Question

我对毕加索并不太熟悉，但我的应用程序使用它来加载他们的URL中的图像但是我想制作一个按钮，当它被点击时，它会将图像标记为收藏，即使它处于离线状态也会显示它。
我正在使用Content Provider保存其他内容（字符串，双精度数）。

所以，我认为实现这一目标的最佳方法是将图像保存为甚至离线显示但是如何保存它们？

Answer 1

使用网址下载图片还有另一个不错的选择。试试这段代码。

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

    new DownloadFile().execute("https://i.stack.imgur.com/w4kCo.jpg");
}
class DownloadFile extends AsyncTask<String,Integer,Long> {
    ProgressDialog mProgressDialog = new ProgressDialog(MainActivity.this);// Change Mainactivity.this with your activity name. 
    String strFolderName;
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        mProgressDialog.setMessage("Downloading Image ...");
        mProgressDialog.setIndeterminate(false);
        mProgressDialog.setMax(100);
        mProgressDialog.setCancelable(false);
        mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        mProgressDialog.show();
    }
    @Override
    protected Long doInBackground(String... aurl) {
        int count;
        try {
            URL url = new URL((String) aurl[0]);
            URLConnection conexion = url.openConnection();
            conexion.connect();
            String targetFileName="downloadedimage.jpg";//Change name and subname

            int lenghtOfFile = conexion.getContentLength();
            String PATH = Environment.getExternalStorageDirectory()+"/myImage/";
            File folder = new File(PATH);
            if(!folder.exists()){
                folder.mkdir();//If there is no folder it will be created.
            }
            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream(PATH+targetFileName);
            byte data[] = new byte[1024];
            long total = 0;
            while ((count = input.read(data)) != -1) {
                total += count;
                       publishProgress ((int)(total*100/lenghtOfFile));
                output.write(data, 0, count);
            }
            output.flush();
            output.close();
            input.close();
        } catch (Exception e) {}
        return null;
    }
    protected void onProgressUpdate(Integer... progress) {
         mProgressDialog.setProgress(progress[0]);
         if(mProgressDialog.getProgress()==mProgressDialog.getMax()){
            mProgressDialog.dismiss();

            Toast.makeText(getApplicationContext(), "Download Completed !", Toast.LENGTH_LONG).show();

         }
    }
    protected void onPostExecute(String result) {
    }
}

将下载的图像位图设置为Imageview。

Answer 2

这是代码。通过这种策略，毕加索将在缓存中查找图像，如果只是失败，那么图像将通过网络下载。

     Picasso.with(context)
                        .load(Uri.parse(getItem(position).getStoryBigThumbUrl()))
                        .networkPolicy(NetworkPolicy.OFFLINE)
                        .into(holder.storyBigThumb, new Callback() {
                            @Override
                            public void onSuccess() {

                            }

                            @Override
                            public void onError() {
                                // Try again online if cache failed
                                Picasso.with(context)
                                        .load(Uri.parse(getItem(position)
                                                .getStoryBigThumbUrl()))
                                .placeholder(R.drawable.user_placeholder)
                                .error(R.drawable.user_placeholder_error)
                                        .into(holder.storyBigThumb);
                            }
                        });

Picasso有自己的缓存，你不需要自己处理任何事情。

如何使用Picasso保存和显示图像

2 个答案: