Android animate drop down/up view proper

Question

Okay I\'m trying to do a proper slide down animation. The view that slides down should push all views bellow it down in one smooth movement and again when it slides up all t

Answer 1

Thank you Warpzit! That was a very helpful answer. In my case, I was only trying to animate views with height that was wrap_content. I tried triggs two-line suggestion, but it didn't work in my case. (I didn't spend much time pursuing why.) I ended up using a slightly modified form of Warpzit's ExpandCollapseAnimation with his static method to determine the height of the view

In slightly more detail:

1. I included his static method setHeightForWrapContent() in the ExpandCollapseAnimation class.
2. I call the setHeightForWrapContent() in the ExpandCollapseAnimation constructor to properly determine the height of the view. To do this, I have to pass the activity in with the constructor.
3. In the applyTransformation() method, when the view is finally reduced to zero height, I return the view's height back to wrap_content. If you don't do this, and change the content of the view later, when you expand it the view will expand to the height previously determined.

The code is here:

public class ExpandCollapseAnimation extends Animation {
    private View mAnimatedView;
    private int mEndHeight;
    private int mType;

    public ExpandCollapseAnimation(View view, int duration, int type, Activity activity) {
        setDuration(duration);
        mAnimatedView = view;

        setHeightForWrapContent(activity, view);

        mEndHeight = mAnimatedView.getLayoutParams().height;

        mType = type;
        if(mType == 0) {
            mAnimatedView.getLayoutParams().height = 0;
            mAnimatedView.setVisibility(View.VISIBLE);
        }
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        super.applyTransformation(interpolatedTime, t);
        if (interpolatedTime < 1.0f) {
            if(mType == 0) {
                mAnimatedView.getLayoutParams().height = (int) (mEndHeight * interpolatedTime);
            } else {
                mAnimatedView.getLayoutParams().height = mEndHeight - (int) (mEndHeight * interpolatedTime);
            }
            mAnimatedView.requestLayout();
        } else {
            if(mType == 0) {
                mAnimatedView.getLayoutParams().height = mEndHeight;
                mAnimatedView.requestLayout();
            } else {
                mAnimatedView.getLayoutParams().height = 0;
                mAnimatedView.setVisibility(View.GONE);
                mAnimatedView.requestLayout();
                mAnimatedView.getLayoutParams().height = LayoutParams.WRAP_CONTENT;     // Return to wrap
            }
        }
    }

    public static void setHeightForWrapContent(Activity activity, View view) {
        DisplayMetrics metrics = new DisplayMetrics();
        activity.getWindowManager().getDefaultDisplay().getMetrics(metrics);

        int screenWidth = metrics.widthPixels;

        int heightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
        int widthMeasureSpec = MeasureSpec.makeMeasureSpec(screenWidth, MeasureSpec.EXACTLY);

        view.measure(widthMeasureSpec, heightMeasureSpec);
        int height = view.getMeasuredHeight();
        view.getLayoutParams().height = height;
    }
}

Thank you again, Warpzit!