Charlie Calvert on Elvenware

Writing Code and Prose on Computers

Elvenware

ViewBinder

If you are working with a database or some other ContentProvider, you may need to format the strings that you display in a TextViews. To do this, you can create a class that implements the SimpleCursorAdapter.ViewBinder interface. You can attach a ViewBinder to an adapter with a single line of code. In this example, I first create an adapter, and then write one additional line of code to associate a ViewBinder with the adapter:

SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.basic_list, cursor, fields, views);
adapter.setViewBinder(new MyViewBinder());

 The ViewBinder interface defines a single method called setViewValue. If the ViewBinder has been associated with an adapter, then each field held by the adapter's Cursor is passed to this method:

package com.ai.android.book.provider;

import java.util.Date;
import android.database.Cursor;
import android.text.format.DateUtils;
import android.view.View;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;

public class MyViewBinder implements SimpleCursorAdapter.ViewBinder 
{
	public boolean setViewValue(View view, Cursor cursor, int columnIndex) 
	{
		if (columnIndex == cursor.getColumnIndex(BookProviderMetaData.BookTableMetaData.MODIFIED_DATE)) 
		{			
			long timestamp = cursor.getLong(columnIndex); 
			CharSequence time = DateUtils.getRelativeTimeSpanString(view.getContext(), timestamp); 
			((TextView) view).setText(time); 
			return true;
		} 
		else 
		{
			return false;
		}		
	}
}

View's are a base class for Widgets such as TextViews, Buttons and EditTexts. As you can see, a View, a Cursor, the index of currently selected Column are all passed to setViewValue().

The code shown here first checks if the View being passed in is associated with the Date field that we want to format as text. If it is, code is written to convert the Date field into a string, and then the View is used to display the text to the user. The View might be a TextView that we placed in our layout, usually as a part of a list of some kind. For instance, if you are displaying the fields from your table in a custom ListView that you defined in a layout, then the TextView will be one of the TextViews you defined in your XML file.

You might also want to look at the other ViewBinders for classes like SimpleAdapter or SimpleCursorTreeAdapter.