onSaveInstance的应用

onSaveInstance 是在Activity可能被杀死时候被调用，实际测试多在onPasuse时候发生，

我们可以利用这个回调记录下状态信息，以便于Activity在被杀死后恢复Activity时候，能

正确的恢复界面

@Override
protected void onSaveInstanceState(Bundle outState) {
    outState.putInt(position, mViewPager.getCurrentItem());
    super.onSaveInstanceState(outState);
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home);
    if (savedInstanceState != null) {
        mCurrentIndex = savedInstanceState.getInt(position);
}