实现3D旋转效果的方法

Android中有一种旋转效果，是将一个图片进行360度的旋转。

Matrix的作用是对平面上的View进行缩放、平移、旋转，每一种操作都配了setXXX、preXXX、postXXX三个函数。

Camera不是物理摄像头，是android.graphic下的一个类，相当于手机的屏幕，他的坐标系是带有Z坐标的。

可以完成对指定View的X,Y,Z轴的变化，所以可以用来完成3D效果。但是变化之后并不是直接作用于View，而是修改View的Matrix的值，最终View再根据Matrix的值来变换。

Android APIDemos中已经提供了一种例子

 /**
  * An animation that rotates the view on the Y axis between two specified angles.
  * This animation also adds a translation on the Z axis (depth) to improve the effect.
  */
 public class Rotate3dAnimation extends Animation {
     private final float mFromDegrees;
     private final float mToDegrees;
     private final float mCenterX;
     private final float mCenterY;
     private final float mDepthZ;
     private final boolean mReverse;
     private Camera mCamera;

     /**
      * Creates a new 3D rotation on the Y axis. The rotation is defined by its
      * start angle and its end angle. Both angles are in degrees. The rotation
      * is performed around a center point on the 2D space, definied by a pair
      * of X and Y coordinates, called centerX and centerY. When the animation
      * starts, a translation on the Z axis (depth) is performed. The length
      * of the translation can be specified, as well as whether the translation
      * should be reversed in time.
      *
      * @param fromDegrees the start angle of the 3D rotation
      * @param toDegrees the end angle of the 3D rotation
      * @param centerX the X center of the 3D rotation
      * @param centerY the Y center of the 3D rotation
      * @param reverse true if the translation should be reversed, false otherwise
      */
     public Rotate3dAnimation(float fromDegrees, float toDegrees,
             float centerX, float centerY, float depthZ, boolean reverse) {
         mFromDegrees = fromDegrees;
         mToDegrees = toDegrees;
         mCenterX = centerX;
         mCenterY = centerY;
         mDepthZ = depthZ;
         mReverse = reverse;
     }

     @Override
     public void initialize(int width, int height, int parentWidth, int parentHeight) {
         super.initialize(width, height, parentWidth, parentHeight);
         mCamera = new Camera();
     }

     @Override
     protected void applyTransformation(float interpolatedTime, Transformation t) {
         final float fromDegrees = mFromDegrees;
         float degrees = fromDegrees + ((mToDegrees - fromDegrees) * interpolatedTime);

         final float centerX = mCenterX;
         final float centerY = mCenterY;
         final Camera camera = mCamera;

         final Matrix matrix = t.getMatrix();

         camera.save();
         if (mReverse) {
             camera.translate(0.0f, 0.0f, mDepthZ * interpolatedTime);
         } else {
             camera.translate(0.0f, 0.0f, mDepthZ * (1.0f - interpolatedTime));
         }
         camera.rotateY(degrees);
         camera.getMatrix(matrix);
         camera.restore();

         matrix.preTranslate(-centerX, -centerY);
         matrix.postTranslate(centerX, centerY);
     }
 }

如果不需要做特别的效果的话，可以直接照搬

 import android.graphics.Camera;
 import android.graphics.Matrix;
 import android.view.animation.Animation;
 import android.view.animation.Transformation;

 /**
  * @author Administrator
  *
  */
 public class Rotate3DAnimation extends Animation {
     // 开始角度
     private final float mFromDegrees;
     // 结束角度
     private final float mToDegrees;
     // 中心点
     private final float mCenterX;
     private final float mCenterY;
     private final float mDepthZ;
     // 是否需要扭曲 ，也就是是否有Z轴方向深度的变化
     private final boolean mReverse;
     // 摄像头
     private Camera mCamera;
     public Rotate3DAnimation(float fromDegrees, float toDegrees, float centerX,
             float centerY, float depthZ, boolean reverse) {
         mFromDegrees = fromDegrees;
         mToDegrees = toDegrees;
         mCenterX = centerX;
         mCenterY = centerY;
         mDepthZ = depthZ;
         mReverse = reverse;
     }
     @Override
     public void initialize(int width, int height, int parentWidth,
             int parentHeight) {
         super.initialize(width, height, parentWidth, parentHeight);
         mCamera = new Camera();
     } 

     /**
      * 生成Transformation,整个动画的过程中会不停的被调用
      * @param interpolatedTime 会逐渐从0增大到1
      * @param Transformation 变换对象
      */
     @Override
     protected void applyTransformation(float interpolatedTime, Transformation t) {
         /**
          * 实际上整个过程就是通过Camera计算出要旋转所要修改的Matrix的值
          * 整个函数结束之后，会根据这个Matrix的值进行变化
          * 也就是说实际最终变换依据的依然是Matrix的值
          */
         final float fromDegrees = mFromDegrees;
         //生成每次的角度
         float degrees = fromDegrees
                 + ((mToDegrees - fromDegrees) * interpolatedTime);
         final float centerX = mCenterX;
         final float centerY = mCenterY;
         final Camera camera = mCamera;
         final Matrix matrix = t.getMatrix();//获取动画对象的矩阵
         camera.save();//保存摄像机的状态
         if (mReverse) { //变化的方向是从小往大变
             camera.translate(0.0f, 0.0f, mDepthZ * interpolatedTime);
         }
         //旋转到指定的角度
         camera.rotateY(degrees);
         //取得变换后的矩阵，修改Matrix的值
         camera.getMatrix(matrix);
         camera.restore();//恢复摄像机的状态 ，每次摄像机变换完后，下次又从摄像机初始位置开始变化
         //将变换的中心点设成中心点
         matrix.preTranslate(-centerX, -centerY);
         matrix.postTranslate(centerX, centerY);
     }
 }

Activity中的代码

 import org.cxjchen.animation.Rotate3DAnimation;
 import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.view.animation.*;
 import android.widget.ImageView;
 import android.widget.TextView;

 /**
  * @author Administrator
  *
  */
 public class Logo_Activity extends Activity {

     private TextView logo_title = null;

     @Override
     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);
         setContentView(R.layout.logo_activity);

         logo_title = (TextView)findViewById(R.id.logo_title);
         logo_title.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 applyRotation(0,360);
             }
         });
     }

     private void applyRotation(float start, float end) {
         // 计算中心点
         final float centerX = logo_title.getWidth() / 2.0f;
         final float centerY = logo_title.getHeight() / 2.0f;
         final Rotate3DAnimation rotation = new Rotate3DAnimation(start, end,
                 centerX, centerY, 360.0f, false);
         rotation.setDuration(1000L);
         //设置变换后是否维持变换状态
         rotation.setFillAfter(true);
         rotation.setInterpolator(new AccelerateInterpolator());
         // 设置监听
         rotation.setAnimationListener(new Animation.AnimationListener() {

             @Override
             public void onAnimationStart(Animation animation) {
             }

             @Override
             public void onAnimationRepeat(Animation animation) {

             }

             @Override
             public void onAnimationEnd(Animation animation) {

             }
         });
         logo_title.startAnimation(rotation);
     } 

 }