Android实现文字翻转动画的效果

本文实现了Android程序文字翻转动画的小程序，具体代码如下：

先上效果图如下：

要求：

沿Y轴正方向看，数值减1时动画逆时针旋转，数值加1时动画顺时针旋转。

实现动画的具体细节见"RotateAnimation.Java"。为方便查看动画旋转方向，可以将RotateAnimation.DEBUG值设置为true即可。


RotateAnimation参考自APIDemos的Rotate3DAnimation


RotateAnimation的构造函数需有三个参数，分别说明动画组件的中心点位置及旋转方向。


RotateAnimation.initialize()将初始化动画组件及其父容器的宽高；通常亦可进行另外的初始化工作，本例中用于执行对camera进行实例化赋值。


RotateAnimation.applyTransformation()第一个参数为动画的进度时间值，取值范围为[0.0f,1.0f]，第二个参数Transformation记录着动画某一帧中变形的原始数据。该方法在动画的每一帧显示过程中都会被调用。


在翻转过程中，为了避免在动画下半部分时图像为镜面效果影响数字的阅读，应将翻转角度做180度的减法。代码为

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; 
} 

动画翻转到一半后，应更新数字内容。为了得知翻转进度，于RotateAnimation中设计一内部静态接口类"InterpolatedTimeListener"，该接口只有一个方法"interpolatedTime(float interpolatedTime)"可以将动画进度传递给监听发起者。

Java代码如下，XML请根据效果图自行实现：


ActRotate.java

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; 
 
public class ActRotate extends Activity implements OnClickListener, InterpolatedTimeListener { 
  private Button btnIncrease, btnDecrease; 
  private TextView txtNumber; 
  private int number; 
   
  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; 
    } 
  } 
} 

RotateAnimation.java

import android.view.animation.Animation; 
import android.view.animation.Transformation; 
 
public class RotateAnimation extends Animation { 
   
  public static final boolean DEBUG = false; 
   
  public static final boolean ROTATE_DECREASE = true; 
   
  public static final boolean ROTATE_INCREASE = false; 
   
  public static final float DEPTH_Z = 310.0f; 
   
  public static final long DURATION = 800l; 
   
  private final boolean type; 
  private final float centerX; 
  private final float centerY; 
  private Camera camera; 
   
  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); 
    } 
  } 
   
  public static interface InterpolatedTimeListener { 
    public void interpolatedTime(float interpolatedTime); 
  } 
} 

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