Not create document under the device.

The structure of files in MtpDocumentsProvider looks like
/device/storage/files. But MtpDocumentsProvider shows files
just under the device if the device has only single storage.

It causes a problem that MtpDocumentsProvider tries to create a file
under the device. Previously it tries to create a file with storageId =
0, which means MTP device choose a storage to store the file.

Because it only happens when the device has a single storage, the file
is properly written to the device. But the database in
MtpDocumentsProvider goes into the illegal state where the file is
placed just under the device.

Bug: 32561572
Test: adb shell am instrument -w -e class com.android.mtp.MtpDocumentsProviderTest com.android.mtp.tests/com.android.mtp.TestResultInstrumentation
Change-Id: I47a373ceee8a64ba9995934317693e79d2497ee0
(cherry picked from commit 35b2ec551f)

packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java

@@ -349,6 +349,34 @@ public class MtpDocumentsProvider extends DocumentsProvider {
                 throw new UnsupportedOperationException(
                         "Writing operation is not supported by the device.");
             }
+
+            final int parentObjectHandle;
+            final int storageId;
+            switch (parentId.mDocumentType) {
+                case MtpDatabaseConstants.DOCUMENT_TYPE_DEVICE:
+                    final String[] storageDocumentIds =
+                            mDatabase.getStorageDocumentIds(parentId.mDocumentId);
+                    if (storageDocumentIds.length == 1) {
+                        final String newDocumentId =
+                                createDocument(storageDocumentIds[0], mimeType, displayName);
+                        notifyChildDocumentsChange(parentDocumentId);
+                        return newDocumentId;
+                    } else {
+                        throw new UnsupportedOperationException(
+                                "Cannot create a file under the device.");
+                    }
+                case MtpDatabaseConstants.DOCUMENT_TYPE_STORAGE:
+                    storageId = parentId.mStorageId;
+                    parentObjectHandle = -1;
+                    break;
+                case MtpDatabaseConstants.DOCUMENT_TYPE_OBJECT:
+                    storageId = parentId.mStorageId;
+                    parentObjectHandle = parentId.mObjectHandle;
+                    break;
+                default:
+                    throw new IllegalArgumentException("Unexpected document type.");
+            }
+
             pipe = ParcelFileDescriptor.createReliablePipe();
             int objectHandle = -1;
             MtpObjectInfo info = null;
@@ -359,8 +387,8 @@ public class MtpDocumentsProvider extends DocumentsProvider {
                         MtpConstants.FORMAT_ASSOCIATION :
                         MediaFile.getFormatCode(displayName, mimeType);
                 info = new MtpObjectInfo.Builder()
-                        .setStorageId(parentId.mStorageId)
+                        .setStorageId(storageId)
-                        .setParent(parentId.mObjectHandle)
+                        .setParent(parentObjectHandle)
                         .setFormat(formatCode)
                         .setName(displayName)
                         .build();

packages/MtpDocumentsProvider/tests/src/com/android/mtp/MtpDocumentsProviderTest.java

@@ -546,7 +546,7 @@ public class MtpDocumentsProviderTest extends AndroidTestCase {
     public void testOpenDocument_writing() throws Exception {
         setupProvider(MtpDatabaseConstants.FLAG_DATABASE_IN_MEMORY);
         setupRoots(0, new MtpRoot[] {
-                new MtpRoot(0, 0, "Storage", 0, 0, "")
+                new MtpRoot(0, 100, "Storage", 0, 0, "")
         });
         final String documentId = mProvider.createDocument("2", "text/plain", "test.txt");
         {
@@ -688,6 +688,29 @@ public class MtpDocumentsProviderTest extends AndroidTestCase {
         }
     }
 
+    public void testCreateDocument() throws Exception {
+        setupProvider(MtpDatabaseConstants.FLAG_DATABASE_IN_MEMORY);
+        setupRoots(0, new MtpRoot[] {
+                new MtpRoot(0, 100, "Storage A", 100, 100, null)
+        });
+        final String documentId = mProvider.createDocument("1", "text/plain", "note.txt");
+        final Uri deviceUri = DocumentsContract.buildChildDocumentsUri(
+                MtpDocumentsProvider.AUTHORITY, "1");
+        final Uri storageUri = DocumentsContract.buildChildDocumentsUri(
+                MtpDocumentsProvider.AUTHORITY, "2");
+        mResolver.waitForNotification(storageUri, 1);
+        mResolver.waitForNotification(deviceUri, 1);
+        try (final Cursor cursor = mProvider.queryDocument(documentId, null)) {
+            assertTrue(cursor.moveToNext());
+            assertEquals(
+                    "note.txt",
+                    cursor.getString(cursor.getColumnIndex(Document.COLUMN_DISPLAY_NAME)));
+            assertEquals(
+                    "text/plain",
+                    cursor.getString(cursor.getColumnIndex(Document.COLUMN_MIME_TYPE)));
+        }
+    }
+
     public void testCreateDocument_noWritingSupport() throws Exception {
         setupProvider(MtpDatabaseConstants.FLAG_DATABASE_IN_MEMORY);
         mMtpManager.addValidDevice(new MtpDeviceRecord(

packages/MtpDocumentsProvider/tests/src/com/android/mtp/TestMtpManager.java

@@ -26,6 +26,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
+import junit.framework.Assert;
 
 public class TestMtpManager extends MtpManager {
     public static final int CREATED_DOCUMENT_HANDLE = 1000;
@@ -151,6 +152,9 @@ public class TestMtpManager extends MtpManager {
     @Override
     int createDocument(int deviceId, MtpObjectInfo objectInfo, ParcelFileDescriptor source)
             throws IOException {
+        Assert.assertNotSame(0, objectInfo.getStorageId());
+        Assert.assertNotSame(-1, objectInfo.getStorageId());
+        Assert.assertNotSame(0, objectInfo.getParent());
         final String key = pack(deviceId, CREATED_DOCUMENT_HANDLE);
         if (mObjectInfos.containsKey(key)) {
             throw new IOException();