Get the MIME type from File and UrlEncode

api/current.txt

@@ -308,6 +308,15 @@ package androidx.core.graphics.drawable {
 
 }
 
+package androidx.core.io {
+
+  public final class FileKt {
+    ctor public FileKt();
+    method public static String? getMimeTypeFromExtension(java.io.File);
+  }
+
+}
+
 package androidx.core.net {
 
   public final class UriKt {
@@ -409,6 +418,7 @@ package androidx.core.text {
   public final class StringKt {
     ctor public StringKt();
     method public static String htmlEncode(String);
+    method public static String urlEncode(String);
   }
 
 }

src/androidTest/java/androidx/core/io/FileTest.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.core.io
+
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertSame
+import org.junit.Test
+import java.io.File
+
+class FileTest {
+
+    @Test fun jpg() {
+        val photo = File("sunset.jpg")
+        val type = photo.mimeTypeFromExtension
+        assertSame("image/jpeg", type)
+    }
+
+    @Test fun png() {
+        val logo = File("images/logo.png")
+        val type = logo.mimeTypeFromExtension
+        assertSame("image/png", type)
+    }
+
+    @Test fun pdfWithSpaces() {
+        val thesis = File("my documents/master thesis-v5.1-final-final2.pdf")
+        val type = thesis.mimeTypeFromExtension
+        assertSame("application/pdf", type)
+    }
+
+    @Test fun noExtension() {
+        val path = File("foo/bar")
+        val type = path.mimeTypeFromExtension
+        assertNull(type)
+    }
+
+    @Test fun unknownExtension() {
+        val unknownFile = File("foo/bar.baz")
+        val type = unknownFile.mimeTypeFromExtension
+        assertNull(type)
+    }
+}

src/main/java/androidx/core/io/File.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.core.io
+
+import android.webkit.MimeTypeMap
+import androidx.core.text.urlEncode
+import java.io.File
+
+/**
+ * Returns the MIME type (content type) of this [File] based on its extension.
+ *
+ * @see MimeUtils
+ * @return The MIME type for the files' extension or null if there is none.
+ */
+val File.mimeTypeFromExtension: String?
+    get() = MimeTypeMap.getFileExtensionFromUrl(path.urlEncode())
+        ?.apply { MimeTypeMap.getSingleton().getMimeTypeFromExtension(toLowerCase()) }

src/main/java/androidx/core/text/String.kt

@@ -18,6 +18,7 @@
 
 package androidx.core.text
 
+import android.net.Uri
 import android.text.TextUtils
 
 /**
@@ -26,3 +27,10 @@ import android.text.TextUtils
  * @see TextUtils.htmlEncode
  */
 inline fun String.htmlEncode(): String = TextUtils.htmlEncode(this)
+
+/**
+ * Url-encode the string.
+ *
+ * @see Uri.encode
+ */
+inline fun String.urlEncode(): String = Uri.encode(this)