diff --git a/packages/DocumentsUI/res/values/strings.xml b/packages/DocumentsUI/res/values/strings.xml
index be21b55c4066e..e67cc8a06da27 100644
--- a/packages/DocumentsUI/res/values/strings.xml
+++ b/packages/DocumentsUI/res/values/strings.xml
@@ -247,4 +247,9 @@
         <item quantity="one">Delete <xliff:g id="count" example="1">%1$d</xliff:g> item?</item>
         <item quantity="other">Delete <xliff:g id="count" example="3">%1$d</xliff:g> items?</item>
     </plurals>
+    <!-- Snackbar shown to users who wanted to select more than 1000 items (files or directories). -->
+    <string name="too_many_selected">Sorry, you can only select up to 1000 items at a time</string>
+    <!-- Snackbar shown to users who wanted to select all, but there were too many items (files or directories).
+         Only the first 1000 items are selected in such case. -->
+    <string name="too_many_in_select_all">Could only select 1000 items</string>
 </resources>
diff --git a/packages/DocumentsUI/src/com/android/documentsui/QuickViewIntentBuilder.java b/packages/DocumentsUI/src/com/android/documentsui/QuickViewIntentBuilder.java
index babde992a90bd..c78face9730a0 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/QuickViewIntentBuilder.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/QuickViewIntentBuilder.java
@@ -17,6 +17,7 @@
 package com.android.documentsui;
 
 import static com.android.documentsui.Shared.DEBUG;
+import static com.android.documentsui.Shared.MAX_DOCS_IN_INTENT;
 import static com.android.documentsui.model.DocumentInfo.getCursorString;
 
 import android.content.ClipData;
@@ -46,7 +47,6 @@ import java.util.List;
 final class QuickViewIntentBuilder {
 
     private static final String TAG = "QuickViewIntentBuilder";
-    private static final int MAX_CLIP_ITEMS = 1000;
 
     private final DocumentInfo mDocument;
     private final Model mModel;
@@ -165,11 +165,11 @@ final class QuickViewIntentBuilder {
         int firstSibling;
         int lastSibling;
         if (documentLocation < uris.size() / 2) {
-            firstSibling = Math.max(0, documentLocation - MAX_CLIP_ITEMS / 2);
-            lastSibling = Math.min(uris.size() - 1, firstSibling + MAX_CLIP_ITEMS - 1);
+            firstSibling = Math.max(0, documentLocation - MAX_DOCS_IN_INTENT / 2);
+            lastSibling = Math.min(uris.size() - 1, firstSibling + MAX_DOCS_IN_INTENT - 1);
         } else {
-            lastSibling = Math.min(uris.size() - 1, documentLocation + MAX_CLIP_ITEMS / 2);
-            firstSibling = Math.max(0, lastSibling - MAX_CLIP_ITEMS + 1);
+            lastSibling = Math.min(uris.size() - 1, documentLocation + MAX_DOCS_IN_INTENT / 2);
+            firstSibling = Math.max(0, lastSibling - MAX_DOCS_IN_INTENT + 1);
         }
 
         if (DEBUG) Log.d(TAG, "Copmuted siblings from index: " + firstSibling
diff --git a/packages/DocumentsUI/src/com/android/documentsui/Shared.java b/packages/DocumentsUI/src/com/android/documentsui/Shared.java
index 1ba836a7fa4a6..07c3cdbcbec03 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/Shared.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/Shared.java
@@ -104,6 +104,11 @@ public final class Shared {
      */
     public static final String EXTRA_BENCHMARK = "com.android.documentsui.benchmark";
 
+    /**
+     * Maximum number of items in a Binder transaction packet.
+     */
+    public static final int MAX_DOCS_IN_INTENT = 1000;
+
     private static final Collator sCollator;
 
     static {
diff --git a/packages/DocumentsUI/src/com/android/documentsui/dirlist/DirectoryFragment.java b/packages/DocumentsUI/src/com/android/documentsui/dirlist/DirectoryFragment.java
index 8c073c9cc616c..297fbc784acd7 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/dirlist/DirectoryFragment.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/dirlist/DirectoryFragment.java
@@ -17,6 +17,7 @@
 package com.android.documentsui.dirlist;
 
 import static com.android.documentsui.Shared.DEBUG;
+import static com.android.documentsui.Shared.MAX_DOCS_IN_INTENT;
 import static com.android.documentsui.State.MODE_GRID;
 import static com.android.documentsui.State.MODE_LIST;
 import static com.android.documentsui.State.SORT_ORDER_UNKNOWN;
@@ -108,9 +109,11 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Objects;
+import java.util.Set;
 
 /**
  * Display the documents inside a single directory.
@@ -475,8 +478,18 @@ public class DirectoryFragment extends Fragment
 
                 final String docMimeType = getCursorString(cursor, Document.COLUMN_MIME_TYPE);
                 final int docFlags = getCursorInt(cursor, Document.COLUMN_FLAGS);
+                if (!mTuner.canSelectType(docMimeType, docFlags)) {
+                    return false;
+                }
 
-                return mTuner.canSelectType(docMimeType, docFlags);
+                if (mSelected.size() >= MAX_DOCS_IN_INTENT) {
+                    Snackbars.makeSnackbar(
+                            getActivity(),
+                            R.string.too_many_selected,
+                            Snackbar.LENGTH_SHORT)
+                            .show();
+                    return false;
+                }
             }
             return true;
         }
@@ -1108,9 +1121,17 @@ public class DirectoryFragment extends Fragment
     public void selectAllFiles() {
         Metrics.logUserAction(getContext(), Metrics.USER_ACTION_SELECT_ALL);
 
-        // Exclude disabled files
-        List<String> enabled = new ArrayList<String>();
-        for (String id : mAdapter.getModelIds()) {
+        // Exclude disabled files.
+        Set<String> enabled = new HashSet<String>();
+        List<String> modelIds = mAdapter.getModelIds();
+
+        // Get the current selection.
+        String[] alreadySelected = mSelectionManager.getSelection().getAll();
+        for (String id : alreadySelected) {
+           enabled.add(id);
+        }
+
+        for (String id : modelIds) {
             Cursor cursor = getModel().getItem(id);
             if (cursor == null) {
                 Log.w(TAG, "Skipping selection. Can't obtain cursor for modeId: " + id);
@@ -1118,7 +1139,15 @@ public class DirectoryFragment extends Fragment
             }
             String docMimeType = getCursorString(cursor, Document.COLUMN_MIME_TYPE);
             int docFlags = getCursorInt(cursor, Document.COLUMN_FLAGS);
-            if (isDocumentEnabled(docMimeType, docFlags)) {
+            if (mTuner.canSelectType(docMimeType, docFlags)) {
+                if (enabled.size() >= MAX_DOCS_IN_INTENT) {
+                    Snackbars.makeSnackbar(
+                        getActivity(),
+                        R.string.too_many_in_select_all,
+                        Snackbar.LENGTH_SHORT)
+                        .show();
+                    break;
+                }
                 enabled.add(id);
             }
         }