Animate view sliding out of another view, pushing views below out of the way

Question

I have a list of buttons. When I press a button, a View should slide in a downwards motion out of the button, like this:

Start:

Answer 1

I believe the simplest approach is to extend Animation class and override applyTransformation() to change the view's height as follows:

import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.view.animation.Animation;
import android.view.animation.Transformation;
import android.widget.LinearLayout;

public class MyCustomAnimation extends Animation {

    public final static int COLLAPSE = 1;
    public final static int EXPAND = 0;

    private View mView;
    private int mEndHeight;
    private int mType;
    private LinearLayout.LayoutParams mLayoutParams;

    public MyCustomAnimation(View view, int duration, int type) {

        setDuration(duration);
        mView = view;
        mEndHeight = mView.getHeight();
        mLayoutParams = ((LinearLayout.LayoutParams) view.getLayoutParams());
        mType = type;
        if(mType == EXPAND) {
            mLayoutParams.height = 0;
        } else {
            mLayoutParams.height = LayoutParams.WRAP_CONTENT;
        }
        view.setVisibility(View.VISIBLE);
    }

    public int getHeight(){
        return mView.getHeight();
    }

    public void setHeight(int height){
        mEndHeight = height;
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {

        super.applyTransformation(interpolatedTime, t);
        if (interpolatedTime < 1.0f) {
            if(mType == EXPAND) {
                mLayoutParams.height =  (int)(mEndHeight * interpolatedTime);
            } else {
                mLayoutParams.height = (int) (mEndHeight * (1 - interpolatedTime));
            }
            mView.requestLayout();
        } else {
            if(mType == EXPAND) {
                mLayoutParams.height = LayoutParams.WRAP_CONTENT;
                mView.requestLayout();
            }else{
                mView.setVisibility(View.GONE);
            }
        }
    }
}

To use it, set your onclick() as follows:

int height;

@Override
public void onClick(View v) {
    if(view2.getVisibility() == View.VISIBLE){
        MyCustomAnimation a = new MyCustomAnimation(view2, 1000, MyCustomAnimation.COLLAPSE);
        height = a.getHeight();
        view2.startAnimation(a);
    }else{
        MyCustomAnimation a = new MyCustomAnimation(view2, 1000, MyCustomAnimation.EXPAND);
        a.setHeight(height);
        view2.startAnimation(a);
    }
}

Regards.