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的中相机相关的操作，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，如图：
3d立体旋转效果.gif
开始之前，先看一下Android系统中的坐标系：
坐标系.png
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="技术鸟\n\n微信号：NiaoTech\n\n上谈【安卓】,下论【苹果】.以扯淡的态度,面对操蛋的技术,用幽默的语言,诠释开发的经典。"
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;
/**
*
* @author 亦枫，微信公众号：技术鸟
* @see http://blog.csdn.net/growing_tree
*/
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。
Demo下载：
http://download.csdn.net/detail/wenbitianxiafeng/9382453
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