Show specific error message for busy device.

When MTP device is busy (e.g. used by other application),
MtpDocumentsProvider cannot open the device. The CL introduces specific
error message for the case.

BUG=26694828

Change-Id: Iffee2e1c554e4089601186469ff0eac2fd04decd

6 files changed, 72 insertions, 2 deletions

diff --git a/packages/MtpDocumentsProvider/res/values/strings.xml b/packages/MtpDocumentsProvider/res/values/strings.xml
index 43a420cf6d97..42bedf1c1cdc 100644
--- a/packages/MtpDocumentsProvider/res/values/strings.xml
+++ b/packages/MtpDocumentsProvider/res/values/strings.xml
@@ -25,4 +25,6 @@
     <string name="accessing_notification_title">Accessing files from <xliff:g id="device_model" example="Nexus 9">%1$s</xliff:g></string>
     <!-- Description of notification showing Files app is accessing files in a MTP device. [CHAR LIMIT=60]-->
     <string name="accessing_notification_description">Don\'t disconnect the device</string>
+    <!-- Error message shown in Files app when the connected MTP device is busy. [CHAR LIMIT=150]-->
+    <string name="error_busy_device">The other device is busy. You can\'t transfer files until it\'s available.</string>
 </resources>
diff --git a/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java b/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java
index 033845401b4b..7eae71a8d8a4 100644
--- a/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java
+++ b/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java
@@ -20,10 +20,12 @@ import android.content.ContentResolver;
 import android.content.res.AssetFileDescriptor;
 import android.content.res.Resources;
 import android.database.Cursor;
+import android.database.MatrixCursor;
 import android.graphics.Point;
 import android.media.MediaFile;
 import android.mtp.MtpConstants;
 import android.mtp.MtpObjectInfo;
+import android.os.Bundle;
 import android.os.CancellationSignal;
 import android.os.ParcelFileDescriptor;
 import android.os.storage.StorageManager;
@@ -35,6 +37,7 @@ import android.util.Log;
 
 import com.android.internal.annotations.GuardedBy;
 import com.android.internal.annotations.VisibleForTesting;
+import com.android.mtp.exceptions.BusyDeviceException;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
@@ -174,6 +177,14 @@ public class MtpDocumentsProvider extends DocumentsProvider {
             // Returns object list from document loader.
             return getDocumentLoader(parentIdentifier).queryChildDocuments(
                     projection, parentIdentifier);
+        } catch (BusyDeviceException exception) {
+            final Bundle bundle = new Bundle();
+            bundle.putString(
+                    DocumentsContract.EXTRA_ERROR,
+                    mResources.getString(R.string.error_busy_device));
+            final Cursor cursor = new MatrixCursor(projection);
+            cursor.setExtras(bundle);
+            return cursor;
         } catch (IOException exception) {
             Log.e(MtpDocumentsProvider.TAG, "queryChildDocuments", exception);
             throw new FileNotFoundException(exception.getMessage());
diff --git a/packages/MtpDocumentsProvider/src/com/android/mtp/MtpManager.java b/packages/MtpDocumentsProvider/src/com/android/mtp/MtpManager.java
index 5519efd5a323..0527790470fb 100644
--- a/packages/MtpDocumentsProvider/src/com/android/mtp/MtpManager.java
+++ b/packages/MtpDocumentsProvider/src/com/android/mtp/MtpManager.java
@@ -33,6 +33,7 @@ import android.util.Log;
 import android.util.SparseArray;
 
 import com.android.internal.annotations.VisibleForTesting;
+import com.android.mtp.exceptions.BusyDeviceException;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
@@ -101,7 +102,8 @@ class MtpManager {
         }
 
         if (!device.open(connection)) {
-            throw new IOException("Failed to open a MTP device.");
+            // We cannot open connection when another application use the device.
+            throw new BusyDeviceException();
         }
 
         // Handle devices that fail to obtain storages just after opening a MTP session.
@@ -134,7 +136,7 @@ class MtpManager {
                 try {
                     roots = getRoots(device.getDeviceId());
                 } catch (IOException exp) {
-                    Log.e(MtpDocumentsProvider.TAG, exp.getMessage());
+                    Log.e(MtpDocumentsProvider.TAG, "Failed to open device", exp);
                     // If we failed to fetch roots for the device, we still returns device model
                     // with an empty set of roots so that the device is shown DocumentsUI as long as
                     // the device is physically connected.
diff --git a/packages/MtpDocumentsProvider/src/com/android/mtp/exceptions/BusyDeviceException.java b/packages/MtpDocumentsProvider/src/com/android/mtp/exceptions/BusyDeviceException.java
new file mode 100644
index 000000000000..55f55b0edbc3
--- /dev/null
+++ b/packages/MtpDocumentsProvider/src/com/android/mtp/exceptions/BusyDeviceException.java
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2016 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 com.android.mtp.exceptions;
+
+import java.io.IOException;
+
+/**
+ * Exception thrown when the device is busy and the requested operation cannon be completed.
+ */
+public class BusyDeviceException extends IOException {
+}
diff --git a/packages/MtpDocumentsProvider/tests/src/com/android/mtp/MtpDocumentsProviderTest.java b/packages/MtpDocumentsProvider/tests/src/com/android/mtp/MtpDocumentsProviderTest.java
index 5b0f55703a2b..4bc016247762 100644
--- a/packages/MtpDocumentsProvider/tests/src/com/android/mtp/MtpDocumentsProviderTest.java
+++ b/packages/MtpDocumentsProvider/tests/src/com/android/mtp/MtpDocumentsProviderTest.java
@@ -29,6 +29,8 @@ import android.provider.DocumentsContract;
 import android.test.AndroidTestCase;
 import android.test.suitebuilder.annotation.MediumTest;
 
+import com.android.mtp.exceptions.BusyDeviceException;
+
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.util.Arrays;
@@ -526,6 +528,32 @@ public class MtpDocumentsProviderTest extends AndroidTestCase {
         }
     }
 
+    public void testBusyDevice() throws Exception {
+        mMtpManager = new TestMtpManager(getContext()) {
+            @Override
+            void openDevice(int deviceId) throws IOException {
+                throw new BusyDeviceException();
+            }
+        };
+        setupProvider(MtpDatabaseConstants.FLAG_DATABASE_IN_MEMORY);
+        mMtpManager.addValidDevice(new MtpDeviceRecord(
+                0, "Device A", false /* unopened */, new MtpRoot[0], null, null));
+
+        mProvider.resumeRootScanner();
+        mResolver.waitForNotification(ROOTS_URI, 1);
+
+        try (final Cursor cursor = mProvider.queryRoots(null)) {
+            assertEquals(1, cursor.getCount());
+        }
+
+        try (final Cursor cursor = mProvider.queryChildDocuments("1", null, null)) {
+            assertEquals(0, cursor.getCount());
+            assertEquals(
+                    "error_busy_device",
+                    cursor.getExtras().getString(DocumentsContract.EXTRA_ERROR));
+        }
+    }
+
     private void setupProvider(int flag) {
         mDatabase = new MtpDatabase(getContext(), flag);
         mProvider = new MtpDocumentsProvider();
diff --git a/packages/MtpDocumentsProvider/tests/src/com/android/mtp/TestResources.java b/packages/MtpDocumentsProvider/tests/src/com/android/mtp/TestResources.java
index b23038b6c3f6..a576a04ac6bb 100644
--- a/packages/MtpDocumentsProvider/tests/src/com/android/mtp/TestResources.java
+++ b/packages/MtpDocumentsProvider/tests/src/com/android/mtp/TestResources.java
@@ -24,6 +24,8 @@ class TestResources extends MockResources {
         switch (id) {
             case R.string.root_name:
                 return "%1$s %2$s";
+            case R.string.error_busy_device:
+                return "error_busy_device";
         }
         throw new NotFoundException();
     }