Update

app/src/main/java/com/hippo/ehviewer/ui/ContentActivity.java

@@ -16,6 +16,7 @@
 package com.hippo.ehviewer.ui;
 
 import android.os.Bundle;
+import android.support.v4.widget.DrawerLayout;
 import android.widget.FrameLayout;
 
 import com.hippo.ehviewer.R;
@@ -24,6 +25,7 @@ import com.hippo.scene.StageActivity;
 
 public class ContentActivity extends StageActivity {
 
+    private DrawerLayout mDrawerLayout;
     private FrameLayout mStage;
 
     @Override
@@ -31,7 +33,9 @@ public class ContentActivity extends StageActivity {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_content);
 
-        mStage = (FrameLayout) findViewById(R.id.stage);
+        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
+        mStage = (FrameLayout) mDrawerLayout.findViewById(R.id.stage);
+
 
         startFirstScene(GalleryListScene.class);
     }

app/src/main/java/com/hippo/scene/Scene.java

@@ -106,4 +106,8 @@ public abstract class Scene {
         mStageActivity.stopSceneRetain(this);
     }
 
+    public void onBackPressed() {
+        finish();
+    }
+
 }

app/src/main/java/com/hippo/scene/StageActivity.java

@@ -133,9 +133,11 @@ public abstract class StageActivity extends AbsActionBarActivity {
 
     void finishScene(Scene scene) {
         if (scene != mRetainedScene && scene != mCurrentScene) {
-            // Remove with out animation
-            getStageView().removeView(scene.getRootView());
-            mSceneStack.remove(scene);
+            if (mSceneStack.contains(scene)) {
+                // Remove without animation
+                getStageView().removeView(scene.getRootView());
+                mSceneStack.remove(scene);
+            }
         } else {
             if (mRetainedScene == null) {
                 // Because scene can't be null, so scene == mCurrentScene
@@ -149,10 +151,8 @@ public abstract class StageActivity extends AbsActionBarActivity {
 
     @Override
     public void onBackPressed() {
-        if (mRetainedScene == null) {
-            // No retained scene, no animation
-            // If not, just miss it.
-            popScense();
+        if (mCurrentScene != null) {
+            mCurrentScene.onBackPressed();
         }
     }
 

app/src/main/java/com/hippo/widget/FixedAspectImageView.java

@@ -26,11 +26,7 @@ import com.hippo.util.ViewUtils;
 
 /**
  * aspect is width / height
- *
- * @author Hippo
- *
  */
-
 public class FixedAspectImageView extends ImageView {
 
     private static final String TAG = FixedAspectImageView.class.getSimpleName();
@@ -69,7 +65,7 @@ public class FixedAspectImageView extends ImageView {
 
         a = context.obtainStyledAttributes(
                 attrs, R.styleable.FixedAspectImageView, defStyle, 0);
-        setAspect(a.getFloat(R.styleable.FixedAspectImageView_aspect, -1f));
+        setAspect(a.getFloat(R.styleable.FixedAspectImageView_faiAspect, -1f));
         a.recycle();
     }
 

app/src/main/java/com/hippo/widget/FixedAspectLayout.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2015 Hippo Seven
+ *
+ * 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
+ * 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.hippo.widget;
+
+import android.annotation.TargetApi;
+import android.content.Context;
+import android.content.res.TypedArray;
+import android.os.Build;
+import android.util.AttributeSet;
+import android.widget.FrameLayout;
+
+import com.hippo.ehviewer.R;
+
+/**
+ * aspect is width / height
+ */
+public class FixedAspectLayout extends FrameLayout {
+
+    private float mAspect = -1f;
+
+    public FixedAspectLayout(Context context) {
+        super(context);
+    }
+
+    public FixedAspectLayout(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        init(context, attrs, 0, 0);
+    }
+
+    public FixedAspectLayout(Context context, AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+        init(context, attrs, defStyleAttr, 0);
+    }
+
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    public FixedAspectLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
+        super(context, attrs, defStyleAttr, defStyleRes);
+        init(context, attrs, defStyleAttr, defStyleRes);
+    }
+
+    private void init(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
+        TypedArray a = context.obtainStyledAttributes(
+                attrs, R.styleable.FixedAspectLayout, defStyleAttr, defStyleRes);
+        setAspect(a.getFloat(R.styleable.FixedAspectLayout_falAspect, -1f));
+        a.recycle();
+    }
+
+    public void setAspect(float ratio) {
+        if (ratio > 0) {
+            mAspect = ratio;
+        } else {
+            mAspect = -1f;
+        }
+        requestLayout();
+    }
+
+    @Override
+    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
+        if (mAspect > 0.0f) {
+            final int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
+            final int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
+            int width;
+            int height;
+            if (widthSpecMode == MeasureSpec.EXACTLY && heightSpecMode != MeasureSpec.EXACTLY) {
+                width = MeasureSpec.getSize(widthMeasureSpec);
+                int maxheight;
+                if (heightSpecMode == MeasureSpec.AT_MOST) {
+                    maxheight = MeasureSpec.getSize(heightMeasureSpec);
+                } else {
+                    maxheight = Integer.MAX_VALUE;
+                }
+                height = Math.min((int) (width / mAspect), maxheight);
+                heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
+            } else if (heightSpecMode == MeasureSpec.EXACTLY && widthSpecMode != MeasureSpec.EXACTLY) {
+                height = MeasureSpec.getSize(heightMeasureSpec);
+                int maxWidth;
+                if (widthSpecMode == MeasureSpec.AT_MOST) {
+                    maxWidth = MeasureSpec.getSize(widthSpecMode);
+                } else {
+                    maxWidth = Integer.MAX_VALUE;
+                }
+                width = Math.min((int) (height * mAspect), maxWidth);
+                widthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);
+            }
+        }
+        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
+    }
+}