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="。" 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。