How to make a buttons bar slide in from bottom upo

问题:

I have a listview with custom listadapter, which populates the listview with a checkbox and some textviews. When the user selects a checkbox, I need a button bar to slide into the view from the bottom of the screen and sit there. I have made the buttons-bar and can make it appear and disappear from screen by changing it's visibility to "gone" and "visible", but it does not do these with slide-in and slide-out effect. How do I make it do those animations??

回答1:

You want to use Animation xml resources.

Here is an example of an Animation xml that will 'slide' the object up from the bottom of the screen to where ever its place is within your layout:

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate android:fromYDelta="100%p" android:toYDelta="0%p" android:duration="300"/>
</set>

You will put that in your res/anim folder then use this java code to animate your view:

slideUpIn = AnimationUtils.loadAnimation(this, R.anim.slide_up_in);
yourButtonBarView.startAnimation(slideUpIn);

You'll want to put the startAnimation call inside where you get the callback that your CheckBox has been checked.

回答2:

Below is the runtime code implementation, modify accordingly if you need it for other purposes.

RelativeLayout rl = new RelativeLayout(this);
ImageButton btnBar = new ImageButton(this);

RelativeLayout.LayoutParams btnParams = new RelativeLayout.LayoutParams(LayoutParams.FILL_PARENT, 80);

btnParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);

btnBar.setLayoutParams(btnParams);
btnBar.setBackgroundColor(Color.RED); // test with red background

TranslateAnimation a = new TranslateAnimation(
                           Animation.RELATIVE_TO_PARENT, 0,
                           Animation.RELATIVE_TO_PARENT, 0,
                           Animation.RELATIVE_TO_PARENT, (float)100, 
                           Animation.RELATIVE_TO_PARENT, (float)0);

a.setDuration(1000);
btnBar.startAnimation(a); // add animation while start

rl.addView(btnBar);
setContentView(rl);