How to avoid total view-hierarchy re-layout when using EditText?

Question

Background

I have a rather complex layout being shown to the user in an activity.

One of the views is an EditText.

Since I had to make one of the views stay behind the soft-keyboard, yet the rest above it, I had to listen to view-layout changes (written about it here).

The problem

I've noticed that whenever the EditText has focus and shows its caret, the entire view-hierarchy gets re-layout.

You can see it by either looking at the log of the listener I've created, or by enabling "show surface updates" via the developers settings.

This causes bad performance on some devices, especially if the layout of the activity is complex or have fragments that have complex layouts.

The code

I'm not going to show the original code, but there is a simple way to reproduce the issue:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.user.myapplication.MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="just some text"/>

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:inputType="phone"
            android:text="write here"
            android:textSize="18dp"/>


        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="just some text 2"/>
    </LinearLayout>
</FrameLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(android.R.id.content).getViewTreeObserver().addOnPreDrawListener(new OnPreDrawListener() {

            @Override
            public boolean onPreDraw() {
                Log.d("AppLog", "onPreDraw");
                return true;
            }
        });
    }
}

What I've tried

When disabling the caret (using "cursorVisible", which for some reason is called a "cursor" instead) , I can see that the problem doesn't exist.

I've tried to find an alternative to the built-in caret behavior, but I can't find. Only thing I've found is this post, but it seems to make it static and I'm not sure as to how well it performs (performance and compatibility vs normal caret).

I've tried to set the size of the EditText forcefully, so that it won't need to cause invalidation of the layout that contains it. It didn't work.

I've also noticed that on the original app, the logs can (for some reason) continue being written even when the app goes to the background.

I've reported about this issue (including sample and video) here, hoping that Google will show what's wrong or a fix for this.

The question

Is there a way to avoid the re-layout of the entire view hierarchy ? A way that will still let the EditText have the same look&feel of normal EditText?

Maybe a way to customize how the EditText behaves with the caret?

Answer 1

I've noticed that whenever the EditText has focus and shows its caret, the entire view-hierarchy gets re-layout.

This is not true. Size and position of EditText is constant - there is no re-layouting. You can check it by using code below.

findViewById(android.R.id.content).getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
  @Override
  public void onGlobalLayout() {
    Log.d("AppLog", "Layout phase");
  }
});

Because of blinking caret - EditText constatly calls invalidate(). This forces the GPU to draw EditText again.

On my nexus 5 (marshmallow) I see that only EditText beeing redrawn (Show GPU view updates - enabled).

Answer 2

How about overriding dispatchOnPreDraw() all the vies you use in activity and having flag to check whether that specific view needs to redraw ?

As you need to disable redraw of all other views only when a text view is on focus. So when a text view is on focus have a flag to disable the redrawing of other views.

if dispatchOnPreDraw() method returns false then refreshing of view will be continues else not. I don't know how complex is your layout and how many views are used, but here a separate class should extent a view used and override that method, and also need a mechanism/variable to distinguish the object in current focus.

Hope this method helps!