Android动画机制与使用技巧（三）Android动画特效

下面来例举一些动画效果实例,让大家熟悉如何通过Android的动画框架来创建赏心悦目的动画

灵动菜单

下图中展示的是灵动菜单的效果图。当用户点击小红点后，弹出菜单，并带有一个缓冲的过渡动画，这也是Google在Material Design中所强调的动画过渡效果





要实现这样一个动画效果,因为它具有交互性，所以肯定不能使用视图动画而必须使用属性动画。其次，只需要针对每个不同的按钮设置不同的动画，并设置相应的插值器就可以实现展开、合拢效果了。代码如下所示：

public class PropertyTest extends Activity implements View.OnClickListener {

private int[] mRes = {R.id.imageView_a, R.id.imageView_b, R.id.imageView_c,
R.id.imageView_d, R.id.imageView_e};
private List<ImageView> mImageViews = new ArrayList<ImageView>();
private boolean mFlag = true;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_custom_anim_instance_property);
for (int i = 0; i < mRes.length; i++) {
ImageView imageView = (ImageView) findViewById(mRes[i]);
imageView.setOnClickListener(this);
mImageViews.add(imageView);
}
}

@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.imageView_a:
if (mFlag) {
startAnim();
} else {
closeAnim();
}
break;
default:
Toast.makeText(PropertyTest.this, "" + v.getId(),
Toast.LENGTH_SHORT).show();
break;
}
}

private void closeAnim() {
ObjectAnimator animator0 = ObjectAnimator.ofFloat(mImageViews.get(0),
"alpha", 0.5F, 1F);
ObjectAnimator animator1 = ObjectAnimator.ofFloat(mImageViews.get(1),
"translationY", 200F, 0);
ObjectAnimator animator2 = ObjectAnimator.ofFloat(mImageViews.get(2),
"translationX", 200F, 0);
ObjectAnimator animator3 = ObjectAnimator.ofFloat(mImageViews.get(3),
"translationY", -200F, 0);
ObjectAnimator animator4 = ObjectAnimator.ofFloat(mImageViews.get(4),
"translationX", -200F, 0);
AnimatorSet set = new AnimatorSet();
set.setDuration(500);
set.setInterpolator(new BounceInterpolator());
set.playTogether(animator0, animator1, animator2, animator3, animator4);
set.start();
mFlag = true;
}

private void startAnim() {
ObjectAnimator animator0 = ObjectAnimator.ofFloat(
mImageViews.get(0),
"alpha",
1F,
0.5F);
ObjectAnimator animator1 = ObjectAnimator.ofFloat(
mImageViews.get(1),
"translationY",
200F);
ObjectAnimator animator2 = ObjectAnimator.ofFloat(
mImageViews.get(2),
"translationX",
200F);
ObjectAnimator animator3 = ObjectAnimator.ofFloat(
mImageViews.get(3),
"translationY",
-200F);
ObjectAnimator animator4 = ObjectAnimator.ofFloat(
mImageViews.get(4),
"translationX",
-200F);
AnimatorSet set = new AnimatorSet();
set.setDuration(500);
set.setInterpolator(new BounceInterpolator());
set.playTogether(
animator0,
animator1,
animator2,
animator3,
animator4);
set.start();
mFlag = false;
}
}

计时器动画

下面通过ValueAnimator来实现计时器的动画效果,当用户点击后数字会不断增加,效果如下所示:





实现原理就是借助ValueAnimator来实现数字的不断增加,并将值设置给TextView,代码如下所示:

public void tvTimer(final View view) {
ValueAnimator valueAnimator = ValueAnimator.ofInt(0, 100);
valueAnimator.addUpdateListener(
new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
((TextView) view).setText("$ " +
(Integer) animation.getAnimatedValue());
}
});
valueAnimator.setDuration(3000);
valueAnimator.start();
}

下拉展开动画

下面再通过ValueAnimator来实现一个下拉展开动画的效果,当点击一个View时的时候，显示下面隐藏的一个View，并且让View在显示时增加一个动画效果，因此需要让隐藏的View的高度不断变化，但不是迅速增加到目标值。所以使用ValueAnimator来模拟这个过程。代码如下：

public class DropTest extends Activity {

private LinearLayout mHiddenView;
private float mDensity;
private int mHiddenViewMeasuredHeight;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_custom_anim_instance_drop);
mHiddenView = (LinearLayout) findViewById(R.id.hidden_view);
// 获取像素密度
mDensity = getResources().getDisplayMetrics().density;
// 获取布局的高度
mHiddenViewMeasuredHeight = (int) (mDensity * 40 + 0.5);
}

public void llClick(View view) {
if (mHiddenView.getVisibility() == View.GONE) {
// 打开动画
animateOpen(mHiddenView);
} else {
// 关闭动画
animateClose(mHiddenView);
}
}

private void animateOpen(final View view) {
view.setVisibility(View.VISIBLE);
ValueAnimator animator = createDropAnimator(
view,
0,
mHiddenViewMeasuredHeight);
animator.start();
}

private void animateClose(final View view) {
int origHeight = view.getHeight();
ValueAnimator animator = createDropAnimator(view, origHeight, 0);
animator.addListener(new AnimatorListenerAdapter() {
public void onAnimationEnd(Animator animation) {
view.setVisibility(View.GONE);
}
});
animator.start();
}

//通过ValueAnimator来创建一个从0到目标值的数值发生器,并由此来改变View的布局属性
private ValueAnimator createDropAnimator(
final View view, int start, int end) {
ValueAnimator animator = ValueAnimator.ofInt(start, end);
animator.addUpdateListener(
new ValueAnimator.AnimatorUpdateListener() {

@Override
public void onAnimationUpdate(ValueAnimator valueAnimator) {
int value = (Integer) valueAnimator.getAnimatedValue();
ViewGroup.LayoutParams layoutParams =
view.getLayoutParams();
layoutParams.height = value;
view.setLayoutParams(layoutParams);
}
});
return animator;
}
}

代码下载