从 Android 中的本地隐藏文件夹下载图像并显示

Question

我正在尝试从 Internet 下载图像并将其存储在本地的某个隐藏文件夹中，用户在他/她的画廊中看不到这些图像。

这是我的代码。仅当设备连接到互联网时才会显示图像。换句话说，图像没有保存在设备中，它正在引发异常。

这是我的 ImageStorage 类：

package com.example.adhish.downloadretriveimage;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 * Created by appy-20 on 6/1/17.
 */

public class ImageStorage {


    public static String saveToSdCard(Bitmap bitmap, String filename) {

        String stored = null;

        File sdcard = Environment.getExternalStorageDirectory() ;

        File folder = new File(sdcard.getAbsoluteFile(), ".test_directory");//the dot makes this directory hidden to the user
        folder.mkdir();
        File file = new File(folder.getAbsoluteFile(), filename + ".jpg") ;
        if (file.exists())
            return stored ;

        try {
            FileOutputStream out = new FileOutputStream(file);
            bitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);
            out.flush();
            out.close();
            stored = "success";
        } catch (Exception e) {
            e.printStackTrace();
        }

        return stored;
    }

    public static File getImage(String imagename) {

        File mediaImage = null;
        try {
            String root = Environment.getExternalStorageDirectory().toString();
            File myDir = new File(root);
            if (!myDir.exists())
                return null;

            mediaImage = new File(myDir.getPath() + "/.test_directory/"+imagename);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return mediaImage;
    }
    public static boolean checkifImageExists(String imagename)
    {
        Bitmap b = null ;
        File file = ImageStorage.getImage("/"+imagename+".jpg");
        String path = file.getAbsolutePath();

        if (path != null)
            b = BitmapFactory.decodeFile(path);

        if(b == null ||  b.equals(""))
        {
            return false ;
        }
        return true ;
    }
}

这是我的 MainActivity.java：

package com.example.adhish.downloadretriveimage;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

import java.io.File;
import java.io.FileOutputStream;
import java.net.URL;
import java.net.URLConnection;

public class MainActivity extends AppCompatActivity {


    ImageView imageView;
    Bitmap b;
    String imagename;
    String imgurl;

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

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

        imagename="394968_538b_7";
        imgurl="https://udemy-images.udemy.com/course/750x422/394968_538b_7.jpg";

        if(ImageStorage.checkifImageExists(imagename))
        {
            File file = ImageStorage.getImage("/"+imagename+".jpg");

//            File file = ImageStorage.getImage("https://udemy-images.udemy.com/course/750x422/394968_538b_7.jpg");

            String path = file.getAbsolutePath();
            if (path != null){
                b = BitmapFactory.decodeFile(path);
                imageView.setImageBitmap(b);
            }
        } else {
            new GetImages(imgurl, imageView, imagename).execute() ;
        }
    }

    private class GetImages extends AsyncTask<Object, Object, Object> {
        private String requestUrl, imagename_;
        private ImageView view;
        private Bitmap bitmap;
        private FileOutputStream fos;

        private GetImages(String requestUrl, ImageView view, String _imagename_) {
            this.requestUrl = requestUrl;
            this.view = view;
            this.imagename_ = _imagename_;
        }

        @Override
        protected Object doInBackground(Object... objects) {
            try {
                URL url = new URL(requestUrl);
                URLConnection conn = url.openConnection();
                bitmap = BitmapFactory.decodeStream(conn.getInputStream());
            } catch (Exception ex) {
            }
            return null;
        }

        @Override
        protected void onPostExecute(Object o) {
            if (!ImageStorage.checkifImageExists(imagename_)) {
                view.setImageBitmap(bitmap);
                ImageStorage.saveToSdCard(bitmap, imagename_);
            }
        }
    }
}

我已经在我的 Manifest 中授予了外部存储读写权限。

Answer 1

我找到了解决这个问题的方法。我将图像存储在 SQLite 数据库中，这是它的代码：

https://github.com/adhishlal/URL_to_DB_Image