Android实现CoverFlow效果

上代码，看了代码什么都明白 

CoverFlow从Gallery继承过来

package com.coverflow;    import android.content.Context;  import android.graphics.Camera;  import android.graphics.Matrix;  import android.util.AttributeSet;  import android.view.View;  import android.view.animation.Transformation;  import android.widget.Gallery;  import android.widget.ImageView;    public class CoverFlow extends Gallery {     private Camera mCamera = new Camera();   private int mMaxRotationAngle = 50;   private int mMaxZoom = -380;   private int mCoveflowCenter;   private boolean mAlphaMode = true;   private boolean mCircleMode = false;     public CoverFlow(Context context) {    super(context);    this.setStaticTransformationsEnabled(true);   }     public CoverFlow(Context context, AttributeSet attrs) {    super(context, attrs);    this.setStaticTransformationsEnabled(true);   }     public CoverFlow(Context context, AttributeSet attrs, int defStyle) {    super(context, attrs, defStyle);    this.setStaticTransformationsEnabled(true);   }     public int getMaxRotationAngle() {    return mMaxRotationAngle;   }     public void setMaxRotationAngle(int maxRotationAngle) {    mMaxRotationAngle = maxRotationAngle;   }     public boolean getCircleMode() {    return mCircleMode;   }     public void setCircleMode(boolean isCircle) {    mCircleMode = isCircle;   }     public boolean getAlphaMode() {    return mAlphaMode;   }     public void setAlphaMode(boolean isAlpha) {    mAlphaMode = isAlpha;   }     public int getMaxZoom() {    return mMaxZoom;   }     public void setMaxZoom(int maxZoom) {    mMaxZoom = maxZoom;   }     private int getCenterOfCoverflow() {    return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2      + getPaddingLeft();   }     private static int getCenterOfView(View view) {    return view.getLeft() + view.getWidth() / 2;   }     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;   }     /**    * 这就是所谓的在大小的布局时,这一观点已经发生了改变。如果 你只是添加到视图层次,有人叫你旧的观念 价值观为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);   }     /**    * 把图像位图的角度通过    *     * @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);    mCamera.translate(0.0f, 0.0f, 100.0f);      // 如视图的角度更少,放大    if (rotation <= mMaxRotationAngle) {     float zoomAmount = (float) (mMaxZoom + (rotation * 1.5));     mCamera.translate(0.0f, 0.0f, zoomAmount);     if (mCircleMode) {      if (rotation < 40)       mCamera.translate(0.0f, 155, 0.0f);      else       mCamera.translate(0.0f, (255 - rotation * 2.5f), 0.0f);     }     if (mAlphaMode) {      ((ImageView) (child)).setAlpha((int) (255 - rotation * 2.5));     }    }    mCamera.rotateY(rotationAngle);    mCamera.getMatrix(imageMatrix);    imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));    imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));    mCamera.restore();   }  }

这个就是CoverFlow类，说明几点：
1. 成员函数
mCamera是用来做类3D效果处理,比如z轴方向上的平移,绕y轴的旋转等
mMaxRotationAngle是图片绕y轴最大旋转角度,也就是屏幕最边上那两张图片的旋转角度
mMaxZoom是图片在z轴平移的距离,视觉上看起来就是放大缩小的效果.
其他的变量都可以无视
也就是说把这个属性设成true的时候每次viewGroup(看Gallery的源码就可以看到它是从ViewGroup间接继承过来的)在重新画它的child的时候都会促发getChildStaticTransformation这个函数,所以我们只需要在这个函数里面去加上旋转和放大的操作就可以了
其他的getter和setter函数都可以无视

ImageAdapter适配器：

package com.coverflow;    import android.content.Context;  import android.graphics.Bitmap;  import android.graphics.BitmapFactory;  import android.graphics.Canvas;  import android.graphics.LinearGradient;  import android.graphics.Matrix;  import android.graphics.Paint;  import android.graphics.PorterDuffXfermode;  import android.graphics.Bitmap.Config;  import android.graphics.PorterDuff.Mode;  import android.graphics.Shader.TileMode;  import android.graphics.drawable.BitmapDrawable;  import android.view.View;  import android.view.ViewGroup;  import android.widget.BaseAdapter;  import android.widget.ImageView;    import com.gallery.R;    public class ImageAdapter extends BaseAdapter {   int mGalleryItemBackground;   private Context mContext;   private Integer[] mImageIds = {      R.drawable.a1,     R.drawable.a2,      R.drawable.a3,     R.drawable.a4,      R.drawable.a5 };     public ImageAdapter(Context c) {    mContext = c;   }     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) {      ImageView i = createReflectedImages(mContext,mImageIds[position]);        i.setLayoutParams(new CoverFlow.LayoutParams(120, 100));    i.setScaleType(ImageView.ScaleType.CENTER_INSIDE);        // 设置的抗锯齿    BitmapDrawable drawable = (BitmapDrawable) i.getDrawable();    drawable.setAntiAlias(true);    return i;   }     public float getScale(boolean focused, int offset) {    return Math.max(0, 1.0f / (float) Math.pow(2, Math.abs(offset)));   }      public ImageView createReflectedImages(Context mContext,int imageId) {      Bitmap originalImage = BitmapFactory.decodeResource(mContext.getResources(), imageId);        final int reflectionGap = 4;        int width = originalImage.getWidth();    int height = originalImage.getHeight();      Matrix matrix = new Matrix();    matrix.preScale(1, -1);      Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,      height / 2, width, height / 2, matrix, false);      Bitmap bitmapWithReflection = Bitmap.createBitmap(width,      (height + height / 2), Config.ARGB_8888);      Canvas canvas = new Canvas(bitmapWithReflection);      canvas.drawBitmap(originalImage, 0, 0, null);      Paint deafaultPaint = new Paint();    canvas.drawRect(0, height, width, height + reflectionGap, deafaultPaint);      canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);      Paint paint = new Paint();    LinearGradient shader = new LinearGradient(0, originalImage      .getHeight(), 0, bitmapWithReflection.getHeight()      + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.MIRROR);      paint.setShader(shader);      paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));      canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()      + reflectionGap, paint);      ImageView imageView = new ImageView(mContext);    imageView.setImageBitmap(bitmapWithReflection);      return imageView;   }     }

BitmapDrawable drawable = (BitmapDrawable) i.getDrawable();
drawable.setAntiAlias(true);
是保证图片绕Y旋转了以后不会出现锯齿.

下面是Activity：

package com.coverflow;    import android.app.Activity;  import android.graphics.Color;  import android.os.Bundle;    import com.gallery.R;    public class HelloAndroid extends Activity {   /** Called when the activity is first created. */   @Override   public void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);      CoverFlow cf = new CoverFlow(this);    // cf.setBackgroundResource(R.drawable.shape);    cf.setBackgroundColor(Color.BLACK);    cf.setAdapter(new ImageAdapter(this));    ImageAdapter imageAdapter = new ImageAdapter(this);    cf.setAdapter(imageAdapter);    // cf.setAlphaMode(false);    // cf.setCircleMode(false);    cf.setSelection(2, true);    cf.setAnimationDuration(1000);    setContentView(cf);   }    }

参考自：
http://www.eoeandroid.com/thread-70209-1-1.html
http://www.apkbus.com/android-18441-1-1.html