The document provides a tutorial on how to use the Android file manager to list root directories and files. It includes code snippets for retrieving the application directory, absolute paths, and checking directory entries. Additionally, it introduces basic building blocks of an Android application interface using XML layout and Java code.

1. Develop on Android
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Lesson : The list of root directories

2. The list of the root directories
• In this lesson, you will learn to use the file manager to list
the list of root files.
• For this, you will use File and listFiles.

3. The list of the root directories
• In order to know the path to the application directory, use the
method getFilesDir().
File file = this.getFilesDir();
• In order to know the absolute path to a directory, use the method
getAbsolutePath() :
String text = "Local storage : " + file.getAbsolutePath();

4. The list of the root directories
• To get the list of directories and files at the root, use the
method listRoots().
File[] files = File.listRoots();

5. The list of the root directories
• To know if an entry of a directory is a directory, use the method
isDirectory() :
if (file.isDirectory()) {
}
• To get he list of the files and directories of a directory, use the
method listFiles() :
rootFile.listFiles()

6. Layout main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<EditText
android:id="@+id/et_output"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10" >
</EditText>
</LinearLayout>

7. File Main.java
public class Main extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
EditText et_output = (EditText)findViewById (R.id.et_output);
File file = this.getFilesDir();
String text = "Local storage : " + file.getAbsolutePath();
File[] files = File.listRoots();
for (int i = 0; i < files.length; i++){
String filename = files[i].getAbsolutePath();
filename.replaceAll (new String(new byte[]{0}), "");
File rootFile = new File (filename);
if (file.isDirectory()) {
for (int j = 0; j < rootFile.listFiles().length; j++){
text += rootFile.listFiles() [j].getAbsolutePath() + "rn";
}
}
}
et_output.setText (text);
}
}

8. Test on your mobile
File_ListRoots

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