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
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。
其他回答
Jens的回答的优化版本与零安全和回退类型。
@NonNull
static String getMimeType(@NonNull File file) {
String type = null;
final String url = file.toString();
final String extension = MimeTypeMap.getFileExtensionFromUrl(url);
if (extension != null) {
type = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension.toLowerCase());
}
if (type == null) {
type = "image/*"; // fallback type. You might set it to */*
}
return type;
}
重要:getFileExtensionFromUrl()只适用于小写字母!
更新(19.03.2018)
好处:上面的方法是一个不那么冗长的Kotlin扩展函数:
fun File.getMimeType(fallback: String = "image/*"): String {
return MimeTypeMap.getFileExtensionFromUrl(toString())
?.run { MimeTypeMap.getSingleton().getMimeTypeFromExtension(toLowerCase()) }
?: fallback // You might set it to */*
}
首先，你应该考虑调用MimeTypeMap#getMimeTypeFromExtension()，就像这样:
// url = file path or whatever suitable URL you want.
public static String getMimeType(String url) {
String type = null;
String extension = MimeTypeMap.getFileExtensionFromUrl(url);
if (extension != null) {
type = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
}
return type;
}
你有多种选择来获得文件扩展名: 字符串文件名= uri.getLastPathSegment();请看这个链接
2-你也可以使用这段代码
filePath .substring(filePath.lastIndexOf(".")+1);
但这不是一个好方法。 3-如果你有文件的URI，那么使用这个代码
String[] projection = { MediaStore.MediaColumns.DATA,
MediaStore.MediaColumns.MIME_TYPE };
4-如果你有URL，那么使用下面的代码:
public static String getMimeType(String url) {
String type = null;
String extension = MimeTypeMap.getFileExtensionFromUrl(url);
if (extension != null) {
type = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
}
return type;
}
享受你的代码:)
是否也返回空值 在我的案例中，路径是
/storage/ emululated /0/Music/01 - Ghost on the Dance Floor.mp3
在工作中使用
瓦尔·奥尼。replace(“”、“”)
方法是这样的
@JvmStatic
fun getMimeType(inUrl: String?): String {
if (inUrl == null) return ""
val url = inUrl.replace(" ","")
var type: String? = null
val extension = MimeTypeMap.getFileExtensionFromUrl(url)
if (extension != null) {
type = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension.toLowerCase())
}
if(type ==null){
val cR = WifiTalkie.getApplicationContext().contentResolver
type = cR.getType(Uri.parse(url))
}
if (type == null) {
type = "*/*" // fallback method_type. You might set it to */*
}
return type
}
结果返回成功结果:
音频/ mpeg
希望能对大家有所帮助
上面的MimeTypeMap解决方案在我的使用中返回null。这很有效，而且更简单:
Uri uri = Uri.fromFile(file);
ContentResolver cR = context.getContentResolver();
String mime = cR.getType(uri);
