Hi,
A good place to start is to look at the ApiDemos application to see if
there is anything there close to what you want. The best I found is
com.example.android.apis.view.Animation2, which uses a ViewFlipper to
transition from one view to another with various animations. It's not
exactly what we want, because we actually want to fade in/out a single
view. But Animation2 does give us the names of the fading animations:
android.R.anim.fade_in and android.R.anim.fade_out.
You can apply an animation to any view (and its children) by calling
startAnimation(). So ...
myView.startAnimation(AnimationUtils.loadAnimation(mContext,
android.R.anim.fade_in))
... would fade in the view and ...
myView.startAnimation(AnimationUtils.loadAnimation(mContext,
android.R.anim.fade_out))
... would fade it out.
The trick is that when the animation ends we want to change the
visibility of the view. If we are fading in then at the end of the
animation we want to make the view visible. If we are fading out then
at the end of the animation we want to make the view invisible.
Luckily, views have a onAnimationEnd() method that is called when the
animation terminates. We can override this method and change the
visibility of the view as appropriate. Because we want to override a
method we will need a custom view. Our custom view might have methods
like this:
public void fadeIn() {
startAnimation(AnimationUtils.loadAnimation(mContext,
android.R.anim.fade_in));
mVisibilityOnAnimationEnd = VISIBLE;
}
public void fadeOut() {
startAnimation(AnimationUtils.loadAnimation(mContext,
android.R.anim.fade_out));
mVisibilityOnAnimationEnd = INVISIBLE;
}
@Override public void onAnimationEnd() {
super.onAnimationEnd(); // make sure to chain up to superclass
method
setVisibility(mVisibilityOnAnimationEnd);
}
private int mVisibilityOnAnimationEnd;
Anyway, that's the simplest way I can think of doing this. Anyone have
other ideas?
Now, we still need to figure out what View to extend. Every view
accepts the onClick event, so we can extend ImageView. But the zoom
control has two clickable images, so more likely we will need to
extend a view group such as LinearLayout.
Getting our view to appear now just requires calling fadeIn() and
getting our view to disappear just requires calling fadeOut(). To get
the view to disappear after a delay create a Handler and either send
it a message with a delay or post a runnable with a delay.
Hope that gets you started.
Greg
On Apr 4, 1:48 am, AllSet <fukangp...@gmail.com> wrote:
> i am trying to make a control which looks like the ZoomControls.
>
> it is supposed to show up when clicking in a certain area and
> disappear a few seconds later.
>
> also it should accept the onClick event.
>
> but i don't know exactly how to realize such a control.
>
> could anybody help me?
>
> thanks in advance!
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