图片左右滚动控件（带倒影）——重写Gallery

今天在网上找了些资料，做了一个图片左右滚动的Demo，类似幻灯片播放，同时，图片带倒影效果，运行效果如下图：

                                                         

实现方式是重写Gallery，使用自定义的Gallery来实现这一效果，工程一共三个文件，一个Activity，一个自定义的Gallery，还有就是一个适配器ImageAdapter，直接上代码：

ScrollGallery.java

public class ScrollGallery extends Gallery {
	private Camera mCamera = new Camera();
	//左右图片倾斜的角度
	private int mMaxRotationAngle = 60;
	//背景区域大小
	private int mMaxZoom = -380;
	private int mCoveflowCenter;

	public ScrollGallery(Context context) {
		super(context);
		this.setStaticTransformationsEnabled(true);
	}

	public ScrollGallery(Context context, AttributeSet attrs) {
		super(context, attrs);
		this.setStaticTransformationsEnabled(true);
	}

	public ScrollGallery(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
		// 在Y轴上移动，上下移动；X轴上左右移动。
		mCamera.translate(0.0f, 0.0f, 100.0f);
		if (rotation < mMaxRotationAngle) {
			float zoomAmount = (float) (mMaxZoom + (rotation * 1.5));
			mCamera.translate(0.0f, 0.0f, zoomAmount);
		}
		// 在Y轴上旋转，竖向向里翻转。
		// 在X轴上旋转，则横向向里翻转。
		mCamera.rotateY(rotationAngle);
		mCamera.getMatrix(imageMatrix);
		imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
		imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
		mCamera.restore();
	}
}

ImageAdapter.java

public class ImageAdapter extends BaseAdapter {
	//倒影的缩放比例
	private static final int REFLECTION = 5;
	
	int mGalleryItemBackground;
	private Context mContext;
	private int[] mImageIds;
	private ImageView[] mImages;

	public ImageAdapter(Context c, int[] ImageIds) {
		mContext = c;
		mImageIds = ImageIds;
		mImages = new ImageView[mImageIds.length];
	}

	public boolean createReflectedImages() {
		final int reflectionGap = 5;
		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 / REFLECTION), 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 ScrollGallery.LayoutParams(180, 240));
			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) {
		return mImages[position];
	}

	public float getScale(boolean focused, int offset) {
		return Math.max(0, 1.0f / (float) Math.pow(2, Math.abs(offset)));
	}
}

ScrollImageActivity.java

public class ScrollImageActivity extends Activity {
    /** Called when the activity is first created. */
	
	private ScrollGallery galleryFlow = null;
	
	int images[] = {R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d,R.drawable.f};
	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.main);
        galleryFlow = (ScrollGallery) this.findViewById(R.id.gf_images);
        ImageAdapter adapter = new ImageAdapter(this, images);
        adapter.createReflectedImages();
        galleryFlow.setAdapter(adapter);
        galleryFlow.setSelection(1);
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <com.ryan.scrollimage.ScrollGallery
        android:id="@+id/gf_images"
        android:layout_width="fill_parent"
        android:layout_height="0dip"
        android:layout_weight="1" />

</LinearLayout>

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