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The and action bar are only available on Android 3.0 and later. To support older platforms, you can fall back to the search dialog. The search dialog is a system provided UI that overlays on top of your application when invoked. http://blog.csdn.net/sergeycao

Set Minimum and Target API levels

To setup the search dialog, first declare in your manifest that you want to support older devices, but want to target Android 3.0 or later versions. When you do this, your application automatically uses the action bar on Android 3.0 or later and uses the traditional menu system on older devices:

   
   
    ...
   

Provide the Search Dialog for Older Devices

To invoke the search dialog on older devices, call whenever a user selects the search menu item from the options menu. Because Android 3.0 and higher devices show the in the action bar (as demonstrated in the first lesson), only versions older than 3.0 call when the user selects the search menu item.

@Overridepublic boolean onOptionsItemSelected(MenuItem item) {    switch (item.getItemId()) {        case R.id.search:            onSearchRequested();            return true;        default:            return false;    }}

Check the Android Build Version at Runtime

At runtime, check the device version to make sure an unsupported use of does not occur on older devices. In our example code, this happens in the method:

@Overridepublic boolean onCreateOptionsMenu(Menu menu) {    MenuInflater inflater = getMenuInflater();    inflater.inflate(R.menu.options_menu, menu);    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {        SearchManager searchManager =                (SearchManager) getSystemService(Context.SEARCH_SERVICE);        SearchView searchView =                (SearchView) menu.findItem(R.id.search).getActionView();        searchView.setSearchableInfo(                searchManager.getSearchableInfo(getComponentName()));        searchView.setIconifiedByDefault(false);    }    return true;}