仅仅实现了图片的倒影效果还不够，因为在coverflow中图片切换是有旋转和缩放效果的，而自带的gallery中并没有实现。因此，我们扩展自带的gallery，实现自己的galleryflow。在原gallery类中，提供了一个方法getChildStaticTransformation()以实现对图片的变换。我们通过覆写这个方法并在其中调用自定义的transformImageBitmap(“每个图片与gallery中心的距离”)方法，，即可实现每个图片做相应的旋转和缩放。其中使用了camera和matrix用于视图变换。具体可参考代码注释。
public class GalleryFlow extendsGallery {
/**
* Graphics Camera used for transforming the matrix of ImageViews
*/
privateCamera mCamera = newCamera();
/**
* The maximum angle the Child ImageView will be rotated by
*/
privateint mMaxRotationAngle =60;
/**
* The maximum zoom on the centre Child
*/
privateint mMaxZoom = -120;
/**
* The Centre of the Coverflow
*/
privateint mCoveflowCenter;
publicGalleryFlow(Context context) {
super(context);
this.setStaticTransformationsEnabled(true);
}
publicGalleryFlow(Context context, AttributeSet attrs) {
super(context, attrs);
this.setStaticTransformationsEnabled(true);
}
publicGalleryFlow(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
this.setStaticTransformationsEnabled(true);
}
/**
* Get the max rotational angle of the image
*
* @return the mMaxRotationAngle
*/
publicint getMaxRotationAngle() {
returnmMaxRotationAngle;
}
/**
* Set the max rotational angle of each image
*
* @param maxRotationAngle
* the mMaxRotationAngle to set
*/
publicvoid setMaxRotationAngle(intmaxRotationAngle) {
mMaxRotationAngle = maxRotationAngle;
}
/**
* Get the Max zoom of the centre image
*
* @return the mMaxZoom
*/
publicint getMaxZoom() {
returnmMaxZoom;
}
/**
* Set the max zoom of the centre image
*
* @param maxZoom
* the mMaxZoom to set
*/
publicvoid setMaxZoom(intmaxZoom) {
mMaxZoom = maxZoom;
}
/**
* Get the Centre of the Coverflow
*
* @return The centre of this Coverflow.
*/
privateint getCenterOfCoverflow() {
return(getWidth() - getPaddingLeft() - getPaddingRight()) / 2
+ getPaddingLeft();
}
/**
* Get the Centre of the View
*
* @return The centre of the given view.
*/
privatestatic int getCenterOfView(View view) {
returnview.getLeft() + view.getWidth() / 2;
}
/**
* {@inheritDoc}
*
* @see #setStaticTransformationsEnabled(boolean)
*/
protectedboolean getChildStaticTransformation(View child, Transformation t) {
finalint childCenter = getCenterOfView(child);
finalint childWidth = child.getWidth();
introtationAngle = 0;
t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);
if(childCenter == mCoveflowCenter) {
transformImageBitmap((ImageView) child, t,0);
}else {
rotationAngle = (int) (((float) (mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle);
if(Math.abs(rotationAngle) > mMaxRotationAngle) {
rotationAngle = (rotationAngle <0) ? -mMaxRotationAngle
: mMaxRotationAngle;
}
transformImageBitmap((ImageView) child, t, rotationAngle);
}
returntrue;
}
/**
* This is called during layout when the size of this view has changed. If
* you were just added to the view hierarchy, you're called with the old
* values of 0.
*
* @param w
* Current width of this view.
* @param h
* Current height of this view.
* @param oldw
* Old width of this view.
* @param oldh
* Old height of this view.
*/
protectedvoid onSizeChanged(intw, int h, int oldw, int oldh) {
mCoveflowCenter = getCenterOfCoverflow();
super.onSizeChanged(w, h, oldw, oldh);
}
/**
* Transform the Image Bitmap by the Angle passed
*
* @param imageView
* ImageView the ImageView whose bitmap we want to rotate
* @param t
* transformation
* @param rotationAngle
* the Angle by which to rotate the Bitmap
*/
privatevoid transformImageBitmap(ImageView child, Transformation t,
introtationAngle) {
mCamera.save();
finalMatrix imageMatrix = t.getMatrix();
finalint imageHeight = child.getLayoutParams().height;
finalint imageWidth = child.getLayoutParams().width;
finalint rotation = Math.abs(rotationAngle);
// 在Z轴上正向移动camera的视角，实际效果为放大图片。
// 如果在Y轴上移动，则图片上下移动；X轴上对应图片左右移动。
mCamera.translate(0.0f,0.0f, 100.0f);
// As the angle of the view gets less, zoom in
if(rotation < mMaxRotationAngle) {
floatzoomAmount = (float) (mMaxZoom + (rotation *1.5));
mCamera.translate(0.0f,0.0f, zoomAmount);
}
// 在Y轴上旋转，对应图片竖向向里翻转。
// 如果在X轴上旋转，则对应图片横向向里翻转。
mCamera.rotateY(rotationAngle);
mCamera.getMatrix(imageMatrix);
imageMatrix.preTranslate(-(imageWidth /2), -(imageHeight /2));
imageMatrix.postTranslate((imageWidth /2), (imageHeight /2));
mCamera.restore();
}
}
