Android gallery 3D效果
阿新 • • 發佈：2018-12-23
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，這個程式在網上參考了一此核心的程式碼，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，建立倒影效果
這個基本思路是：
1，建立一個源圖一樣的圖，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為源圖的一半 srcBitmap.getWidth(), // 寬度與源圖一樣 srcBitmap.getHeight() / 2, // 高度與源圖的一半 matrix, false);
2，建立一個最終效果的圖，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。
4，建立LinearGradient，從而給定一個由上到下的漸變色。// 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);
二，擴充套件Gallery
擴充套件系統的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呼叫，必須執行如下兩行程式碼，文件上面是有說明的。
// 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;
}
}這裡為什麼要計算drawing order，因為從上圖中看到，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），我們需要去修改它裡面的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 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();
}這裡，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，我這裡簡寫為 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。這裡生成了一個旋轉矩陣，記為 R 。經過這兩步，此時呼叫mCamera.getMatrix(imageMatrix); 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
imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));
// (T2 * S) * T1
imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));M = T * （S * R） * T1 （這裡在T1表示與T相反）。
三，完整程式碼
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 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;
}
}