DUCK Examples and Demos Getting Started

Files Example

This example shows how to access files on external storage media.

A screenshot of the application.

We begin by declaring a unique namespace for the package we are creating. This is typically based on the reversed form of a domain name and should be unique to this package.

__package__ = "com.example.files"

We also import the classes that will be needed by the application. The most relevant one is Environment, which gives us access to constants that describe the locations of resources.

from java.io import File
from android.app import Activity
from android.os import Bundle, Environment
from android.view import ViewGroup
from android.widget import LinearLayout, ListView, TextView

We also import an adapter class that will let us expose arrays of strings to views.

from serpentine.adapters import StringArrayAdapter

The FilesActivity class is derived from the standard Activity class and represents the application.

class FilesActivity(Activity):

    def __init__(self):
    
        Activity.__init__(self)

The initialisation method only needs to call the base class's implementation.

The onCreate method sets up the user interface, creating and populating a vertical layout and making it the main content view of the activity.

    @args(void, [Bundle])
    def onCreate(self, bundle):
    
        Activity.onCreate(self, bundle)
        
        layout = LinearLayout(self)
        layout.setLayoutParams(ViewGroup.LayoutParams(
            ViewGroup.LayoutParams.MATCH_PARENT,
            ViewGroup.LayoutParams.WRAP_CONTENT))
        layout.setOrientation(LinearLayout.VERTICAL)

We obtain a constant that describes the location of images.

        t = Environment.DIRECTORY_DCIM

Using the constant, we obtain a File object that corresponds to a directory on the filing system. We pass this to the addList method to populate the layout with TextViews that show the names of files in the directory.

        externalDir = self.getExternalFilesDir(t)
        self.addList(externalDir, layout)

This time we obtain a File object for a different external storage location that we pass to the same method as before, adding more TextViews to the layout.

        envDir = Environment.getExternalStoragePublicDirectory(t)
        self.addList(envDir, layout)
        
        self.setContentView(layout)

This custom method creates a ListView instance for each directory supplied by our onCreate method that contains files, or a placeholder TextView widget if no files are found. The view created is added to the specified layout.

    @args(void, [File, ViewGroup])
    def addList(self, directory, layout):
    
        textView = TextView(self)
        textView.setText(directory.getAbsolutePath())
        textView.setTextColor(0xffff0000)
        layout.addView(textView)
        
        files = directory.list()
        
        if len(files) == 0:
            textView = TextView(self)
            textView.setText("(No files)")
            layout.addView(textView)
        else:
            adapter = StringArrayAdapter(files)
            
            listView = ListView(self)
            listView.setAdapter(adapter)
            layout.addView(listView)

Files