Android实现文字翻转动画的效果

RotateAnimation.applyTransformation()中的：
if (overHalf) { 
  // 翻转过半的情况下，为保证数字仍为可读的文字而非镜面效果的文字，需翻转180度。 
  degree = degree - 180; 
} 

package lab.sodino.rotate; 
 
import lab.sodino.rotate.RotateAnimation.InterpolatedTimeListener; 
import android.app.Activity; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.TextView; 
 
/** 
 * @author Sodino E-mail:sodinoopen@hotmail.com 
 * @version Time：2012-6-27 上午07:32:00 
 */ 
public class ActRotate extends Activity implements OnClickListener, InterpolatedTimeListener { 
  private Button btnIncrease, btnDecrease; 
  private TextView txtNumber; 
  private int number; 
  /** TextNumber是否允许显示最新的数字。 */ 
  private boolean enableRefresh; 
 
  public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
 
    btnIncrease = (Button) findViewById(R.id.btnIncrease); 
    btnDecrease = (Button) findViewById(R.id.btnDecrease); 
    txtNumber = (TextView) findViewById(R.id.txtNumber); 
 
    btnIncrease.setOnClickListener(this); 
    btnDecrease.setOnClickListener(this); 
 
    number = 3; 
    txtNumber = (TextView) findViewById(R.id.txtNumber); 
    txtNumber.setText(Integer.toString(number)); 
  } 
 
  public void onClick(View v) { 
    enableRefresh = true; 
    RotateAnimation rotateAnim = null; 
    float cX = txtNumber.getWidth() / 2.0f; 
    float cY = txtNumber.getHeight() / 2.0f; 
    if (v == btnDecrease) { 
      number--; 
      rotateAnim = new RotateAnimation(cX, cY, RotateAnimation.ROTATE_DECREASE); 
    } else if (v == btnIncrease) { 
      number++; 
      rotateAnim = new RotateAnimation(cX, cY, RotateAnimation.ROTATE_INCREASE); 
    } 
    if (rotateAnim != null) { 
      rotateAnim.setInterpolatedTimeListener(this); 
      rotateAnim.setFillAfter(true); 
      txtNumber.startAnimation(rotateAnim); 
    } 
  } 
 
  @Override 
  public void interpolatedTime(float interpolatedTime) { 
    // 监听到翻转进度过半时，更新txtNumber显示内容。 
    if (enableRefresh && interpolatedTime > 0.5f) { 
      txtNumber.setText(Integer.toString(number)); 
      Log.d("ANDROID_LAB", "setNumber:" + number); 
      enableRefresh = false; 
    } 
  } 
} 

import android.view.animation.Animation; 
import android.view.animation.Transformation; 
 
/** 
 * @author Sodino E-mail:sodinoopen@hotmail.com 
 * @version Time：2012-6-27 上午07:32:00 
 */ 
public class RotateAnimation extends Animation { 
  /** 值为true时可明确查看动画的旋转方向。 */ 
  public static final boolean DEBUG = false; 
  /** 沿Y轴正方向看，数值减1时动画逆时针旋转。 */ 
  public static final boolean ROTATE_DECREASE = true; 
  /** 沿Y轴正方向看，数值减1时动画顺时针旋转。 */ 
  public static final boolean ROTATE_INCREASE = false; 
  /** Z轴上最大深度。 */ 
  public static final float DEPTH_Z = 310.0f; 
  /** 动画显示时长。 */ 
  public static final long DURATION = 800l; 
  /** 图片翻转类型。 */ 
  private final boolean type; 
  private final float centerX; 
  private final float centerY; 
  private Camera camera; 
  /** 用于监听动画进度。当值过半时需更新txtNumber的内容。 */ 
  private InterpolatedTimeListener listener; 
 
  public RotateAnimation(float cX, float cY, boolean type) { 
    centerX = cX; 
    centerY = cY; 
    this.type = type; 
    setDuration(DURATION); 
  } 
 
  public void initialize(int width, int height, int parentWidth, int parentHeight) { 
    // 在构造函数之后、getTransformation()之前调用本方法。 
    super.initialize(width, height, parentWidth, parentHeight); 
    camera = new Camera(); 
  } 
 
  public void setInterpolatedTimeListener(InterpolatedTimeListener listener) { 
    this.listener = listener; 
  } 
 
  protected void applyTransformation(float interpolatedTime, Transformation transformation) { 
    // interpolatedTime:动画进度值，范围为[0.0f,10.f] 
    if (listener != null) { 
      listener.interpolatedTime(interpolatedTime); 
    } 
    float from = 0.0f, to = 0.0f; 
    if (type == ROTATE_DECREASE) { 
      from = 0.0f; 
      to = 180.0f; 
    } else if (type == ROTATE_INCREASE) { 
      from = 360.0f; 
      to = 180.0f; 
    } 
    float degree = from + (to - from) * interpolatedTime; 
    boolean overHalf = (interpolatedTime > 0.5f); 
    if (overHalf) { 
      // 翻转过半的情况下，为保证数字仍为可读的文字而非镜面效果的文字，需翻转180度。 
      degree = degree - 180; 
    } 
    // float depth = 0.0f; 
    float depth = (0.5f - Math.abs(interpolatedTime - 0.5f)) * DEPTH_Z; 
    final Matrix matrix = transformation.getMatrix(); 
    camera.save(); 
    camera.translate(0.0f, 0.0f, depth); 
    camera.rotateY(degree); 
    camera.getMatrix(matrix); 
    camera.restore(); 
    if (DEBUG) { 
      if (overHalf) { 
        matrix.preTranslate(-centerX * 2, -centerY); 
        matrix.postTranslate(centerX * 2, centerY); 
      } 
    } else { 
      //确保图片的翻转过程一直处于组件的中心点位置 
      matrix.preTranslate(-centerX, -centerY); 
      matrix.postTranslate(centerX, centerY); 
    } 
  } 
 
  /** 动画进度监听器。 */ 
  public static interface InterpolatedTimeListener { 
    public void interpolatedTime(float interpolatedTime); 
  } 
}