Android3D动画翻转效果

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.
Android中并没有提供直接做3D翻转的动画，所以关于3D翻转的动画效果需要我们自己实现，那么我们首先来分析一下Animation 和 Transformation。
Animation动画的主要接口，其中主要定义了动画的一些属性比如开始时间，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，矩阵是用来做平移，旋转和缩放动画的，而alpha值是用来做alpha动画的，要实现3D旋转动画我们需要继承自Animation类来实现，我们需要重载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，然后将这些差值点传给applyTransformation，这个函数将根据这些点来生成不同的Transformation。下面是具体实现：


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1 package com.example.textviewtest;
2
3 import android.graphics.Camera;
4 import android.graphics.Matrix;
5 import android.view.animation.Animation;
6 import android.view.animation.Transformation;
7
8 public class Rotate3dAnimation extends Animation {
9     // 开始角度
10     private final float mFromDegrees;
11     // 结束角度
12     private final float mToDegrees;
13     // 中心点
14     private final float mCenterX;
15     private final float mCenterY;
16     private final float mDepthZ;
17     // 是否需要扭曲
18     private final boolean mReverse;
19     // 摄像头
20     private Camera mCamera;
21
22     public Rotate3dAnimation(float fromDegrees, float toDegrees, float centerX,
23             float centerY, float depthZ, boolean reverse) {
24         mFromDegrees = fromDegrees;
25         mToDegrees = toDegrees;
26         mCenterX = centerX;
27         mCenterY = centerY;
28         mDepthZ = depthZ;
29         mReverse = reverse;
30     }
31
32     @Override
33     public void initialize(int width, int height, int parentWidth,
34             int parentHeight) {
35         super.initialize(width, height, parentWidth, parentHeight);
36         mCamera = new Camera();
37     }
38
39     // 生成Transformation
40     @Override
41     protected void applyTransformation(float interpolatedTime, Transformation t) {
42         final float fromDegrees = mFromDegrees;
43         // 生成中间角度
44         float degrees = fromDegrees
45                 + ((mToDegrees - fromDegrees) * interpolatedTime);
46
47         final float centerX = mCenterX;
48         final float centerY = mCenterY;
49         final Camera camera = mCamera;
50
51         final Matrix matrix = t.getMatrix();
52
53         camera.save();
54         if (mReverse) {
55             camera.translate(0.0f, 0.0f, mDepthZ * interpolatedTime);
56         } else {
57             camera.translate(0.0f, 0.0f, mDepthZ * (1.0f - interpolatedTime));
58         }
59         camera.rotateY(degrees);
60         // 取得变换后的矩阵
61         camera.getMatrix(matrix);
62         camera.restore();
63
64         matrix.preTranslate(-centerX, -centerY);
65         matrix.postTranslate(centerX, centerY);
66     }
67 }

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，这里我们主要分析applyTransformation函数，其中第一个参数就是通过getTransformation函数传递的差指点，然后我们根据这个差值通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，因此我们首先通过t.getMatrix()取得当前的矩阵，然后通过camera.translate来对矩阵进行平移变换操作，camera.rotateY进行旋转。这样我们就可以很轻松的实现3D旋转效果了。
下面是布局文件main.xml:


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1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
2     xmlns:tools="http://schemas.android.com/tools"
3     android:layout_width="match_parent"
4     android:layout_height="match_parent"
5     android:background="@drawable/main_screen_bg"
6     android:gravity="center_horizontal"
7     android:orientation="vertical"
8     tools:context=".MainActivity" >
9
10     <Button
11         android:id="@+id/next_btn"
12         android:layout_width="wrap_content"
13         android:layout_height="wrap_content"
14         android:layout_marginTop="20dip"
15         android:drawableTop="@drawable/qiangpiao_dropdown"
16         android:text="下一个" />
17
18     <TextView
19         android:id="@+id/tv"
20         android:layout_width="300dip"
21         android:layout_height="300dip"
22         android:layout_gravity="center"
23         android:background="@drawable/call_show_frame_safe"
24         android:gravity="center"
25         android:textColor="#ffffff"
26         android:textSize="15sp" />
27
28 </LinearLayout>

MainActivity的代码如下：


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1 package com.example.textviewtest;
2
3 import android.app.Activity;
4 import android.os.Bundle;
5 import android.view.Menu;
6 import android.view.View;
7 import android.view.animation.AccelerateInterpolator;
8 import android.view.animation.Animation;
9 import android.view.animation.DecelerateInterpolator;
10 import android.widget.Button;
11 import android.widget.TextView;
12
13 public class MainActivity extends Activity {
14     private TextView tv;
15     private Button btn;
16     private int count = 1;
17
18     @Override
19     protected void onCreate(Bundle savedInstanceState) {
20         super.onCreate(savedInstanceState);
21         setContentView(R.layout.activity_main);
22         tv = (TextView) findViewById(R.id.tv);
23         tv.setText(String.valueOf(count));
24         btn = (Button) findViewById(R.id.next_btn);
25         applyRotation(0, 90);
26
27         btn.setOnClickListener(new View.OnClickListener() {
28
29             @Override
30             public void onClick(View v) {
31                 applyRotation(0, 90);
32             }
33         });
34
35     }
36
37     private void applyRotation(float start, float end) {
38         // 计算中心点
39         final float centerX = tv.getWidth() / 2.0f;
40         final float centerY = tv.getHeight() / 2.0f;
41
42         final Rotate3dAnimation rotation = new Rotate3dAnimation(start, end,
43                 centerX, centerY, 310.0f, true);
44         rotation.setDuration(500);
45         rotation.setFillAfter(true);
46         rotation.setInterpolator(new AccelerateInterpolator());
47         // 设置监听
48         rotation.setAnimationListener(new DisplayNextView());
49
50         tv.startAnimation(rotation);
51     }
52
53     private final class DisplayNextView implements Animation.AnimationListener {
54
55         public void onAnimationStart(Animation animation) {
56         }
57
58         // 动画结束
59         public void onAnimationEnd(Animation animation) {
60             tv.post(new SwapViews());
61         }
62
63         public void onAnimationRepeat(Animation animation) {
64         }
65     }
66
67     private final class SwapViews implements Runnable {
68
69         public void run() {
70             final float centerX = tv.getWidth() / 2.0f;
71             final float centerY = tv.getHeight() / 2.0f;
72             Rotate3dAnimation rotation = null;
73
74             tv.requestFocus();
75
76             rotation = new Rotate3dAnimation(90, 0, centerX, centerY, 310.0f,
77                     false);
78             rotation.setDuration(500);
79             rotation.setFillAfter(true);
80             rotation.setInterpolator(new DecelerateInterpolator());
81             // 开始动画
82             tv.startAnimation(rotation);
83             tv.setText(String.valueOf(count++));
84         }
85     }
86
87     @Override
88     public boolean onCreateOptionsMenu(Menu menu) {
89         getMenuInflater().inflate(R.menu.activity_main, menu);
90         return true;
91     }
92
93 }