我试图创建SD卡上创建新的文件为Android 5.0及以上。 因此,首先,我让用户通过授予SAF权限。 这是怎么了检查所选目录是SD卡或不。
public static boolean wrong_directory_selected(Uri uri, Context con)
{
final File uri_path=new File(FileUtil.getFullPathFromTreeUri(uri,con));
if(uri_path.getName().toLowerCase().equals(new File("SD CARD PATH").getName().toLowerCase()))
{
return false;
}
return true;
}
然后,这就是我想创建一个新的文件。
DocumentFile move = DocumentFile(new File("path)).createFile(mime,"name); // But I am getting java.lang.NullPointerException
下面是我现在用得到DocumentFile为到该文件必须创建的目录的方法。
public static DocumentFile DocumentFile(final File file)
{
DocumentFile rootDocFile = DocumentFile.fromTreeUri(con, permission().getUri());
String[] parts = (file.getPath()).split("\\/");
for (int i = 3; i < parts.length; i++)
{
rootDocFile = rootDocFile.findFile(parts[i]);
}
return rootDocFile;
}
public static UriPermission permission()
{
for (UriPermission permissionUri : con.getContentResolver().getPersistedUriPermissions())
{
final File uri_path = new File(FileUtil.getFullPathFromTreeUri(permissionUri.getUri(), con));
if (uri_path.getName().toLowerCase().equals(new File("SD_CARD_PATH").getName().toLowerCase()))
{
return permissionUri;
}
}
return null;
}
该代码工作正常的大部分时间,但有时我得到java.lang.NullPointerException
。
任何帮助将不胜感激。
编辑:这是我的FileUtil类
public final class FileUtil {
private static final String PRIMARY_VOLUME_NAME = "primary";
@Nullable
public static String getFullPathFromTreeUri(@Nullable final Uri treeUri, Context con)
{
if (treeUri == null)
{
return null;
}
String volumePath = FileUtil.getVolumePath(FileUtil.getVolumeIdFromTreeUri(treeUri),con);
if (volumePath == null)
{
return File.separator;
}
if (volumePath.endsWith(File.separator))
{
volumePath = volumePath.substring(0, volumePath.length() - 1);
}
String documentPath = FileUtil.getDocumentPathFromTreeUri(treeUri);
if (documentPath.endsWith(File.separator))
{
documentPath = documentPath.substring(0, documentPath.length() - 1);
}
if (documentPath.length() > 0)
{
if (documentPath.startsWith(File.separator))
{
return volumePath + documentPath;
}
else {
return volumePath + File.separator + documentPath;
}
}
else
{
return volumePath;
}
}
private static String getVolumePath(final String volumeId, Context con)
{
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP)
{
return null;
}
try {
StorageManager mStorageManager =
(StorageManager) con.getSystemService(Context.STORAGE_SERVICE);
Class<?> storageVolumeClazz = Class.forName("android.os.storage.StorageVolume");
Method getVolumeList = mStorageManager.getClass().getMethod("getVolumeList");
Method getUuid = storageVolumeClazz.getMethod("getUuid");
Method getPath = storageVolumeClazz.getMethod("getPath");
Method isPrimary = storageVolumeClazz.getMethod("isPrimary");
Object result = getVolumeList.invoke(mStorageManager);
final int length = Array.getLength(result);
for (int i = 0; i < length; i++)
{
Object storageVolumeElement = Array.get(result, i);
String uuid = (String) getUuid.invoke(storageVolumeElement);
Boolean primary = (Boolean) isPrimary.invoke(storageVolumeElement);
// primary volume?
if (primary && PRIMARY_VOLUME_NAME.equals(volumeId))
{
return (String) getPath.invoke(storageVolumeElement);
}
// other volumes?
if (uuid != null)
{
if (uuid.equals(volumeId))
{
return (String) getPath.invoke(storageVolumeElement);
}
}
}
// not found.
return null;
}
catch (Exception ex)
{
return null;
}
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private static String getVolumeIdFromTreeUri(final Uri treeUri)
{
final String docId = DocumentsContract.getTreeDocumentId(treeUri);
final String[] split = docId.split(":");
if (split.length > 0)
{
return split[0];
}
else
{
return null;
}
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private static String getDocumentPathFromTreeUri(final Uri treeUri)
{
final String docId = DocumentsContract.getTreeDocumentId(treeUri);
final String[] split = docId.split(":");
if ((split.length >= 2) && (split[1] != null))
{
return split[1];
}
else
{
return File.separator;
}
}
}
编辑2:
在该文件已被创建的路径是不错,我也检查了URI的权限,甚至是不为空。
值是
该文件具有路径是created- /storage/external_SD
许可URI- content://com.android.externalstorage.documents/tree/6634-3765%3A
编辑3:
我使用这个库找到SD卡路径。