3D翻转效果介绍,Android动画分析

时间 2019-11-07

原文原文链接

android中的翻转动画效果的实现，首先看一下运行效果如上图所示。,更多android面试题.. html

Android中并无提供直接作3D翻转的动画，因此关于3D翻转的动画效果须要咱们本身实现，那么咱们首先来分析一下Animation 和 Transformation。 java

Animation动画的主要接口，其中主要定义了动画的一些属性好比开始时间，持续时间，是否重复播放等等。而Transformation中则包含一个矩阵和alpha值，矩阵是用来作平移，旋转和缩放动画的，而alpha值是用来作alpha动画的，要实现3D旋转动画咱们须要继承自Animation类来实现，咱们须要重载getTransformation和applyTransformation，在getTransformation中Animation会根据动画的属性来产生一系列的差值点，而后将这些差值点传给applyTransformation，这个函数将根据这些点来生成不一样的Transformation。下面是具体实现： android

package com.example.textviewtest;
 
 import android.graphics.Camera;
 import android.graphics.Matrix;
 import android.view.animation.Animation;
 import android.view.animation.Transformation;
 
 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;
     // 是否须要扭曲
     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
     @Override
     protected void applyTransformation(float interpolatedTime, Transformation t) {
         final float fromDegrees = mFromDegrees;
         // 生成中间角度
         float degrees = fromDegrees
                 + ((mToDegrees - fromDegrees) * interpolatedTime);
 
         final float centerX = mCenterX;
         final float centerY = mCenterY;
         final Camera camera = mCamera;
 
         final Matrix matrix = t.getMatrix();
 
         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);
         // 取得变换后的矩阵
         camera.getMatrix(matrix);
         camera.restore();
 
         matrix.preTranslate(-centerX, -centerY);
         matrix.postTranslate(centerX, centerY);
     }
 }

其中包括了旋转的开始和结束角度，中心点、是否扭曲、和一个Camera，这里咱们主要分析applyTransformation函数，其中第一个参数就是经过getTransformation函数传递的差指点，而后咱们根据这个差值经过线性差值算法计算出一个中间角度degrees，Camera类是用来实现绕Y轴旋转后透视投影的，所以咱们首先经过t.getMatrix()取得当前的矩阵，而后经过camera.translate来对矩阵进行平移变换操做，camera.rotateY进行旋转。这样咱们就能够很轻松的实现3D旋转效果了。面试

下面是布局文件main.xml：算法

MainActivity的代码以下： app

package com.example.textviewtest;
 
 import android.app.Activity;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.View;
 import android.view.animation.AccelerateInterpolator;
 import android.view.animation.Animation;
 import android.view.animation.DecelerateInterpolator;
 import android.widget.Button;
 import android.widget.TextView;
 
 public class MainActivity extends Activity {
     private TextView tv;
     private Button btn;
     private int count = 1;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         tv = (TextView) findViewById(R.id.tv);
         tv.setText(String.valueOf(count));
         btn = (Button) findViewById(R.id.next_btn);
         applyRotation(0, 90);
 
         btn.setOnClickListener(new View.OnClickListener() {
 
             @Override
             public void onClick(View v) {
                 applyRotation(0, 90);
             }
         });
 
     }
 
     private void applyRotation(float start, float end) {
         // 计算中心点
         final float centerX = tv.getWidth() / 2.0f;
         final float centerY = tv.getHeight() / 2.0f;
 
         final Rotate3dAnimation rotation = new Rotate3dAnimation(start, end,
                 centerX, centerY, 310.0f, true);
         rotation.setDuration(500);
         rotation.setFillAfter(true);
         rotation.setInterpolator(new AccelerateInterpolator());
         // 设置监听
         rotation.setAnimationListener(new DisplayNextView());
 
         tv.startAnimation(rotation);
     }
 
     private final class DisplayNextView implements Animation.AnimationListener {
 
         public void onAnimationStart(Animation animation) {
         }
 
         // 动画结束
         public void onAnimationEnd(Animation animation) {
             tv.post(new SwapViews());
         }
 
         public void onAnimationRepeat(Animation animation) {
         }
     }
 
     private final class SwapViews implements Runnable {
 
         public void run() {
             final float centerX = tv.getWidth() / 2.0f;
             final float centerY = tv.getHeight() / 2.0f;
             Rotate3dAnimation rotation = null;
 
             tv.requestFocus();
 
             rotation = new Rotate3dAnimation(90, 0, centerX, centerY, 310.0f,
                     false);
             rotation.setDuration(500);
             rotation.setFillAfter(true);
             rotation.setInterpolator(new DecelerateInterpolator());
             // 开始动画
             tv.startAnimation(rotation);
             tv.setText(String.valueOf(count++));
         }
     }
 
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.activity_main, menu);
         return true;
     }
 
 }

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