Android: how to make keyboard enter button say "Search" and handle its click?

In the layout set your input method options to search.

<EditText
    android:imeOptions="actionSearch" 
    android:inputType="text" />

In the java add the editor action listener.

editText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
    @Override
    public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
        if (actionId == EditorInfo.IME_ACTION_SEARCH) {
            performSearch();
            return true;
        }
        return false;
    }
});

In xml file, put imeOptions="actionSearch" and inputType="text", maxLines="1":

<EditText
    android:id="@+id/search_box"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="@string/search"
    android:imeOptions="actionSearch"
    android:inputType="text"
    android:maxLines="1" />

Hide keyboard when user clicks search. Addition to Robby Pond answer

private void performSearch() {
    editText.clearFocus();
    InputMethodManager in = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
    in.hideSoftInputFromWindow(editText.getWindowToken(), 0);
    //...perform search
}