代码为了复用，多写在fragment里，以备需求到处改变位置，比如首页的fragment，希望从单独入口进入。所需操作仅仅需几行代码。

<pre>
public classImageGridActivityextendsFragmentActivity {
private static finalStringTAG="ImageGridActivity";
@Override
protected voidonCreate(Bundle savedInstanceState) {
if(BuildConfig.DEBUG) {
Utils.enableStrictMode();
}

     super.onCreate(savedInstanceState);
     if(getSupportFragmentManager().findFragmentByTag(TAG) ==null) {
     finalFragmentTransaction ft = getSupportFragmentManager().beginTransaction();
     ft.add(android.R.id.content, newImageGridFragment(),TAG);
    ft.commit();
  }

}
}
</pre>