在Android中，可以通过使用ObjectAnimator和RotationY属性实现3D垂直翻转动画。
Android实现3D垂直翻转动画
在移动应用开发中，动画效果可以极大地提升用户体验，本文将详细介绍如何在Android中实现一个3D垂直翻转动画，使视图（如ImageView）能够像翻书页一样上下翻转，这个动画不仅具有视觉吸引力，还能为用户提供更直观的交互体验，我们将一步步展示如何通过XML文件和Java代码来实现这一动画效果。
动画资源文件定义
我们需要定义两个动画资源文件，分别用于控制图像的缩小、旋转和透明度变化。
card_flip_left_out.xml
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<!-先缩小 -->
<objectAnimator
android:duration="200"
android:propertyName="scaleX"
android:valueFrom="1.0"
android:valueTo="0.8" />
<objectAnimator
android:duration="200"
android:propertyName="scaleY"
android:valueFrom="1.0"
android:valueTo="0.8" />
<!-再旋转 -->
<objectAnimator
android:duration="@integer/card_flip_time_full"
android:interpolator="@android:interpolator/accelerate_decelerate"
android:propertyName="rotationY"
android:startOffset="200"
android:valueFrom="0"
android:valueTo="90" />
<!-同时透明度变化 -->
<objectAnimator
android:duration="@integer/card_flip_time_full"
android:propertyName="alpha"
android:startOffset="200"
android:valueFrom="1.0"
android:valueTo="0.0" />
</set>card_flip_left_in.xml
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<!-立即设置为透明 -->
<objectAnimator
android:duration="0"
android:propertyName="alpha"
android:valueFrom="1.0"
android:valueTo="0.0" />
<!-旋转 -->
<objectAnimator
android:duration="@integer/card_flip_time_full"
android:interpolator="@android:interpolator/accelerate_decelerate"
android:propertyName="rotationY"
android:valueFrom="-90"
android:valueTo="0" />
<!-旋转一半的时间，逐渐显示 -->
<objectAnimator
android:duration="1"
android:propertyName="alpha"
android:startOffset="@integer/card_flip_time_half"
android:valueFrom="0.0"
android:valueTo="1.0" />
<!-最后放大 -->
<objectAnimator
android:duration="200"
android:propertyName="scaleX"
android:startOffset="@integer/card_flip_time_full"
android:valueFrom="0.8"
android:valueTo="1.0" />
<objectAnimator
android:duration="200"
android:propertyName="scaleY"
android:startOffset="@integer/card_flip_time_full"
android:valueFrom="0.8"
android:valueTo="1.0" />
</set>Java代码实现
我们在Activity中编写相应的Java代码来加载并执行这些动画，当用户点击ImageView时，将触发垂直翻转动画，如果需要更换图片，可以在动画结束时进行图片的替换。
ImageFlipActivity.java
package com.example.android.animationsdemo;
import android.animation.Animator;
import android.animation.AnimatorInflater;
import android.animation.AnimatorListenerAdapter;
import android.animation.AnimatorSet;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageView;
public class ImageFlipActivity extends Activity {
private ImageView imageView;
private int clickCount = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_image_flip);
imageView = (ImageView) findViewById(R.id.iv_show);
imageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
playFlipAnimation();
}
});
}
private void playFlipAnimation() {
clickCount++;
AnimatorSet animatorSetOut = (AnimatorSet) AnimatorInflater.loadAnimator(this, R.animator.card_flip_left_out);
final AnimatorSet animatorSetIn = (AnimatorSet) AnimatorInflater.loadAnimator(this, R.animator.card_flip_left_in);
animatorSetOut.setTarget(imageView);
animatorSetIn.setTarget(imageView);
animatorSetOut.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
// 翻转90度之后，换图
if (clickCount % 2 == 0) {
imageView.setImageResource(R.drawable.image1);
} else {
imageView.setImageResource(R.drawable.image2);
}
animatorSetIn.start();
}
});
animatorSetOut.start();
}
}在这个示例中，我们创建了一个ImageFlipActivity类，该类包含一个ImageView和一个点击监听器，当用户点击ImageView时，会依次播放退出和进入的动画，根据点击次数的不同，图片会在两张图片之间切换。
3. 自定义Rotate3dAnimation类（可选）
如果你希望更灵活地控制动画，比如动态设置旋转角度、中心点等，可以实现一个自定义的Rotate3dAnimation类，以下是一个简单的示例：
Rotate3dAnimation.java
package com.example.android.animationsdemo;
import android.graphics.Camera;
import android.graphics.Matrix;
import android.view.animation.Animation;
import android.view.animation.Transformation;
public class Rotate3dAnimation extends Animation {
private final float mFromDegrees;
private final float mToDegrees;
private final float mCenterX;
private final float mCenterY;
private final boolean mReverse;
private Camera mCamera;
public Rotate3dAnimation(float fromDegrees, float toDegrees, float centerX, float centerY, boolean reverse) {
mFromDegrees = fromDegrees;
mToDegrees = toDegrees;
mCenterX = centerX;
mCenterY = centerY;
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) {
final float fromDegrees = mFromDegrees;
final float toDegrees = mToDegrees;
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, centerX + width * 0.5f, -centerY height * 0.5f);
camera.rotateY(fromDegrees);
camera.rotateY(toDegrees fromDegrees);
} else {
camera.translate(0.0f, centerX + width * 0.5f, -centerY height * 0.5f);
camera.rotateY(toDegrees);
camera.rotateY(-fromDegrees); // Rotate in reverse direction for flip back effect
}
camera.getMatrix(matrix); // Apply the rotation to the matrix
camera.restore(); // Restore the camera position before applying next transformation
}
}使用此类时，你可以动态设置旋转的角度、中心点以及是否反向旋转。
Rotate3dAnimation rotate3dAnimation = new Rotate3dAnimation(0, 90, imageView.getWidth() / 2.0f, imageView.getHeight() / 2.0f, false); imageView.startAnimation(rotate3dAnimation);
这种方式提供了更高的灵活性，适用于更复杂的场景，可以在按钮点击事件中启动和停止旋转动画，以下是一个使用按钮控制旋转动画的示例：
public class Test3DRotateActivity extends Activity {
private ImageView image;
private Button start, stop;
private Rotate3dAnimation rotation;
private StartNextRotate startNext;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
image = (ImageView) findViewById(R.id.image);
start = (Button) findViewById(R.id.start);
stop = (Button) findViewById(R.id.stop);
start.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startRotation(0, 360); // 进行360度的旋转
}
});
stop.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
image.clearAnimation(); // 停止当前的动画
}
});
}
private void startRotation(float start, float end) {
final float centerX = image.getWidth() / 2.0f; final float centerY = image.getHeight() / 2.0f; rotation = new Rotate3dAnimation(start, end, centerX, centerY, false); rotation.setDuration(2000); rotation.setFillAfter(true); rotation.setInterpolator(new LinearInterpolator()); startNext = new StartNextRotate(); rotation.setAnimationListener(startNext); image.startAnimation(rotation); } private class StartNextRotate implements Animation.AnimationListener { public void onAnimationEnd(Animation animation) { image.startAnimation(rotation); } public void onAnimationRepeat(Animation animation) {} public void onAnimationStart(Animation animation) {} } } }``此示例展示了如何通过按钮控制3D旋转动画的启动和停止。StartNextRotate内部类用于在动画结束时重新启动动画，从而实现连续旋转的效果，这种方法适用于需要频繁控制动画的场景，如游戏中的动画控制或复杂的用户交互界面，通过结合XML动画资源和自定义动画类，开发者可以根据需求灵活地实现各种复杂的动画效果，合理利用动画监听器（如AnimatorListenerAdapter`）可以在动画的关键帧执行特定操作，进一步增强动画的表现力和互动性，无论是简单的视图转换还是复杂的3D动画，掌握这些技术都能帮助你在Android应用中创造出更加丰富和吸引人的用户体验。