }

    //handling the image chooser activity result
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK && data != null && data.getData() != null) {
            filePath = data.getData();
            try {
                Bitmap bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), filePath);
                imageView.setImageBitmap(bitmap);

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    //this method will upload the file
    private void uploadFile() {
        //if there is a file to upload
        if (filePath != null) {
            //displaying a progress dialog while upload is going on
            final ProgressDialog progressDialog = new ProgressDialog(this);
            progressDialog.setTitle("Uploading");
            progressDialog.show();

            StorageReference riversRef = storageReference.child("images/pic.jpg");
            riversRef.putFile(filePath)
                    .addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
                        @Override
                        public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
                            //if the upload is successfull
                            //hiding the progress dialog
                            progressDialog.dismiss();
                            Uri downloadUri = taskSnapshot.getDownloadUrl();

                            Picasso.with(ProfilePhotoUI.this).load(downloadUri).transform(new CircleTransform()).into(imageView);


                            //and displaying a success toast
                            Toast.makeText(getApplicationContext(), "File Uploaded ", Toast.LENGTH_LONG).show();

                        }
                    })
                    .addOnFailureListener(new OnFailureListener() {
                        @Override
                        public void onFailure(@NonNull Exception exception) {
                            //if the upload is not successfull
                            //hiding the progress dialog
                            progressDialog.dismiss();

                            //and displaying error message
                            Toast.makeText(getApplicationContext(), exception.getMessage(), Toast.LENGTH_LONG).show();
                        }
                    })
                    .addOnProgressListener(new OnProgressListener<UploadTask.TaskSnapshot>() {
                        @Override
                        public void onProgress(UploadTask.TaskSnapshot taskSnapshot) {
                            //calculating progress percentage
                            double progress = (100.0 * taskSnapshot.getBytesTransferred()) / taskSnapshot.getTotalByteCount();

                            //displaying percentage in progress dialog
                            progressDialog.setMessage("Uploaded " + ((int) progress) + "%...");
                        }
                    });
        }
        //if there is not any file
        else {
            //you can display an error toast
        }
    }

    @Override
    public void onClick(View view) {
        //if the clicked button is choose
        if (view == buttonChoose) {
            showFileChooser();
        }
        //if the clicked button is upload
        else if (view == buttonUpload) {
            uploadFile();
        }
    }
}

Answer 1

I usually see people saving the DownloadUrl variable in Firebase Database, but you can also save it in a SQL Database.

Wherever you save your DownloadUrl, you can use it in Picasso as shown below:

Picasso.with(getActivity())
.load(imageUrl)
.networkPolicy(NetworkPolicy.OFFLINE)
.into(imageView, new Callback() {
    @Override
    public void onSuccess() {

    }

    @Override
    public void onError() {
        //Try again online if cache failed
        Picasso.with(getActivity())
                .load(posts.get(position).getImageUrl())
                .error(R.drawable.header)
                .into(imageView, new Callback() {
            @Override
            public void onSuccess() {

            }

            @Override
            public void onError() {
                Log.v("Picasso","Could not fetch image");
            }
        });
    }
});

Where networkPolicy(NetworkPolicy.OFFLINE) will force Picasso look for it first in hard disk. In case of clear cache, Picasso will look for it online.

Picasso will save your image in the following path (e.g. Emulator):

/data/data/com.example.myapp/cache/picasso-cache

Once Picasso has saved your image in cache, I have no idea how to have access to the image without using Picasso.

You can also download your image into the cache directory by using DownloadManager. Where (String) destinationDirectory = getContext().getCacheDir().getPath().toString()

private void downloadFile(Context context, final String fileName, final String fileExtension, String destinationDirectory, String url) {

        BroadcastReceiver onComplete;

        DownloadManager downloadManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);

        Uri uri = Uri.parse(url);

        DownloadManager.Request request = new DownloadManager.Request(uri);

        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
        request.setDestinationUri(Uri.fromFile(new File(destinationDirectory,fileName + fileExtension)));
        request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI | DownloadManager.Request.NETWORK_MOBILE);

        onComplete = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                String action = intent.getAction();
                if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {

                    //DO WHATEVER YOU NEED AFTER FILE HAS BEEN DOWNLOADED HERE

                }

            }
        };

        getActivity().registerReceiver(onComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));

        downloadManager.enqueue(request);


    }

After downloading your Image, you have to save your new ImagePath. I hope it helps!