Add FoldableLinearLayout for advanced options

res/layout/foldable_linearlayout.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical" >
+
+    <LinearLayout
+        android:id="@+id/foldableControl"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:clickable="true"
+        android:orientation="horizontal" >
+
+        <ImageButton
+            android:id="@+id/foldableIcon"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="center_vertical"
+            android:layout_marginRight="10dp"
+            android:background="@android:color/transparent"
+            android:src="@drawable/ic_action_expand" />
+
+        <TextView
+            android:id="@+id/foldableText"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="center_vertical"
+            android:text=""
+            android:textColor="@android:color/darker_gray" />
+    </LinearLayout>
+
+    <LinearLayout
+        android:id="@+id/foldableContainer"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:visibility="gone" />
+
+</LinearLayout>

res/values/attrs.xml

@@ -58,5 +58,12 @@
     <declare-styleable name="SliderPreference">
         <attr name="android:summary" />
     </declare-styleable>
+    
+    <declare-styleable name="FoldableLinearLayout">
+        <attr name="foldedLabel" format="string" />
+        <attr name="unFoldedLabel" format="string" />
+        <attr name="foldedIcon" format="string" />
+        <attr name="unFoldedIcon" format="string" />
+    </declare-styleable>
 
 </resources>

src/com/fsck/k9/view/FoldableLinearLayout.java

@@ -0,0 +1,168 @@
+package com.fsck.k9.view;
+
+import com.fsck.k9.R;
+
+import android.content.Context;
+import android.content.res.TypedArray;
+import android.util.AttributeSet;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.animation.AlphaAnimation;
+import android.view.animation.Animation;
+import android.widget.ImageButton;
+import android.widget.LinearLayout;
+import android.widget.TextView;
+
+/**
+ * Class representing a LinearLayout that can fold and hide it's content when
+ * pressed To use just add the following to your xml layout
+ * <org.sufficientlysecure.keychain.ui.widget.FoldableLinearLayout
+ * android:layout_width="wrap_content" android:layout_height="wrap_content"
+ * custom:foldedLabel="@string/TEXT_TO_DISPLAY_WHEN_FOLDED"
+ * custom:unFoldedLabel="@string/TEXT_TO_DISPLAY_WHEN_UNFOLDED"
+ * custom:foldedIcon="ICON_NAME_FROM_FontAwesomeText_TO_USE_WHEN_FOLDED"
+ * custom:unFoldedIcon="ICON_NAME_FROM_FontAwesomeText_TO_USE_WHEN_UNFOLDED">
+ * <include layout="@layout/ELEMENTS_TO_BE_FOLDED"/>
+ * </org.sufficientlysecure.keychain.ui.widget.FoldableLinearLayout>
+ */
+public class FoldableLinearLayout extends LinearLayout {
+    private ImageButton mFoldableIcon;
+    private boolean mFolded;
+    private boolean mHasMigrated = false;
+    private Integer mShortAnimationDuration = null;
+    private TextView mFoldableTextView = null;
+    private LinearLayout mFoldableContainer = null;
+    private View mFoldableLayout = null;
+    private String mFoldedLabel;
+    private String mUnFoldedLabel;
+
+    public FoldableLinearLayout(Context context) {
+        super(context);
+        processAttributes(context, null);
+    }
+
+    public FoldableLinearLayout(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        processAttributes(context, attrs);
+    }
+
+    public FoldableLinearLayout(Context context, AttributeSet attrs, int defStyle) {
+        super(context, attrs);
+        processAttributes(context, attrs);
+    }
+
+    /**
+     * Load given attributes to inner variables,
+     * 
+     * @param context
+     * @param attrs
+     */
+    private void processAttributes(Context context, AttributeSet attrs) {
+        if (attrs != null) {
+            TypedArray a = context.obtainStyledAttributes(attrs,
+                    R.styleable.FoldableLinearLayout, 0, 0);
+            mFoldedLabel = a.getString(R.styleable.FoldableLinearLayout_foldedLabel);
+            mUnFoldedLabel = a.getString(R.styleable.FoldableLinearLayout_unFoldedLabel);
+            a.recycle();
+        }
+        // If any attribute isn't found then set a default one
+        mFoldedLabel = (mFoldedLabel == null) ? "No text!" : mFoldedLabel;
+        mUnFoldedLabel = (mUnFoldedLabel == null) ? "No text!" : mUnFoldedLabel;
+    }
+
+    @Override
+    protected void onFinishInflate() {
+        // if the migration has already happened
+        // there is no need to move any children
+        if (!mHasMigrated) {
+            migrateChildrenToContainer();
+            mHasMigrated = true;
+        }
+        initialiseInnerViews();
+        super.onFinishInflate();
+    }
+
+    /**
+     * Migrates Child views as declared in xml to the inner foldableContainer
+     */
+    private void migrateChildrenToContainer() {
+        // Collect children of FoldableLinearLayout as declared in XML
+        int childNum = getChildCount();
+        View[] children = new View[childNum];
+        for (int i = 0; i < childNum; i++) {
+            children[i] = getChildAt(i);
+        }
+        if (children[0].getId() == R.id.foldableControl) {
+        }
+        // remove all of them from FoldableLinearLayout
+        detachAllViewsFromParent();
+        // Inflate the inner foldable_linearlayout.xml
+        LayoutInflater inflator = (LayoutInflater) getContext().getSystemService(
+                Context.LAYOUT_INFLATER_SERVICE);
+        mFoldableLayout = inflator.inflate(R.layout.foldable_linearlayout, this, true);
+        mFoldableContainer = (LinearLayout) mFoldableLayout.findViewById(R.id.foldableContainer);
+        // Push previously collected children into foldableContainer.
+        for (int i = 0; i < childNum; i++) {
+            addView(children[i]);
+        }
+    }
+
+    private void initialiseInnerViews() {
+        mFoldableIcon = (ImageButton) mFoldableLayout.findViewById(R.id.foldableIcon);
+        mFoldableIcon.setImageResource(R.drawable.ic_action_expand);
+        mFoldableTextView = (TextView) mFoldableLayout.findViewById(R.id.foldableText);
+        mFoldableTextView.setText(mFoldedLabel);
+        // retrieve and cache the system's short animation time
+        mShortAnimationDuration = getResources().getInteger(android.R.integer.config_shortAnimTime);
+        LinearLayout foldableControl = (LinearLayout) mFoldableLayout
+                .findViewById(R.id.foldableControl);
+        foldableControl.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+                mFolded = !mFolded;
+                if (mFolded) {
+                    mFoldableIcon.setImageResource(R.drawable.ic_action_collapse);
+                    mFoldableContainer.setVisibility(View.VISIBLE);
+                    AlphaAnimation animation = new AlphaAnimation(0f, 1f);
+                    animation.setDuration(mShortAnimationDuration);
+                    mFoldableContainer.startAnimation(animation);
+                    mFoldableTextView.setText(mUnFoldedLabel);
+                } else {
+                    mFoldableIcon.setImageResource(R.drawable.ic_action_expand);
+                    AlphaAnimation animation = new AlphaAnimation(1f, 0f);
+                    animation.setDuration(mShortAnimationDuration);
+                    animation.setAnimationListener(new Animation.AnimationListener() {
+                        @Override
+                        public void onAnimationStart(Animation animation) {
+                        }
+
+                        @Override
+                        public void onAnimationEnd(Animation animation) {
+                            // making sure that at the end the container is
+                            // completely removed from view
+                            mFoldableContainer.setVisibility(View.GONE);
+                        }
+
+                        @Override
+                        public void onAnimationRepeat(Animation animation) {
+                        }
+                    });
+                    mFoldableContainer.startAnimation(animation);
+                    mFoldableTextView.setText(mFoldedLabel);
+                }
+            }
+        });
+    }
+
+    /**
+     * Adds provided child view to foldableContainer View
+     * 
+     * @param child
+     */
+    @Override
+    public void addView(View child) {
+        if (mFoldableContainer != null) {
+            mFoldableContainer.addView(child);
+        }
+    }
+}