int height = originalImage.getHeight();
// This will not scale but will flip on the Y axis
Matrix matrix = new Matrix();
matrix.preScale(1, -1);
// Create a Bitmap with the flip matrix applied to it.
// We only want the bottom half of the image
Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,
height / 2, width, height / 2, matrix, false);
// Create a new bitmap with same width but taller to fit
// reflection
Bitmap bitmapWithReflection = Bitmap.createBitmap(width,
(height + height / 2), Config.ARGB_8888);
// Create a new Canvas with the bitmap that's big enough for
// the image plus gap plus reflection
Canvas canvas = new Canvas(bitmapWithReflection);
// Draw in the original image
canvas.drawBitmap(originalImage, 0, 0, null);
// Draw in the gap
Paint deafaultPaint = new Paint();
canvas.drawRect(0, height, width, height + reflectionGap,
deafaultPaint);
// Draw in the reflection
canvas.drawBitmap(reflectionImage, 0, height + reflectionGap,
null);
// Create a shader that is a linear gradient that covers the
// reflection
Paint paint = new Paint();
LinearGradient shader = new LinearGradient(0,
originalImage.getHeight(), 0,
bitmapWithReflection.getHeight() + reflectionGap,
0x70ffffff, 0x00ffffff, TileMode.CLAMP);
// Set the paint to use this shader (linear gradient)
paint.setShader(shader);
// Set the Transfer mode to be porter duff and destination in
paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
// Draw a rectangle using the paint with our linear gradient
canvas.drawRect(0, height, width,
bitmapWithReflection.getHeight() + reflectionGap, paint);
ImageView imageView = new ImageView(mContext);
imageView.setImageBitmap(bitmapWithReflection);
imageView
.setLayoutParams(new GalleryFlow.LayoutParams(160, 240));
// imageView.setScaleType(ScaleType.MATRIX);
mImages[index++] = imageView;
}
return true;
}
public int getCount() {
return mImageIds.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
// Use this code if you want to load from resources
/*
* ImageView i = new ImageView(mContext);
* i.setImageResource(mImageIds[position]); i.setLayoutParams(new
* CoverFlow.LayoutParams(350,350));
* i.setScaleType(ImageView.ScaleType.CENTER_INSIDE);
*
* //Make sure we set anti-aliasing otherwise we get jaggies
* BitmapDrawable drawable = (BitmapDrawable) i.getDrawable();
* drawable.setAntiAlias(true); return i;
*/
return mImages[position];
}
/**
* Returns the size (0.0f to 1.0f) of the views depending on the
* 'offset' to the center.
/
public float getScale(boolean focused, int offset) {
/ Formula: 1 / (2 ^ offset) */
return Math.max(0, 1.0f / (float) Math.pow(2, Math.abs(offset)));
}
}
}复制代码
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 extends Gallery {
/**
* Graphics Camera used for transforming the matrix of ImageViews
*/
private Camera mCamera = new Camera();
/**
* The maximum angle the Child ImageView will be rotated by
*/
private int mMaxRotationAngle = 60;
/**
* The maximum zoom on the centre Child
*/
private int mMaxZoom = -120;
/**
* The Centre of the Coverflow
*/
private int mCoveflowCenter;
public GalleryFlow(Context context) {
super(context);
this.setStaticTransformationsEnabled(true);
}
public GalleryFlow(Context context, AttributeSet attrs) {
super(context, attrs);
this.setStaticTransformationsEnabled(true);
}
public GalleryFlow(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
this.setStaticTransformationsEnabled(true);
}
/**
* Get the max rotational angle of the image
*
* @return the mMaxRotationAngle
*/
public int getMaxRotationAngle() {
return mMaxRotationAngle;
}
/**
* Set the max rotational angle of each image
*
* @param maxRotationAngle
*the mMaxRotationAngle to set
*/
public void setMaxRotationAngle(int maxRotationAngle) {
mMaxRotationAngle = maxRotationAngle;
}
/**
* Get the Max zoom of the centre image
*
* @return the mMaxZoom
*/
public int getMaxZoom() {
return mMaxZoom;
}
/**
* Set the max zoom of the centre image
*
* @param maxZoom
*the mMaxZoom to set
*/
public void setMaxZoom(int maxZoom) {
mMaxZoom = maxZoom;
}
/**
* Get the Centre of the Coverflow
*
* @return The centre of this Coverflow.
*/
private int getCenterOfCoverflow() {
return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2
+ getPaddingLeft();
}
/**
* Get the Centre of the View
*
* @return The centre of the given view.
*/
private static int getCenterOfView(View view) {
return view.getLeft() + view.getWidth() / 2;
}
/**
* {@inheritDoc}
*
* @see #setStaticTransformationsEnabled(boolean)
*/
protected boolean getChildStaticTransformation(View child, Transformation t) {
final int childCenter = getCenterOfView(child);
final int childWidth = child.getWidth();
int rotationAngle = 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);
}
return true;
}
/**
* 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.
*/
protected void onSizeChanged(int w, 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
*/
private void transformImageBitmap(ImageView child, Transformation t,
int rotationAngle) {
mCamera.save();
final Matrix imageMatrix = t.getMatrix();
final int imageHeight = child.getLayoutParams().height;
final int imageWidth = child.getLayoutParams().width;
final int 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) {
float zoomAmount = (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();
}
}复制代码
代码到这里就结束了。有兴趣的话可以自行调整里面的参数来实现更多更炫的效果。
下面是调用的示例：
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_gallery);
Integer[] images = { R.drawable.img0001, R.drawable.img0030,
R.drawable.img0100, R.drawable.img0130, R.drawable.img0200,
R.drawable.img0230, R.drawable.img0300, R.drawable.img0330,
R.drawable.img0354 };
ImageAdapter adapter = new ImageAdapter(this, images);
adapter.createReflectedImages();
GalleryFlow galleryFlow = (GalleryFlow) findViewById(R.id.gallery_flow);
galleryFlow.setAdapter(adapter);
}复制代码
PS1:
可以看出来这样实现的gallery锯齿问题比较严重。可以在createReflectedImages()使用以下代码：
BitmapDrawable bd = new BitmapDrawable(bitmapWithReflection);
bd.setAntiAlias(true);
...复制代码然后用iv.setImageDrawable(bd);
代替iv.setImageBitmap(bitmapWithReflection);
即可基本消除锯齿。
PS2:
ImageAdapter 有待确定的MemoryLeak问题，貌似的Bitmap的decode方法会造成ML，使用ImageAdapter时多次旋转屏幕后会出现OOM。目前可以通过将使用完毕的bimap调用recycle()方法和设置null并及时调用system.gc()得到一些改善，但是问题并不明显。
庆祝精华和推荐，增加3个PS~
