Android补间动画：坐标如何在翻译中工作？

Question

I'm learning Tween Animation now, so I made a really simple animation looks like

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:shareInterpolator="false"
    android:duration="5000"
    android:fillAfter="true"
    android:interpolator="@android:anim/accelerate_decelerate_interpolator">

    <translate 
        android:fromXDelta="100%p"
        android:toXDelta="0%p"/>

</set>

I want the ImageView to move from right edge of the screen to the left. The ImageView is in a fragment on the bottom of the screen,

public class BottomFragment extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.bottom_fragment, container, false);

    ImageView back = (ImageView)view.findViewById(R.id.bottomback);
    Animation move = AnimationUtils.loadAnimation(getActivity(), R.anim.move);
    back.startAnimation(move);

    return view;
}
}

I thought fromXDelta="100%p" will put the left top corner of the image at the right edge, and toXDelta="0%p" will put the left top corner of the image at the left edge. But the image seems to move from far away from the edge into the screen and stop at the middle of the screen. And it seems like the position is the centre of the image instead of the left top corner. I'm confused. How does coordinate system in Tween Animation works? How should I make it start at the edge of the screen/fragment?

Answer 1

Well, now it seems like:

1. The position of the picture is its centre, instead of left top corner.
2. By using percentage, distance is relative to the width of the screen width. So, 0% means centre of the picture falls on the middle of the screen, 50% means the edge. Thus, if I want the picture to move from one edge, I should make width of the picture the same as width of the screen, and then set fromXDelta=100% or 100%p .