Android 拖动图片特效，

Android 拖动图片特效，

在开始之前，必须了解什么是Context以及widget里的 BaseAdpater ,在Acitivity当中，Context就如同是张Canvas画布，随时等着被处理或覆盖。
主程序中较为重要的部分是在其中创建一个继承自BaseAdapter的ImageAdapter方法，这个ImageAdapter的存在目的，是为了要暂存欲显示的图片，并作为Gallery控件图片的源引用。

1.ActivityMain.java

import Android.app.Activity;
import Android.os.Bundle;
import Android.view.View;
import Android.widget.AdapterView;
import Android.widget.Gallery;
import Android.widget.Toast;
import Android.widget.AdapterView.OnItemClickListener;

public class ActivityMain extends Activity {

    GalleryFlow galleryFlow = null;
    OnItemClickListener onItemClickListen = null;
    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) findViewById(R.id.Gallery01);
        galleryFlow.setAdapter(adapter);
        onItemClickListen = new OnItemClickListener()
        {
            public void onItemClick(AdapterView<?> parent, View view, int position, long id)
            {
                Toast.makeText( ActivityMain.this,"你选择了"+(position+1)+" 号图片", Toast.LENGTH_SHORT).show();
            }
        };
        galleryFlow.setOnItemClickListener(onItemClickListen);

    }
}

2.GalleryFlow.java

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 GalleryFlow extends Gallery  
{
    private Camera mCamera = new Camera();
    private int mMaxRotationAngle = 60;
    private int mMaxZoom = -120;
    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);
    }
    public int getMaxRotationAngle()
    {
        return mMaxRotationAngle;
    }
    public void setMaxRotationAngle(int maxRotationAngle)
    {
        mMaxRotationAngle = maxRotationAngle;
    }
    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;
    }
 
    protected void onSizeChanged(int w, int h, int oldw, int oldh)
    {
        mCoveflowCenter = getCenterOfCoverflow();
        super.onSizeChanged(w, h, oldw, oldh);
    }
 
    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();
    }
} 

3.ImageAdapter.java

import Android.content.Context;
import Android.content.res.Resources;
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.view.View;
import Android.view.ViewGroup;
import Android.widget.BaseAdapter;
import Android.widget.ImageView;
 
public class ImageAdapter extends BaseAdapter
{
    int mGalleryItemBackground;
    private Context mContext;
    private Integer[] mImageIds;
    private ImageView[] mImages;
 
    public ImageAdapter(Context c, Integer[] ImageIds)  
    {
        mContext = c;
        mImageIds = ImageIds;
        mImages = new ImageView[mImageIds.length];
    }
    public ImageAdapter( Context c )
    {
        mContext = c;
    }
    
    public void SetImages( Integer[] ImageIds )
    {
        mImageIds = ImageIds;
        mImages = new ImageView[mImageIds.length];
    }
 
    public boolean createReflectedImages()
    {
        final int reflectionGap = 4;
        int index = 0;
        
        for (int imageId : mImageIds)  
        {
            Bitmap originalImage = BitmapFactory.decodeResource(mContext.getResources(), imageId);
            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.CLAMP);
            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);
            imageView.setLayoutParams(new GalleryFlow.LayoutParams(100, 100));
//            imageView.setScaleType(ScaleType.MATRIX);
            mImages[index++] = imageView;
        }
        return true;
    }
 
    private Resources getResources()  
    {
        // TODO Auto-generated method stub
        return null;
    }
 
    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)  
    {
        return mImages[position];
    }
 
    public float getScale(boolean focused, int offset)  
    {
        return Math.max(0, 1.0f / (float) Math.pow(2, Math.abs(offset)));
    }
}