Android\OPhone动画分析之翻转效果

2011年9月1日10:52:28 发表评论 15 views

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\OPhone动画分析之翻转效果

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AnimationTransformation

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);
		}
	}
}
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