Use dynamically placed editable elements in Android Table Layout

It may be very useful if in an activity of an Android application, the user is allowed to define dynamically the number of elements in a Table Layout. These elements maybe editable like Check Boxes, Edit Text fields or Spinners. After the user interacts with these elements the data are passed to the next activity generating some results.
Here is an example of an application in the first activity of which the user is allowed to define the number of CheckBoxes that will appear in a Table Layouts in the next activity. Then, the user may check some boxes and this will affect the text appearing in the final activity. The text in the final activity is a binary string where 1 stands for a checked corresponding CheckBox and 0 for an unchecked one.
I must give credit to the useful ideas found in the answers of a post of stackoverflow; find it is here.

In the main activity it is enough to place an EditText field in which the user will enter the desired number of CheckBoxes and a button that will activate an intent like the following which will send the number to the next activity.

        EditText editText1 = (EditText) findViewById(R.id.editText1);
        fnum=Integer.parseInt(editText1.getText().toString());
        Intent intent1 = new Intent(MainActivity.this, TableActivity.class);
        intent1.putExtra(DATA, fnum);
        startActivity(intent1);

In the next activity I form a layout with a scrollable Table Layout

     <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/TextView02"
        android:layout_above="@+id/button1" >

    <TableLayout
        android:id="@+id/table1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/TextView02"
        android:layout_marginTop="30dp"
        android:layout_above="@+id/button1" >
    </TableLayout>
    </ScrollView>

Then in the Table Layout, there is a number of Check Boxes dynamically placed using a loop to add it in a Table Row.

       public class TableActivity extends Activity {
       public final static String LIST = "com.TableActivity.LIST";
       int fnum;
      TableLayout table;
      int[] data;
  
    @Override
       protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_table);
      
        Intent intent1 = getIntent();
        fnum=intent1.getIntExtra(MainActivity.DATA, 0);
        table = new TableLayout(this);
        for (int i = 0; i < fnum; i++) {
            TableRow row = new TableRow(this);
            CheckBox checkbox = new CheckBox(this);
            checkbox.setText("Box #"+Integer.toString(i+1));                   
            row.addView(checkbox);
            table.addView(row);
          }

        TableLayout tablelayout = (TableLayout) findViewById(R.id.table1);
        tablelayout.addView(table);
        }

Also I use a method in order to pass in the next activity the information of whether each Check Box is checked or not.

           public void done(View view){
            data=new int[fnum];
            TableLayout tablelayout1 = (TableLayout) table;
           
            for(int i=0;i<fnum;i++){
                TableRow tablerow = (TableRow) tablelayout1.getChildAt(i);
                CheckBox checkbox = (CheckBox) tablerow.getChildAt(0);
                if(checkbox.isChecked()){
                    data[i] = 1;
            }
            else{
                data[i]=0;
            }       
          }

It is easy to show the result in the last activity.

        Intent intent1 = getIntent();
        data=intent1.getIntArrayExtra(TableActivity.LIST);
        String s=Arrays.toString(data);
        TextView textView = (TextView) findViewById(R.id.testView);
        textView.setTextSize(20);
        textView.setText(s);

You may find the layout and java source files here.

Rating of password strength using entropy

A usual method for the estimation of password strength is the computation of entropy on every string that is a candidate password, see Wikipedia article. Passwords need to be complex so to be difficult for anyone to guess or discover it using some brute-force method. Entropy provides a measure of strength as it expresses the information content in a string S and our uncertainty about it.

Entropy is defined on x which is the probability of appearance of every symbol s in S and hence H(X)=-Σxlog(x); I used logarithm of base 2. Probability x is defined on the set of symbols that are available to the user for the formation of the string. In this consideration there is a vague issue. Does the user exploit all the range of the character set? In case where the user formats the string of the password using only a subset of the available character set then the entropy as described on x is not representative.

Especially in handheld devices, the user has to change the keyboard configuration in order to access different parts of the character set. The user has to specify if the keyboard will input upper or lower case characters, numbers or special symbols and the language of the characters. Hence the estimation of the password strength has to take this issue under consideration.

On this issue, I thought of using entropy. So for any symbol s I define y as the probability of s to be upper case, lower case, number or special symbol in S and H(Y)=-Σylog(y). Variables X and Y are independent as the probability of appearance of one symbol in S is not relevant to whether this symbol is upper / lower case, number or special symbol. In order to simplify things let us suppose that all the characters belong to the same set of locale character set. For independent variables we then compute the joint entropy H(X,Y)=H(X)+H(Y).

Based on this approach, I developed an Android application which is distributed for free from Amazon Appstore and also in Google Play. This is an easy way to implement and distribute an idea.