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利用Android的ApiDemos的Rotate3dAnimation實現了個圖片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::
Rotate3dAnimation.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,用于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,繼續用于下次的計算 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
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <Button android:id="@+id/start" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="開始" /> <Button android:id="@+id/stop" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="結束" /> <ImageView android:id="@+id/image" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/t1" /> </LinearLayout>
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,之后從Camera中取出完成該動畫的Matrix,然后畫我們的物體,這個就是這個3D動畫實現的原理。
具體的解釋見代碼中注釋部分,重點說一下Rotate3dAnimation.java中的
matrix.preTranslate(-centerX, -centerY); matrix.postTranslate(centerX, centerY);
由于旋轉是以(0,0)為中心的,所以為了把界面的中心與(0,0)對齊,就要preTranslate(-centerX, -centerY),旋轉完成后,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軸旋轉了。
你還可以把上面代碼改成
matrix.preTranslate(-centerX, 0); matrix.postTranslate(centerX, 0);
看有什么不同效果。
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