Question

I’ve run into what I can only categorize as a memory leak for ScrollView elements when using the Gallery component.

A short background. I’ve got an existing app that is a photo slideshow app.
It uses the Gallery component, but each element in the adapter is displayed in full-screen.
(full source is available at this link)

The adapter View element consist of an ImageView, and two TextViews for title and description.
As the photos are of a quite high-resolution, the app uses quite a lot of memory but the Gallery has in general manage to recycle them well.

However, when I am now implementing a ScrollView for the description TextView, I almost immediately run into memory problems. This the only change I made

<ScrollView
android:id="@+id/description_scroller"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:scrollbars="vertical"
android:fillViewport="true">
  <TextView
    android:id="@+id/slideshow_description"
    android:textSize="@dimen/description_font_size"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textColor="@color/white"
    android:layout_below="@id/slideshow_title"
    android:singleLine="false"
    android:maxLines="4"/>  
</ScrollView> 

I did a heap dump and could clearly see that it was the Scrollview which was the root of the memory problems.

Here are two screenshots from the heap dump analysis. Note that the ScrollView retains a reference to mParent which includes the large photo I use

PS same problem occurs if I use the TextView’s scrolling (android:scrollbars = “vertical” and .setMovementMethod(new ScrollingMovementMethod());

PSS Tried switching off persistent drawing cache, but no different dreaandroid:persistentDrawingCache=”none”

Answer 1

Just add this -> android:isScrollContainer=”false”

<ScrollView
    android:id="@+id/description_scroller"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:scrollbars="vertical"
    android:fillViewport="true"
    android:isScrollContainer="false">

There is some source why this is appear:
http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/4.0.1_r1/android/view/View.java

the problem is:

setScrollContainer(boolean isScrollContainer)

by default:

boolean setScrollContainer = false;  

but in some cases like this

if (!setScrollContainer && (viewFlagValues&SCROLLBARS_VERTICAL) != 0) {
    setScrollContainer(true);
}

it can be true, and when it happends

/**
* Change whether this view is one of the set of scrollable containers in
* its window. This will be used to determine whether the window can
* resize or must pan when a soft input area is open — scrollable
* containers allow the window to use resize mode since the container
* will appropriately shrink.
*/

public void setScrollContainer(boolean isScrollContainer) {
    if (isScrollContainer) {
        if (mAttachInfo != null && (mPrivateFlags&SCROLL_CONTAINER_ADDED) == 0) {
            mAttachInfo.mScrollContainers.add(this);
            mPrivateFlags |= SCROLL_CONTAINER_ADDED;
        }
        mPrivateFlags |= SCROLL_CONTAINER;
    } else {
        if ((mPrivateFlags&SCROLL_CONTAINER_ADDED) != 0) {
            mAttachInfo.mScrollContainers.remove(this);
        }
        mPrivateFlags &= ~(SCROLL_CONTAINER|SCROLL_CONTAINER_ADDED);
    }
}

mAttachInfo.mScrollContainers.add(this) – all view put into ArrayList this lead to leak of memory sometimes