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。
代码如下：
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.tra