Question

我正在尝试从互联网下载图像并将其存储在本地存储在某个隐藏文件夹中，其中图像对用户在他/她的图库中不可见。

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，而是抛出异常。

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中给出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，以下是代码：

https://github.com/adhishlal/URL_to_DB_Image

从Android中的本地隐藏文件夹下载图像并显示

1 个答案: