Android 将图像保存到 SQLite 或 SDCard 或内存

Question

我需要从服务器获取图像和其他一些数据，然后将其显示在列表中。但是由于记录的数量可能非常大，所以我不确定是否应该将图像保存到 SQLite 数据库或将其保存到 SDCard 或将它们保存到内存中。

谢谢， 无

Answer 1

始终养成将图像路径保存到数据库的习惯。对于列表视图，请确保只使用这些图像的缩略图。这将帮助您在列表中快速加载这些图像。

 long selectedImageUri = ContentUris.parseId(Uri.parse(anniEntry.getUri()));
 Bitmap bm = MediaStore.Images.Thumbnails.getThumbnail(
                    mContext.getContentResolver(), selectedImageUri,MediaStore.Images.Thumbnails.MICRO_KIND,
                    null );

这里anniEntry.getUri()是图片的uri。现在，把它放在第二个代码中。U可以根据需要得到微型或迷你缩略图

Answer 2

在数据库中保存像图像一样的二进制数据通常被认为是不好的形式。在大多数情况下，由于某些技术原因，它实际上最终会损害数据库的性能。相反，将要缓存的图像保存到 SD 卡中，并将这些图像的文件路径存储在数据库中。

Answer 3

如果您需要下载图片并保存在 SD 卡中。请按照以下代码操作：

package com.tablet;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
import java.net.UnknownHostException;


import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

/*
 * This class download & store the media in external storage 
 * */
public class DownloadActivity extends Activity {

    private static String fileName = "android.jgp";

    private Button btnDownload;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        btnDownload = (Button) findViewById(R.id.download);
        btnDownload.setOnClickListener(new View.OnClickListener() {

            public void onClick(View view) {
                // TODO Auto-generated method stub
                download();
            }
        });


    private void download()
    {
        System.out.println("Inside Download");
        try {
            // this is the file you want to download from the remote server
            String path = "http://code.google.com/android/goodies/wallpaper/android-wallpaper5_1024x768.jpg";

            URL u = new URL(path);
            HttpURLConnection c = (HttpURLConnection) u.openConnection();
            c.setRequestMethod("GET");
            c.setDoOutput(true);
            c.connect();

            String PATH = "/data/Kamal"
                //Environment.getExternalStorageDirectory()
            // + "/download/";
                    + "/";

            Log.v("log_tag", "PATH: " + PATH);
            File file = new File(PATH);
            file.mkdirs();
            File outputFile = new File(file, fileName);

            FileOutputStream f = new FileOutputStream(outputFile);
            InputStream in = c.getInputStream();
            Log.v("log_tag"," InputStream consist of : "+in.read());
            byte[] buffer = new byte[1024];
            int len1 = 0;
            while ((len1 = in.read(buffer)) > 0) {
                //System.out.println("Reading byte : "+in.read(buffer));
                f.write(buffer, 0, len1);
            }
            Toast.makeText(this, "Download Completed Successfully @ "+PATH, Toast.LENGTH_LONG).show();
            f.close();


        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Toast.makeText(this, "MalformedURLException", Toast.LENGTH_LONG).show();
        } catch (ProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Toast.makeText(this, "ProtocolException", Toast.LENGTH_LONG).show();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Toast.makeText(this, "FileNotFoundException", Toast.LENGTH_LONG).show();
        }catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Toast.makeText(this, "UnknownHostException", Toast.LENGTH_LONG).show();
        }
        catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Toast.makeText(this, "IOException", Toast.LENGTH_LONG).show();
        }
    }



}

Answer 4

这是应用程序需求及其实现的问题。我建议使用内部或 sd 卡来存储图像并将路径保存在 db 中

Answer 5

存储任何不需要根据应用的查询（如图像、视频）返回该数据子部分的行为的大量数据，不应存储在数据库中，而应仅存储对该数据的引用.