假设我有一个完整的文件路径:(/sdcard/tlogo.png)。我想知道它的mime类型。
我为它创建了一个函数
public static String getMimeType(File file, Context context)
{
Uri uri = Uri.fromFile(file);
ContentResolver cR = context.getContentResolver();
MimeTypeMap mime = MimeTypeMap.getSingleton();
String type = mime.getExtensionFromMimeType(cR.getType(uri));
return type;
}
但当我调用它时，它返回null。
File file = new File(filePath);
String fileType=CommonFunctions.getMimeType(file, context);
当前回答
Intent myIntent = new Intent(android.content.Intent.ACTION_VIEW);
File file = new File(filePatch);
Uri uris = Uri.fromFile(file);
String mimetype = null;
if
(uris.getScheme().equals(ContentResolver.SCHEME_CONTENT)) {
ContentResolver cr =
getApplicationContext().getContentResolver();
mimetype = cr.getType(uris);
} else {
String fileExtension =
MimeTypeMap.getFileExtensionFromUrl(uris.toString());
mimetype = MimeTypeMap.getSingleton().getMimeTypeFromExtension(fileExtension.toLowerCase());
}
其他回答
有时Jeb和Jens的答案不工作并返回null。在这种情况下，我使用跟随解决方案。文件头通常包含类型签名。我阅读了它，并与已知的签名列表进行了比较。
/**
*
* @param is InputStream on start of file. Otherwise signature can not be defined.
* @return int id of signature or -1, if unknown signature was found. See SIGNATURE_ID_(type) constants to
* identify signature by its id.
* @throws IOException in cases of read errors.
*/
public static int getSignatureIdFromHeader(InputStream is) throws IOException {
// read signature from head of source and compare with known signatures
int signatureId = -1;
int sigCount = SIGNATURES.length;
int[] byteArray = new int[MAX_SIGNATURE_LENGTH];
StringBuilder builder = new StringBuilder();
for (int i = 0; i < MAX_SIGNATURE_LENGTH; i++) {
byteArray[i] = is.read();
builder.append(Integer.toHexString(byteArray[i]));
}
if (DEBUG) {
Log.d(TAG, "head bytes=" + builder.toString());
}
for (int i = 0; i < MAX_SIGNATURE_LENGTH; i++) {
// check each bytes with known signatures
int bytes = byteArray[i];
int lastSigId = -1;
int coincidences = 0;
for (int j = 0; j < sigCount; j++) {
int[] sig = SIGNATURES[j];
if (DEBUG) {
Log.d(TAG, "compare" + i + ": " + Integer.toHexString(bytes) + " with " + sig[i]);
}
if (bytes == sig[i]) {
lastSigId = j;
coincidences++;
}
}
// signature is unknown
if (coincidences == 0) {
break;
}
// if first bytes of signature is known we check signature for full coincidence
if (coincidences == 1) {
int[] sig = SIGNATURES[lastSigId];
int sigLength = sig.length;
boolean isSigKnown = true;
for (; i < MAX_SIGNATURE_LENGTH && i < sigLength; i++) {
bytes = byteArray[i];
if (bytes != sig[i]) {
isSigKnown = false;
break;
}
}
if (isSigKnown) {
signatureId = lastSigId;
}
break;
}
}
return signatureId;
}
signatureId是签名数组中签名的索引。例如,
private static final int[] SIGNATURE_PNG = hexStringToIntArray("89504E470D0A1A0A");
private static final int[] SIGNATURE_JPEG = hexStringToIntArray("FFD8FF");
private static final int[] SIGNATURE_GIF = hexStringToIntArray("474946");
public static final int SIGNATURE_ID_JPEG = 0;
public static final int SIGNATURE_ID_PNG = 1;
public static final int SIGNATURE_ID_GIF = 2;
private static final int[][] SIGNATURES = new int[3][];
static {
SIGNATURES[SIGNATURE_ID_JPEG] = SIGNATURE_JPEG;
SIGNATURES[SIGNATURE_ID_PNG] = SIGNATURE_PNG;
SIGNATURES[SIGNATURE_ID_GIF] = SIGNATURE_GIF;
}
现在我有了文件类型，即使文件的URI没有。接下来我得到mime类型的文件类型。如果你不知道要获取哪种mime类型，你可以在这个表中找到proper。
它适用于许多文件类型。但是对于视频，它不起作用，因为你需要知道视频编解码器来获得mime类型。为了获得视频的mime类型，我使用mediametadatareretrieve。
而从资产/文件(注意，在MimeTypeMap中缺少一些情况)。
private String getMimeType(String path) {
if (null == path) return "*/*";
String extension = path;
int lastDot = extension.lastIndexOf('.');
if (lastDot != -1) {
extension = extension.substring(lastDot + 1);
}
// Convert the URI string to lower case to ensure compatibility with MimeTypeMap (see CB-2185).
extension = extension.toLowerCase(Locale.getDefault());
if (extension.equals("3ga")) {
return "audio/3gpp";
} else if (extension.equals("js")) {
return "text/javascript";
} else if (extension.equals("woff")) {
return "application/x-font-woff";
} else {
// TODO
// anyting missing from the map (http://www.sitepoint.com/web-foundations/mime-types-complete-list/)
// reference: http://grepcode.com/file/repo1.maven.org/maven2/com.google.okhttp/okhttp/20120626/libcore/net/MimeUtils.java#MimeUtils
}
return MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
}
而使用ContentResolver
contentResolver.getType(uri)
当http/https请求
try {
HttpURLConnection conn = httpClient.open(new URL(uri.toString()));
conn.setDoInput(false);
conn.setRequestMethod("HEAD");
return conn.getHeaderField("Content-Type");
} catch (IOException e) {
}
它适用于我和灵活的内容和文件
public static String getMimeType(Context context, Uri uri) {
String extension;
//Check uri format to avoid null
if (uri.getScheme().equals(ContentResolver.SCHEME_CONTENT)) {
//If scheme is a content
final MimeTypeMap mime = MimeTypeMap.getSingleton();
extension = mime.getExtensionFromMimeType(context.getContentResolver().getType(uri));
} else {
//If scheme is a File
//This will replace white spaces with %20 and also other special characters. This will avoid returning null values on file name with spaces and special characters.
extension = MimeTypeMap.getFileExtensionFromUrl(Uri.fromFile(new File(uri.getPath())).toString());
}
return extension;
}
上面的解决方案在.rar文件的情况下返回null，使用URLConnection.guessContentTypeFromName(url)在这种情况下工作。
我也遇到过类似的问题。到目前为止，我知道不同的名字可能会有不同的结果，所以最终得出了这个解决方案。
public String getMimeType(String filePath) {
String type = null;
String extension = null;
int i = filePath.lastIndexOf('.');
if (i > 0)
extension = filePath.substring(i+1);
if (extension != null)
type = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
return type;
}
