Android利用Camera实现中轴3D卡牌翻转效果

在Android系统API中，有两个Camera类：

• android.graphics.Camera
• android.hardware.Camera
  

第二个应用于手机硬件中的相机相关的操作，本文讲述的是利用第一个Camera类实现中轴3D转换的卡牌翻转效果，开始之前，先看一下Android系统中的坐标系：

对应于三维坐标系中的三个方向，Camera提供了三种旋转方法：

• rotateX()
• rotateY()
• rotateX()

调用这三种方法，传入旋转角度参数，即可实现视图沿着坐标轴旋转的功能。本文的中轴3D旋转效果就是让视图沿着Y轴旋转的。

系统API Demos中已经为我们提供了一个非常好用的3D旋转动画的工具类：
Rotate3dAnimation.java：

package com.feng.androidtest;

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

/**
 * 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();

  Log.i("interpolatedTime", interpolatedTime+"");
  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);
 }
}

可以看出， Rotate3dAnimation 总共做了两件事：在构造函数中赋值了旋转动画所需要的参数，以及重写（override）父类Animation中的applyTransformation()方法，下面分类阐述一下：

• fromDegrees与toDegrees
• 视图旋转的开始角度和结束角度，当toDegree处于90倍数时，视图将变得不可见。
• centerX与centerY
• 视图旋转的中心点。
• depthZ
• Z轴移动基数，用于计算Camera在Z轴移动距离
• reverse
• boolean类型，控制Z轴移动方向，达到视觉远近移动导致的视图放大缩小效果。
• applyTransformation()
• 根据动画播放的时间 interpolatedTime （动画start到end的过程，interpolatedTime从0.0变化到1.0），让Camera在Z轴方向上进行相应距离的移动，实现视觉上远近移动的效果。然后调用 rotateX()方法，让视图围绕Y轴进行旋转，产生3D立体旋转效果。最后再通过Matrix来确定旋转的中心点的位置。

activity_main.xml布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:background="@android:color/white" >

 <Button
  android:id="@+id/btn_open"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:layout_margin="16dp"
  android:onClick="onClickView"
  android:text="打开"
  android:textColor="@android:color/black"
  android:textSize="16sp" />

 <RelativeLayout
  android:id="@+id/rl_content"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:layout_below="@id/btn_open"
  android:layout_marginTop="16dp"
  android:background="@android:color/black">

  <ImageView
   android:id="@+id/iv_logo"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:contentDescription="@null"
   android:src="@drawable/ic_qrcode"
   android:scaleType="centerInside"/>

  <TextView
   android:id="@+id/tv_desc"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:padding="16dp"
   android:text="我们。"
   android:textColor="@android:color/white"
   android:textSize="18sp"
   android:visibility="gone"/>
 </RelativeLayout>

</RelativeLayout>

布局中配置了卡牌正面的图片控件，卡牌背面的文本控件，以及他们的parent容器，也就是本文中的旋转动画的执行对象。

MainActivity.java文件：

package com.feng.androidtest;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.Animation;
import android.view.animation.Animation.AnimationListener;
import android.view.animation.DecelerateInterpolator;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.TextView;

import com.example.androidtest.R;

public class MainActivity extends Activity {

 private RelativeLayout mContentRl;
 private ImageView mLogoIv;
 private TextView mDescTv;
 private Button mOpenBtn;

 private int centerX;
 private int centerY;
 private int depthZ = 400;
 private int duration = 600;
 private Rotate3dAnimation openAnimation;
 private Rotate3dAnimation closeAnimation;

 private boolean isOpen = false;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  mContentRl = (RelativeLayout) findViewById(R.id.rl_content);
  mLogoIv = (ImageView) findViewById(R.id.iv_logo);
  mDescTv = (TextView) findViewById(R.id.tv_desc);
  mOpenBtn = (Button) findViewById(R.id.btn_open);

 }

 /**
  * 卡牌文本介绍打开效果：注意旋转角度
  */
 private void initOpenAnim() {
  //从0到90度，顺时针旋转视图，此时reverse参数为true，达到90度时动画结束时视图变得不可见，
  openAnimation = new Rotate3dAnimation(0, 90, centerX, centerY, depthZ, true);
  openAnimation.setDuration(duration);
  openAnimation.setFillAfter(true);
  openAnimation.setInterpolator(new AccelerateInterpolator());
  openAnimation.setAnimationListener(new AnimationListener() {

   @Override
   public void onAnimationStart(Animation animation) {

   }

   @Override
   public void onAnimationRepeat(Animation animation) {

   }

   @Override
   public void onAnimationEnd(Animation animation) {
    mLogoIv.setVisibility(View.GONE);
    mDescTv.setVisibility(View.VISIBLE);

    //从270到360度，顺时针旋转视图，此时reverse参数为false，达到360度动画结束时视图变得可见
    Rotate3dAnimation rotateAnimation = new Rotate3dAnimation(270, 360, centerX, centerY, depthZ, false);
    rotateAnimation.setDuration(duration);
    rotateAnimation.setFillAfter(true);
    rotateAnimation.setInterpolator(new DecelerateInterpolator());
    mContentRl.startAnimation(rotateAnimation);
   }
  });
 }

 /**
  * 卡牌文本介绍关闭效果：旋转角度与打开时逆行即可
  */
 private void initCloseAnim() {
  closeAnimation = new Rotate3dAnimation(360, 270, centerX, centerY, depthZ, true);
  closeAnimation.setDuration(duration);
  closeAnimation.setFillAfter(true);
  closeAnimation.setInterpolator(new AccelerateInterpolator());
  closeAnimation.setAnimationListener(new AnimationListener() {

   @Override
   public void onAnimationStart(Animation animation) {

   }

   @Override
   public void onAnimationRepeat(Animation animation) {

   }

   @Override
   public void onAnimationEnd(Animation animation) {
    mLogoIv.setVisibility(View.VISIBLE);
    mDescTv.setVisibility(View.GONE);

    Rotate3dAnimation rotateAnimation = new Rotate3dAnimation(90, 0, centerX, centerY, depthZ, false);
    rotateAnimation.setDuration(duration);
    rotateAnimation.setFillAfter(true);
    rotateAnimation.setInterpolator(new DecelerateInterpolator());
    mContentRl.startAnimation(rotateAnimation);
   }
  });
 }

 public void onClickView(View v) {
  //以旋转对象的中心点为旋转中心点，这里主要不要再onCreate方法中获取，因为视图初始绘制时，获取的宽高为0
  centerX = mContentRl.getWidth()/2;
   centerY = mContentRl.getHeight()/2;
   if (openAnimation == null) {
   initOpenAnim();
   initCloseAnim();
  }

   //用作判断当前点击事件发生时动画是否正在执行
  if (openAnimation.hasStarted() && !openAnimation.hasEnded()) {
   return;
  }
  if (closeAnimation.hasStarted() && !closeAnimation.hasEnded()) {
   return;
  }

  //判断动画执行
  if (isOpen) {
   mContentRl.startAnimation(closeAnimation);

  }else {

   mContentRl.startAnimation(openAnimation);
  }

  isOpen = !isOpen;
  mOpenBtn.setText(isOpen ? "关闭" : "打开");
 }
}

代码中已对核心的地方做了注释解释，主要弄清楚 rotate3dAnimation构造参数中的 fromDegrees和toDegrees、depthZ、reverse参数，同时在动画中设置了速度插播器，如动画的前半程使用加速器 AccelerateInterpolator，后半程使用减速器 DecelerateInterpolator，使动画体验更加人性化。

以上就是本文的全部内容，希望对大家的学习Android软件编程有所帮助。