CollapseAnimation.java

package org.qii.weiciyuan.ui.animation;

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

/**
 * User: qii
 * Date: 13-2-15
 */
public class CollapseAnimation extends Animation {
    private View mAnimatedView;
    private LinearLayout.LayoutParams mViewLayoutParams;
    private int mMarginStart, mMarginEnd;
    private boolean mIsVisibleAfter = false;
    private boolean mWasEndedAlready = false;

    public CollapseAnimation(View view, int duration) {
        setDuration(duration);
        mAnimatedView = view;
        mViewLayoutParams = (LinearLayout.LayoutParams) view.getLayoutParams();

        // decide to show or hide the view
        mIsVisibleAfter = (view.getVisibility() == View.VISIBLE);

        mMarginStart = mViewLayoutParams.bottomMargin;
        mMarginEnd = (mMarginStart == 0 ? (0 - view.getHeight()) : 0);

        view.setVisibility(View.VISIBLE);
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        super.applyTransformation(interpolatedTime, t);
        if (interpolatedTime < 1.0f) {
            // Calculating the new bottom margin, and setting it
            mViewLayoutParams.bottomMargin = mMarginStart
                    + (int) ((mMarginEnd - mMarginStart) * interpolatedTime);

            // Invalidating the layout, making us seeing the changes we made
            mAnimatedView.requestLayout();

            // Making sure we didn't run the ending before (it happens!)
        } else if (!mWasEndedAlready) {
            mViewLayoutParams.bottomMargin = mMarginEnd;
            mAnimatedView.requestLayout();

            if (mIsVisibleAfter) {
                mAnimatedView.setVisibility(View.GONE);
            }
            mWasEndedAlready = true;
        }
    }
}