From 903605cba59773341f511ab3d14b9f9de939c210 Mon Sep 17 00:00:00 2001
From: Kirill Grouchnikov <kirillg@google.com>
Date: Fri, 4 Dec 2015 15:26:49 -0500
Subject: [PATCH] Align DrawerLayout width with Material design spec.

Bug: 26027590
Change-Id: If5e80c99f3be5ebd89c0b5d2e915db4c0da14adc
---
 .../res/layout/drawer_layout.xml              | 12 ++++--
 .../widget/DrawerLayoutActivity.java          | 40 +++++++++++++++++++
 2 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/samples/Support7Demos/res/layout/drawer_layout.xml b/samples/Support7Demos/res/layout/drawer_layout.xml
index 1a72b06f5..f8d22d15a 100644
--- a/samples/Support7Demos/res/layout/drawer_layout.xml
+++ b/samples/Support7Demos/res/layout/drawer_layout.xml
@@ -17,6 +17,8 @@
 <!--
     A DrawerLayout is indended to be used as the top-level content view
     using match_parent for both width and height to consume the full space available.
+    See https://www.google.com/design/spec/patterns/navigation-drawer.html#navigation-drawer-specs
+    for the full spec of a drawer in Material design.
 -->
 <android.support.v4.widget.DrawerLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
@@ -61,15 +63,17 @@
 
     <!-- android:layout_gravity="start" tells DrawerLayout to treat
          this as a sliding drawer on the starting side, which is
-         left for left-to-right locales. The drawer is given a fixed
-         width in dp and extends the full height of the container. A
+         left for left-to-right locales. The drawer is given arbitrary
+         initial width and extends the full height of the container. A
          solid background is used for contrast with the content view.
          android:fitsSystemWindows="true" tells the system to have
          DrawerLayout span the full height of the screen, including the
-         system status bar on Lollipop+ versions of the plaform. -->
+         system status bar on Lollipop+ versions of the plaform. The actual
+         width of drawer will be determined at runtime based on the screen
+         size according to the Material spec. -->
     <ListView
             android:id="@+id/start_drawer"
-            android:layout_width="300dp"
+            android:layout_width="wrap_content"
             android:layout_height="match_parent"
             android:layout_gravity="start"
             android:background="#ff333333"
diff --git a/samples/Support7Demos/src/com/example/android/supportv7/widget/DrawerLayoutActivity.java b/samples/Support7Demos/src/com/example/android/supportv7/widget/DrawerLayoutActivity.java
index 8cdf927c2..d6548739c 100644
--- a/samples/Support7Demos/src/com/example/android/supportv7/widget/DrawerLayoutActivity.java
+++ b/samples/Support7Demos/src/com/example/android/supportv7/widget/DrawerLayoutActivity.java
@@ -17,6 +17,8 @@
 package com.example.android.supportv7.widget;
 
 import android.content.res.Configuration;
+import android.content.res.Resources;
+import android.content.res.TypedArray;
 import android.os.Bundle;
 import android.support.v4.view.GravityCompat;
 import android.support.v4.widget.DrawerLayout;
@@ -25,6 +27,8 @@ import android.support.v7.app.AppCompatActivity;
 import android.support.v7.widget.Toolbar;
 import android.view.MenuItem;
 import android.view.View;
+import android.view.ViewGroup;
+import android.view.ViewTreeObserver;
 import android.widget.AdapterView;
 import android.widget.ArrayAdapter;
 import android.widget.ListView;
@@ -142,6 +146,42 @@ public class DrawerLayoutActivity extends AppCompatActivity {
         final int metalBlueColor = getResources().getColor(R.color.drawer_sample_metal_blue);
         mDrawerLayout.setStatusBarBackgroundColor(metalBlueColor);
         mToolbar.setBackgroundColor(metalBlueColor);
+
+        // Register a pre-draw listener to get the initial width of the DrawerLayout so
+        // that we can determine the width of the drawer based on the Material spec at
+        // https://www.google.com/design/spec/patterns/navigation-drawer.html#navigation-drawer-specs
+        mDrawerLayout.getViewTreeObserver().addOnPreDrawListener(
+                new ViewTreeObserver.OnPreDrawListener() {
+                    @Override
+                    public boolean onPreDraw() {
+                        // What is the width of the entire DrawerLayout?
+                        final int drawerLayoutWidth = mDrawerLayout.getWidth();
+
+                        // What is the action bar size?
+                        final Resources.Theme theme = mDrawerLayout.getContext().getTheme();
+                        final TypedArray a = theme.obtainStyledAttributes(
+                                new int[] { android.support.v7.appcompat.R.attr.actionBarSize });
+                        final int actionBarSize = a.getDimensionPixelSize(0, 0);
+                        if (a != null) {
+                            a.recycle();
+                        }
+
+                        // Compute the width of the drawer and set it on the layout params.
+                        final int idealDrawerWidth = 5 * actionBarSize;
+                        final int maxDrawerWidth = Math.max(0, drawerLayoutWidth - actionBarSize);
+                        final int drawerWidth = Math.min(idealDrawerWidth, maxDrawerWidth);
+
+                        final DrawerLayout.LayoutParams drawerLp =
+                                (DrawerLayout.LayoutParams) mDrawer.getLayoutParams();
+                        drawerLp.width = drawerWidth;
+                        mDrawer.setLayoutParams(drawerLp);
+
+                        // Remove ourselves as the pre-draw listener since this is a one-time
+                        // configuration.
+                        mDrawerLayout.getViewTreeObserver().removeOnPreDrawListener(this);
+                        return true;
+                    }
+        });
     }
 
     @Override