Save and restore state

build.gradle

@@ -3,6 +3,6 @@ buildscript {
     mavenCentral()
   }
   dependencies {
-    classpath 'com.android.tools.build:gradle:2.1.0'
+    classpath 'com.android.tools.build:gradle:2.1.2'
   }
 }

drawer-behavior/src/main/java/com/jakewharton/behavior/drawer/BehaviorDelegate.java

@@ -17,6 +17,8 @@
 package com.jakewharton.behavior.drawer;
 
 import android.os.Build;
+import android.os.Bundle;
+import android.os.Parcelable;
 import android.os.SystemClock;
 import android.support.design.widget.CoordinatorLayout;
 import android.support.v4.view.GravityCompat;
@@ -26,6 +28,7 @@
 import android.view.Gravity;
 import android.view.MotionEvent;
 import android.view.View;
+import android.view.ViewTreeObserver;
 import android.view.accessibility.AccessibilityEvent;
 
 import static android.view.View.INVISIBLE;
@@ -38,6 +41,7 @@ final class BehaviorDelegate extends ViewDragHelper.Callback {
   private static final int FLAG_IS_OPENING = 0x2;
   private static final int FLAG_IS_CLOSING = 0x4;
   private static final int DEFAULT_SCRIM_COLOR = 0x99000000;
+  private static final String BEHAVIOR_STATE = "behavior_state";
 
   private final CoordinatorLayout parent;
   private final View child;
@@ -325,8 +329,7 @@ private void updateChildrenImportantForAccessibility(View drawerView, boolean is
     }
   }
 
-  @Override
-  public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
+  @Override public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
     int childWidth = changedView.getWidth();
 
     // This reverses the positioning shown in onLayout.
@@ -456,4 +459,31 @@ boolean onLayoutChild() {
     }
     return true;
   }
+
+  public Parcelable onSaveInstanceState() {
+    Bundle outState = new Bundle();
+    outState.putInt(BEHAVIOR_STATE, openState);
+    return outState;
+  }
+
+  public void onRestoreInstanceState(Parcelable state) {
+    if (state instanceof Bundle) {
+      Bundle savedState = (Bundle) state;
+      openState = savedState.getInt(BEHAVIOR_STATE);
+      // Check if the drawer was open according to the previous state -
+      // TODO call isDrawerOpen() and reset openState after
+      child.getViewTreeObserver()
+          .addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
+            @Override public void onGlobalLayout() {
+              //TODO call openDrawer() here
+              if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
+                child.getViewTreeObserver().removeOnGlobalLayoutListener(this);
+              } else {
+                //noinspection deprecation
+                child.getViewTreeObserver().removeGlobalOnLayoutListener(this);
+              }
+            }
+          });
+    }
+  }
 }

drawer-behavior/src/main/java/com/jakewharton/behavior/drawer/DrawerBehavior.java

@@ -17,6 +17,7 @@
 
 import android.content.Context;
 import android.content.res.TypedArray;
+import android.os.Parcelable;
 import android.support.annotation.Keep;
 import android.support.design.widget.CoordinatorLayout;
 import android.support.v4.util.SimpleArrayMap;
@@ -80,4 +81,13 @@ public boolean onInterceptTouchEvent(CoordinatorLayout parent, View child, Motio
   @Override public boolean onTouchEvent(CoordinatorLayout parent, View child, MotionEvent ev) {
     return delegate(parent, child).onTouchEvent(ev);
   }
+
+  @Override public Parcelable onSaveInstanceState(CoordinatorLayout parent, View child) {
+    return delegate(parent, child).onSaveInstanceState();
+  }
+
+  @Override
+  public void onRestoreInstanceState(CoordinatorLayout parent, View child, Parcelable state) {
+    delegate(parent,child).onRestoreInstanceState(state);
+  }
 }

sample/src/main/res/layout/drawer_behavior.xml

@@ -2,11 +2,13 @@
 <android.support.design.widget.CoordinatorLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:id="@+id/coordinatorLayout"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="#feee"
     >
   <View
+      android:id="@+id/drawerView"
       android:layout_width="200dp"
       android:layout_height="match_parent"
       android:layout_gravity="start"