【Android UI】案例01Cover Flow3D效果的实现

       本例主要介绍CoverFlow3D的实现。首先介绍一下Cover Flow。Cover Flow是苹果首创的将多首歌曲的封面以3D界面的形式显示出来的方式。

       本案例摘自网络http://www.cnblogs.com/yyyyy5101/archive/2011/12/14/2287871.html，该案例在真机测试中，出现显示效果的差异，由此可见该演示工程存在一定的兼容性的问题，往浏览本文的有志之士，可以给以指正与修改。最后补充一下，虽然不同机器显示的效果有差异，但是显示效果的确也算优秀。
【转载使用，请注明出处：http://blog.csdn.net/mahoking】
       本案例的演示工程设计三个类文件分别为：Activity(CoverFlowActivity)、Gallery(GalleryFlow)、BaseAdapter(ImageAdapter)和布局文件activity_02_gallery.xml。

CoverFlowActivity

import android.app.Activity;
import android.os.Bundle;

public class CoverFlowActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		 setContentView(R.layout.activity_02_gallery);
		Integer[] images = { R.drawable.image01, R.drawable.image02,R.drawable.image03};
		ImageAdapter adapter = new ImageAdapter(this, images);
		adapter.createReflectedImages();
		GalleryFlow galleryFlow = (GalleryFlow) findViewById(R.id.activity_01_galleryFlow);
		galleryFlow.setAdapter(adapter);
	}
}

       Gallery是android的一个浏览图片的组件（不只是图片，可以用适配器），Gallery的中文意思也是画廊的意思，就是说把图片排成一行，然后手动滑动阅览。本文只是入门介绍，如果要深入了解Gallery还需读者自行不断深入了解。

       GalleryFlow  gallery在拖动图片过程中，会不断调用getChildStaticTransformation 方法,在该方法中,用Camera实现Z轴旋转。

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;
	}

	@Override
	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;
	}

	@Override
	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();
	}
}

ImageAdapter

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
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 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(180*2, 240*2));
//            imageView.setLayoutParams(new GalleryFlow.LayoutParams(180*4, 240*4));
//          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)));
    }
 
}

activity_02_gallery.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <com.mahaochen.app.uisharing.example02.GalleryFlow 
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/activity_01_galleryFlow"/>

</LinearLayout>

演示效果截图：