android api Demo之自定义Animation，实现3D旋转效果

android的API Demo提供了很多有趣+有用的Demo，本系列将学习基于4.4.2版本的API，其中涉及到的代码大部分是出于android 自带的Demo，本人根据自己的学习、理解，加以注释。

public class Rotate3DAnimation extends Animation {
	private final float mFromDegrees;//开始角度
    private final float mToDegrees;//结束角度
    private final float mCenterX;//中心X点
    private final float mCenterY;//中心Y点
    private final float mDepthZ;//深度Z，越大缩放越明显
    private final boolean mReverse;//是否相反,true:视角由近到远 false:视角由远到近(缩放效果)
    private Camera mCamera;
   
	public Rotate3DAnimation(float mFromDegrees, float mToDegrees,
			float mCenterX, float mCenterY, float mDepthZ, boolean mReverse) {
		super();
		this.mFromDegrees = mFromDegrees;
		this.mToDegrees = mToDegrees;
		this.mCenterX = mCenterX;
		this.mCenterY = mCenterY;
		this.mDepthZ = mDepthZ;
		this.mReverse = mReverse;
	}
	
	
	@Override
	public void initialize(int width, int height, int parentWidth,
			int parentHeight) {
		super.initialize(width, height, parentWidth, parentHeight);
		mCamera=new Camera();
		// 动画时间
		setDuration(500);
		// 动画完成后保持完成的状态
		setFillAfter(true);
		
	}
	//当动画开始时，会不断调用applyTransformation,这个过程是动态的，不断在变化
    //interpolatedTime 代表当前方法掉用时，动画进行的一个时间点，这个值的范围是0到1，也就是说动画刚开始的时候
	//传进来的interpolatedTime为0，动画进行中的时候，传进来的是0到1之间的小数，动画结束的时候传进来的是1。
	@Override
	protected void applyTransformation(float interpolatedTime, Transformation t) {
		final float fromDegrees = mFromDegrees;
		//计算每次变化的角度
		float degrees = fromDegrees + ((mToDegrees - fromDegrees) * interpolatedTime);
		final float centerX = mCenterX;
	    final float centerY = mCenterY;
	    final Camera camera = mCamera;
	    //获取原始矩阵
	    final Matrix matrix = t.getMatrix();
	    
	    camera.save();
	    if(mReverse){//视图离镜头越来越远，即缩小视角
	    	camera.translate(0.0f, 0.0f, mDepthZ*interpolatedTime);
	    }else{//视图离镜头越来越近，即放大视角
	    	camera.translate(0.0f, 0.0f, mDepthZ*(1.0f-interpolatedTime));
	    }
	    //以Y轴为旋转中心轴，旋转degrees角度
	    camera.rotateY(degrees);
	    camera.getMatrix(matrix);
	    camera.restore();
	    //pre是前乘，参数给出的矩阵乘以当前的矩阵。在旋转之前，先平移(-centerX, -centerY)
	    matrix.preTranslate(-centerX, -centerY);
	    //post是后乘，当前的矩阵乘以参数给出的矩阵。旋转之后，在平移(centerX, centerY)
	    matrix.postTranslate(centerX, centerY);
	    //总的来说，就是在绕Y轴旋转之前，先把旋转中心点从(0,0)移到(centerX,centerY)，然后以Y轴为轴线，
	    //(centerX,centerY)为轴心旋转degrees后，将中心点复原为(0,0),这样看起来就是以视图的中心，绕Y轴旋转了。
	}
}

Rotate3DAnimation是封装了3D旋转动画效果的类，注释是我对其的理解

public class Transition3dActivity extends Activity implements
		OnItemClickListener, OnClickListener {
	private ListView mPhotosList;
	private ViewGroup mContainer;
	private ImageView mImageView;

	// Names of the photos we show in the list
	private static final String[] PHOTOS_NAMES = new String[] { "Lyon",
			"Livermore", "Tahoe Pier", "Lake Tahoe", "Grand Canyon", "Bodie" };
	// 显示的图片资源
	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) {
		// TODO Auto-generated method stub
		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);

		// Prepare the ListView
		final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
				android.R.layout.simple_list_item_1, PHOTOS_NAMES);

		mPhotosList.setAdapter(adapter);
		mPhotosList.setOnItemClickListener(this);

		// Prepare the ImageView
		mImageView.setClickable(true);
		mImageView.setFocusable(true);
		mImageView.setOnClickListener(this);

		// Since we are caching large views, we want to keep their cache
		// between each animation(缓存)
		mContainer.setPersistentDrawingCache(ViewGroup.PERSISTENT_ANIMATION_CACHE);
	}

	/**
	 * 3D旋转视图 2014-11-13 下午1:31:06
	 * 
	 * @param position
	 *            item位置
	 * @param start
	 *            开始角度
	 * @param end
	 *            结束角度
	 * @TODO
	 */
	private void applyRotation(int position, float start, float end) {
		// 获取视图中心点
		float centerX = mContainer.getWidth() / 2.0f;
		float centerY = mContainer.getHeight() / 2.0f;
		// 构建3D旋转动画对象
		final Rotate3DAnimation rotation = new Rotate3DAnimation(start, end,
				centerX, centerY, 310.0f, true);
		// 设置动画速度变化曲线为加速
		rotation.setInterpolator(new AccelerateInterpolator());
		// 动画监听
		rotation.setAnimationListener(new DisplayNextView(position));

		mContainer.startAnimation(rotation);
	}

	@Override
	public void onItemClick(AdapterView<?> parent, View view, int position,
			long id) {
		mImageView.setImageResource(PHOTOS_RESOURCES[position]);
		// 每次点击item时，将mContainer根布局旋转角度从0到90(可将自己的左手正面朝上当作mContainer容器，逆时针旋转90度的过程)---①
		applyRotation(position, 0, 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) {
		}

		public void onAnimationEnd(Animation animation) {
			// 当ListView动画结束时，ListView隐藏，不显示，此时图片开始显示
			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) {// 点击的是item
				mPhotosList.setVisibility(View.GONE);
				mImageView.setVisibility(View.VISIBLE);
				mImageView.requestFocus();
				// 由于第①步的旋转，此时mContainer是处于90度的，再次旋转90度，从90到180，
				// 等于此时的mContainer已经旋转了180度，处于“背面”向上-----②
				// (相当于左手手心起始向右，向下转动的过程，直至手心向下，手背在上面，而这个过程正是图片从无到有,ListView从有到无的过程)
				rotation = new Rotate3DAnimation(90, 180, centerX, centerY,
						310.0f, false);
			} else {// 点击的是ImageView(mPosition=-1)
				mImageView.setVisibility(View.GONE);
				mPhotosList.setVisibility(View.VISIBLE);
				mPhotosList.requestFocus();
				// 由于第③步，此时的mContainer处于90度，然后再次旋转90度，从90到0，复原了初始状态(左手手心向右顺时针旋转90度至手心向上的原始状态)
				rotation = new Rotate3DAnimation(90, 0, centerX, centerY,
						310.0f, false);
			}
			// 设置动画速度变化曲线为减速
			rotation.setInterpolator(new DecelerateInterpolator());
			mContainer.startAnimation(rotation);
		}
	}

	@Override
	public void onClick(View v) {
		// 由于第②步的结果，使mContainer处于旋转了180的状态，当点击ImageView时，使mContainer状态复原回去
		// 从180到旋转到90-----③(当点击图片时，左手旋转的动作是一个相反的过程，即从左手手心向下，手背在上的状态，顺时针旋转90度至手心向右)
		applyRotation(-1, 180, 90);
	}
}

xml布局animations_main_screen.xml

<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"
        />

    <ImageView
        android:id="@+id/picture"
        android:scaleType="fitCenter"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="gone" />

</FrameLayout>

效果图：