CoverFlow in Android – Complete implementation with source code.

Have you seen the coverflow in iPhone.
This is the Android implementation of CoverFlow.

Please leave your comments if this article is helpful for you.

Let’s see how.

This is the CoverFlow class that extends the Gallery.

package com.coderzheaven.coverflow;

import android.content.Context;
import android.graphics.Camera;
import android.graphics.Color;
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;

@SuppressWarnings("deprecation")
public class CoverFlow extends Gallery {

	/**
	 * Graphics Camera used for transforming the matrix of ImageViews
	 */
	private Camera mCamera = new Camera();

	/**
	 * The maximum angle the Child ImageView will be rotated by
	 */
	private int mMaxRotationAngle = 60;

	/**
	 * The maximum zoom on the centre Child
	 */
	private int mMaxZoom = -120;

	/**
	 * The Centre of the Coverflow
	 */
	private int mCoveflowCenter;

	public CoverFlow(Context context) {
		super(context);
		this.setStaticTransformationsEnabled(true);
		this.setBackgroundColor(Color.BLACK);
	}

	public CoverFlow(Context context, AttributeSet attrs) {
		super(context, attrs);
		this.setStaticTransformationsEnabled(true);
		this.setBackgroundColor(Color.BLACK);
	}

	public CoverFlow(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		this.setStaticTransformationsEnabled(true);
		this.setBackgroundColor(Color.BLACK);
	}

	/**
	 * Get the max rotational angle of the image
	 * 
	 * @return the mMaxRotationAngle
	 */
	public int getMaxRotationAngle() {
		return mMaxRotationAngle;
	}

	/**
	 * Set the max rotational angle of each image
	 * 
	 * @param maxRotationAngle
	 *            the mMaxRotationAngle to set
	 */
	public void setMaxRotationAngle(int maxRotationAngle) {
		mMaxRotationAngle = maxRotationAngle;
	}

	/**
	 * Get the Max zoom of the centre image
	 * 
	 * @return the mMaxZoom
	 */
	public int getMaxZoom() {
		return mMaxZoom;
	}

	/**
	 * Set the max zoom of the centre image
	 * 
	 * @param maxZoom
	 *            the mMaxZoom to set
	 */
	public void setMaxZoom(int maxZoom) {
		mMaxZoom = maxZoom;
	}

	/**
	 * Get the Centre of the Coverflow
	 * 
	 * @return The centre of this Coverflow.
	 */
	private int getCenterOfCoverflow() {
		return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2
				+ getPaddingLeft();
	}

	/**
	 * Get the Centre of the View
	 * 
	 * @return The centre of the given view.
	 */
	private static int getCenterOfView(View view) {
		return view.getLeft() + view.getWidth() / 2;
	}

	/**
	 * {@inheritDoc}
	 * 
	 * @see #setStaticTransformationsEnabled(boolean)
	 */
	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;
	}

	/**
	 * This is called during layout when the size of this view has changed. If
	 * you were just added to the view hierarchy, you're called with the old
	 * values of 0.
	 * 
	 * @param w
	 *            Current width of this view.
	 * @param h
	 *            Current height of this view.
	 * @param oldw
	 *            Old width of this view.
	 * @param oldh
	 *            Old height of this view.
	 */
	protected void onSizeChanged(int w, int h, int oldw, int oldh) {
		mCoveflowCenter = getCenterOfCoverflow();
		super.onSizeChanged(w, h, oldw, oldh);
	}

	/**
	 * Transform the Image Bitmap by the Angle passed
	 * 
	 * @param imageView
	 *            ImageView the ImageView whose bitmap we want to rotate
	 * @param t
	 *            transformation
	 * @param rotationAngle
	 *            the Angle by which to rotate the Bitmap
	 */
	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);

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

Now the main activity that implements the coverflow.

package com.coderzheaven.coverflow;

import android.app.Activity;
import android.content.Context;
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.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;

public class CoverFlowDemo extends Activity {

	@SuppressWarnings("deprecation")
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		CoverFlow coverFlow;
		coverFlow = new CoverFlow(this);

		coverFlow.setAdapter(new ImageAdapter(this));

		ImageAdapter coverImageAdapter = new ImageAdapter(this);

		coverFlow.setAdapter(coverImageAdapter);

		coverFlow.setSpacing(-25);
		coverFlow.setSelection(4, true);
		coverFlow.setAnimationDuration(1000);

		setContentView(coverFlow);
	}

	public class ImageAdapter extends BaseAdapter {
		int mGalleryItemBackground;
		private Context mContext;

		private Integer[] mImageIds = { R.drawable.android,
				R.drawable.img1, R.drawable.img2,
				R.drawable.img3, R.drawable.img4,
				R.drawable.img1, R.drawable.img2,
				R.drawable.img3, R.drawable.img4
		};

		private ImageView[] mImages;

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

		@SuppressWarnings("deprecation")
		public boolean createReflectedImages() {
			// The gap we want between the reflection and the original image
			final int reflectionGap = 4;

			int index = 0;
			for (int imageId : mImageIds) {
				Bitmap originalImage = BitmapFactory.decodeResource(
						getResources(), imageId);
				int width = originalImage.getWidth();
				int height = originalImage.getHeight();

				// This will not scale but will flip on the Y axis
				Matrix matrix = new Matrix();
				matrix.preScale(1, -1);

				// Create a Bitmap with the flip matrix applied to it.
				// We only want the bottom half of the image
				Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,
						height / 2, width, height / 2, matrix, false);

				// Create a new bitmap with same width but taller to fit
				// reflection
				Bitmap bitmapWithReflection = Bitmap.createBitmap(width,
						(height + height / 2), Config.ARGB_8888);

				// Create a new Canvas with the bitmap that's big enough for
				// the image plus gap plus reflection
				Canvas canvas = new Canvas(bitmapWithReflection);
				// Draw in the original image
				canvas.drawBitmap(originalImage, 0, 0, null);
				// Draw in the gap
				Paint deafaultPaint = new Paint();
				canvas.drawRect(0, height, width, height + reflectionGap,
						deafaultPaint);
				// Draw in the reflection
				canvas.drawBitmap(reflectionImage, 0, height + reflectionGap,
						null);

				// Create a shader that is a linear gradient that covers the
				// reflection
				Paint paint = new Paint();
				LinearGradient shader = new LinearGradient(0,
						originalImage.getHeight(), 0,
						bitmapWithReflection.getHeight() + reflectionGap,
						0x70ffffff, 0x00ffffff, TileMode.CLAMP);
				// Set the paint to use this shader (linear gradient)
				paint.setShader(shader);
				// Set the Transfer mode to be porter duff and destination in
				paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
				// Draw a rectangle using the paint with our linear gradient
				canvas.drawRect(0, height, width,
						bitmapWithReflection.getHeight() + reflectionGap, paint);

				ImageView imageView = new ImageView(mContext);
				imageView.setImageBitmap(bitmapWithReflection);
				android.widget.Gallery.LayoutParams imgLayout = new CoverFlow.LayoutParams(
						320, 480);
				imageView.setLayoutParams(imgLayout);
				imageView.setPadding(30, 100, 20, 20);
				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;
		}

		@SuppressWarnings("deprecation")
		public View getView(int position, View convertView, ViewGroup parent) {

			// Use this code if you want to load from resources
			ImageView i = new ImageView(mContext);
			i.setImageResource(mImageIds[position]);
			i.setLayoutParams(new CoverFlow.LayoutParams(380, 450));
			i.setScaleType(ImageView.ScaleType.CENTER_INSIDE);

			// Make sure we set anti-aliasing otherwise we get jaggies
			BitmapDrawable drawable = (BitmapDrawable) i.getDrawable();
			drawable.setAntiAlias(true);
			return i;

			// return mImages[position];
		}

		/**
		 * Returns the size (0.0f to 1.0f) of the views depending on the
		 * 'offset' to the center.
		 */
		public float getScale(boolean focused, int offset) {
			/* Formula: 1 / (2 ^ offset) */
			return Math.max(0, 1.0f / (float) Math.pow(2, Math.abs(offset)));
		}

	}
}

OK Done. Now go on and Run your project.

Download the Complete android source code from here.