Android - 将URL中的图像保存到SD卡上

Question

我想将图像从URL保存到SD卡(以备将来使用),然后从SD卡加载该图像,将其用作Google地图的可绘制叠加层.

这是函数的保存部分:

//SAVE TO FILE

String filepath = Environment.getExternalStorageDirectory().getAbsolutePath(); 
String extraPath = "/Map-"+RowNumber+"-"+ColNumber+".png";
filepath += extraPath;

FileOutputStream fos = null;
fos = new FileOutputStream(filepath); 

bmImg.compress(CompressFormat.PNG, 75, fos);

//LOAD IMAGE FROM FILE
Drawable d = Drawable.createFromPath(filepath);
return d;

图像以succuessfully的形式保存到SD卡,但在到达createFromPath()线路时失败.我不明白为什么它会保存到那个目的地但不加载它....

Answer 1

试试这个代码.它有效......

try
{   
  URL url = new URL("Enter the URL to be downloaded");
  HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
  urlConnection.setRequestMethod("GET");
  urlConnection.setDoOutput(true);                   
  urlConnection.connect();                  
  File SDCardRoot = Environment.getExternalStorageDirectory().getAbsoluteFile();
  String filename="downloadedFile.png";   
  Log.i("Local filename:",""+filename);
  File file = new File(SDCardRoot,filename);
  if(file.createNewFile())
  {
    file.createNewFile();
  }                 
  FileOutputStream fileOutput = new FileOutputStream(file);
  InputStream inputStream = urlConnection.getInputStream();
  int totalSize = urlConnection.getContentLength();
  int downloadedSize = 0;   
  byte[] buffer = new byte[1024];
  int bufferLength = 0;
  while ( (bufferLength = inputStream.read(buffer)) > 0 ) 
  {                 
    fileOutput.write(buffer, 0, bufferLength);                  
    downloadedSize += bufferLength;                 
    Log.i("Progress:","downloadedSize:"+downloadedSize+"totalSize:"+ totalSize) ;
  }             
  fileOutput.close();
  if(downloadedSize==totalSize) filepath=file.getPath();    
} 
catch (MalformedURLException e) 
{
  e.printStackTrace();
} 
catch (IOException e)
{
  filepath=null;
  e.printStackTrace();
}
Log.i("filepath:"," "+filepath) ;
return filepath;

Answer 2

DownloadManager为您完成所有这些工作.

public void downloadFile(String uRl) {
    File direct = new File(Environment.getExternalStorageDirectory()
            + "/AnhsirkDasarp");

    if (!direct.exists()) {
        direct.mkdirs();
    }

    DownloadManager mgr = (DownloadManager) getActivity().getSystemService(Context.DOWNLOAD_SERVICE);

    Uri downloadUri = Uri.parse(uRl);
    DownloadManager.Request request = new DownloadManager.Request(
            downloadUri);

    request.setAllowedNetworkTypes(
            DownloadManager.Request.NETWORK_WIFI
                    | DownloadManager.Request.NETWORK_MOBILE)
            .setAllowedOverRoaming(false).setTitle("Demo")
            .setDescription("Something useful. No, really.")
            .setDestinationInExternalPublicDir("/AnhsirkDasarpFiles", "fileName.jpg");

    mgr.enqueue(request);

    // Open Download Manager to view File progress
    Toast.makeText(getActivity(), "Downloading...",Toast.LENGTH_LONG).show();
    startActivity(Intent(DownloadManager.ACTION_VIEW_DOWNLOADS));

}

Answer 3

尝试使用此代码将图像从URL保存到SDCard.

URL url = new URL ("file://some/path/anImage.png"); 
InputStream input = url.openStream(); 
try {     
    File storagePath = Environment.getExternalStorageDirectory();
    OutputStream output = new FileOutputStream (storagePath, "myImage.png");     
    try {         
        byte[] buffer = new byte[aReasonableSize];         
        int bytesRead = 0;         
        while ((bytesRead = input.read(buffer, 0, buffer.length)) >= 0) {
                output.write(buffer, 0, bytesRead);         
        }     
    }   
    finally {         
        output.close();     
    } 
} 

finally {     
    input.close(); 
}

如果要在SD卡上创建子目录,请使用:

File storagePath = new File(Environment.getExternalStorageDirectory(),"Wallpaper");
storagePath.mkdirs();

创建子目录"/ sdcard/Wallpaper /".

希望它会对你有所帮助.

请享用.:)

Answer 4

我相信它失败了，因为您正在将位图的压缩版本写入输出流，该输出流应该加载BitmapFactory.decodeStream(). 快速浏览一下这方面的文档。

如果您需要Drawable(decodeStream()返回 a Bitmap)，只需调用Drawable d = new BitmapDrawable(bitmap).