在Android中，如何将数据从类传递到相应的布局/片段文件？

Question

Background : I am writing an Android app, mostly following instructions from the official developer guides . I have some experience with writing Java code but little with xml and Android.

Question : I would like to pass information from variables in my static class "PlaceholderFragment" (which is contained by my "BoardContainer" class) to my fragment layout file "fragment_board.xml". PlaceholderFragment looks like this (mostly unedited after Eclipse created it for me):

public static class PlaceholderFragment extends Fragment {

     public int nButtons = 2;
     public static class PlaceholderFragment extends Fragment {

         private int nButtons = 2;

         public PlaceholderFragment() {
         }

         @Override
         public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_board,
                container, false);
         return rootView;
         }
     }

(other lifecycle callbacks have not yet been implemented).

Now my fragment_board.xml is like this:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.exampletest.MainGame$PlaceholderFragment" >

        <ImageButton
            android:id="@+id/imageButton1"
            android:layout_width="49dp"
            android:layout_height="49dp"
            android:contentDescription="@null"
            android:onClick="buttonPressed" //not yet implemented
            android:src="@drawable/grid2" />

</RelativeLayout>

Here I would like to use the int instance variable nButtons so that, for example, if nButtons==7 , then we get android:src="@drawable/grid7 instead of grid2 , or that the layout file will contain seven ImageButtons instead of just one, and so forth. In other words, how do I make the xml file read and understand the instance variables from its corresponding class?

Answer 1

Unfortunately XML files can not read and understand the variables from its corresponding class . Instead we can alter them programatically by obtaining a handle to components contained within XML files in a class file and altering them like this:

ImageButton imgHandle = (ImageButton) findViewById(R.id.imageButton1);

if(nButtons == 7) {
    imgHandle.setImageResource(R.id.grid7);
}

In a fragment you're going to need to use rootView inside of your onCreateView method:

ImageButton imgHandle = (ImageButton)rootView.findViewById(R.id.imageButton1);