我正在将10张图片从网络加载到SD卡，我的代码在SD卡中创建了子文件夹并加载了所有10张图片，但仅在第一次之后它没有加载并存储任何图像，在logcat中也没有错误。这是我的代码：
reviewImageLink = u_image;
URL reviewImageURL;
String name = reviewImageLink.substring(reviewImageLink.lastIndexOf("/") + 1);
try {
reviewImageURL = new URL(reviewImageLink);
if (!hasExternalStoragePublicPicture(name)) {
isImage = false;
new DownloadImageTask().execute(reviewImageURL);
Log.v("log_tag", "if");
isImage = true;
File sdImageMainDirectory = new File(Environment.getExternalStorageDirectory(), getResources().getString(R.string.directory));
sdImageMainDirectory.mkdirs();
file = new File(sdImageMainDirectory, name);
Log.v("log_tag", "Directory created");
}
} catch (MalformedURLException e) {
Log.v(TAG, e.toString());
}
DownloadImageTask：
class DownloadImageTask extends AsyncTask<URL, Integer, Bitmap> {
// This class definition states that DownloadImageTask will take String
// parameters, publish Integer progress updates, and return a Bitmap
protected Bitmap doInBackground(URL... paths) {
URL url;
try {
url = paths[0];
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
int length = connection.getContentLength();
InputStream is = (InputStream) url.getContent();
byte[] imageData = new byte[length];
int buffersize = (int) Math.ceil(length / (double) 100);
int downloaded = 0;
int read;
while (downloaded < length) {
if (length < buffersize) {
read = is.read(imageData, downloaded, length);
} else if ((length - downloaded) <= buffersize) {
read = is.read(imageData, downloaded, length
- downloaded);
} else {
read = is.read(imageData, downloaded, buffersize);
}
downloaded += read;
publishProgress((downloaded * 100) / length);
}
Bitmap bitmap = BitmapFactory.decodeByteArray(imageData, 0,
length);
if (bitmap != null) {
Log.i(TAG, "Bitmap created");
} else {
Log.i(TAG, "Bitmap not created");
}
is.close();
return bitmap;
} catch (MalformedURLException e) {
Log.e(TAG, "Malformed exception: " + e.toString());
} catch (IOException e) {
Log.e(TAG, "IOException: " + e.toString());
} catch (Exception e) {
Log.e(TAG, "Exception: " + e.toString());
}
return null;
}
protected void onPostExecute(Bitmap result) {
String name = reviewImageLink.substring(reviewImageLink
.lastIndexOf("/") + 1);
if (result != null) {
hasExternalStoragePublicPicture(name);
saveToSDCard(result, name);
isImage = true;
} else {
isImage = false;
}
}
}
public void saveToSDCard(Bitmap bitmap, String name) {
boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
mExternalStorageAvailable = mExternalStorageWriteable = true;
Log.v(TAG, "SD Card is available for read and write "+ mExternalStorageAvailable + mExternalStorageWriteable);
saveFile(bitmap, name);
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
mExternalStorageAvailable = true;
mExternalStorageWriteable = false;
Log.v(TAG, "SD Card is available for read "+ mExternalStorageAvailable);
} else {
mExternalStorageAvailable = mExternalStorageWriteable = false;
Log.v(TAG, "Please insert a SD Card to save your Video "+ mExternalStorageAvailable + mExternalStorageWriteable);
}
}
private void saveFile(Bitmap bitmap, String name)
{
String filename = name;
ContentValues values = new ContentValues();
File sdImageMainDirectory = new File(Environment.getExternalStorageDirectory(), getResources().getString(R.string.directory));
sdImageMainDirectory.mkdirs();
File outputFile = new File(sdImageMainDirectory, filename);
values.put(MediaStore.MediaColumns.DATA, outputFile.toString());
values.put(MediaStore.MediaColumns.TITLE, filename);
values.put(MediaStore.MediaColumns.DATE_ADDED, System.currentTimeMillis());
values.put(MediaStore.MediaColumns.MIME_TYPE, "output.png");
Uri uri = this.getContentResolver().insert(android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI,values);
try
{
OutputStream outStream = this.getContentResolver().openOutputStream(uri);
bitmap.compress(Bitmap.CompressFormat.PNG, 95, outStream);
outStream.flush();
outStream.close();
}
catch (FileNotFoundException e)
{
e.printStackTrace();
} catch (IOException e)
{
e.printStackTrace();
}
}
private boolean hasExternalStoragePublicPicture(String name) {
File sdImageMainDirectory = new File(Environment.getExternalStorageDirectory(), getResources().getString(R.string.directory));
File file = new File(sdImageMainDirectory, name);
if (file != null)
{
file.delete();
}
return file.exists();
}
这里是logcat：
02-20 08:49:46.999: D/dalvikvm(346): GC_FOR_MALLOC freed 5254 objects / 245320 bytes in 69ms
02-20 08:50:00.138: I/Topten(346): Bitmap created
02-20 08:50:00.148: V/Topten(346): SD Card is available for read and write truetrue
02-20 08:50:03.628: D/dalvikvm(346): GC_EXTERNAL_ALLOC freed 4548 objects / 238192 bytes in 68ms
02-20 08:50:03.728: I/Topten(346): Bitmap created
02-20 08:50:03.738: V/Topten(346): SD Card is available for read and write truetrue
02-20 08:50:04.898: D/dalvikvm(346): GC_EXTERNAL_ALLOC freed 585 objects / 85272 bytes in 107ms
02-20 08:50:05.018: I/Topten(346): Bitmap created
02-20 08:50:05.049: V/Topten(346): SD Card is available for read and write truetrue
02-20 08:50:05.528: I/Topten(346): Bitmap created
02-20 08:50:06.409: V/Topten(346): SD Card is available for read and write truetrue
02-20 08:50:10.968: I/Topten(346): Bitmap created
02-20 08:50:10.968: V/Topten(346): SD Card is available for read and write truetrue
02-20 08:50:12.368: I/Topten(346): Bitmap created
02-20 08:50:12.380: V/Topten(346): SD Card is available for read and write truetrue
02-20 08:50:15.569: D/dalvikvm(346): GC_EXTERNAL_ALLOC freed 4584 objects / 358728 bytes in 58ms
02-20 08:50:15.619: I/Topten(346): Bitmap created
02-20 08:50:15.629: V/Topten(346): SD Card is available for read and write truetrue
02-20 08:50:22.179: I/Topten(346): Bitmap created
02-20 08:50:22.189: V/Topten(346): SD Card is available for read and write truetrue
答案 0 :(得分：1)
修改 你的代码似乎是正确的..我没有发现任何错误。 我不确定是不是这个原因但是...... 在创建目录之前检查目录是否存在
if(!sdImageMainDirectory.exists()){
sdImageMainDirectory.mkdirs();
}
检查一次并回复我...进一步分析......我希望这对你有所帮助。
您还没有将文件写入刚刚创建文件的外部存储中...尝试将文件写入外部存储并确保您已设置权限外部存储写入
答案 1 :(得分：0)
如果我没错，你的变量 reviewImageLink 是一个类变量。然后，在您的DownloadImageTask中，您使用 reviewImageLink 生成文件名并将图像保存在此文件中。
问题是：如果你一个接一个地调用你的函数10次，你的类变量 reviewImageLink 将被最后一次调用覆盖。这可能会导致您的应用始终只保存一张图片。
我的建议是你可以在DownloadImageTask中生成你的图像文件名。因此，下载完成后，它会将图像文件保存在单独的文件中。
以下是我如何下载图片并保存在本地。我把下载和保存放在AsyncTask类中。我还决定AsyncTask中的文件名。所以其他下载过程之间没有冲突。请检查我的 DownloadImageTask 类。