Add directory selection to DocumentsProvider.

Introduce new ACTION_PICK_DIRECTORY that allows users to grant access
to an entire document subtree.  Instead of requiring grants for each
individual document, this leverages new prefix URI permission grants
by defining new "via"-style URIs:

content://com.example/via/12/document/24/

This references document 24 by using a prefix grant given for
document 12.  Internally, we use isChildDocument() to enforce that
24 is actually a descendant (child, grandchild, etc) of 12.  Since
this is an optional API, providers indicate support with
Root.FLAG_SUPPORTS_DIR_SELECTION.

Extend DocumentsUI to support picking directories.  Expose
createDocument() API to work with returned directories.

Offer to canonicalize via-style URIs into direct URIs, generating
exact permission grants along the way.  Override openAssetFile()
to pass through CancellationSignal.  Move testing code into ApiDemos.

Bug: 10607375
Change-Id: Ifffc1cff878870f8152eb6ca0199c5d014b9cb07

8 files changed, 226 insertions, 291 deletions

diff --git a/packages/DocumentsUI/AndroidManifest.xml b/packages/DocumentsUI/AndroidManifest.xml
index 6b77a7c..159ee66 100644
--- a/packages/DocumentsUI/AndroidManifest.xml
+++ b/packages/DocumentsUI/AndroidManifest.xml
@@ -9,18 +9,17 @@
         android:label="@string/app_label"
         android:supportsRtl="true">
 
-        <!-- TODO: allow rotation when state saving is in better shape -->
         <activity
             android:name=".DocumentsActivity"
             android:theme="@style/Theme"
             android:icon="@drawable/ic_doc_text">
-            <intent-filter android:priority="100">
+            <intent-filter>
                 <action android:name="android.intent.action.OPEN_DOCUMENT" />
                 <category android:name="android.intent.category.DEFAULT" />
                 <category android:name="android.intent.category.OPENABLE" />
                 <data android:mimeType="*/*" />
             </intent-filter>
-            <intent-filter android:priority="100">
+            <intent-filter>
                 <action android:name="android.intent.action.CREATE_DOCUMENT" />
                 <category android:name="android.intent.category.DEFAULT" />
                 <category android:name="android.intent.category.OPENABLE" />
@@ -33,6 +32,10 @@
                 <data android:mimeType="*/*" />
             </intent-filter>
             <intent-filter>
+                <action android:name="android.intent.action.PICK_DIRECTORY" />
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
+            <intent-filter>
                 <action android:name="android.provider.action.MANAGE_ROOT" />
                 <category android:name="android.intent.category.DEFAULT" />
                 <data android:mimeType="vnd.android.document/root" />
@@ -57,14 +60,5 @@
                 <data android:scheme="package" />
             </intent-filter>
         </receiver>
-
-        <!-- TODO: remove when we have real clients -->
-        <activity android:name=".TestActivity" android:enabled="false">
-            <intent-filter>
-                <action android:name="android.intent.action.MAIN" />
-                <category android:name="android.intent.category.DEFAULT" />
-                <category android:name="android.intent.category.LAUNCHER" />
-            </intent-filter>
-        </activity>
     </application>
 </manifest>
diff --git a/packages/DocumentsUI/res/layout/fragment_pick.xml b/packages/DocumentsUI/res/layout/fragment_pick.xml
new file mode 100644
index 0000000..4a2fd03
--- /dev/null
+++ b/packages/DocumentsUI/res/layout/fragment_pick.xml
@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2014 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.
+-->
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical">
+
+    <!-- Le sigh, this really should be an asset -->
+    <View
+        android:layout_width="match_parent"
+        android:layout_height="1dp"
+        android:background="#ccc" />
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:baselineAligned="false"
+        android:gravity="center_vertical"
+        android:background="#ddd"
+        android:minHeight="?android:attr/listPreferredItemHeightSmall">
+
+        <Button
+            android:id="@android:id/button1"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:background="?android:attr/selectableItemBackground"
+            android:textAppearance="?android:attr/textAppearanceSmall"
+            android:textAllCaps="false"
+            android:padding="8dp" />
+
+    </LinearLayout>
+
+</LinearLayout>
diff --git a/packages/DocumentsUI/res/values/strings.xml b/packages/DocumentsUI/res/values/strings.xml
index 92c30ba..c1a9d72 100644
--- a/packages/DocumentsUI/res/values/strings.xml
+++ b/packages/DocumentsUI/res/values/strings.xml
@@ -44,6 +44,8 @@
     <string name="menu_share">Share</string>
     <!-- Menu item title that deletes the selected documents [CHAR LIMIT=24] -->
     <string name="menu_delete">Delete</string>
+    <!-- Menu item title that selects the current directory [CHAR LIMIT=48] -->
+    <string name="menu_select">Select \"<xliff:g id="directory" example="My Directory">^1</xliff:g>\"</string>
 
     <!-- Action mode title summarizing the number of documents selected [CHAR LIMIT=32] -->
     <string name="mode_selected_count"><xliff:g id="count" example="3">%1$d</xliff:g> selected</string>
diff --git a/packages/DocumentsUI/src/com/android/documentsui/DocumentsActivity.java b/packages/DocumentsUI/src/com/android/documentsui/DocumentsActivity.java
index 4212e96..9f76991 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/DocumentsActivity.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/DocumentsActivity.java
@@ -24,6 +24,7 @@ import static com.android.documentsui.DocumentsActivity.State.ACTION_CREATE;
 import static com.android.documentsui.DocumentsActivity.State.ACTION_GET_CONTENT;
 import static com.android.documentsui.DocumentsActivity.State.ACTION_MANAGE;
 import static com.android.documentsui.DocumentsActivity.State.ACTION_OPEN;
+import static com.android.documentsui.DocumentsActivity.State.ACTION_PICK_DIRECTORY;
 import static com.android.documentsui.DocumentsActivity.State.MODE_GRID;
 import static com.android.documentsui.DocumentsActivity.State.MODE_LIST;
 
@@ -202,6 +203,8 @@ public class DocumentsActivity extends Activity {
             final String mimeType = getIntent().getType();
             final String title = getIntent().getStringExtra(Intent.EXTRA_TITLE);
             SaveFragment.show(getFragmentManager(), mimeType, title);
+        } else if (mState.action == ACTION_PICK_DIRECTORY) {
+            PickFragment.show(getFragmentManager());
         }
 
         if (mState.action == ACTION_GET_CONTENT) {
@@ -209,7 +212,8 @@ public class DocumentsActivity extends Activity {
             moreApps.setComponent(null);
             moreApps.setPackage(null);
             RootsFragment.show(getFragmentManager(), moreApps);
-        } else if (mState.action == ACTION_OPEN || mState.action == ACTION_CREATE) {
+        } else if (mState.action == ACTION_OPEN || mState.action == ACTION_CREATE
+                || mState.action == ACTION_PICK_DIRECTORY) {
             RootsFragment.show(getFragmentManager(), null);
         }
 
@@ -236,6 +240,8 @@ public class DocumentsActivity extends Activity {
             mState.action = ACTION_CREATE;
         } else if (Intent.ACTION_GET_CONTENT.equals(action)) {
             mState.action = ACTION_GET_CONTENT;
+        } else if (Intent.ACTION_PICK_DIRECTORY.equals(action)) {
+            mState.action = ACTION_PICK_DIRECTORY;
         } else if (DocumentsContract.ACTION_MANAGE_ROOT.equals(action)) {
             mState.action = ACTION_MANAGE;
         }
@@ -434,7 +440,8 @@ public class DocumentsActivity extends Activity {
             actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
             actionBar.setIcon(new ColorDrawable());
 
-            if (mState.action == ACTION_OPEN || mState.action == ACTION_GET_CONTENT) {
+            if (mState.action == ACTION_OPEN || mState.action == ACTION_GET_CONTENT
+                    || mState.action == ACTION_PICK_DIRECTORY) {
                 actionBar.setTitle(R.string.title_open);
             } else if (mState.action == ACTION_CREATE) {
                 actionBar.setTitle(R.string.title_save);
@@ -576,7 +583,7 @@ public class DocumentsActivity extends Activity {
         sortSize.setVisible(mState.showSize);
 
         final boolean searchVisible;
-        if (mState.action == ACTION_CREATE) {
+        if (mState.action == ACTION_CREATE || mState.action == ACTION_PICK_DIRECTORY) {
             createDir.setVisible(cwd != null && cwd.isCreateSupported());
             searchVisible = false;
 
@@ -586,7 +593,9 @@ public class DocumentsActivity extends Activity {
                 list.setVisible(false);
             }
 
-            SaveFragment.get(fm).setSaveEnabled(cwd != null && cwd.isCreateSupported());
+            if (mState.action == ACTION_CREATE) {
+                SaveFragment.get(fm).setSaveEnabled(cwd != null && cwd.isCreateSupported());
+            }
         } else {
             createDir.setVisible(false);
 
@@ -819,7 +828,7 @@ public class DocumentsActivity extends Activity {
 
         if (cwd == null) {
             // No directory means recents
-            if (mState.action == ACTION_CREATE) {
+            if (mState.action == ACTION_CREATE || mState.action == ACTION_PICK_DIRECTORY) {
                 RecentsCreateFragment.show(fm);
             } else {
                 DirectoryFragment.showRecentsOpen(fm, anim);
@@ -848,6 +857,15 @@ public class DocumentsActivity extends Activity {
             }
         }
 
+        if (mState.action == ACTION_PICK_DIRECTORY) {
+            final PickFragment pick = PickFragment.get(fm);
+            if (pick != null) {
+                final CharSequence displayName = (mState.stack.size() <= 1) ? root.title
+                        : cwd.displayName;
+                pick.setPickTarget(cwd, displayName);
+            }
+        }
+
         final RootsFragment roots = RootsFragment.get(fm);
         if (roots != null) {
             roots.onCurrentRootChanged();
@@ -1002,12 +1020,18 @@ public class DocumentsActivity extends Activity {
         new CreateFinishTask(mimeType, displayName).executeOnExecutor(getCurrentExecutor());
     }
 
+    public void onPickRequested(DocumentInfo pickTarget) {
+        final Uri viaUri = DocumentsContract.buildViaUri(pickTarget.authority,
+                pickTarget.documentId);
+        new PickFinishTask(viaUri).executeOnExecutor(getCurrentExecutor());
+    }
+
     private void saveStackBlocking() {
         final ContentResolver resolver = getContentResolver();
         final ContentValues values = new ContentValues();
 
         final byte[] rawStack = DurableUtils.writeToArrayOrNull(mState.stack);
-        if (mState.action == ACTION_CREATE) {
+        if (mState.action == ACTION_CREATE || mState.action == ACTION_PICK_DIRECTORY) {
             // Remember stack for last create
             values.clear();
             values.put(RecentColumns.KEY, mState.stack.buildKey());
@@ -1040,6 +1064,11 @@ public class DocumentsActivity extends Activity {
 
         if (mState.action == ACTION_GET_CONTENT) {
             intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
+        } else if (mState.action == ACTION_PICK_DIRECTORY) {
+            intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION
+                    | Intent.FLAG_GRANT_WRITE_URI_PERMISSION
+                    | Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION
+                    | Intent.FLAG_GRANT_PREFIX_URI_PERMISSION);
         } else {
             intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION
                     | Intent.FLAG_GRANT_WRITE_URI_PERMISSION
@@ -1121,6 +1150,25 @@ public class DocumentsActivity extends Activity {
         }
     }
 
+    private class PickFinishTask extends AsyncTask<Void, Void, Void> {
+        private final Uri mUri;
+
+        public PickFinishTask(Uri uri) {
+            mUri = uri;
+        }
+
+        @Override
+        protected Void doInBackground(Void... params) {
+            saveStackBlocking();
+            return null;
+        }
+
+        @Override
+        protected void onPostExecute(Void result) {
+            onFinished(mUri);
+        }
+    }
+
     public static class State implements android.os.Parcelable {
         public int action;
         public String[] acceptMimes;
@@ -1154,7 +1202,8 @@ public class DocumentsActivity extends Activity {
         public static final int ACTION_OPEN = 1;
         public static final int ACTION_CREATE = 2;
         public static final int ACTION_GET_CONTENT = 3;
-        public static final int ACTION_MANAGE = 4;
+        public static final int ACTION_PICK_DIRECTORY = 4;
+        public static final int ACTION_MANAGE = 5;
 
         public static final int MODE_UNKNOWN = 0;
         public static final int MODE_LIST = 1;
diff --git a/packages/DocumentsUI/src/com/android/documentsui/PickFragment.java b/packages/DocumentsUI/src/com/android/documentsui/PickFragment.java
new file mode 100644
index 0000000..a9e488a1
--- /dev/null
+++ b/packages/DocumentsUI/src/com/android/documentsui/PickFragment.java
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2014 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.documentsui;
+
+import android.app.Fragment;
+import android.app.FragmentManager;
+import android.app.FragmentTransaction;
+import android.os.Bundle;
+import android.text.TextUtils;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import com.android.documentsui.model.DocumentInfo;
+
+import java.util.Locale;
+
+/**
+ * Display pick confirmation bar, usually for selecting a directory.
+ */
+public class PickFragment extends Fragment {
+    public static final String TAG = "PickFragment";
+
+    private DocumentInfo mPickTarget;
+
+    private View mContainer;
+    private Button mPick;
+
+    public static void show(FragmentManager fm) {
+        final PickFragment fragment = new PickFragment();
+
+        final FragmentTransaction ft = fm.beginTransaction();
+        ft.replace(R.id.container_save, fragment, TAG);
+        ft.commitAllowingStateLoss();
+    }
+
+    public static PickFragment get(FragmentManager fm) {
+        return (PickFragment) fm.findFragmentByTag(TAG);
+    }
+
+    @Override
+    public View onCreateView(
+            LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+        mContainer = inflater.inflate(R.layout.fragment_pick, container, false);
+
+        mPick = (Button) mContainer.findViewById(android.R.id.button1);
+        mPick.setOnClickListener(mPickListener);
+
+        setPickTarget(null, null);
+
+        return mContainer;
+    }
+
+    private View.OnClickListener mPickListener = new View.OnClickListener() {
+        @Override
+        public void onClick(View v) {
+            final DocumentsActivity activity = DocumentsActivity.get(PickFragment.this);
+            activity.onPickRequested(mPickTarget);
+        }
+    };
+
+    public void setPickTarget(DocumentInfo pickTarget, CharSequence displayName) {
+        mPickTarget = pickTarget;
+
+        if (mPickTarget != null) {
+            mContainer.setVisibility(View.VISIBLE);
+            final Locale locale = getResources().getConfiguration().locale;
+            final String raw = getString(R.string.menu_select).toUpperCase(locale);
+            mPick.setText(TextUtils.expandTemplate(raw, displayName));
+        } else {
+            mContainer.setVisibility(View.GONE);
+        }
+    }
+}
diff --git a/packages/DocumentsUI/src/com/android/documentsui/RootsCache.java b/packages/DocumentsUI/src/com/android/documentsui/RootsCache.java
index f1dca1d..933dbe0 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/RootsCache.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/RootsCache.java
@@ -104,7 +104,8 @@ public class RootsCache {
         mRecentsRoot.authority = null;
         mRecentsRoot.rootId = null;
         mRecentsRoot.icon = R.drawable.ic_root_recent;
-        mRecentsRoot.flags = Root.FLAG_LOCAL_ONLY | Root.FLAG_SUPPORTS_CREATE;
+        mRecentsRoot.flags = Root.FLAG_LOCAL_ONLY | Root.FLAG_SUPPORTS_CREATE
+                | Root.FLAG_SUPPORTS_DIR_SELECTION;
         mRecentsRoot.title = mContext.getString(R.string.root_recent);
         mRecentsRoot.availableBytes = -1;
 
@@ -349,12 +350,15 @@ public class RootsCache {
         final List<RootInfo> matching = Lists.newArrayList();
         for (RootInfo root : roots) {
             final boolean supportsCreate = (root.flags & Root.FLAG_SUPPORTS_CREATE) != 0;
+            final boolean supportsDir = (root.flags & Root.FLAG_SUPPORTS_DIR_SELECTION) != 0;
             final boolean advanced = (root.flags & Root.FLAG_ADVANCED) != 0;
             final boolean localOnly = (root.flags & Root.FLAG_LOCAL_ONLY) != 0;
             final boolean empty = (root.flags & Root.FLAG_EMPTY) != 0;
 
             // Exclude read-only devices when creating
             if (state.action == State.ACTION_CREATE && !supportsCreate) continue;
+            // Exclude roots that don't support directory picking
+            if (state.action == State.ACTION_PICK_DIRECTORY && !supportsDir) continue;
             // Exclude advanced devices when not requested
             if (!state.showAdvanced && advanced) continue;
             // Exclude non-local devices when local only
diff --git a/packages/DocumentsUI/src/com/android/documentsui/TestActivity.java b/packages/DocumentsUI/src/com/android/documentsui/TestActivity.java
deleted file mode 100644
index 1a47308..0000000
--- a/packages/DocumentsUI/src/com/android/documentsui/TestActivity.java
+++ /dev/null
@@ -1,268 +0,0 @@
-/*
- * Copyright (C) 2013 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.documentsui;
-
-import android.app.Activity;
-import android.content.Context;
-import android.content.Intent;
-import android.net.Uri;
-import android.os.Bundle;
-import android.provider.DocumentsContract;
-import android.util.Log;
-import android.view.View;
-import android.view.View.OnClickListener;
-import android.widget.Button;
-import android.widget.CheckBox;
-import android.widget.LinearLayout;
-import android.widget.ScrollView;
-import android.widget.TextView;
-
-import libcore.io.IoUtils;
-import libcore.io.Streams;
-
-import java.io.InputStream;
-import java.io.OutputStream;
-
-public class TestActivity extends Activity {
-    private static final String TAG = "TestActivity";
-
-    private static final int CODE_READ = 42;
-    private static final int CODE_WRITE = 43;
-
-    private TextView mResult;
-
-    @Override
-    public void onCreate(Bundle icicle) {
-        super.onCreate(icicle);
-
-        final Context context = this;
-
-        final LinearLayout view = new LinearLayout(context);
-        view.setOrientation(LinearLayout.VERTICAL);
-
-        mResult = new TextView(context);
-        view.addView(mResult);
-
-        final CheckBox multiple = new CheckBox(context);
-        multiple.setText("ALLOW_MULTIPLE");
-        view.addView(multiple);
-        final CheckBox localOnly = new CheckBox(context);
-        localOnly.setText("LOCAL_ONLY");
-        view.addView(localOnly);
-
-        Button button;
-        button = new Button(context);
-        button.setText("OPEN_DOC */*");
-        button.setOnClickListener(new OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
-                intent.addCategory(Intent.CATEGORY_OPENABLE);
-                intent.setType("*/*");
-                if (multiple.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
-                }
-                if (localOnly.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);
-                }
-                startActivityForResult(intent, CODE_READ);
-            }
-        });
-        view.addView(button);
-
-        button = new Button(context);
-        button.setText("OPEN_DOC image/*");
-        button.setOnClickListener(new OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
-                intent.addCategory(Intent.CATEGORY_OPENABLE);
-                intent.setType("image/*");
-                if (multiple.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
-                }
-                if (localOnly.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);
-                }
-                startActivityForResult(intent, CODE_READ);
-            }
-        });
-        view.addView(button);
-
-        button = new Button(context);
-        button.setText("OPEN_DOC audio/ogg");
-        button.setOnClickListener(new OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
-                intent.addCategory(Intent.CATEGORY_OPENABLE);
-                intent.setType("audio/ogg");
-                if (multiple.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
-                }
-                if (localOnly.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);
-                }
-                startActivityForResult(intent, CODE_READ);
-            }
-        });
-        view.addView(button);
-
-        button = new Button(context);
-        button.setText("OPEN_DOC text/plain, application/msword");
-        button.setOnClickListener(new OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
-                intent.addCategory(Intent.CATEGORY_OPENABLE);
-                intent.setType("*/*");
-                intent.putExtra(Intent.EXTRA_MIME_TYPES, new String[] {
-                        "text/plain", "application/msword" });
-                if (multiple.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
-                }
-                if (localOnly.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);
-                }
-                startActivityForResult(intent, CODE_READ);
-            }
-        });
-        view.addView(button);
-
-        button = new Button(context);
-        button.setText("CREATE_DOC text/plain");
-        button.setOnClickListener(new OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                Intent intent = new Intent(Intent.ACTION_CREATE_DOCUMENT);
-                intent.addCategory(Intent.CATEGORY_OPENABLE);
-                intent.setType("text/plain");
-                intent.putExtra(Intent.EXTRA_TITLE, "foobar.txt");
-                if (localOnly.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);
-                }
-                startActivityForResult(intent, CODE_WRITE);
-            }
-        });
-        view.addView(button);
-
-        button = new Button(context);
-        button.setText("CREATE_DOC image/png");
-        button.setOnClickListener(new OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                Intent intent = new Intent(Intent.ACTION_CREATE_DOCUMENT);
-                intent.addCategory(Intent.CATEGORY_OPENABLE);
-                intent.setType("image/png");
-                intent.putExtra(Intent.EXTRA_TITLE, "mypicture.png");
-                if (localOnly.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);
-                }
-                startActivityForResult(intent, CODE_WRITE);
-            }
-        });
-        view.addView(button);
-
-        button = new Button(context);
-        button.setText("GET_CONTENT */*");
-        button.setOnClickListener(new OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
-                intent.addCategory(Intent.CATEGORY_OPENABLE);
-                intent.setType("*/*");
-                if (multiple.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
-                }
-                if (localOnly.isChecked()) {
-                    intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);
-                }
-                startActivityForResult(Intent.createChooser(intent, "Kittens!"), CODE_READ);
-            }
-        });
-        view.addView(button);
-
-        final ScrollView scroll = new ScrollView(context);
-        scroll.addView(view);
-
-        setContentView(scroll);
-    }
-
-    @Override
-    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
-        mResult.setText(null);
-        String result = "resultCode=" + resultCode + ", data=" + String.valueOf(data);
-
-        if (requestCode == CODE_READ) {
-            final Uri uri = data != null ? data.getData() : null;
-            if (uri != null) {
-                if (DocumentsContract.isDocumentUri(this, uri)) {
-                    result += "; DOC_ID";
-                }
-                try {
-                    getContentResolver().takePersistableUriPermission(
-                            uri, Intent.FLAG_GRANT_READ_URI_PERMISSION);
-                } catch (SecurityException e) {
-                    result += "; FAILED TO TAKE";
-                    Log.e(TAG, "Failed to take", e);
-                }
-                InputStream is = null;
-                try {
-                    is = getContentResolver().openInputStream(uri);
-                    final int length = Streams.readFullyNoClose(is).length;
-                    result += "; read length=" + length;
-                } catch (Exception e) {
-                    result += "; ERROR";
-                    Log.e(TAG, "Failed to read " + uri, e);
-                } finally {
-                    IoUtils.closeQuietly(is);
-                }
-            } else {
-                result += "no uri?";
-            }
-        } else if (requestCode == CODE_WRITE) {
-            final Uri uri = data != null ? data.getData() : null;
-            if (uri != null) {
-                if (DocumentsContract.isDocumentUri(this, uri)) {
-                    result += "; DOC_ID";
-                }
-                try {
-                    getContentResolver().takePersistableUriPermission(
-                            uri, Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
-                } catch (SecurityException e) {
-                    result += "; FAILED TO TAKE";
-                    Log.e(TAG, "Failed to take", e);
-                }
-                OutputStream os = null;
-                try {
-                    os = getContentResolver().openOutputStream(uri);
-                    os.write("THE COMPLETE WORKS OF SHAKESPEARE".getBytes());
-                } catch (Exception e) {
-                    result += "; ERROR";
-                    Log.e(TAG, "Failed to write " + uri, e);
-                } finally {
-                    IoUtils.closeQuietly(os);
-                }
-            } else {
-                result += "no uri?";
-            }
-        }
-
-        Log.d(TAG, result);
-        mResult.setText(result);
-    }
-}
diff --git a/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java b/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java
index 559e052..16fc3e5 100644
--- a/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java
+++ b/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java
@@ -27,6 +27,7 @@ import android.net.Uri;
 import android.os.CancellationSignal;
 import android.os.Environment;
 import android.os.FileObserver;
+import android.os.FileUtils;
 import android.os.ParcelFileDescriptor;
 import android.os.storage.StorageManager;
 import android.os.storage.StorageVolume;
@@ -143,7 +144,7 @@ public class ExternalStorageProvider extends DocumentsProvider {
                 final RootInfo root = new RootInfo();
                 root.rootId = rootId;
                 root.flags = Root.FLAG_SUPPORTS_CREATE | Root.FLAG_LOCAL_ONLY | Root.FLAG_ADVANCED
-                        | Root.FLAG_SUPPORTS_SEARCH;
+                        | Root.FLAG_SUPPORTS_SEARCH | Root.FLAG_SUPPORTS_DIR_SELECTION;
                 if (ROOT_ID_PRIMARY_EMULATED.equals(rootId)) {
                     root.title = getContext().getString(R.string.root_internal_storage);
                 } else {
@@ -240,8 +241,8 @@ public class ExternalStorageProvider extends DocumentsProvider {
                 flags |= Document.FLAG_DIR_SUPPORTS_CREATE;
             } else {
                 flags |= Document.FLAG_SUPPORTS_WRITE;
+                flags |= Document.FLAG_SUPPORTS_DELETE;
             }
-            flags |= Document.FLAG_SUPPORTS_DELETE;
         }
 
         final String displayName = file.getName();
@@ -284,11 +285,26 @@ public class ExternalStorageProvider extends DocumentsProvider {
     }
 
     @Override
+    public boolean isChildDocument(String parentDocId, String docId) {
+        try {
+            final File parent = getFileForDocId(parentDocId).getCanonicalFile();
+            final File doc = getFileForDocId(docId).getCanonicalFile();
+            return FileUtils.contains(parent, doc);
+        } catch (IOException e) {
+            throw new IllegalArgumentException(
+                    "Failed to determine if " + docId + " is child of " + parentDocId + ": " + e);
+        }
+    }
+
+    @Override
     public String createDocument(String docId, String mimeType, String displayName)
             throws FileNotFoundException {
         final File parent = getFileForDocId(docId);
-        File file;
+        if (!parent.isDirectory()) {
+            throw new IllegalArgumentException("Parent document isn't a directory");
+        }
 
+        File file;
         if (Document.MIME_TYPE_DIR.equals(mimeType)) {
             file = new File(parent, displayName);
             if (!file.mkdir()) {
@@ -317,6 +333,7 @@ public class ExternalStorageProvider extends DocumentsProvider {
 
     @Override
     public void deleteDocument(String docId) throws FileNotFoundException {
+        // TODO: extend to delete directories
         final File file = getFileForDocId(docId);
         if (!file.delete()) {
             throw new IllegalStateException("Failed to delete " + file);