Android scale animation on view

Solution 1:

Here is a code snip to do exactly that.

public void scaleView(View v, float startScale, float endScale) {
    Animation anim = new ScaleAnimation(
            1f, 1f, // Start and end values for the X axis scaling
            startScale, endScale, // Start and end values for the Y axis scaling
            Animation.RELATIVE_TO_SELF, 0f, // Pivot point of X scaling
            Animation.RELATIVE_TO_SELF, 1f); // Pivot point of Y scaling
    anim.setFillAfter(true); // Needed to keep the result of the animation
    anim.setDuration(1000);
    v.startAnimation(anim);
}

The ScaleAnimation constructor used here takes 8 args, 4 related to handling the X-scale which we don't care about (1f, 1f, ... Animation.RELATIVE_TO_SELF, 0f, ...).

The other 4 args are for the Y-scaling we do care about.

startScale, endScale - In your case, you'd use 0f, 0.6f.

Animation.RELATIVE_TO_SELF, 1f - This specifies where the shrinking of the view collapses to (referred to as the pivot in the documentation). Here, we set the float value to 1f because we want the animation to start growing the bar from the bottom. If we wanted it to grow downward from the top, we'd use 0f.

Finally, and equally important, is the call to anim.setFillAfter(true). If you want the result of the animation to stick around after the animation completes, you must run this on the animator before executing the animation.

So in your case, you can do something like this:

View v = findViewById(R.id.viewContainer);
scaleView(v, 0f, .6f);

Solution 2:

In XML, this what I use for achieving the same result. May be this is more intuitive.

scale_up.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" >

<scale
    android:duration="200"
    android:fromXScale="1.0"
    android:fromYScale="0.0"
    android:pivotX="50%"
    android:pivotY="100%"
    android:toXScale="1.0"
    android:toYScale="1.0" />

</set>

scale_down.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" >

<scale
    android:duration="200"
    android:fromXScale="1.0"
    android:fromYScale="1.0"
    android:pivotX="50%"
    android:pivotY="100%"
    android:toXScale="1.0"
    android:toYScale="0.0" />

</set>

See the animation on the X axis is from 1.0 -> 1.0 which means you don't have any scaling up in that direction and stays at the full width while, on the Y axis you get 0.0 -> 1.0 scaling, as shown in the graphic in the question. Hope this helps someone.

Some might want to know the java code as we see one requested.

Place the animation files in anim folder and then load and set animation files something like.

Animation scaleDown = AnimationUtils.loadAnimation(youContext, R.anim.scale_down);
ImagView v = findViewById(R.id.your_image_view);
v.startAnimation(scaleDown);