进阶七之Android UI介面之（滑动倒影效果）

只有你学会把自己已有的成绩都归零，才能腾出空间去接纳更多的新东西，如此才能使自己不断的超越自己。

本讲内容：介面滑动倒影效果

一、倒影原理：

倒影效果是主要由原图+间距+倒影三部分组成，高度大约为原图的3/2（原图为1、倒影为1/2）

原图，就是我们看到了最开始的图片

间距，是原图与倒影之间的间隙，如：reflectionGap = 4;

倒影，是原图下半部分1/2高度，通过矩阵变换matrix.preScale(1, -1); 获取倒立图片，然后再加上线性遮罩和阴影实现

示例一效果图：

下面是res/layout/activity_main.xml
布局文件：

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

    <TextView
        android:id="@+id/tvTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:textSize="16sp" />

    <com.example.imagereflect.myGallery
        android:id="@+id/mygallery"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/tvTitle"
        android:layout_marginTop="10dip" />

</RelativeLayout>

com.example.imagereflect  是包名

下面是myGallery.java文件：

public class myGallery extends Gallery {

	private Camera mCamera = new Camera();
	private int mMaxRotationAngle = 60;		// 最大旋转角度 60
	private int mMaxZoom = -120;
	private int mCoveflowCenter;

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

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

	public myGallery(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;
	}

	/** 获取Gallery的中心x */
	private int getCenterOfCoverflow() {
		return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
	}

	/** 获取View的中心x */
	private static int getCenterOfView(View view) {
		return view.getLeft() + view.getWidth() / 2;
	}

	@Override
	protected void onSizeChanged(int w, int h, int oldw, int oldh) {
		mCoveflowCenter = getCenterOfCoverflow();
		super.onSizeChanged(w, h, oldw, oldh);
	}

	@Override
	protected boolean getChildStaticTransformation(View child, Transformation trans) {
		final int childCenter = getCenterOfView(child);
		final int childWidth = child.getWidth();
		int rotationAngle = 0;

		trans.clear();
		trans.setTransformationType(Transformation.TYPE_BOTH);		// alpha 和 matrix 都变换

		if (childCenter == mCoveflowCenter) {	// 正中间的childView
			transformImageBitmap((ImageView) child, trans, 0);
		} else {		// 两侧的childView
			rotationAngle = (int) ( ( (float) (mCoveflowCenter - childCenter) / childWidth ) * mMaxRotationAngle );
			if (Math.abs(rotationAngle) > mMaxRotationAngle) {
				rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle;
			}
			transformImageBitmap((ImageView) child, trans, rotationAngle);
		}

		return true;
	}

	private void transformImageBitmap(ImageView child, Transformation trans, int rotationAngle) {
		mCamera.save();

		final Matrix imageMatrix = trans.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);
		}

		mCamera.rotateY(rotationAngle);		// rotationAngle 为正，沿y轴向内旋转； 为负，沿y轴向外旋转

		mCamera.getMatrix(imageMatrix);
		imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
		imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));

		mCamera.restore();
	}
}

下面是ImageAdapter.java文件：

public class ImageAdapter extends BaseAdapter {
	private ImageView[] mImages;		// 保存倒影图片的数组

	private Context mContext;
	public List<Map<String, Object>> list;

	public Integer[] imgs = { R.drawable.img01, R.drawable.img02, R.drawable.img03,
							  R.drawable.img04, R.drawable.img05, R.drawable.img06, R.drawable.img07 };
	public String[] titles = { "乡村季风", "活到九十九", "健康超市", "每周一台戏", "热线村村通", "快乐生活", "戏迷时间" };

	public ImageAdapter(Context c) {
		this.mContext = c;
		list = new ArrayList<Map<String, Object>>();
		for (int i = 0; i < imgs.length; i++) {
			HashMap<String, Object> map = new HashMap<String, Object>();
			map.put("image", imgs[i]);
			list.add(map);
		}
		mImages = new ImageView[list.size()];
	}

	/** 反射倒影 */
	public boolean createReflectedImages() {
		final int reflectionGap = 4;
		int index = 0;
		for (Map<String, Object> map : list) {
			Integer id = (Integer) map.get("image");
			Bitmap originalImage = BitmapFactory.decodeResource(mContext.getResources(), id);	// 获取原始图片
			int width = originalImage.getWidth();
			int height = originalImage.getHeight();

			Matrix matrix = new Matrix();
			matrix.preScale(1, -1);			// 图片矩阵变换（从低部向顶部的倒影）
			Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height/2, width, height/2, matrix, false);	// 截取原图下半部分
			Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + height / 2), Config.ARGB_8888);			// 创建倒影图片（高度为原图3/2）

			Canvas canvas = new Canvas(bitmapWithReflection);	// 绘制倒影图（原图 + 间距 + 倒影）
			canvas.drawBitmap(originalImage, 0, 0, null);		// 绘制原图
			Paint paint = new Paint();
			canvas.drawRect(0, height, width, height + reflectionGap, paint);		// 绘制原图与倒影的间距
			canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);	// 绘制倒影图

			paint = new Paint();
			LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0, bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP);
			paint.setShader(shader);	// 线性渐变效果
			paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));		// 倒影遮罩效果
			canvas.drawRect(0, height, width, bitmapWithReflection.getHeight() + reflectionGap, paint);		// 绘制倒影的阴影效果

			ImageView imageView = new ImageView(mContext);
			imageView.setImageBitmap(bitmapWithReflection);		// 设置倒影图片
			imageView.setLayoutParams(new myGallery.LayoutParams(180, 240));
			imageView.setScaleType(ScaleType.MATRIX);
			mImages[index++] = imageView;
		}
		return true;
	}

	@Override
	public int getCount() {
		return imgs.length;
	}

	@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];		// 显示倒影图片（当前获取焦点）
	}

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

}

下面是MainActivity.java主界面文件：

public class MainActivity extends Activity {

	private TextView tvTitle;
	private myGallery gallery;
	private ImageAdapter adapter;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		initRes();
	}

	private void initRes(){
		tvTitle = (TextView) findViewById(R.id.tvTitle);
		gallery = (myGallery) findViewById(R.id.mygallery);

		adapter = new ImageAdapter(this);
		adapter.createReflectedImages();	// 创建倒影效果
		gallery.setAdapter(adapter);

		gallery.setOnItemSelectedListener(new OnItemSelectedListener() {	// 设置选择事件监听
			@Override
			public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
				tvTitle.setText(adapter.titles[position]);
			}

			@Override
			public void onNothingSelected(AdapterView<?> parent) {
			}
		});

		gallery.setOnItemClickListener(new OnItemClickListener() {			// 设置点击事件监听
			@Override
			public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
				Toast.makeText(MainActivity.this, "img " + (position+1) + " selected", Toast.LENGTH_SHORT).show();
			}
		});
	}
}

Take your time and enjoy it