gallery3d_Android gallery 3D效果(2)

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(); } }

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