ALERTDIALOGS AND BACK BUTTON in android

11. ALERTDIALOGS AND BACK BUTTON

11.1 DIALOGS

A dialog is usually a small window that appears in front of the current Activity. The underlying Activity loses focus and the dialog accepts all user interaction. Dialogs are normally used for notifications that should interupt the user and to perform short tasks that directly relate to the application in progress (such as a progress bar or a login prompt).

The Dialog class is the base class for creating dialogs. However, you typically should not instantiate a Dialog directly. Instead, you should use one of the following subclasses:

AlertDialog

A dialog that can manage zero, one, two, or three buttons, and/or a list of selectable items that can include checkboxes or radio buttons. The AlertDialog is capable of constructing most dialog user interfaces and is the suggested dialog type.

ProgressDialog

A dialog that displays a progress wheel or progress bar. Because it's an extension of the AlertDialog, it also supports buttons.

DatePickerDialog

A dialog that allows the user to select a date.

TimePickerDialog

A dialog that allows the user to select a time

In this session we will be dealing with alertdialogue box only and is the most commonly used among the four types.

11.2 ALERTDIALOG

It’s very familiar to see dialogue box in our android phones while opening certain apps and all. Now we are going to discuss about dialog box, along with it we going to give/edit the function of back button (in phone).

Before jumping into program, You will be very familiar with back button on your phone we can add function to it by writing code. In our progam we give a name in edittext in first activity then got to second activity there on clicking the back button our alertdialog pops up.

 An example is shown below

package a.b.c; import android.app.Activity; import android.content.Intent; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; public class BackbttnActivity extends Activity {       TextView t1;       EditText e1;       Button b1,b2;       String s1,s2;       SQLiteDatabase mydb1=null;     /** Called when the activity is first created. */     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);                  t1=(TextView)findViewById(R.id.tv1);          e1=(EditText)findViewById(R.id.ed1);                           mydb1 =  BackbttnActivity.this.openOrCreateDatabase("Database1", MODE_PRIVATE, null);         mydb1.execSQL("CREATE TABLE IF NOT EXISTS Table1 (usrnme varchar(10));");             }     public void Submit(View v)     {       s1= e1.getText().toString();             mydb1.execSQL("INSERT INTO Table1 VALUES('"+s1+"') ");       Intent i = new Intent(BackbttnActivity.this,second.class);       Bundle bundle = new Bundle();       bundle.putString("KEY", s1);       i.putExtras(bundle);       startActivity(i);     }     public void Cancel(View v )     {       e1.setText(" ");           }         }

second.java

package a.b.c; import android.app.Activity; import android.app.AlertDialog; import android.content.DialogInterface; import android.content.Intent; import android.os.Bundle; import android.view.KeyEvent; import android.widget.TextView; import android.widget.Toast; public class second extends Activity{       TextView t1;       public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.second);                 Intent i = getIntent();         Bundle bundle2 = i.getExtras();         String s = bundle2.getString("KEY");                 t1=(TextView)findViewById(R.id.tv3);         t1.setText("Welcome "+s);       } //back button control       public boolean onKeyDown(int keyCode, KeyEvent event) {         if (keyCode == KeyEvent.KEYCODE_BACK) {                                     AlertDialog alertbox = new AlertDialog.Builder(second.this).create();                         alertbox.setMessage("Do you really want to exit");                         alertbox.setTitle("Warning");                         alertbox.setButton("Yes", new DialogInterface.OnClickListener() {                                                             @Override                               public void onClick(DialogInterface arg0, int arg1) {                                     Intent yes = new Intent(second.this,BackbttnActivity.class);                                     startActivity(yes);                                     Toast.makeText(getApplicationContext(), "You clicked Yes", Toast.LENGTH_LONG).show();                                                                   }                         });                         alertbox.setButton2("No", new DialogInterface.OnClickListener() {                                                             @Override                               public void onClick(DialogInterface arg0, int arg1) {                                     Toast.makeText(getApplicationContext(), "You clicked No", Toast.LENGTH_LONG).show();                                                                   }                         });                         alertbox.show();                               return true;         }         return super.onKeyDown(keyCode, event);     }       }