Android ConstraintLayout performance improvements - Missing in action

问题

I have created a custom view and inserted logging for an estimated performance comparison

public class CustomInAppKeyboard extends LinearLayoutCompat  {

    private static final String TAG = "MyKeyboard";

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        if(BuildConfig.DEBUG){
            Log.e("CustomInAppKeyboard", "w:" + widthMeasureSpec + " :: " +  MeasureSpec.toString(widthMeasureSpec));
            Log.e("CustomInAppKeyboard", "h:" + heightMeasureSpec + " :: "  + MeasureSpec.toString(heightMeasureSpec));
        }

    }

    public CustomInAppKeyboard(Context context) {
        this(context, null, 0);
    }

    public CustomInAppKeyboard(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CustomInAppKeyboard(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context, attrs);
    }
    private void init(Context context, AttributeSet attrs) {

        LayoutInflater.from(context).inflate(R.layout.keyboard_alphanumeric, this, true);
    }

}

then using start & end times of "MyKeyboard" logs... I end up with the following values:

ConstraintLayout withguides 14.32
ConstraintLayout with chains 13.62
LinearLayout (nested weights) 4.88

That was based on these xml layouts files in the following gist: - https://gist.github.com/CrandellWS/fc7946ea653cf90828580b3c00d8da57

So how can I get the ConstraintLayout to render as fast as the nested LinearLayout? What could I do differently or change to get the ConstraintLayout to more closely match the LinearLayout performance?

"actual" Keyboard layout files are known to be different

Note that there is an inability to use Systrace on my physical device https://stackoverflow.com/a/52836747/1815624 ... hence the rudimentary performance test method...

回答1:

In order to answer this question, we'll have to take a detour for that.

I am assuming that you have read about how ConstraintLayout works internally, so let me just stick to the point. Yes, I agree that ConstraintLayout is slower than LinearLayout but it's only when the number of child views are less in number.

When you start building larger layouts, say which consist of 20-30 Views, the ConstraintLayout comes handy. If you'll then use LinearLayout or any other layout, say RelativeLayout then you'll end up using multiple child ViewGroups and your Layout Graph might end up like this

LinearLayout(orientation vertical)
   -> SomeChildView (let's say a TextView)
   -> LinearLayout (orientation horizontal)
            -> ChilView 1  -> ChildView 2
   -> ImageView
   -> ButtonView
   -> ViewGroup (FrameLayout)
           -> ImageView1
           -> idk, maybe TextView?

and the list goes on.

Now, with such kind of Layout, traditional ViewGroups will end up computing more number of views than ConstraintLayout

So, we can come up with a conclusion that, no ViewGroup is perfect!! We just have to use them in accordance to our need..

Bonus!! ConstraintLayout should be avoided inside RecyclerView because it calls onMeasure() multiple times than any other layout.

I once made some research on ConstraintLayout back then before applying it to my project.

来源：https://stackoverflow.com/questions/52847213/android-constraintlayout-performance-improvements-missing-in-action

标签

android-layout

android-constraintlayout