您需要编写 ContentProvider，它将向您传递 ContentUri 的客户端提供 InputStream，或者如果文件路径存在于 SdCard 或内部存储中，您可以直接提供文件路径，因为您需要处理uri 并传递 InputStream 。注意：ExtraStream 最适合用于从 Internet 访问的设备中不存在的文件。
public class SampleContentProvider extends ContentProvider implements ContentProvider.PipeDataWriter<InputStream> {
static final UriMatcher uriMatcher;
static {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
//Uri matcher for different
}
/**
* Database specific constant declarations
*/
private SQLiteDatabase db;
@Override
public boolean onCreate() {
return true;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
throw new SQLException("Insert operation not supported for " + uri);
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
//condition just for files. You can try something else
if (uri.toString().contains("files")) {
//you get the file name
String lastSegment = uri.getLastPathSegment();
if (projection == null) {
projection = new String[]{OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE};
}
File file = //Code to read the file as u have the directory, just get the file from the file name obtained from the uri
if (null == file) {
throw new IllegalArgumentException("Unknown File for Uri " + uri);
}
String[] cols = new String[projection.length];
Object[] values = new Object[projection.length];
int i = 0;
for (String col : projection) {
if (OpenableColumns.DISPLAY_NAME.equals(col)) {
cols[i] = OpenableColumns.DISPLAY_NAME;
values[i++] = //file name;
} else if (OpenableColumns.SIZE.equals(col)) {
cols[i] = OpenableColumns.SIZE;
values[i++] = //file size;
}
}
cols = copyOf(cols, i);
values = copyOf(values, i);
final MatrixCursor cursor = new MatrixCursor(cols, 1);
cursor.addRow(values);
return cursor;
}
return super.query(uri, projection, selection, selectionArgs, sortOrder);
}
@Override
public String getType(Uri uri) {
return null;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
return super.delete(uri, selection, selectionArgs);
}
private static String[] copyOf(String[] original, int newLength) {
final String[] result = new String[newLength];
System.arraycopy(original, 0, result, 0, newLength);
return result;
}
private static Object[] copyOf(Object[] original, int newLength) {
final Object[] result = new Object[newLength];
System.arraycopy(original, 0, result, 0, newLength);
return result;
}
@Nullable
@Override
public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException {
File file = //read the file
if (file != null) {
try {
StrictMode.ThreadPolicy tp = StrictMode.ThreadPolicy.LAX;
StrictMode.setThreadPolicy(tp);
InputStream in = //Code to get the inputstream;
// Start a new thread that pipes the stream data back to the caller.
return openPipeHelper(uri, null, null, in, this);
} catch (IOException e) {
FileNotFoundException fnf = new FileNotFoundException("Unable to open " + uri);
throw fnf;
}
}
throw new IllegalArgumentException("Unknown URI " + uri);
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
return super.update(uri, values, selection, selectionArgs);
}
@Override
public void writeDataToPipe(ParcelFileDescriptor output, Uri uri, String mimeType,
Bundle opts, InputStream args) {
// Transfer data from the asset to the pipe the client is reading.
byte[] buffer = new byte[8192];
int n;
FileOutputStream fout = new FileOutputStream(output.getFileDescriptor());
try {
while ((n = args.read(buffer)) >= 0) {
fout.write(buffer, 0, n);
}
} catch (IOException e) {
} finally {
try {
args.close();
} catch (IOException e) {
}
try {
fout.close();
} catch (IOException e) {
}
}
}
}