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。
以下是该功能的保存部分：
//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;
图像以可疑方式保存到SD卡，但在到达createFromPath()行时失败。我不明白为什么它会保存到该目的地，但不能从它加载.......
答案 0 :(得分：28)
试试此代码。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;
答案 1 :(得分：25)
DownloadManager为您完成所有这些。
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));
}
答案 2 :(得分：6)
尝试使用此代码将图像从URL保存到SD卡。
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。
享受。 ：）
答案 3 :(得分：3)
我也遇到了同样的问题并用此解决了我的问题。试试这个
private class ImageDownloadAndSave extends AsyncTask<String, Void, Bitmap>
{
@Override
protected Bitmap doInBackground(String... arg0)
{
downloadImagesToSdCard("","");
return null;
}
private void downloadImagesToSdCard(String downloadUrl,String imageName)
{
try
{
URL url = new URL(img_URL);
/* making a directory in sdcard */
String sdCard=Environment.getExternalStorageDirectory().toString();
File myDir = new File(sdCard,"test.jpg");
/* if specified not exist create new */
if(!myDir.exists())
{
myDir.mkdir();
Log.v("", "inside mkdir");
}
/* checks the file and if it already exist delete */
String fname = imageName;
File file = new File (myDir, fname);
if (file.exists ())
file.delete ();
/* Open a connection */
URLConnection ucon = url.openConnection();
InputStream inputStream = null;
HttpURLConnection httpConn = (HttpURLConnection)ucon;
httpConn.setRequestMethod("GET");
httpConn.connect();
if (httpConn.getResponseCode() == HttpURLConnection.HTTP_OK)
{
inputStream = httpConn.getInputStream();
}
FileOutputStream fos = new FileOutputStream(file);
int totalSize = httpConn.getContentLength();
int downloadedSize = 0;
byte[] buffer = new byte[1024];
int bufferLength = 0;
while ( (bufferLength = inputStream.read(buffer)) >0 )
{
fos.write(buffer, 0, bufferLength);
downloadedSize += bufferLength;
Log.i("Progress:","downloadedSize:"+downloadedSize+"totalSize:"+ totalSize) ;
}
fos.close();
Log.d("test", "Image Saved in sdcard..");
}
catch(IOException io)
{
io.printStackTrace();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
在AsyncTask中声明您的网络操作，因为它会将其作为后台任务加载。不要在主线程上加载网络操作。 在按钮点击或内容视图中调用此类之后
new ImageDownloadAndSave().execute("");
不要忘记将nework权限添加为：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.INTERNET" />
希望这可以帮助某人： - ）
答案 4 :(得分：1)
我认为它失败了，因为您正在将位图的压缩版本写入输出流，应该使用BitmapFactory.decodeStream()加载。在此文档上有一个quick look。
如果您需要Drawable（decodeStream()返回Bitmap），只需致电Drawable d = new BitmapDrawable(bitmap)。
答案 5 :(得分：1)
试试此代码..工作正常
public static Bitmap loadImageFromUrl(String url) {
URL m;
InputStream i = null;
BufferedInputStream bis = null;
ByteArrayOutputStream out =null;
try {
m = new URL(url);
i = (InputStream) m.getContent();
bis = new BufferedInputStream(i,1024 * 8);
out = new ByteArrayOutputStream();
int len=0;
byte[] buffer = new byte[1024];
while((len = bis.read(buffer)) != -1){
out.write(buffer, 0, len);
}
out.close();
bis.close();
} catch (MalformedURLException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
byte[] data = out.toByteArray();
Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
//Drawable d = Drawable.createFromStream(i, "src");
return bitmap;
}
并将位图保存到目录
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
_bitmap.compress(Bitmap.CompressFormat.JPEG, 40, bytes);
//you can create a new file name "test.jpg" in sdcard folder.
File f = new File(Environment.getExternalStorageDirectory()
+ File.separator + "test.jpg")
f.createNewFile();
//write the bytes in file
FileOutputStream fo = new FileOutputStream(f);
fo.write(bytes.toByteArray());
// remember close de FileOutput
fo.close();
并且不要忘记添加清单
的权限<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
答案 6 :(得分：1)
试试这个......完成任务的简单方法。
Picasso.with(getActivity())
.load(url)
.into(new Target() {
@Override
public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
try {
String root = Environment.getExternalStorageDirectory().toString();
File myDir = new File(root + "/yourDirectory");
if (!myDir.exists()) {
myDir.mkdirs();
}
String name = new Date().toString() + ".jpg";
myDir = new File(myDir, name);
FileOutputStream out = new FileOutputStream(myDir);
bitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);
out.flush();
out.close();
} catch(Exception e){
// some action
}
}
@Override
public void onBitmapFailed(Drawable errorDrawable) {
}
@Override
public void onPrepareLoad(Drawable placeHolderDrawable) {
}
}
);