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Android\OPhone动画分析之翻转效果
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看到很多人在问如何实现三维的翻转效果,所以今天在这里简单的给大家分析一下,其实在APIDemo中就有这样一个例子,那么我们就以其为例来学习Android中的翻转动画效果的实现,首先看一下运行效果如下图所示。

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:

    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;  
        }  
     
        @Override 
        public void initialize(int width, int height, int parentWidth, int parentHeight) {  
            super.initialize(width, height, parentWidth, parentHeight);  
            mCamera = new Camera();  
        }  
        //生成Transformation  
        @Override 
        protected 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,该例子的原意是通过一个列表来供用户选择要实现翻转的图像,所以我们分析至少需要定义两个控 件:ListView和ImageView(要翻转的图像),主界面的xml布局定义如下所示。

    <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" 
        android:id="@+id/container" 
        android:layout_width="match_parent" 
        android:layout_height="match_parent"> 
     
        <ListView 
            android:id="@android:id/list" 
            android:persistentDrawingCache="animation|scrolling" 
            android:layout_width="match_parent" 
            android:layout_height="match_parent" 
            android:layoutAnimation="@anim/layout_bottom_to_top_slide" /> 
     
        <ImageView 
            android:id="@+id/picture" 
            android:scaleType="fitCenter" 
            android:layout_width="match_parent" 
            android:layout_height="match_parent" 
            android:visibility="gone" /> 
     
    </FrameLayout> 

然后准备好需要的资源,在onCreate函数中准备好 ListView和ImageView,因为要旋转所以我们需要保存视图的缓存信息,通过 setPersistentDrawingCache(ViewGroup.PERSISTENT_ANIMATION_CACHE);可以设置该功能, 当我们选择列表中的图像资源后在onItemClick中将选择的资源Id对应的图像设置到ImageView中,然后通过applyRotation来 启动一个动画,前面有了Rotate3dAnimation的实现,我们要完成3D翻转动画就很简单,直接构建一个Rotate3dAnimation对 象,设置其属性(包括动画监听),这里将动画的监听设置为DisplayNextView,可以用来显示下一个视图,在其中的动画结束监听 (onAnimationEnd)中,通过一个县城SwapViews来交换两个画面,交换过程则是设置ImageView和ListView的显示相关 属性,并构建一个Rotate3dAnimation对象,对另一个界面进行旋转即可,然后启动动画,整个转换过程实际上就是将第一个界面从0度转好90 度,然后就爱你过第二个界面从90度转到0度,这样就形成了一个翻转动画,完整代码如下,我们也加入了一些必要的注解,大家也可以参考APIDemo中的 Transition3d例子。

    public class Transition3d extends Activity implements 
            AdapterView.OnItemClickListener, View.OnClickListener {  
        //照片列表  
        private ListView mPhotosList;  
        private ViewGroup mContainer;  
        private ImageView mImageView;  
     
        // 照片的名字,用于显示在list中  
        private static final String[] PHOTOS_NAMES = new String[] {  
                "Lyon",  
                "Livermore",  
                "Tahoe Pier",  
                "Lake Tahoe",  
                "Grand Canyon",  
                "Bodie" 
        };  
     
        // 资源id  
        private static final int[] PHOTOS_RESOURCES = new int[] {  
                R.drawable.photo1,  
                R.drawable.photo2,  
                R.drawable.photo3,  
                R.drawable.photo4,  
                R.drawable.photo5,  
                R.drawable.photo6  
        };  
     
        @Override 
        protected void onCreate(Bundle savedInstanceState) {  
            super.onCreate(savedInstanceState);  
     
            setContentView(R.layout.animations_main_screen);  
     
            mPhotosList = (ListView) findViewById(android.R.id.list);  
            mImageView = (ImageView) findViewById(R.id.picture);  
            mContainer = (ViewGroup) findViewById(R.id.container);  
     
            // 准备ListView  
            final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,  
                    android.R.layout.simple_list_item_1, PHOTOS_NAMES);  
     
            mPhotosList.setAdapter(adapter);  
            mPhotosList.setOnItemClickListener(this);  
     
            // 准备ImageView  
            mImageView.setClickable(true);  
            mImageView.setFocusable(true);  
            mImageView.setOnClickListener(this);  
     
            //设置需要保存缓存  
            mContainer.setPersistentDrawingCache(ViewGroup.PERSISTENT_ANIMATION_CACHE);  
        }  
     
        /**  
         * Setup a new 3D rotation on the container view.  
         *  
         * @param position the item that was clicked to show a picture, or -1 to show the list  
         * @param start the start angle at which the rotation must begin  
         * @param end the end angle of the rotation  
         */ 
        private void applyRotation(int position, float start, float end) {  
            // 计算中心点  
            final float centerX = mContainer.getWidth() / 2.0f;  
            final float centerY = mContainer.getHeight() / 2.0f;  
     
            // Create a new 3D rotation with the supplied parameter  
            // The animation listener is used to trigger the next animation  
            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(position));  
     
            mContainer.startAnimation(rotation);  
        }  
     
        public void onItemClick(AdapterView parent, View v, int position, long id) {  
            // 设置ImageView  
            mImageView.setImageResource(PHOTOS_RESOURCES[position]);  
            applyRotation(position, 0, 90);  
        }  
        //点击图像时,返回listview  
        public void onClick(View v) {  
            applyRotation(-1, 180, 90);  
        }  
     
        /**  
         * This class listens for the end of the first half of the animation.  
         * It then posts a new action that effectively swaps the views when the container  
         * is rotated 90 degrees and thus invisible.  
         */ 
        private final class DisplayNextView implements Animation.AnimationListener {  
            private final int mPosition;  
     
            private DisplayNextView(int position) {  
                mPosition = position;  
            }  
     
            public void onAnimationStart(Animation animation) {  
            }  
            //动画结束  
            public void onAnimationEnd(Animation animation) {  
                mContainer.post(new SwapViews(mPosition));  
            }  
     
            public void onAnimationRepeat(Animation animation) {  
            }  
        }  
     
        /**  
         * This class is responsible for swapping the views and start the second  
         * half of the animation.  
         */ 
        private final class SwapViews implements Runnable {  
            private final int mPosition;  
     
            public SwapViews(int position) {  
                mPosition = position;  
            }  
     
            public void run() {  
                final float centerX = mContainer.getWidth() / 2.0f;  
                final float centerY = mContainer.getHeight() / 2.0f;  
                Rotate3dAnimation rotation;  
                  
                if (mPosition > -1) {  
                    //显示ImageView  
                    mPhotosList.setVisibility(View.GONE);  
                    mImageView.setVisibility(View.VISIBLE);  
                    mImageView.requestFocus();  
     
                    rotation = new Rotate3dAnimation(90, 180, centerX, centerY, 310.0f, false);  
                } else {  
                    //返回listview  
                    mImageView.setVisibility(View.GONE);  
                    mPhotosList.setVisibility(View.VISIBLE);  
                    mPhotosList.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  
                mContainer.startAnimation(rotation);  
            }  
        }  
     
    } 

本文出自 “yarin's blog™” 博客

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