Arthur Arthur - 6 months ago 163
Android Question

Precise control over Androids AnimatedVectorDrawable

I want to animate multiple elements of one image and link the animation to ViewPagers position (so multiple elements are morphing or flying in/out depending on the current page being dragged).

So, is there a way to precisely control the current frame of the animation? For example let's assume i have this set:

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<objectAnimator
android:interpolator="@android:anim/decelerate_interpolator"
android:duration="800"
android:propertyName="scaleY"
android:valueFrom="0"
android:valueTo="1" />
<objectAnimator
android:interpolator="@android:anim/decelerate_interpolator"
android:duration="800"
android:propertyName="scaleX"
android:valueFrom="0"
android:valueTo="1" />
<objectAnimator
android:interpolator="@android:anim/decelerate_interpolator"
android:duration="800"
android:propertyName="rotation"
android:valueFrom="0"
android:valueTo="360" />
</set>


Animated vector file:

<animated-vector xmlns:android="http://schemas.android.com/apk/res/android"
android:drawable="@drawable/pre_signup_1" >
<target
android:name="plus_button"
android:animation="@anim/pre_signup_1_plus_container" />
<target
android:name="plus"
android:animation="@anim/pre_signup_1_plus_sign" />
</animated-vector>


Java code to run the animation:

ImageView mImage1 = (ImageView) findViewById(R.id.image_1);
AnimatedVectorDrawableCompat animated = (AnimatedVectorDrawableCompat) mImage1.getDrawable();

animated.start();


Is there a way to control the animation like
setCurrentDuration(400)
which will presumably set the current state of the animation to it's half? Maybe there is a way to split that vector drawable into layers and animate them programmatically? Thanks in advance!

Answer

Okay, so after a some research I ended up duplicating the following classes from the android.support.graphics.drawable package: AndroidResources, PathParser, TypedArrayUtils, VectorDrawableCommon and VectorDrawableCompat.

Next we need to make the following method and classes public inside of the VectorDrawableCompat class: getTargetByName, VGroup and VFullPath.

Next in the VectorDrawableCompat class remove the block that checks for Android version (Build.VERSION.SDK_INT >= 23). Don't know why, but if you don't do it, the animating won't work on android API 23 and up (need more research).

I may have missed a couple of private methods, but it's just a matter of making them public if you run into problems.

So, now we have access to the layers of our VectorDrawable! Here is a small example of scaling a vector group depending on the ViewPager's position:

<?xml version="1.0" encoding="utf-8"?>
<vector xmlns:android="http://schemas.android.com/apk/res/android"
    android:width="276dp"
    android:height="359dp"
    android:viewportWidth="276"
    android:viewportHeight="359">

    <group
        android:pivotX="205.5"
        android:pivotY="214.5"
        android:name="my_group">
        <path
            android:strokeColor="#4D394B"
            android:strokeWidth="7"
            android:strokeLineJoin="bevel"
            android:fillColor="#1ED761"
            android:pathData="M206.5,180 C186.9,180,171,195.9,171,215.5 S186.9,251,206.5,251
C226.1,251,242,235.1,242,215.5 S226.1,180,206.5,180 Z" />
        <path
            android:fillColor="#4D394B"
            android:pathData="M210,211 L210,190 L202,190 L202,211 L181,211 L181,219 L202,219 L202,241 L210,241
L210,219 L232,219 L232,211 Z" />
    </group>
</vector>

And this is the code used to animate the group:

ImageView myImageView;
VectorDrawableCompat.VGroup myVectorGroup;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_welcome);

    myImageView = (ImageView) findViewById(R.id.image_1);

    VectorDrawableCompat vectorDrawable = VectorDrawableCompat.create(getResources(), R.drawable.my_vector_drawable, null);
    vectorDrawable.setAllowCaching(false); // Important to allow image updates
    myVectorGroup = (VectorDrawableCompat.VGroup) vectorDrawable.getTargetByName("my_group");

    myImageView.setImageDrawable(vectorDrawable);

    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            if(myVectorGroup != null && position < 1) {
                myVectorGroup.setScaleX(1f - positionOffset);
                myVectorGroup.setScaleY(1f - positionOffset);

                myImageView.invalidate();
            }
        }
    });
}

I need some more testing to determine compatibility, but it works for now!