利用Android的ApiDemos的Rotate3dAnimation實現瞭個圖片3D旋轉的動畫，圍繞Y軸進行旋轉，還可以實現Z軸的縮放。點擊開始按鈕開始旋轉，點擊結束按鈕停止旋轉。
代碼如下：:vcD4KPHA+Um90YXRlM2RBbmltYXRpb24uamF2YTwvcD4KPHByZSBjbGFzcz0=”brush:java;”>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;
/**
* 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) {
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();
//保存一次camera初始狀態，用於restore()
camera.save();
if (mReverse) {
camera.translate(0.0f, 0.0f, mDepthZ * interpolatedTime);
} else {
camera.translate(0.0f, 0.0f, mDepthZ * (1.0f – interpolatedTime));
}
//圍繞Y軸旋轉degrees度
camera.rotateY(degrees);
//行camera中取出矩陣，賦值給matrix
camera.getMatrix(matrix);
//camera恢復到初始狀態，繼續用於下次的計算
camera.restore();
matrix.preTranslate(-centerX, -centerY);
matrix.postTranslate(centerX, centerY);
}
}
Test3DRotateActivity.java
public class Test3DRotateActivity extends Activity {
/** Called when the activity is first created. */
private final String TAG="Test3DRotateActivity";
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 OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
//進行360度的旋轉
startRotation(0,360);
}
});
stop.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
image.clearAnimation();
}
});
}
private void startRotation(float start, float end) {
// 計算中心點
final float centerX = image.getWidth() / 2.0f;
final float centerY = image.getHeight() / 2.0f;
Log.d(TAG, "centerX="+centerX+", centerY="+centerY);
// Create a new 3D rotation with the supplied parameter
// The animation listener is used to trigger the next animation
//final Rotate3dAnimation rotation =new Rotate3dAnimation(start, end, centerX, centerY, 310.0f, true);
//Z軸的縮放為0
rotation =new Rotate3dAnimation(start, end, centerX, centerY, 0f, true);
rotation.setDuration(2000);
rotation.setFillAfter(true);
//rotation.setInterpolator(new AccelerateInterpolator());
//勻速旋轉
rotation.setInterpolator(new LinearInterpolator());
//設置監聽
startNext = new StartNextRotate();
rotation.setAnimationListener(startNext);
image.startAnimation(rotation);
}
private class StartNextRotate implements AnimationListener{
public void onAnimationEnd(Animation animation) {
// TODO Auto-generated method stub
Log.d(TAG, "onAnimationEnd......");
image.startAnimation(rotation);
}
public void onAnimationRepeat(Animation animation) {
// TODO Auto-generated method stub
}
public void onAnimationStart(Animation animation) {
// TODO Auto-generated method stub
}
}
}
main.xml
代碼中用Camera來實現動畫，Camera就是一個攝像機，一個物體原地不動，我們帶著攝像機按設定的角度進行移動，之後從Camera中取出完成該動畫的Matrix，然後畫我們的物體，這個就是這個3D動畫實現的原理。
具體的解釋見代碼中註釋部分，重點說一下Rotate3dAnimation.java中的
matrix.preTranslate(-centerX, -centerY);
matrix.postTranslate(centerX, centerY);
由於旋轉是以(0,0)為中心的,所以為瞭把界面的中心與(0,0)對齊,就要preTranslate(-centerX, -centerY),旋轉完成後,調用postTranslate(centerX, centerY),再把圖片移回來,這樣看到的動畫效果就是activity的界面圖片從在centerX為中心繞Y軸旋轉瞭。
你還可以把上面代碼改成
matrix.preTranslate(-centerX, 0);
matrix.postTranslate(centerX, 0);
看有什麼不同效果。