kankan转载：Android实现3d翻转效果

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：

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;// 是否需要扭曲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;}@Overridepublic void initialize(int width, int height, int parentWidth,int parentHeight) {super.initialize(width, height, parentWidth, parentHeight);mCamera = new Camera();}// 生成Transformation@Overrideprotected 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:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:background="@drawable/main_screen_bg"    android:gravity="center_horizontal"    android:orientation="vertical"    tools:context=".MainActivity" >    <Button        android:id="@+id/next_btn"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_marginTop="20dip"        android:drawableTop="@drawable/qiangpiao_dropdown"        android:text="下一个" />    <TextView        android:id="@+id/tv"        android:layout_width="300dip"        android:layout_height="300dip"        android:layout_gravity="center"        android:background="@drawable/call_show_frame_safe"        android:gravity="center"        android:textColor="#ffffff"        android:textSize="15sp" /></LinearLayout>

MainActivity的代码如下：

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;@Overrideprotected 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() {@Overridepublic 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++));}}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {getMenuInflater().inflate(R.menu.activity_main, menu);return true;}}