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My program crashes and I don't know why

I'm learning how to program in Java for Android and my program keeps crashing. It's suppoesed to convert from Celsius to Fahrenheit.
package com.example.myapplication;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;
import android.widget.RadioGroup.OnCheckedChangeListener;
public class MainActivity extends Activity implements RadioGroup.OnCheckedChangeListener
{
public static final int MY_CODE=2;
EditText temp;
RadioButton converttoF,converttoC,selectedtype;
RadioGroup conversion;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
conversion = (RadioGroup)findViewById(R.id.conversion);
conversion.setOnCheckedChangeListener(this);
converttoF = (RadioButton)findViewById(R.id.converttoF);
converttoC = (RadioButton)findViewById(R.id.converttoC);
}
#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, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
public void onCheckedChanged(RadioGroup group, int checkedId)
{
selectedtype = (RadioButton) findViewById(checkedId);
Intent i = new Intent(this, Activity4Result.class);
i.putExtra("temper", temp.getText().toString());
if(selectedtype.equals(converttoC))
{
Toast.makeText(this,"C chosen", Toast.LENGTH_SHORT).show();
i.putExtra("type", 'c');
startActivityForResult(i, MY_CODE);
}
else
{
Toast.makeText(this,"F chosen", Toast.LENGTH_SHORT).show();
i.putExtra("type", 'f');
startActivityForResult(i, MY_CODE);
}
}
}
My guess is that the problem is happening in the "onCheckedChanged", because it crashes when I push any RadioButton.

I assume (It would be better if you post the crash log along with your question, so that we can help you better and stop assuming) you are getting a null pointer exception on the following code:
i.putExtra("temper", temp.getText().toString());
In your code you declared temp, but it is never initialised. You need to initialise temp before using it.

Declaration of MapView (ArcGIS for Android) Center and Zoom

I am begginer in java and ArcGIS for android. I want to make simple app with MapView.
I have problem with declaration of MapView center and Zoom. I need to do it programmatically (application startup) in java file, not in xml file. I will try explain it on on simple example.
Problem is in mMapView.setMapOptions(options); I need to do in onCreate(), if I make Button with mMapView.setMapOptions(options); everything is OK. I searched solution in samples and on the internet, but I think, that I do not know how to ask on it.
Sorry for my english and thank you for your comments.
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import com.esri.android.map.MapOptions;
import com.esri.android.map.MapView;
public class MainActivity extends Activity {
MapView mMapView = null;
Button b1;
MapOptions options = new MapOptions(MapOptions.MapType.TOPO, 49.591241, 17.255503, 16);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mMapView = (MapView) findViewById(R.id.map);
//mMapView.centerAndZoom(49.591241, 17.255503, 8);
btnClick();
mMapView.setMapOptions(options);
mMapView.setAllowRotationByPinch(true);
mMapView.setRotationAngle(25);
mMapView.enableWrapAround(true);
}
public void btnClick() {
b1 = (Button) findViewById(R.id.button);
b1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
//mMapView.centerAndZoom(49.591241, 17.255503, 10);
mMapView.setMapOptions(options);
}
});
}
#Override
protected void onPause() {
super.onPause();
// Call MapView.pause to suspend map rendering while the activity is paused, which can save battery usage.
mMapView.pause();
}
#Override
protected void onResume() {
super.onResume();
// Call MapView.unpause to resume map rendering when the activity returns to the foreground.
mMapView.unpause();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}

You could remove the MapView declaration from your XML and create it inside the activity. Then just add the MapView to your layout.
XML (details omitted)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="#+id/mapLayout"></LinearLayout>
MainActivity.java
#Override
protected void onCreate(Bundle savedInstanceState) {
MapView mapView = MapView(MainActivity.this, mapOpts);
// other logic/initializations
ViewGroup mapLayout = findViewById(R.id.mapLayout);
mapLayout.addView(mapView); // might have to specify index param if you need buttons

This is my solution by previous answer. Thanks zec!
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import com.esri.android.map.MapOptions;
import com.esri.android.map.MapView;
public class MainActivity extends Activity {
MapView mMapView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MapOptions options = new MapOptions(MapOptions.MapType.TOPO, 49.591241, 17.255503, 16);
mMapView = new MapView(MainActivity.this, options);
setContentView(mMapView);
}
#Override
protected void onPause() {
super.onPause();
// Call MapView.pause to suspend map rendering while the activity is paused, which can save battery usage.
mMapView.pause();
}
#Override
protected void onResume() {
super.onResume();
// Call MapView.unpause to resume map rendering when the activity returns to the foreground.
mMapView.unpause();
}
}

Error with android.R

Hi I am developing an android application, nothing fancy just something small for college. Where I use R I recieve an error on the final bit. example R.id.mediAware
Any help would be greatly appreciated.
Here is my code if that helps:
package com.example.medicalapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.animation.Animation;
import android.view.animation.Animation.AnimationListener;
import android.view.animation.AnimationUtils;
import android.widget.ImageView;
import android.widget.TextView;
import com.example.medicalapp.R;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageView img1 = (ImageView) findViewById(R.id.mediAware);
ImageView splash_image2 = (ImageView) findViewById(R.id.mediAware2);
Animation fade1 = AnimationUtils.loadAnimation(this, R.anim.fadein);
Animation fade2 = AnimationUtils.loadAnimation(this, R.anim.fadein2);
fade2.setAnimationListener(new AnimationListener() {
public void onAnimationEnd (Animation animation) {
Intent intent = new Intent(new Intent(MainActivity.this, MenuActivity.class));
startActivity(intent);
}
public void onAnimationStart(Animation animation){
}
public void onAnimationRepeat(Animation animation){
}
});
splash_image.startAnimation(fade1);
splash_image2.startAnimation(fade2);
}
#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, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}

I figured out my problem. I was missing the R.java file. To add the file i simply created a folder in src called gen and then cleaned the project, this created the R.java file and removed my errors, appreciate the help that was given

Cannot get google tutorial to work [closed]

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Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 8 years ago.
Improve this question
I just starting learning to develop an android app and for that i followed google's basic tutorial.
In the tutorial there is simply a textbox and a button. On pressing the button it takes the text from the textbox and displays it in another activity. But somehow the button isn't working for me.
Here is the code for the fragment_main.xml, MainActivity.java and DisplayMessageActivity.java. I just want to know if i am doing something wrong or if i am missing something.
fragmant_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="horizontal">
<EditText android:id="#+id/edit_message"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:hint="#string/edit_message" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send"
onClick="sendMessage" />
</LinearLayout>
MainActivity.java:
package com.example.first;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
public class MainActivity extends ActionBarActivity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
#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, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
/** Called when the user clicks the Send button */
public void sendMessage(View view) {
Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editText = (EditText) findViewById(R.id.edit_message);
String message = editText.getText().toString();
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
}
}
DisplayMessageActivity.java
package com.example.first;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class DisplayMessageActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Get the message from the intent
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
// Create the text view
TextView textView = new TextView(this);
textView.setTextSize(40);
textView.setText(message);
// Set the text view as the activity layout
setContentView(textView);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.display_message, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_display_message,
container, false);
return rootView;
}
}
}

EDIT **
In your fragment_main.xml file the the last line of your Button tag should be : android:onClick="sendMessage" instead of onClick="sendMessage"

Android SDK - Changing Properties in Array List

Can anyone please help me out. I'm having problems changing my array list properties. I am more familiar with changing properties via the XML file. Here is my code:
package com.example.examproject;
import java.util.Random;
import android.os.Bundle;
import android.app.ListActivity;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.content.Intent;
public class Menu_Lists extends ListActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
String[] myAttractions = new String[2];
myAttractions[0] = "Grocery List";
myAttractions[1] = "Go Back";
setListAdapter(new ArrayAdapter(this, android.R.layout.simple_list_item_1, myAttractions));
}
protected void onListItemClick(ListView l, View v, int position, long id) {
switch(position) {
case 0: {
startActivity(new Intent(Menu_Lists.this, MainActivity.class));
break;
}
default: {
startActivity(new Intent(Menu_Lists.this, MainActivity.class));
}
}
}
#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, menu);
return true;
}
}
What I would like to do is to change the background color. That's my main goal. I would also like each option to change color whenever the user hovers over a specific option.
Please go easy with the terminologies as well. I am still a beginner with Android SDK.
Thanks in advance.