Android实现CoverFlow效果控件的实例代码

 package pym.test.gallery3d.widget;
 import pym.test.gallery3d.util.BitmapScaleDownUtil;
 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.Bitmap.Config;
 import android.graphics.Canvas;
 import android.graphics.LinearGradient;
 import android.graphics.Matrix;
 import android.graphics.Paint;
 import android.graphics.PaintFlagsDrawFilter;
 import android.graphics.PorterDuff.Mode;
 import android.graphics.PorterDuffXfermode;
 import android.graphics.Shader.TileMode;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.BaseAdapter;
 import android.widget.Gallery;
 import android.widget.ImageView;
 /**
 * @author pengyiming
 * @date 2013-9-30
 * @function GalleryFlow适配器
 */
 public class ImageAdapter extends BaseAdapter
 {
 /* 数据段begin */
 private final String TAG = "ImageAdapter";
 private Context mContext; 
 //图片数组
 private int[] mImageIds ;
 //图片控件数组
 private ImageView[] mImages;
 //图片控件LayoutParams
 private GalleryFlow.LayoutParams mImagesLayoutParams;
 /* 数据段end */
 /* 函数段begin */
 public ImageAdapter(Context context, int[] imageIds)
 {
 mContext = context;
 mImageIds = imageIds;
 mImages = new ImageView[mImageIds.length];
 mImagesLayoutParams = new GalleryFlow.LayoutParams(Gallery.LayoutParams.WRAP_CONTENT, Gallery.LayoutParams.WRAP_CONTENT);
 } 
 /**
 * @function 根据指定宽高创建待绘制的Bitmap，并绘制到ImageView控件上
 * @param imageWidth
 * @param imageHeight
 * @return void
 */
 public void createImages(int imageWidth, int imageHeight)
 {
 // 原图与倒影的间距5px
 final int gapHeight = 5; 
 int index = 0;
 for (int imageId : mImageIds)
 {
 /* step1 采样方式解析原图并生成倒影 */
 // 解析原图，生成原图Bitmap对象
 // Bitmap originalImage = BitmapFactory.decodeResource(mContext.getResources(), imageId);
 Bitmap originalImage = BitmapScaleDownUtil.decodeSampledBitmapFromResource(mContext.getResources(), imageId, imageWidth, imageHeight);
 int width = originalImage.getWidth();
 int height = originalImage.getHeight(); 
 // Y轴方向反向，实质就是X轴翻转
 Matrix matrix = new Matrix();
 matrix.setScale(1, -1);
 // 且仅取原图下半部分创建倒影Bitmap对象
 Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height / 2, width, height / 2, matrix, false);
  /* step2 绘制 */
 // 创建一个可包含原图+间距+倒影的新图Bitmap对象
 Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + gapHeight + height / 2), Config.ARGB_8888);
 // 在新图Bitmap对象之上创建画布
 Canvas canvas = new Canvas(bitmapWithReflection);
 // 抗锯齿效果
 canvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG));
 // 绘制原图
 canvas.drawBitmap(originalImage, 0, 0, null);
 // 绘制间距
 Paint gapPaint = new Paint();
 gapPaint.setColor(0xFFCCCCCC);
 canvas.drawRect(0, height, width, height + gapHeight, gapPaint);
 // 绘制倒影
 canvas.drawBitmap(reflectionImage, 0, height + gapHeight, null); 
 /* step3 渲染 */
 // 创建一个线性渐变的渲染器用于渲染倒影
 Paint paint = new Paint();
 LinearGradient shader = new LinearGradient(0, height, 0, (height + gapHeight + height / 2), 0x70ffffff, 0x00ffffff, TileMode.CLAMP);
 // 设置画笔渲染器
 paint.setShader(shader);
 // 设置图片混合模式
 paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
 // 渲染倒影+间距
 canvas.drawRect(0, height, width, (height + gapHeight + height / 2), paint); 
 /* step4 在ImageView控件上绘制 */
 ImageView imageView = new ImageView(mContext);
 imageView.setImageBitmap(bitmapWithReflection);
 imageView.setLayoutParams(mImagesLayoutParams);
 // 打log
 imageView.setTag(index);
  /* step5 释放heap */
 originalImage.recycle();
 reflectionImage.recycle();
 // bitmapWithReflection.recycle();
 mImages[index++] = imageView;
 }
 }
 @Override
 public int getCount()
 {
 return Integer.MAX_VALUE;
 } 
 @Override
 public Object getItem(int position)
 {
 return mImages[position];
 } 
 @Override
 public long getItemId(int position)

 {
 return position;
 } 
 @Override
 public View getView(int position, View convertView, ViewGroup parent)

 {
 return mImages[position % mImages.length];
 }
 /* 函数段end */
 }

package pym.test.gallery3d.widget;
 import android.content.Context;
 import android.graphics.Camera;
 import android.graphics.Matrix;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.View;
 import android.view.animation.Transformation;
 import android.widget.Gallery;
 /**
 * @author pengyiming
 * @date 2013-9-30
 * @function 自定义控件
 */
 public class GalleryFlow extends Gallery
 {
 /* 数据段begin */
 private final String TAG = "GalleryFlow";
 // 边缘图片最大旋转角度
 private final float MAX_ROTATION_ANGLE = 75;
 // 中心图片最大前置距离
 private final float MAX_TRANSLATE_DISTANCE = -100;
 // GalleryFlow中心X坐标
 private int mGalleryFlowCenterX;
 // 3D变换Camera
 private Camera mCamera = new Camera();
 /* 数据段end */
 /* 函数段begin */
 public GalleryFlow(Context context, AttributeSet attrs)
 {
 super(context, attrs); 
 // 开启，在滑动过程中，回调getChildStaticTransformation()
 this.setStaticTransformationsEnabled(true);
 } 
 /**
 * @function 获取GalleryFlow中心X坐标
 * @return
 */
 private int getCenterXOfCoverflow()
 {
 return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
 } 
 /**
 * @function 获取GalleryFlow子view的中心X坐标
 * @param childView
 * @return
 */
 private int getCenterXOfView(View childView)
 {
 return childView.getLeft() + childView.getWidth() / 2;
 } 
 /**
 * @note step1 系统调用measure()方法时，回调此方法；表明此时系统正在计算view的大小
 */
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
 {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
 mGalleryFlowCenterX = getCenterXOfCoverflow();
 Log.d(TAG, "onMeasure, mGalleryFlowCenterX = " + mGalleryFlowCenterX);
 } 
 /**
 * @note step2 系统调用layout()方法时，回调此方法；表明此时系统正在给child view分配空间
 * @note 必定在onMeasure()之后回调，但与onSizeChanged()先后顺序不一定
 */
 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b)
 {
 super.onLayout(changed, l, t, r, b); 
 mGalleryFlowCenterX = getCenterXOfCoverflow();
 Log.d(TAG, "onLayout, mGalleryFlowCenterX = " + mGalleryFlowCenterX);
 } 
 /**
 * @note step2 系统调用measure()方法后，当需要绘制此view时，回调此方法；表明此时系统已计算完view的大小
 * @note 必定在onMeasure()之后回调，但与onSizeChanged()先后顺序不一定
 */
 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh)
 {
 super.onSizeChanged(w, h, oldw, oldh); 
 mGalleryFlowCenterX = getCenterXOfCoverflow();
 Log.d(TAG, "onSizeChanged, mGalleryFlowCenterX = " + mGalleryFlowCenterX);
 } 
 @Override
 protected boolean getChildStaticTransformation(View childView, Transformation t)
 {
 // 计算旋转角度
 float rotationAngle = calculateRotationAngle(childView); 
 // 计算前置距离

 float translateDistance = calculateTranslateDistance(childView); 
 // 开始3D变换
 transformChildView(childView, t, rotationAngle, translateDistance); 
 return true;
 } 
 /**
 * @function 计算GalleryFlow子view的旋转角度
 * @note1 位于Gallery中心的图片不旋转
 * @note2 位于Gallery中心两侧的图片按照离中心点的距离旋转
 * @param childView
 * @return
 */
 private float calculateRotationAngle(View childView)
 {
 final int childCenterX = getCenterXOfView(childView);
 float rotationAngle = 0;
 
 rotationAngle = (mGalleryFlowCenterX - childCenterX) / (float) mGalleryFlowCenterX * MAX_ROTATION_ANGLE;
  if (rotationAngle > MAX_ROTATION_ANGLE)

 {
 rotationAngle = MAX_ROTATION_ANGLE;
 }
 else if (rotationAngle < -MAX_ROTATION_ANGLE)
 {
 rotationAngle = -MAX_ROTATION_ANGLE;
 } 
 return rotationAngle;
 } 
 /**
 * @function 计算GalleryFlow子view的前置距离
 * @note1 位于Gallery中心的图片前置
 * @note2 位于Gallery中心两侧的图片不前置
 * @param childView
 * @return
 */
 private float calculateTranslateDistance(View childView)
 {
 final int childCenterX = getCenterXOfView(childView);
 float translateDistance = 0; 
 if (mGalleryFlowCenterX == childCenterX)
 {
 translateDistance = MAX_TRANSLATE_DISTANCE;
 } 
 return translateDistance;
 } 
 /**
 * @function 开始变换GalleryFlow子view
 * @param childView
 * @param t
 * @param rotationAngle
 * @param translateDistance
 */
 private void transformChildView(View childView, Transformation t, float rotationAngle, float translateDistance)

 {
 t.clear();
 t.setTransformationType(Transformation.TYPE_MATRIX); 

 final Matrix imageMatrix = t.getMatrix();
 final int imageWidth = childView.getWidth();
 final int imageHeight = childView.getHeight();
  mCamera.save(); 
 /* rotateY */
 // 在Y轴上旋转，位于中心的图片不旋转，中心两侧的图片竖向向里或向外翻转。
 mCamera.rotateY(rotationAngle);
 /* rotateY */
  /* translateZ */
 // 在Z轴上前置，位于中心的图片会有放大的效果
 mCamera.translate(0, 0, translateDistance);
 /* translateZ */ 
 // 开始变换（我的理解是：移动Camera，在2D视图上产生3D效果）
 mCamera.getMatrix(imageMatrix);
 imageMatrix.preTranslate(-imageWidth / 2, -imageHeight / 2);
 imageMatrix.postTranslate(imageWidth / 2, imageHeight / 2); 
 mCamera.restore();
 }
 /* 函数段end */
 }

 package pym.test.gallery3d.util;
 import android.content.res.Resources;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.view.Display;
 /**
 * @author pengyiming
 * @date 2013-9-30
 * @function Bitmap缩放处理工具类
 */
 public class BitmapScaleDownUtil
 {
 /* 数据段begin */
 private final String TAG = "BitmapScaleDownUtil";
 /* 数据段end */ 
 /* 函数段begin */
 /**
 * @function 获取屏幕大小
 * @param display
 * @return 屏幕宽高
 */
 public static int[] getScreenDimension(Display display)
 {
 int[] dimension = new int[2];
 dimension[0] = display.getWidth();
 dimension[1] = display.getHeight(); 
 return dimension;
 } 

 /**
 * @function 以取样方式加载Bitmap 
 * @param res
 * @param resId
 * @param reqWidth
 * @param reqHeight
 * @return 取样后的Bitmap
 */
 public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight)
 {
 // step1，将inJustDecodeBounds置为true，以解析Bitmap真实尺寸
 final BitmapFactory.Options options = new BitmapFactory.Options();
 options.inJustDecodeBounds = true;
 BitmapFactory.decodeResource(res, resId, options);
 // step2，计算Bitmap取样比例
 options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight); 
 // step3，将inJustDecodeBounds置为false，以取样比列解析Bitmap
 options.inJustDecodeBounds = false;
 return BitmapFactory.decodeResource(res, resId, options);
 }
 /**
 * @function 计算Bitmap取样比例
 * @param options
 * @param reqWidth
 * @param reqHeight
 * @return 取样比例
 */
 private static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight)
 {
 // 默认取样比例为1:1
 int inSampleSize = 1;
 // Bitmap原始尺寸
 final int width = options.outWidth;
 final int height = options.outHeight; 
 // 取最大取样比例
 if (height > reqHeight || width > reqWidth)
 {
 final int widthRatio = Math.round((float) width / (float) reqWidth);
 final int heightRatio = Math.round((float) height / (float) reqHeight);
 // 取样比例为X:1，其中X>=1
 inSampleSize = Math.max(widthRatio, heightRatio);
 } 
 return inSampleSize;
 }
 /* 函数段end */
 }

 package pym.test.gallery3d.main;
 import pym.test.gallery3d.R;
 import pym.test.gallery3d.util.BitmapScaleDownUtil;
 import pym.test.gallery3d.widget.GalleryFlow;
 import pym.test.gallery3d.widget.ImageAdapter;
 import android.app.Activity;
 import android.content.Context;
 import android.os.Bundle; 
 /**
 * @author pengyiming
 * @date 2013-9-30
 */
 public class Gallery3DActivity extends Activity
 {
 /* 数据段begin */
 private final String TAG = "Gallery3DActivity";
 private Context mContext;
 // 图片缩放倍率（相对屏幕尺寸的缩小倍率）
 public static final int SCALE_FACTOR = 8; 
 // 图片间距（控制各图片之间的距离）
 private final int GALLERY_SPACING = -10;
 // 控件
 private GalleryFlow mGalleryFlow;
 /* 数据段end */ 
 /* 函数段begin */
 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 mContext = getApplicationContext();
  setContentView(R.layout.gallery_3d_activity_layout);
 initGallery();
 }
 private void initGallery()
 {
 // 图片ID
 int[] images = {
  R.drawable.picture_1,
  R.drawable.picture_2,
 R.drawable.picture_3,
 R.drawable.picture_4,
 R.drawable.picture_5,
  R.drawable.picture_6,
  R.drawable.picture_7 }; 
 ImageAdapter adapter = new ImageAdapter(mContext, images);
 // 计算图片的宽高
 int[] dimension = BitmapScaleDownUtil.getScreenDimension(getWindowManager().getDefaultDisplay());
 int imageWidth = dimension[0] / SCALE_FACTOR;
 int imageHeight = dimension[1] / SCALE_FACTOR;
 // 初始化图片
 adapter.createImages(imageWidth, imageHeight); 
 // 设置Adapter，显示位置位于控件中间，这样使得左右均可"无限"滑动
 mGalleryFlow = (GalleryFlow) findViewById(R.id.gallery_flow);
 mGalleryFlow.setSpacing(GALLERY_SPACING);
 mGalleryFlow.setAdapter(adapter);
 mGalleryFlow.setSelection(Integer.MAX_VALUE / 2);
 }
 /* 函数段end */
 }