/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.helloanimation.threed;

import android.view.animation.Animation;
import android.view.animation.Transformation;
import android.graphics.Camera;
import android.graphics.Matrix;

/**
 * An animation that rotates the view on the Y axis between two specified
 * angles.
 * This animation also adds a translation on the Z axis (depth) to improve the
 * effect.
 */
public class Rotate3dAnimation extends Animation {
	private final float mFromDegrees;
	private final float mToDegrees;
	private final float mCenterX;
	private final float mCenterY;
	private final float mDepthZ;
	private final boolean mReverse;
	private Camera mCamera;

	// a Camera can translate a view in the third dimension by giving it a
	// perspective (Projection in 2D) and then allows you the same interms of
	// rotation across any axis.

	/**
	 * Creates a new 3D rotation on the Y axis. The rotation is defined by its
	 * start angle and its end angle. Both angles are in degrees. The rotation
	 * is performed around a center point on the 2D space, definied by a pair
	 * of X and Y coordinates, called centerX and centerY. When the animation
	 * starts, a translation on the Z axis (depth) is performed. The length
	 * of the translation can be specified, as well as whether the translation
	 * should be reversed in time.
	 * 
	 * @param fromDegrees
	 *            the start angle of the 3D rotation
	 * @param toDegrees
	 *            the end angle of the 3D rotation
	 * @param centerX
	 *            the X center of the 3D rotation
	 * @param centerY
	 *            the Y center of the 3D rotation
	 * @param reverse
	 *            true if the translation should be reversed, false otherwise
	 */
	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();
	}

	@Override
	protected void applyTransformation(float interpolatedTime, Transformation t) {

		// 根据时间和起始终止的角度值，插值算出当前的角度：degrees
		final float fromDegrees = mFromDegrees;
		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);
		camera.getMatrix(matrix);
		camera.restore();

		//pre:
		matrix.preTranslate(-centerX, -centerY);
		//post:
		matrix.postTranslate(centerX, centerY);
	}
}