动画 -- 按钮 --- 从无到有（中心）

 1 //        sa = new ScaleAnimation(0, 1, 0, 1,100,50);
 2 //        sa = new ScaleAnimation(0, 1, 0, 1, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f)
 3 //        sa.setDuration(1000);
 4         
 5         findViewById(R.id.btnScaleMe).setOnClickListener(new View.OnClickListener() {
 6             @Override
 7             public void onClick(View arg0) {
 8                 arg0.startAnimation(AnimationUtils.loadAnimation(MainActivity.this, R.anim.sa));
 9             }
10         });

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <scale xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:fromXScale="0"
 4     android:toXScale="1"
 5     android:fromYScale="0"
 6     android:toYScale="1"
 7     android:duration="1000"
 8     android:pivotX="50%"
 9     android:pivotY="50%" >
10 
11 </scale>