Android gallery 3D效果

其实实现这个效果很简单，下面作一个简单的介绍

一，创建倒影效果

这个基本思路是：

1，创建一个源图一样的图，利用martrix将图片旋转180度。这个倒影图的高是源图的一半。

Matrix matrix = new Matrix();
// 1表示放大比例，不放大也不缩小。
// -1表示在y轴上相反，即旋转180度。
matrix.preScale(1, -1);
Bitmap reflectionBitmap = Bitmap.createBitmap(
srcBitmap,
0,
srcBitmap.getHeight() / 2,  // top为源图的一半
srcBitmap.getWidth(),       // 宽度与源图一样
srcBitmap.getHeight() / 2,  // 高度与源图的一半
matrix,
false);

2，创建一个最终效果的图，即源图 + 间隙 + 倒影。

final int REFLECTION_GAP = 5;
Bitmap bitmapWithReflection = Bitmap.createBitmap(
reflectionWidth,
srcHeight + reflectionHeight + REFLECTION_GAP,
Config.ARGB_8888);

3，依次将源图、倒影图绘制在最终的bitmap上面。

// Prepare the canvas to draw stuff.
Canvas canvas = new Canvas(bitmapWithReflection);
// Draw the original bitmap.
canvas.drawBitmap(srcBitmap, 0, 0, null);
// Draw the reflection bitmap.
canvas.drawBitmap(reflectionBitmap, 0, srcHeight + REFLECTION_GAP, null);

4，创建LinearGradient，从而给定一个由上到下的渐变色。

Paint paint = new Paint();
paint.setAntiAlias(true);
LinearGradient shader = new LinearGradient(
0,
srcHeight,
0,
bitmapWithReflection.getHeight() + REFLECTION_GAP,
0x70FFFFFF,
0x00FFFFFF,
TileMode.MIRROR);
paint.setShader(shader);
paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN));
// Draw the linear shader.
canvas.drawRect(
0,
srcHeight,
srcWidth,
bitmapWithReflection.getHeight() + REFLECTION_GAP,
paint);

二，扩展Gallery

扩展系统的gallery，我们需要重写两个方法，getChildStaticTransformation()和getChildDrawingOrder()，同时，要使这两个方法能被调用，必须执行如下两行代码，文档上面是有说明的。

// Enable set transformation.
this.setStaticTransformationsEnabled(true);
// Enable set the children drawing order.
this.setChildrenDrawingOrderEnabled(true);

getChildDrawingOrder的实现

@Override
protected int getChildDrawingOrder(int childCount, int i)
{
// Current selected index.
int selectedIndex = getSelectedItemPosition() - getFirstVisiblePosition();
if (selectedIndex < 0)
{
return i;
}
if (i < selectedIndex)
{
return i;
}
else if (i >= selectedIndex)
{
return childCount - 1 - i + selectedIndex;
}
else
{
return i;
}
}

这里为什么要计算drawing order，因为从上图中看到，我们的效果是：中间左边的顺序是 0， 1， 2，右边的child覆盖左边的child，而在中间右边的顺序正好相反，左边的覆盖右边的，所以我们要重写这个方法，而gallery自身的实现，不是这种效果。

@Override
protected boolean getChildStaticTransformation(View child, Transformation t)
{
super.getChildStaticTransformation(child, t);
final int childCenter = getCenterOfView(child);
final int childWidth  = child.getWidth();
int rotationAngle = 0;
t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);
// If the child is in the center, we do not rotate it.
if (childCenter == mCoveflowCenter)
{
transformImageBitmap(child, t, 0);
}
else
{
// Calculate the rotation angle.
rotationAngle = (int)(((float)(mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle);
// Make the angle is not bigger than maximum.
if (Math.abs(rotationAngle) > mMaxRotationAngle)
{
rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle;
}
transformImageBitmap(child, t, rotationAngle);
}
return true;
}

这个方法就是根据child来计算它的transformation（变换），我们需要去修改它里面的matrix，从而达到旋转的效果。根据位置和角度来计算的matrix的方法写在另外一个方法transformImageBitmap中实现。

transformImageBitmap()的实现

private void transformImageBitmap(View child, Transformation t, int rotationAngle)
{
mCamera.save();
final Matrix imageMatrix = t.getMatrix();
final int imageHeight = child.getHeight();
final int imageWidth  = child.getWidth();
final int rotation    = Math.abs(rotationAngle);
// Zoom on Z axis.
mCamera.translate(0, 0, mMaxZoom);
if (rotation < mMaxRotationAngle)
{
float zoomAmount = (float)(mMaxZoom + rotation * 1.5f);
mCamera.translate(0, 0, zoomAmount);
}
// Rotate the camera on Y axis.
mCamera.rotateY(rotationAngle);
// Get the matrix from the camera, in fact, the matrix is S (scale) transformation.
mCamera.getMatrix(imageMatrix);
// The matrix final is T2 * S * T1, first translate the center point to (0, 0),
// then scale, and then translate the center point to its original point.
// T * S * T
// S * T1
imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
// (T2 * S) * T1
imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
mCamera.restore();
}

这里，简单说明一个，

第一，先在Z轴上平称，其实就是得到一个缩放矩阵变换，我这里简写为 S。

第二，是利用camera这个类来生成matrix，其实mCamera.rotateY就是围绕Y轴旋转。这里生成了一个旋转矩阵，记为 R 。经过这两步，此时调用mCamera.getMatrix(imageMatrix); 从Camera中得到matrix，此时这个矩阵中包含了S * R。

第三，最关键是下面两句

// S * T1
imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
// (T2 * S) * T1
imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));

由于这里涉及到旋转与缩放，缩放操作其实应该是针对Child中点进行了，这里就是作一个平衡操作，我们必须是先平移，再缩放，再平移回原来位置，所以，我们最终的矩阵变换应该是这样的：

M = T * （S * R） * T1 （这里在T1表示与T相反）。

三，完整代码

GalleryFlow.java

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;
public class GalleryFlow extends Gallery
{
/**
* The camera class is used to 3D transformation matrix.
*/
private Camera mCamera = new Camera();
/**
* The max rotation angle.
*/
private int mMaxRotationAngle = 60;
/**
* The max zoom value (Z axis).
*/
private int mMaxZoom = -120;
/**
* The center of the gallery.
*/
private int mCoveflowCenter = 0;
public GalleryFlow(Context context)
{
this(context, null);
}
public GalleryFlow(Context context, AttributeSet attrs)
{
this(context, attrs, 0);
}
public GalleryFlow(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
// Enable set transformation.
this.setStaticTransformationsEnabled(true);
// Enable set the children drawing order.
this.setChildrenDrawingOrderEnabled(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;
}
@Override
protected int getChildDrawingOrder(int childCount, int i)
{
// Current selected index.
int selectedIndex = getSelectedItemPosition() - getFirstVisiblePosition();
if (selectedIndex < 0)
{
return i;
}
if (i < selectedIndex)
{
return i;
}
else if (i >= selectedIndex)
{
return childCount - 1 - i + selectedIndex;
}
else
{
return i;
}
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh)
{
mCoveflowCenter = getCenterOfCoverflow();
super.onSizeChanged(w, h, oldw, oldh);
}
private int getCenterOfView(View view)
{
return view.getLeft() + view.getWidth() / 2;
}
@Override
protected boolean getChildStaticTransformation(View child, Transformation t)
{
super.getChildStaticTransformation(child, t);
final int childCenter = getCenterOfView(child);
final int childWidth  = child.getWidth();
int rotationAngle = 0;
t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);
// If the child is in the center, we do not rotate it.
if (childCenter == mCoveflowCenter)
{
transformImageBitmap(child, t, 0);
}
else
{
// Calculate the rotation angle.
rotationAngle = (int)(((float)(mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle);
// Make the angle is not bigger than maximum.
if (Math.abs(rotationAngle) > mMaxRotationAngle)
{
rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle;
}
transformImageBitmap(child, t, rotationAngle);
}
return true;
}
private int getCenterOfCoverflow()
{
return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
}
private void transformImageBitmap(View child, Transformation t, int rotationAngle)
{
mCamera.save();
final Matrix imageMatrix = t.getMatrix();
final int imageHeight = child.getHeight();
final int imageWidth  = child.getWidth();
final int rotation    = Math.abs(rotationAngle);
// Zoom on Z axis.
mCamera.translate(0, 0, mMaxZoom);
if (rotation < mMaxRotationAngle)
{
float zoomAmount = (float)(mMaxZoom + rotation * 1.5f);
mCamera.translate(0, 0, zoomAmount);
}
// Rotate the camera on Y axis.
mCamera.rotateY(rotationAngle);
// Get the matrix from the camera, in fact, the matrix is S (scale) transformation.
mCamera.getMatrix(imageMatrix);
// The matrix final is T2 * S * T1, first translate the center point to (0, 0),
// then scale, and then translate the center point to its original point.
// T * S * T
// S * T1
imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
// (T2 * S) * T1
imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
mCamera.restore();
}
}

BitmapUtil.java

package com.lee.gallery3d.utils;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuffXfermode;
import android.graphics.Shader.TileMode;
import android.graphics.drawable.Drawable;
public class BitmapUtil
{
public static Bitmap createReflectedBitmap(Bitmap srcBitmap)
{
if (null == srcBitmap)
{
return null;
}
// The gap between the reflection bitmap and original bitmap.
final int REFLECTION_GAP = 4;
int srcWidth  = srcBitmap.getWidth();
int srcHeight = srcBitmap.getHeight();
int reflectionWidth  = srcBitmap.getWidth();
int reflectionHeight = srcBitmap.getHeight() / 2;
if (0 == srcWidth || srcHeight == 0)
{
return null;
}
// The matrix
Matrix matrix = new Matrix();
matrix.preScale(1, -1);
try
{
// The reflection bitmap, width is same with original's, height is half of original's.
Bitmap reflectionBitmap = Bitmap.createBitmap(
srcBitmap,
0,
srcHeight / 2,
srcWidth,
srcHeight / 2,
matrix,
false);
if (null == reflectionBitmap)
{
return null;
}
// Create the bitmap which contains original and reflection bitmap.
Bitmap bitmapWithReflection = Bitmap.createBitmap(
reflectionWidth,
srcHeight + reflectionHeight + REFLECTION_GAP,
Config.ARGB_8888);
if (null == bitmapWithReflection)
{
return null;
}
// Prepare the canvas to draw stuff.
Canvas canvas = new Canvas(bitmapWithReflection);
// Draw the original bitmap.
canvas.drawBitmap(srcBitmap, 0, 0, null);
// Draw the reflection bitmap.
canvas.drawBitmap(reflectionBitmap, 0, srcHeight + REFLECTION_GAP, null);
Paint paint = new Paint();
paint.setAntiAlias(true);
LinearGradient shader = new LinearGradient(
0,
srcHeight,
0,
bitmapWithReflection.getHeight() + REFLECTION_GAP,
0x70FFFFFF,
0x00FFFFFF,
TileMode.MIRROR);
paint.setShader(shader);
paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN));
// Draw the linear shader.
canvas.drawRect(
0,
srcHeight,
srcWidth,
bitmapWithReflection.getHeight() + REFLECTION_GAP,
paint);
return bitmapWithReflection;
}
catch (Exception e)
{
e.printStackTrace();
}
return null;
}
}

Demo下载

原创来自：http://blog.csdn.net/leehong2005/article/details/8070538