This example most simplest program on Android
which is Date Picker. You can change the date which is being displayed
in a Text View.
java code for it...
here the java class extends from Activity class ......
public class DatePicker extends Activity {
private TextView mDateDisplay;
private Button mPickDate;
private int mYear;
private int mMonth;
private int mDay;
static final int DATE_DIALOG_ID = 0;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// capture our View elements
mDateDisplay = (TextView) findViewById(R.id.dateDisplay);
mPickDate = (Button) findViewById(R.id.pickDate);
// add a click listener to the button
mPickDate.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
showDialog(DATE_DIALOG_ID);
}
});
// get the current date
final Calendar c = Calendar.getInstance();
mYear = c.get(Calendar.YEAR);
mMonth = c.get(Calendar.MONTH);
mDay = c.get(Calendar.DAY_OF_MONTH);
// display the current date
updateDisplay();
}
As you can see first we are getting or capturing front end controls in our Java variables and then we have defined a OnClickListen event on button click...
CreateDialog method is responsible of opening a window which has a GUI related to date.
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DATE_DIALOG_ID:
return new DatePickerDialog(this,
mDateSetListener,
mYear, mMonth, mDay);
}
return null;
}
// the callback received when the user "sets" the date in the dialog
private DatePickerDialog.OnDateSetListener mDateSetListener =
new DatePickerDialog.OnDateSetListener() {
public void onDateSet(DatePicker view, int year,
int monthOfYear, int dayOfMonth) {
mYear = year;
mMonth = monthOfYear;
mDay = dayOfMonth;
updateDisplay();
}
};
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DATE_DIALOG_ID:
return new DatePickerDialog(this,
mDateSetListener,
mYear, mMonth, mDay);
}
return null;
}
Now your main.xml should look like this
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView android:id="@+id/dateDisplay"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""/>
<Button android:id="@+id/pickDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Change the date"/>
</LinearLayout>
java code for it...
here the java class extends from Activity class ......
public class DatePicker extends Activity {
private TextView mDateDisplay;
private Button mPickDate;
private int mYear;
private int mMonth;
private int mDay;
static final int DATE_DIALOG_ID = 0;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// capture our View elements
mDateDisplay = (TextView) findViewById(R.id.dateDisplay);
mPickDate = (Button) findViewById(R.id.pickDate);
// add a click listener to the button
mPickDate.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
showDialog(DATE_DIALOG_ID);
}
});
// get the current date
final Calendar c = Calendar.getInstance();
mYear = c.get(Calendar.YEAR);
mMonth = c.get(Calendar.MONTH);
mDay = c.get(Calendar.DAY_OF_MONTH);
// display the current date
updateDisplay();
}
As you can see first we are getting or capturing front end controls in our Java variables and then we have defined a OnClickListen event on button click...
CreateDialog method is responsible of opening a window which has a GUI related to date.
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DATE_DIALOG_ID:
return new DatePickerDialog(this,
mDateSetListener,
mYear, mMonth, mDay);
}
return null;
}
// the callback received when the user "sets" the date in the dialog
private DatePickerDialog.OnDateSetListener mDateSetListener =
new DatePickerDialog.OnDateSetListener() {
public void onDateSet(DatePicker view, int year,
int monthOfYear, int dayOfMonth) {
mYear = year;
mMonth = monthOfYear;
mDay = dayOfMonth;
updateDisplay();
}
};
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DATE_DIALOG_ID:
return new DatePickerDialog(this,
mDateSetListener,
mYear, mMonth, mDay);
}
return null;
}
Now your main.xml should look like this
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView android:id="@+id/dateDisplay"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""/>
<Button android:id="@+id/pickDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Change the date"/>
</LinearLayout>
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