Android gallery 3D效果

轉載來自:http://blog.csdn.net/leehong2005/article/details/8070538

在看了iOS上面的CoverFlow後，感覺效果真的不錯，就想在android上面實現一個，這個程序在網上參考了一此核心的代碼，當然我添加了一些其他的東西，廢話不多說，先看效果，不然就是無圖無真相。

其實實現這個效果很簡單，下面作一個簡單的介紹

一，創建倒影效果

這個基本思路是：

1.創建一個源圖一樣的圖，利用martrix將圖片旋轉180度。這個倒影圖的高是源圖的一半。

Matrix matrix = new Matrix();
// 1表示放大比例，不放大也不縮小。
// -1表示在y軸上相反，即旋轉180度。
matrix.preScale(1, -1);
Bitmap reflectionBitmap = Bitmap.createBitmap(
    srcBitmap,
    0,
    srcBitmap.getHeight() / 2,  // top爲源圖的一半
    srcBitmap.getWidth(),       // 寬度與源圖一樣
    srcBitmap.getHeight() / 2,  // 高度與源圖的一半
    matrix,
    false);

2，創建一個最終效果的圖，即源圖 + 間隙 + 倒影。

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

3，依次將源圖、倒影圖繪製在最終的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，創建LinearGradient，從而給定一個由上到下的漸變色。

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，擴展Gallery

擴展系統的gallery，我們需要重寫兩個方法，getChildStaticTransformation()和getChildDrawingOrder()，同時，要使這兩個方法能被調用，必須執行如下兩行代碼，文檔上面是有說明的。

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

getChildDrawingOrder的實現

@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;
    }
}

這裏爲什麼要計算drawing order，因爲從上圖中看到，我們的效果是：中間左邊的順序是 0， 1， 2，右邊的child覆蓋左邊的child，而在中間右邊的順序正好相反，左邊的覆蓋右邊的，所以我們要重寫這個方法，而gallery自身的實現，不是這種效果。

getChildStaticTransformation的實現

@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;
}

這個方法就是根據child來計算它的transformation（變換），我們需要去修改它裏面的matrix，從而達到旋轉的效果。根據位置和角度來計算的matrix的方法寫在另外一個方法transformImageBitmap中實現。

transformImageBitmap()的實現

private void transformImageBitmap(View child, Transformation t, int rotationAngle)
{
    mCamera.save();
                      
    final Matrix p_w_picpathMatrix = t.getMatrix();
    final int p_w_picpathHeight = child.getHeight();
    final int p_w_picpathWidth  = 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(p_w_picpathMatrix);
                      
    // 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
    p_w_picpathMatrix.postTranslate((p_w_picpathWidth / 2), (p_w_picpathHeight / 2));
    // (T2 * S) * T1
    p_w_picpathMatrix.preTranslate(-(p_w_picpathWidth / 2), -(p_w_picpathHeight / 2));
                      
    mCamera.restore();
}

這裏，簡單說明一個，

第一，先在Z軸上平稱，其實就是得到一個縮放矩陣變換，我這裏簡寫爲 S。

第二，是利用camera這個類來生成matrix，其實mCamera.rotateY就是圍繞Y軸旋轉。這裏生成了一個旋轉矩陣，記爲 R 。經過這兩步，此時調用mCamera.getMatrix(p_w_picpathMatrix); 從Camera中得到matrix，此時這個矩陣中包含了S * R。

第三，最關鍵是下面兩句

// S * T1
 p_w_picpathMatrix.postTranslate((p_w_picpathWidth / 2), (p_w_picpathHeight / 2));
 // (T2 * S) * T1
 p_w_picpathMatrix.preTranslate(-(p_w_picpathWidth / 2), -(p_w_picpathHeight / 2));

於這裏涉及到旋轉與縮放，縮放操作其實應該是針對Child中點進行了，這裏就是作一個平衡操作，我們必須是先平移，再縮放，再平移回原來位置，所以，我們最終的矩陣變換應該是這樣的：

M = T * （S * R） * T1 （這裏在T1表示與T相反）。

三，完整代碼

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 p_w_picpathMatrix = t.getMatrix();
        final int p_w_picpathHeight = child.getHeight();
        final int p_w_picpathWidth  = 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(p_w_picpathMatrix);
              
        // 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
        p_w_picpathMatrix.postTranslate((p_w_picpathWidth / 2), (p_w_picpathHeight / 2));
        // (T2 * S) * T1
        p_w_picpathMatrix.preTranslate(-(p_w_picpathWidth / 2), -(p_w_picpathHeight / 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;
    }
}

Android gallery 3D效果

一，創建倒影效果

二，擴展Gallery

三，完整代碼

Android系統編譯系統分析大全(二)

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android中常用的開源項目

我的友情鏈接

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

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