getting nullpointer exception when click on button - blackberry

Question

I am use a button and when u click this button a text field is automatic created and button status is automatic disable but if u click on disable button text field is automatic delete and button status is changed to enable.i going through this process.
public class ConfigurationScreen extends MainScreen implements FieldChangeListener{
TextField tf_text;
tf_text = new TextField(TextField.TYPE_PLAIN,img_text[1],img_text[0],TextField.FIELD_HCENTER);
tf_text.setWidth(Display.getWidth()/2+20);
ImageButton btn_en;
btn_en = new ImageButton(imgs_tmintrvl1,"enable",ImageButton.FIELD_HCENTER);
ImageButton btn_dis;
btn_dis=new ImageButton(imgs_tmintrvl1,"Disable",ImageButton.FIELD_HCENTER);
add(btn_en);
btn_en.setChangeListener(this);
public void fieldChanged(Field field, int context) {
if( field==btn_en)
{
delete(btn_en);
insert(btn_dis, 4);
insert(tf_text, 5);
System.out.println(ex);
}else if (field == btn_dis){
delete(btn_dis);
delete(tf_text);
insert(btn_en, 4);
System.out.println("Disable Button="+ex);
}
}
But when i run this code i am getting null pointerr exception please help me where i am making mistake.

Answer 1

package org.maxmobility.wmp.beta;
import com.maxmobility.customfield.H_FieldManager;
import com.maxmobility.customfield.ImageButton;
import com.maxmobility.customfield.LabelField;
import com.maxmobility.customfield.PillButtonField;
import com.maxmobility.customfield.PillButtonSet;
import com.maxmobility.customfield.TextArea;
import com.maxmobility.customfield.TextField;
import com.maxmobility.util.AppColors;
import net.rim.device.api.collection.List;
import net.rim.device.api.system.Bitmap;
import net.rim.device.api.system.Display;
import net.rim.device.api.system.EncodedImage;
import net.rim.device.api.ui.Color;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.FocusChangeListener;
import net.rim.device.api.ui.Font;
import net.rim.device.api.ui.Manager;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.container.HorizontalFieldManager;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
import net.rim.device.api.ui.decor.Background;
import net.rim.device.api.ui.decor.BackgroundFactory;
public class ConfigurationScreen extends MainScreen implements FieldChangeListener{
TextField tf_phn1;
TextField tf_phn2;
TextField tf_msg;
TextArea ta_msg;
ImageButton btn_add;
ImageButton btn_subtract;
ImageButton btn_en;
ImageButton btn_dis;
ImageButton btn_time1, btn_time2, btn_time3;
LabelField lf_msg;
LabelField lf_time;
LabelField lf1,lf2,lf3,lf4;
private Bitmap[] imgs_addbtn;
private Bitmap[] imgs_subbtn;
private Bitmap[] imgs_tmintrvl1;
private Bitmap[] imgs_tmintrvl2;
private Bitmap[] imgs_tmintrvl3;
private EncodedImage[] img_text;
private H_FieldManager hfm1 , hfm2;
private HorizontalFieldManager hfm3,hfm4;
private VerticalFieldManager vfm;
private boolean show = false;
PillButtonField pbf1;
PillButtonField pbf2;
PillButtonField pbf3;
PillButtonSet pbf_set;
public ConfigurationScreen(){
super(USE_ALL_HEIGHT | USE_ALL_WIDTH);
Background background = BackgroundFactory
.createSolidBackground(AppColors.APP_BG);
this.getMainManager().setBackground(background);
LabelField lf = new LabelField("Configuration Screen", LabelField.FIELD_HCENTER | LabelField.USE_ALL_WIDTH);
lf.setColor(Color.RED);
setTitle(lf);
img_text = new EncodedImage[2];
img_text[0] = EncodedImage.getEncodedImageResource("edittext_selected.png");
img_text[1] = EncodedImage.getEncodedImageResource("edittext.png");
imgs_addbtn = new Bitmap[3];
imgs_addbtn[0] = Bitmap.getBitmapResource("btn_add_sub.png");
imgs_addbtn[1] = Bitmap.getBitmapResource("btn_add_subfocused.png");
imgs_addbtn[2] = Bitmap.getBitmapResource("btn_add_subfocused.png");
imgs_subbtn = new Bitmap[3];
imgs_subbtn[0] = Bitmap.getBitmapResource("btn_add_sub.png");
imgs_subbtn[1] = Bitmap.getBitmapResource("btn_add_subfocused.png");
imgs_subbtn[2] = Bitmap.getBitmapResource("btn_add_subfocused.png");
imgs_tmintrvl1 = new Bitmap[3];
imgs_tmintrvl1[0] = Bitmap.getBitmapResource("default_btn_Unfocused.png");
imgs_tmintrvl1[1] = Bitmap.getBitmapResource("default_btn_focused.png");
imgs_tmintrvl1[2] = Bitmap.getBitmapResource("default_btn_focused.png");
// imgs_tmintrvl2 = new Bitmap[3];
// imgs_tmintrvl2[0] = Bitmap.getBitmapResource("default_btn_Unfocused.png");
// imgs_tmintrvl2[1] = Bitmap.getBitmapResource("default_btn_focused.png");
// imgs_tmintrvl2[2] = Bitmap.getBitmapResource("default_btn_focused.png");
//
// imgs_tmintrvl3 = new Bitmap[3];
// imgs_tmintrvl3[0] = Bitmap.getBitmapResource("default_btn_Unfocused.png");
// imgs_tmintrvl3[1] = Bitmap.getBitmapResource("default_btn_focused.png");
// imgs_tmintrvl3[2] = Bitmap.getBitmapResource("default_btn_focused.png");
//
tf_phn1 = new TextField(TextField.TYPE_PHONE,img_text[1],img_text[0],TextField.FIELD_LEFT);
tf_phn2 = new TextField(TextField.TYPE_PHONE,img_text[1],img_text[0],TextField.FIELD_LEFT);
tf_msg = new TextField(TextField.TYPE_PLAIN,img_text[1],img_text[0],TextField.FIELD_HCENTER);
tf_phn1.setWidth(Display.getWidth()/2+50);
tf_phn2.setWidth(Display.getWidth()/2+50);
tf_msg.setWidth(Display.getWidth()/2+95);
ta_msg = new TextArea(Display.getWidth()/2+130, 100,TextArea.FIELD_HCENTER);
btn_add = new ImageButton(imgs_addbtn," +",ImageButton.FIELD_HCENTER);
btn_subtract = new ImageButton(imgs_subbtn," -",ImageButton.FIELD_RIGHT);
btn_en = new ImageButton(imgs_tmintrvl1,"Enable",ImageButton.FIELD_HCENTER);
btn_dis = new ImageButton(imgs_tmintrvl1,"Disable",ImageButton.FIELD_HCENTER);
// btn_time1 = new ImageButton(imgs_tmintrvl1, "15 min",ImageButton.FIELD_LEFT);
// btn_time2 = new ImageButton(imgs_tmintrvl1, "30 min",ImageButton.FIELD_HCENTER);
// btn_time3 = new ImageButton(imgs_tmintrvl1, "45 min",ImageButton.FIELD_RIGHT);
// btn_time1.set_Margin(35,0, 0,0);
// btn_time2.set_Margin(0,0, 0,0);
// btn_time3.set_Margin(0,0, 0,0);
//btn_add.set_Margin(0,0, 8,8);
LabelField lf1 = new LabelField("",Display.getWidth(),45,LabelField.FIELD_LEFT);
LabelField lf2 = new LabelField("",Display.getWidth(),45,LabelField.FIELD_LEFT);
LabelField lf3 = new LabelField("",Display.getWidth(),45,LabelField.FIELD_LEFT);
LabelField lf4 = new LabelField("",Display.getWidth(),45,LabelField.FIELD_LEFT);
lf_msg = new LabelField("Alert Message",LabelField.FIELD_LEFT);
lf_msg.set_pos(35,0);
lf_time = new LabelField("Select Time Interval",LabelField.FIELD_LEFT);
lf_time.set_pos(35,20);
pbf1 = new PillButtonField("15 min");
pbf2 = new PillButtonField("30 min");
pbf3 = new PillButtonField("45 min");
pbf_set = new PillButtonSet(300,40);
pbf_set.add(pbf1);
pbf_set.add(pbf2);
pbf_set.add(pbf3);
hfm1 = new H_FieldManager(tf_phn1, btn_add, true, H_FieldManager.FIELD_HCENTER);
hfm2 = new H_FieldManager(tf_phn2, btn_subtract, true, H_FieldManager.FIELD_HCENTER);
// hfm3 = new HorizontalFieldManager(HORIZONTAL_SCROLL_MASK);
hfm4 = new HorizontalFieldManager(pbf1.FIELD_HCENTER);
// hfm3.add(btn_time1);
// hfm3.add(btn_time2);
// hfm3.add(btn_time3);
hfm4.add(pbf_set);
vfm = new VerticalFieldManager();
add(lf1);
add(hfm1);
add(lf_msg);
//add(tf_msg);
add(ta_msg);
add(btn_en);
add(lf_time);
//add(hfm3);
add(hfm4);
System.out.println(" insert label");
btn_add.setChangeListener(this);
btn_subtract.setChangeListener(this);
btn_en.setChangeListener(this);
btn_dis.setChangeListener(this);
}
public void fieldChanged(Field field, int context) {
// TODO Auto-generated method stub
if(field == btn_add){
insert(hfm2, 2);
}else if(field == btn_subtract){
delete(hfm2);
//}
}else if(field == btn_en){
replace(btn_en, btn_dis);
insert(tf_msg, 5);
}else if(field == btn_dis){
replace(btn_dis, btn_en);
delete(tf_msg);
}
}
}
I hope your Problem will solve in this code.