public class WelcomeActivity extends Activity {

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_welcome);
  }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent">

  <ImageView
    android:id="@+id/iv_entry"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:scaleType="fitXY"
    android:src="@drawable/welcomimg1"/>

  <View
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/welcomimg_bg"/>


  <TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_marginBottom="100dp"
    android:gravity="center"
    android:text="xialong"
    android:textColor="@android:color/white"
    android:textSize="23sp"/>

  <ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@mipmap/google_logo"
    android:layout_alignParentBottom="true"
    android:layout_marginBottom="60dp"
    android:layout_centerInParent="true"
    android:tint="@android:color/white" />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">

  <gradient
    android:angle="90"
    android:startColor="@color/black"
    android:endColor="@android:color/transparent"
    />

</shape>

public class WelcomeActivity extends Activity {

  @Bind(R.id.iv_entry)
  ImageView mIVEntry;

  private static final int ANIM_TIME = 2000;

  private static final float SCALE_END = 1.15F;

  private static final int[] Imgs={
      R.drawable.welcomimg1,R.drawable.welcomimg2,
      R.drawable.welcomimg3,R.drawable.welcomimg4,
      R.drawable.welcomimg5, R.drawable.welcomimg6,
      R.drawable.welcomimg7,R.drawable.welcomimg8,
      R.drawable.welcomimg9,R.drawable.welcomimg10,
      R.drawable.welcomimg11,R.drawable.welcomimg12,};

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_welcome);
    ButterKnife.bind(this);

    Random random = new Random(SystemClock.elapsedRealtime());//SystemClock.elapsedRealtime() 从开机到现在的毫秒数（手机睡眠(sleep)的时间也包括在内）
    mIVEntry.setImageResource(Imgs[random.nextInt(Imgs.length)]);

    Observable.timer(1000, TimeUnit.MILLISECONDS)
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(new Action1<Long>()
        {

          @Override
          public void call(Long aLong)
          {
            startAnim();
          }
        });
  }


  private void startAnim() {

    ObjectAnimator animatorX = ObjectAnimator.ofFloat(mIVEntry, "scaleX", 1f, SCALE_END);
    ObjectAnimator animatorY = ObjectAnimator.ofFloat(mIVEntry, "scaleY", 1f, SCALE_END);

    AnimatorSet set = new AnimatorSet();
    set.setDuration(ANIM_TIME).play(animatorX).with(animatorY);
    set.start();

    set.addListener(new AnimatorListenerAdapter()
    {

      @Override
      public void onAnimationEnd(Animator animation)
      {

        startActivity(new Intent(WelcomeActivity.this, MainActivity.class));
        WelcomeActivity.this.finish();
      }
    });
  }
}