我可以在 mode_private 中保存图像吗？

Question

目前我使用以下方法将 XML 文件保存在 mode_private 中：

public void Save_Data(String filename, String Datastring, Context context) {
    FileOutputStream fos;

    try {
        fos = context.openFileOutput(filename, context.MODE_PRIVATE);
        fos.write(Datastring.getBytes());
        fos.close();
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

我想在 mode_private 中将 URL 中大约 5kb 的小图像保存到我的应用程序空间中。是否可以在 mode_private 中保存图像？如果是这样，谁能告诉我如何修改下面的方法来做到这一点？

public void DownloadFromUrl(final String DownloadUrl, final String fileName) {


    Thread web = new Thread(){
        public void run(){


       try {
               File root = Environment.getExternalStorageDirectory();               

               File dir = new File (root.getAbsolutePath() + "/Chats");
               if(dir.exists()==false) {
                    dir.mkdirs();
               }

               URL url = new URL(DownloadUrl); //you can write here any link
               File file = new File(dir, fileName);

               long startTime = System.currentTimeMillis();
               Log.d("DownloadManager", "download begining");
               Log.d("DownloadManager", "download url:" + url);
               Log.d("DownloadManager", "downloaded file name:" + fileName);

               /* Open a connection to that URL. */
               URLConnection ucon = url.openConnection();

               /*
                * Define InputStreams to read from the URLConnection.
                */
               InputStream is = ucon.getInputStream();
               BufferedInputStream bis = new BufferedInputStream(is);

               /*
                * Read bytes to the Buffer until there is nothing more to read(-1).
                */
               ByteArrayBuffer baf = new ByteArrayBuffer(5000);
               int current = 0;
               while ((current = bis.read()) != -1) {
                  baf.append((byte) current);
               }


               /* Convert the Bytes read to a String. */
               FileOutputStream fos = new FileOutputStream(file);
               fos.write(baf.toByteArray());
               fos.flush();
               fos.close();
               Log.d("DownloadManager", "download ready in " + ((System.currentTimeMillis() - startTime) / 1000) + " sec");

       } catch (IOException e) {
           Log.d("DownloadManager", "Error: " + e);
       }

        }
        };
        web.start();
    }

Answer 1

所以我终于想出了如何在 mode_private 中保存图像

以下方法获取一个位图并将其保存到您的应用程序私有空间中的 mode_private。

 public String writeFileToInternalStorage(Bitmap outputImage){
        String fileName = fileName + ".png";

        FileOutputStream fos = null;
  try {
   fos = openFileOutput(fileName, Context.MODE_PRIVATE);
  } catch (FileNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
        outputImage.compress(Bitmap.CompressFormat.PNG, 90, fos);

  return fileName;
    }

这会从应用程序的私有空间读取图像并将其转换为位图：

 Bitmap bitmap = BitmapFactory.decodeFile(this.getApplicationContext().getFilesDir() + "/"+fileName);

希望这对某人有所帮助。

Answer 2

根据 Randrm 的回答，我实现了以下两种方法来存储/检索应用程序私有数据空间中 ImageView 中存在的位图图像。基本上是他的答案的清理版本，取自编译代码。

如果您希望 Activity 在恢复时快速恢复其视图的内容，这可能会很有用。 ImageView 由 R.string.myImage 标识，该位图通过类的 myBitmap 成员访问。

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    // we will be stopped and perhaps later on destroyed;
    // store displayed image for quick retrieval in private data space
    try {
        FileOutputStream output =
           openFileOutput(this.getString(R.string.myImage), Context.MODE_PRIVATE);
        myBitmap.compress(Bitmap.CompressFormat.PNG, 100, output);
    } catch (Exception e) {
        Log.e(LOG_TAG, "could not save image to private space");
    }

    // superclass to save the view hierarchy state
    super.onSaveInstanceState(savedInstanceState);
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
    // superclass to restore the view hierarchy
    super.onRestoreInstanceState(savedInstanceState);

    // retrieve image stored earlier
    try {
        FileInputStream input = openFileInput(this.getString(R.string.myImage));
        ((ImageView) findViewById(R.id.det_mainimage)).
          setImageBitmap(BitmapFactory.decodeStream(input));            
    } catch (Exception e) {
        Log.e(LOG_TAG, "could not retrieve image from private space");
    }
}

享受吧。