The Android Developers documentation specifies the constructor as follows:
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public TranslateAnimation (int fromXType, float fromXValue, int toXType, float toXValue, int fromYType, float fromYValue, int toYType, float toYValue)
Since: API Level 1
Constructor to use when building a TranslateAnimation from code
Parameters
fromXType Specifies how fromXValue should be interpreted. One of Animation.ABSOLUTE, Animation.RELATIVE_TO_SELF, or Animation.RELATIVE_TO_PARENT.
===we choose: Animation.RELATIVE_TO_SELF because in this way we can easily specify the amount by how much more the view must Translate relative to its current state of animation!
fromXValueChange in X coordinate to apply at the start of the animation. This value can either be an absolute number if fromXType is ABSOLUTE, or a percentage (where 1.0 is 100%) otherwise.
===we choose:0.0f because this is the initial stage
toXTypeSpecifies how toXValue should be interpreted. One of Animation.ABSOLUTE, Animation.RELATIVE_TO_SELF, or Animation.RELATIVE_TO_PARENT.
===we choose: Animation.RELATIVE_TO_SELF because in this way we can easily specify the amount by how much more the view must Translate relative to its current state of animation!
toXValueChange in X coordinate to apply at the end of the animation. This value can either be an absolute number if toXType is ABSOLUTE, or a percentage (where 1.0 is 100%) otherwise.
===we choose:0.0f because this is vertical animation the change in x values is therefore not required
fromYTypeSpecifies how fromYValue should be interpreted. One of Animation.ABSOLUTE, Animation.RELATIVE_TO_SELF, or Animation.RELATIVE_TO_PARENT.
===we choose: Animation.RELATIVE_TO_SELF because in this way we can easily specify the amount by how much more the view must Translate relative to its current state of animation!
fromYValueChange in Y coordinate to apply at the start of the animation. This value can either be an absolute number if fromYType is ABSOLUTE, or a percentage (where 1.0 is 100%) otherwise.
===we choose:0.0f because this is the initial stage
toYTypeSpecifies how toYValue should be interpreted. One of Animation.ABSOLUTE, Animation.RELATIVE_TO_SELF, or Animation.RELATIVE_TO_PARENT.
===we choose: Animation.RELATIVE_TO_SELF because in this way we can easily specify the amount by how much more the view must Translate relative to its current state of animation!
toYValueChange in Y coordinate to apply at the end of the animation. This value can either be an absolute number if toYType is ABSOLUTE, or a percentage (where 1.0 is 100%) otherwise
===we choose:-1.0f . this is vertical animation and the final change should be 100 percent of its y coordinates.that is it should totally overlaop the underlying view.The sign is -ve because the final value of y is greater than the initial vaue of y (since animation is vertically downwards)