Question

I am using the Gallery UI controller to provide a full-screen slideshow.
It is setup to display only on photo at the time.

The standard transistion between is to slide-out the old photo and slide-in the new.
This is smooth and works good on most platforms, but I having some performance problems on other (with very high resolution).

My workaround would be to use a different transition, preferable fade-out and fade-in.

I’ve already extended the Gallery control and have overwritten the
onKeyDown method.

By using the setSelection I am able to skip the default transition, but I am not able to include my on transition.

Has any one added a different transition to the Gallery component?

Is there another component which might give me better results?

Gallery source: http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/2.1_r2/android/widget/Gallery.java

Answer 1

Think, I’ve managed to crack this nut.
The strategy is as follows:

1. All items in the Gallery must have a ViewAnimator as root.
2. Extend the standard Gallery, and overwrite onKeyDown
3. Make sure onKeyDown is used from the Gallery after a time job for example gallery.onKeyDown(KeyEvent.KEYCODE_DPAD_RIGHT, new KeyEvent(0,0));
4. When the key is captured in the extended Gallery, get the current View which is an instance of ViewAnimator, get the next view from the Gallery’s adapter and create an animation to the next view
5. Once the animation is done, call setSelection(getSelectedItemPosition()+1); (it is needed to be checked for wrapping)

Here is an early Proof of concept that works, although it is missing some checks.

<ViewAnimator 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/slideshow_animator"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">



package com.elsewhat.slideshow.api;



public class CustomGallery extends Gallery implements AnimationListener {
boolean mDoTransition=false;

public CustomGallery(Context context) {
    super(context);
}

public CustomGallery(Context context, AttributeSet attrs) {
    super(context, attrs);
}

public CustomGallery(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}

/*
 * (non-Javadoc)
 * 
 * @see android.widget.Gallery#onKeyDown(int, android.view.KeyEvent)
 */
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if(mDoTransition==true){
        //leave the transition to the super class
        return super.onKeyDown(keyCode, event);
    }else {
        //handle the switch without transition ourselves
        switch (keyCode) {
        case KeyEvent.KEYCODE_DPAD_LEFT:
            //to be implemented similar as below
            return true;

        case KeyEvent.KEYCODE_DPAD_RIGHT:
            if (getCount() > 0 && getSelectedItemPosition() < getCount() - 1) {
                View currentView = getSelectedView();

                View unboundNewView= getAdapter().getView(getSelectedItemPosition()+1, null, null);



                ViewAnimator viewAnimator = (ViewAnimator)currentView;
                Animation inAnimation = new AlphaAnimation(0.0f, 1.0f);
                inAnimation.setDuration(1000);
                inAnimation.setAnimationListener(this);
                viewAnimator.setInAnimation(inAnimation);

                Animation outAnimation = new AlphaAnimation(1.0f, 0.0f);
                outAnimation.setDuration(1000);
                viewAnimator.setOutAnimation(outAnimation);

                viewAnimator.addView(unboundNewView);
                viewAnimator.showNext();


            }
            return true;

        case KeyEvent.KEYCODE_DPAD_CENTER:
        case KeyEvent.KEYCODE_ENTER:
        }

        return super.onKeyDown(keyCode, event);
    }

}

public void setDoTransition(boolean doTransition){
    mDoTransition= doTransition;
}

public boolean getDoTransition(){
    return mDoTransition;
}

@Override
public void onAnimationEnd(Animation arg0) {
    setSelection(getSelectedItemPosition()+1);

}

@Override
public void onAnimationRepeat(Animation animation) {
    // TODO Auto-generated method stub

}

@Override
public void onAnimationStart(Animation animation) {
    // TODO Auto-generated method stub

}

}