Develop Reference

Using a nested if to make spinner string conditional selections with a bottun using intent

I am a beginner and I want the user to select three fields from a spinner, and using conditional statements to test all the three fields with an if condition and the and operator to decide which activity to be started using a button and intent.
activity level_menu
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/choose_txt"
android:textSize="30sp"
android:textStyle="bold"
android:layout_gravity="center"
android:textColor="#ff000000"
android:layout_marginBottom="30dp"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/prog"
android:textSize="32sp"
android:textStyle="bold"
android:textColor="#ff000000"
/>
<Spinner
android:id="#+id/program_spinner"
android:layout_width="match_parent"
android:layout_height="40dp"
android:entries="#array/program_list"
android:prompt="#string/programm_prompt"
android:layout_marginBottom="30sp"
android:backgroundTint="#e9ffc1"
android:background="#e9ffc1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/lev"
android:textSize="32sp"
android:textStyle="bold"
android:textColor="#ff000000"
/>
<Spinner
android:id="#+id/level_spinner"
android:layout_width="match_parent"
android:layout_height="40dp"
android:layout_marginBottom="30sp"
android:backgroundTint="#e9ffc1"
android:background="#e9ffc1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/sem"
android:textSize="32sp"
android:textStyle="bold"
android:textColor="#ff000000"/>
<Spinner
android:id="#+id/sem_spinner"
android:layout_width="match_parent"
android:layout_height="40dp"
android:backgroundTint="#e9ffc1"
android:background="#e9ffc1"
android:layout_marginBottom="20dp"></Spinner>
<Button
android:id="#+id/btnEnter"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/enter"
android:textSize="25sp"
android:textStyle="bold"
android:textColor="#ff000000"
/>
level_menu.java
package inc.zibit.com.conware;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.app.Activity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;
import android.widget.AdapterView.OnItemSelectedListener;
public class Level_menu extends ActionBarActivity implements OnItemSelectedListener {
private Spinner program_spinner;
private Spinner level_spinner;
private Spinner sem_spinner;
private Button btnEnter;
ArrayAdapter<String> program_adapter;
List<String> program_list = new ArrayList<String>(Arrays.asList(getResources().getStringArray(R.array.program_list)));
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_level_menu);
addItemsOnSpinner2();
addItemsOnSpinner3();
addListenerOnButton();
// addListenerOnSpinnerItemSelection();
program_spinner = (Spinner) findViewById(R.id.program_spinner);
level_spinner = (Spinner) findViewById(R.id.level_spinner);
sem_spinner = (Spinner) findViewById(R.id.sem_spinner);
program_spinner.setOnItemSelectedListener(this);
level_spinner.setOnItemSelectedListener(this);
sem_spinner.setOnItemSelectedListener(this);
program_adapter=new ArrayAdapter<String>(getBaseContext(),android.R.layout.simple_spinner_item, program_list);
program_adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
program_spinner.setAdapter(program_adapter);
}
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
if (!(program_spinner.getSelectedItem().toString().trim().equals("Bsc. Computer Science"))) {
if (level_spinner.getSelectedItem().toString().trim().equals("Level 100")) {
if (sem_spinner.getSelectedItem().toString().trim().equals("1st Semester")) {
startActivity(new Intent(Level_menu.this, CompScience.class));
}
}
}
}
#Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
// add items into spinner dynamically
public void addItemsOnSpinner2() {
level_spinner = (Spinner)findViewById(R.id.level_spinner);
List<String> list = new ArrayList<String>();
list.add("Level 100");
list.add("Level 200");
list.add("Level 300");
list.add("Level 400");
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
level_spinner.setAdapter(dataAdapter);
}
public void addItemsOnSpinner3() {
sem_spinner = (Spinner)findViewById(R.id.sem_spinner);
List<String> list = new ArrayList<String>();
list.add("1st Semester");
list.add("2nd Semester");
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sem_spinner.setAdapter(dataAdapter);
}
public void addListenerOnButton() {
btnEnter = (Button) findViewById(R.id.btnEnter);
btnEnter.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if ( v.getId()==R.id.btnEnter){
Intent intent = new Intent(Level_menu.this,CompScience.class);
startActivity(intent);
}
}
});
}
}
When i run it crashes.. what am I not doing right?

Without any logs provided, my best guess would be that NullPointerException causes your crash inside onItemSelected() callback. If any of those 3 spinners have nothing selected, you will get NPE.
I suggest you first make sure that spinner.getSelectedItem() is not null, before comparing strings.

Add user input into a ListView on button click

I am trying to make a TO DO LIST. I have a EditText, Button, and ListView. On button click I want to add, what I typed into the EditText into a ListView.
main_activity.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<EditText
android:id="#+id/editText"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:hint="Enter task"
android:textSize="24dp"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<Button
android:id="#+id/addTaskBtn"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Add Task"
android:layout_below="#+id/editText"
android:layout_alignParentLeft="true" />
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text=" Task"
android:id="#+id/header"
android:layout_below="#+id/addTaskBtn"
android:background="#5e5e5e"
android:textColor="#FFFFFF"
android:textSize="14dp"/>
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/list"
android:layout_below="#+id/header"
android:layout_centerHorizontal="true" />
Main_ToDoList.java
package com.example.todolist;
import android.app.Activity;
import android.app.ListActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import java.util.ArrayList;
public class Main_ToDoList extends Activity implements OnClickListener
{
private Button btnAdd;
private EditText et;
private ListView lv;
ArrayList<String> list = new ArrayList<String>();
ArrayAdapter<String> adapter;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity);
btnAdd = (Button)findViewById(R.id.addTaskBtn);
btnAdd.setOnClickListener(this);
et = (EditText)findViewById(R.id.editText);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, list);
lv.setAdapter(adapter);
}
public void onClick(View v)
{
String input = et.getText().toString();
if(input.length() > 0)
{
list.add(input);
adapter.notifyDataSetChanged();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu)
{
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main__to_do_list, menu);
return true;
}
}
The code doesn't work, new to android developing, and just trying to create a simple To Do List. Thanks for your help!

This should do it.
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity);
btnAdd = (Button)findViewById(R.id.addTaskBtn);
btnAdd.setOnClickListener(this);
et = (EditText)findViewById(R.id.editText);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, list);
// set the lv variable to your list in the xml
lv=(ListView)findViewById(R.id.list);
lv.setAdapter(adapter);
}
public void onClick(View v)
{
String input = et.getText().toString();
if(input.length() > 0)
{
// add string to the adapter, not the listview
adapter.add(input);
// no need to call adapter.notifyDataSetChanged(); as it is done by the adapter.add() method
}
}

you need to find your listview and then set the adapter:
lv=(ListView)findViewById(android.R.id.yourlistview);
lv.setAdapter(adapter);

Want to add item in a list in android at runtime

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<EditText
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="#+id/speed"
android:inputType="number"></EditText>"
<TextView
android:id="#+id/TextViewSpeed"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text ="Speed"
android:layout_below="#+id/speed"
/>
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:text="AddValue"
android:id="#+id/AddValue"
>
</Button>
<ListView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/ListView"
android:layout_below="#+id/AddValue"
>
</ListView>
</RelativeLayout>
This is my layout code. I wanted to add a text data from EditText to the ListView which is on same page. How to write a code to add text to the list when I click on the AddValue Button.
Thanks in advance.

use this code
addbutton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String val = edittext.getText().toString();
list.add(val);
((ArrayAdapter<Object>) listView.getAdapter()).notifyDataSetChanged();
}
});

Below snippet wil help you.
package org.sample;
import android.app.ListActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
public class SampleActivity extends Activity
{
private Button add;
private EditText speedText;
private ArrayAdapter<String> adapter;
private ListView AddValue;
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1);
AddValue=(ListView)findViewById(R.id.AddValue);
AddValue.setAdapter(adapter);
add = (Button) findViewById(R.id.add);
speedText = (EditText) findViewById(R.id.speed);
add.setOnClickListener(new OnClickListener()
{
#Override
public void onClick(View arg0)
{
if (speedText.getText().toString().length() != 0)
{
adapter.add(speedText.getText().toString());
adapter.notifyDataSetChanged();
}
}
});
}
}

displaying a string on the textview when clicking a button in android

I'm very new to Android development and just started to study.
What I'm trying is to add a button and when that button is pressed a text "my first project" to get displayed in the text view.
With the help of some experts I created the button and text view.
So the button is showing in the simulator but when I click that button nothing happens.
Can anyone please help me with how can I display the text when pressing the button?
.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/txtView"
android:layout_width="150dp"
android:layout_height="150dp"
android:text="#string/hello" />
<Button
android:id="#+id/mybtn"
android:layout_width="50dp"
android:layout_height="30dp" />
<TextView
android:id="#+id/viewwidth"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<TextView
android:id="#+id/viewheight"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</LinearLayout>
.java
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.TextView;
import android.view.View;
import android.widget.Toast;
public class NameonbuttonclickActivity extends Activity implements View.OnClickListener {
Button mybtn;
TextView txtView;
String hello;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.main);
super.onCreate(savedInstanceState);
mybtn= new Button(this);
txtView=new TextView(this);
mybtn.setOnClickListener(this);
printmyname();
mybtn = (Button)findViewById(R.id.mybtn);
txtView=(TextView)findViewById(R.id.txtView);
txtView = (TextView)findViewById(R.id.viewwidth);
txtView = (TextView)findViewById(R.id.viewheight);
hello="This is my first project";
//setContentView(mybtn);
// setContentView(R.layout.main);
}
public void onClick(View view){
txtView.setText(hello);
//printmyname();
Toast.makeText(NameonbuttonclickActivity.this, hello, Toast.LENGTH_LONG).show();
}
private void printmyname(){
System.out.println("coming");
}
}

You can do like this:
String hello;
public void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.main);
super.onCreate(savedInstanceState);
mybtn = (Button)findViewById(R.id.mybtn);
txtView=(TextView)findViewById(R.id.txtView);
txtwidth = (TextView)findViewById(R.id.viewwidth);
hello="This is my first project";
mybtn.setOnClickListener(this);
}
public void onClick(View view){
txtView.setText(hello);
}
Check your textview names. Both are same . You must use different object names and you have mentioned that textview object which is not available in your xml layout file.
Hope this will help you.

First create xml file as follows. Create one textview and a button:
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/hello" />
<Button
android:id="#+id/mybutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Click Me" />
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>
The first TextView is created by default. You can leave or remove it if you want.
Next one is to create a button
The next one is TextView where you want to display text.
Now coming to the main activity code...
package com.android.example.simple;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class SimpleActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final TextView textView=(TextView)findViewById(R.id.textView1);
final Button button1 = (Button)findViewById(R.id.mybutton);
//Implement listener for your button so that when you click the
//button, android will listen to it.
button1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Perform action on click
textView.setText("You clicked the button");
} });
}
}

This is because you DON'T associated the OnClickListener() on the button retrieve from the XML layout.
You don't need to create object because they are already created by the Android system when you inflate XML file (with the Activity.setContentLayout( int resourceLayoutId ) method).
Just retrieve them with the findViewById(...) method.

Just check your code in .java class
You had written below line
mybtn.setOnClickListener(this);
before initializing the mybtn object I mean
mybtn = (Button)findViewById(R.id.mybtn);
just switch this two line or put that line "mybtn.setOnClickListener(this)" after initializing your mybtn object and you will get the answer what you want..

Try this
public void onClick(View view){
txtView.setText("hello");
//printmyname();
Toast.makeText(NameonbuttonclickActivity.this, "hello", Toast.LENGTH_LONG).show();
}
Also in toast use "Hello"

you use this as txtView.setText("hello");

MainActivity.java:
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import android.view.View;
import android.view.View.OnClickListener;
public class MainActivity extends Activity {
Button button1;
TextView textView1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button1=(Button)findViewById(R.id.button1);
textView1=(TextView)findViewById(R.id.textView1);
button1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
textView1.setText("TextView displayed Successfully");
}
});
}
}
activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Click here" />
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>

public void onCreate(Bundle savedInstanceState)
{
setContentView(R.layout.main);
super.onCreate(savedInstanceState);
mybtn = (Button)findViewById(R.id.mybtn);
txtView=(TextView)findViewById(R.id.txtView);
mybtn .setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
txtView.SetText("Your Message");
}
});
}

Check this:
hello.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View paramView) {
text.setText("hello");
}
});

Android 2.2 requestFocus() and spinners

I'm having problems using s.requestFocus() when s is a spinner. Is there a special treatment to get it to work when it's a spinner ?
Thanks

try this code..
spinner.setFocusable(true);
spinner.setFocusableInTouchMode(true);

I'm guessing you aren't literally just looking to "give focus" to the spinner. When you give focus to an EditText, the keyboard pops up, so you may be expecting the spinner selection to "open up" on focus - but it doesn't work that way (don't ask me why). Use s.performClick() to do this - it will act just as if the user clicked on the spinner control.

use this
import java.util.ArrayList;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.text.Editable;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;
public class dynamic_spinner_main extends Activity {
private Spinner m_myDynamicSpinner;
private EditText m_addItemText;
private ArrayAdapter<CharSequence> m_adapterForSpinner;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_spinner);
///////////////////////////////////////////////////////////////
//grab our UI elements so we can manipulate them (in the case of the Spinner)
// or add listeners to them (in the case of the buttons)
m_myDynamicSpinner = (Spinner)findViewById(R.id.dynamicSpinner);
m_addItemText = (EditText)findViewById(R.id.newSpinnerItemText);
Button addButton = (Button)findViewById(R.id.AddBtn);
Button clearButton = (Button)findViewById(R.id.ClearBtn);
////////////////////////////////////////////////////////////////
//create an arrayAdapter an assign it to the spinner
m_adapterForSpinner = new ArrayAdapter(this, android.R.layout.simple_spinner_item);
m_adapterForSpinner.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
m_myDynamicSpinner.setAdapter(m_adapterForSpinner);
m_adapterForSpinner.add("gr");
m_myDynamicSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {
// your code here
Intent mIntent=new Intent(dynamic_spinner_main.this,sampleLocalization.class);
mIntent.putExtra("lang", m_myDynamicSpinner.getItemIdAtPosition(position));
System.out.println("Spinner value...."+m_myDynamicSpinner.getSelectedItem().toString());
startActivity(mIntent);
}
#Override
public void onNothingSelected(AdapterView<?> parentView) {
// your code here
}
});
////////////////////////////////////////////////////////////////
//add listener for addButton
addButton.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View v) {
addNewSpinnerItem();
}
});
////////////////////////////////////////////////////////////////
//add listener for addButton
clearButton.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View v) {
clearSpinnerItems();
}
});
}
private void addNewSpinnerItem() {
CharSequence textHolder = "" + m_addItemText.getText();
m_adapterForSpinner.add(textHolder);
}
private void clearSpinnerItems() {
m_adapterForSpinner.clear();
m_adapterForSpinner.add("dummy item");
}
}
main_spinner.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:layout_height="wrap_content"
android:layout_margin="4px"
android:id="#+id/newSpinnerItemText"
android:layout_width="fill_parent"></EditText>
<Button android:layout_height="wrap_content"
android:id="#+id/AddBtn"
android:layout_margin="4px"
android:layout_width="fill_parent"
android:text="Add To Spinner"></Button>
<Button android:layout_height="wrap_content"
android:id="#+id/ClearBtn"
android:layout_margin="4px"
android:layout_width="fill_parent"
android:text="Clear Spinner Items"></Button>
<Spinner android:layout_height="wrap_content"
android:id="#+id/dynamicSpinner"
android:layout_margin="4px"
android:layout_width="fill_parent"></Spinner>
</LinearLayout>

Spinner isn't focusable by default (source). So you have to make it focusable either in xml
<Spinner
android:id="#+id/spinner"
android:focusable="true"
android:layout_width="wrap_conten"
android:layout_height="wrap_content" />
or in code
findViewById(R.id.spinner).setFocusable(true);