Develop Reference

Problems with creating a new/next Android activity

I just wanted to click on a button in the MainActivity. After I clicked on this button a new activity appears. In this activity is also a button and when I click on this button a text appears. My Problem now is, that the text doesn't appear, when I click on the button. My code for clicking on a button so that a text appears is actually working. But not if I use it in a new Activity/Layout/ page. So there must be s.th. wrong with the Connection between the first and the second activity?!
MainActivity.java:
package com.example.xxx;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#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;}
{}
public void page2 (View view){
setContentView(R.layout.pagetwo);
}}
activity_main.xml:
<RelativeLayout 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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<Button
android:id="#+id/BtnKlick"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_marginTop="178dp"
android:text="Button"
android:onClick="page2"/>
</RelativeLayout>
Pagetwo.java:
package com.example.xxx;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class Pagetwo extends Activity implements OnClickListener {
public Button btn1;
public TextView tw1;
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.pagetwo);
btn1 = (Button) findViewById(R.id.BtnKlick);
tw1 = (TextView) findViewById(R.id.Text);
btn1.setOnClickListener(this);
}
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
tw1.setText("Hallo");
}}
pagetwo.xml:
<?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" >
<Button
android:id="#+id/BtnKlick"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Klick" />
<TextView
android:id="#+id/Text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="87dp" />
</RelativeLayout>
AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.xxx"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.xxx.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

Update
All you seem to be doing is swapping your layouts within PageOne activity.
Change
public void page2 (View view){
setContentView(R.layout.pagetwo);
}
to
public void page2 (View view){
Intent i = new Intent(this, Pagetwo.class);
startActivity(i);
}
This will actually launch your pagetwo activity rather than just swapping layouts within pageone activity
Make that change and all should be good. You will most likely have to add some imports, at least for the intent class
Also Activities must be registered in the manifest. To add the activity to your manifest check the code below
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.xxx.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="Pagetwo"
android:label="#string/app_name" >
</activity>
</application>
Change the label to something more appropriate than app name once you have it working
End update
Try renaming your xml view id's to meet coding standards by using all lower case letters and separating words with underscores. The Android platform may well be getting confused as Text is a reserved word.
so
<TextView
android:id="#+id/Text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="71dp"
android:textSize="70sp" />
becomes
<TextView
android:id="#+id/tv_hallo"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="71dp"
android:textSize="70sp" />
and your code becomes
...
public TextView tw;
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.eclipse);
btn = (Button) findViewById(R.id.BtnKlick);
tw = (TextView) findViewById(R.id.tv_hallo);
btn.setOnClickListener(this);
}
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
tw.setText("Hallo");
}
...
Not sure if this is going to have much of an effect but it is just possible android is getting the word Text confused
Also check your logcat output to see if there are any errors.

unfortunately API demo has stopped while running

I have developed an app for page navigation . when a button is clicked the page should navigate to the second page. when i run the project and opened my app its showing unfortunately API demo has stopped. I have posted the entire code of my app . PLS HELP ME OUT...
//MAIN ACTIVITY
<RelativeLayout 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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="#+id/textView1"
android:layout_marginLeft="73dp"
android:layout_marginTop="14dp"
android:text="Click" />
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/button1"
android:layout_alignParentTop="true"
android:layout_marginLeft="14dp"
android:layout_marginTop="34dp"
android:text="Main Activity" />
</RelativeLayout>
//SECONDSCREEN ACTIVITY
<?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" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Sceond Screen Activity"
tools:context=".SecondScreenActivity"/>
</LinearLayout>
//JAVA CODE FOR MAIN ACTIVITY
package com.example.navigate;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addButtonOnClickEventListener();
}
public void addButtonOnClickEventListener()
{
Button button = (Button)findViewById(R.id.button1);
final Context context = this;
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(context,SecondScreenActivity.class);
startActivity(intent);
}
});
}
#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;
}
}
// JAVA CODE FOR SECOND SCREEN ACTIVITY
package com.example.navigate;
import android.app.Activity;
public class SecondScreenActivity extends Activity {
}
// MANIFEST FILE
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.navigate"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.navigate.SecondScreenActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name = "android.intent.action.MAIN"/>
<category android:name = "android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>

First problem MainActivity is your launcher page here but you define the secondactivity as luncher in manifest.change it first.
Add an oncreate() to secondactivity otherwise there is nothing to show when the button click.
Third change your MainActivity Context to activity which is MainActivity.this not local
Other things are fine , and hope you understand your small problems..
Change your manifest to something like this:
// MANIFEST FILE
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.navigate.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name = "android.intent.action.MAIN"/>
<category android:name = "android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<activity android:name = ".SecondScreenActivity" />
</application>
And in your SecondScreenActivity add an oncreate method with the contet view like:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.secondactivity_layout);
}
And also in your mainactivity change the context to MainActivity.this . Here you define the context inside onclicklistener which links to your local method not the class.

android app one page to another page not working

Here I done code for 5 buttons like Aboutus,development,carriers,services,contactus.
Here I clicked about us button that shows errors as unfortunately app closed.
Here is my code :
MainActivity.java
public class MainActivity extends Activity {
Button aboutus,development,service,carriers,contactus;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button aboutus=(Button) findViewById(R.id.aboutus);
aboutus.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent i = new Intent(v.getContext(),aboutus.class);
startActivity(i);
}
});
}
#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;
}
}
activity_main.xml
<RelativeLayout 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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<Button
android:id="#+id/aboutus"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="About us"
/>
<Button
android:id="#+id/services"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Services"
/>
<Button
android:id="#+id/development"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Development"
/>
<Button
android:id="#+id/carriers"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Carriers"
/>
<Button
android:id="#+id/contactus"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Contact Us"
/>
</LinearLayout>
</RelativeLayout>
aboutus.java
public class aboutus extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.aboutus);
}
}
aboutus.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="Aboutus Page"/>
</LinearLayout>
AndroidManifest.xml is this correct ?
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.globalinfosoft"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.globalinfosoft.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<Activity android:name= "aboutus"/>
</application>
</manifest>

MainActivity.java
package com.example.a;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.widget.Button;
public class MainActivity extends Activity {
Button aboutus, development, service, carriers, contactus;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button aboutus = (Button) findViewById(R.id.aboutus);
aboutus.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
//Starting a new Intent
Intent nextScreen = new Intent(getApplicationContext(),aboutus.class);
startActivity(nextScreen);
}
});
}
}
Here is Androidmanifest.xml :
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.a"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.a.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.example.a.aboutus"></activity>
</application>
</manifest>

Instead of v.getContext() use 'getApplicationContext()'.
Intent i = new Intent(getApplicationContext(),aboutus.class);
startActivity(i);

Try this ..
Button aboutus=(Button) findViewById(R.id.aboutus);
aboutus.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent i = new Intent(getApplicationContext(),aboutus.class);
startActivity(i);
}
});

First, you should make sure that you have declared the aboutus acitivity in your AndroidManifest.xml file.
<Activity android:name= "aboutus"/>
Second, you can use
Intent i = new Intent(getApplicationContext(),aboutus.class);
or
Intent i = new Intent(MainActivity.this,aboutus.class);
instead of
Intent i = new Intent(v.getContext(),aboutus.class);

Intent i = new Intent(v.getContext(),aboutus.class);
startActivity(i);
instead of code use following code and instruction:
Intent i = new Intent(MainActivity.this,aboutus.class);
startActivity(i);
you have to declare the About us activity on AndroidManifest.xml like this
<Activity android:name= ".aboutus"/>

Moving from one activity to another Activity in Android

I want to move from one activity to another (using virtual device). When I click on button to move, My emulator ones a dialog box showing unfortunately SMS1 has stopped working (SMS1 is my app name).
Can anybody help me in correcting my code?
MainActivity.java:
package com.example.sms1;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity implements OnClickListener
{
Button b1;
TextView tv1;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1 = (Button) findViewById(R.id.button1);
tv1 = (TextView) findViewById(R.id.textView1);
b1.setOnClickListener(this);
}
#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 void onClick(View v)
{
// TODO Auto-generated method stub
Intent i = new Intent(getApplicationContext(),NextActivity.class);
startActivity(i);
setContentView(R.layout.avtivity_next);
}
}
Here is the NextActivity
package com.example.sms1;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.TextView;
public class NextActivity extends Activity {
TextView tv1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.avtivity_next);
tv1 = (TextView) findViewById(R.id.textView1);
}
#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;
}
}
Manifest.XML
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.sms1"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.sms1.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
NextActivityLayout
<RelativeLayout 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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".NextActivity" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="next activity" />
</RelativeLayout>
MainActivity Layout
<RelativeLayout 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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/hello_world" />
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/textView1"
android:layout_marginTop="80dp"
android:layout_toRightOf="#+id/textView1"
android:text="Button" />
</RelativeLayout>

First You have to use this code in MainActivity.java class
#Override
public void onClick(View v)
{
// TODO Auto-generated method stub
Intent i = new Intent(getApplicationContext(),NextActivity.class);
startActivity(i);
}
You can pass intent this way.
Second
add proper entry into manifest.xml file.
<activity android:name=".NextActivity" />
Now see what happens.

You haven't defined NextActivity in the AndroidManifest.xml file.
Add these lines in android manifest after</activity> tag. It should work.
<activity
android:name=".NextActivity" >
</activity>
final code will be
<application
android:allowBackup="true"
android:icon="#drawable/app_icon"
android:label="#string/app_name" >
<activity
android:name=".MainActivity"
android:label="Main Activity" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".NextActivity" >
</activity>
</application>

button1 in activity2
code written in activity 2
button1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v)
{
// starting background task to update product
Intent fp=new Intent(getApplicationContext(),activity1.class);
startActivity(fp);
}
});
This might help

Simply add your NextActivity in the Manifest.XML file
<activity
android:name="com.example.sms1.NextActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
</intent-filter>
</activity>

public void onClick(View v)
{
startActivity(new Intent(getApplicationContext(), Next.class));
}
it is direct way to move second activity and there is no need for call intent

#Override
public void onClick(View v)
{
// TODO Auto-generated method stub
Intent intent = new Intent(Activity1.this,Activity2.class);
startActivity(intent);
}

1) place setContentView(R.layout.avtivity_next); to the next-activity's onCreate() method just like this (main) activity's onCreate()
2) if you have not defined the next-activity in your-apps manifest file then do this also, like:
<application
android:allowBackup="true"
android:icon="#drawable/app_icon"
android:label="#string/app_name" >
<activity
android:name=".MainActivity"
android:label="Main Activity" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".NextActivity"
android:label="Next Activity" >
</activity>
</application>
You must have to perform the 2nd step every time you create a new activity, otherwise your app will crash

When you have to go from one page to another page in android changes made in 2 files
Intent intentSignUP = new Intent(this,SignUpActivity.class);
startActivity(intentSignUP);
add activity in androidManifest file also like
<activity android:name=".SignUpActivity"></activity>

setContentView(R.layout.avtivity_next);
I think this line of code should be moved to the next activity...

Below code is working fine with Android 4.3:
Intent i = new Intent(this,MainActivity2.class);
startActivity(i);

First you have to declare the activity in Manifest. It is important. You can add this inside application like this.

It is mainly due to unregistered activity in manifest file as "NextActivity"
Firstly register NextActivity in Manifest like
<activity android:name=".NextActivity">
then use the code in the where you want
Intent intent=new Intent(MainActivity.this,NextActivity.class);
startActivity(intent);
where you have to call the NextActivity..

Register your java class on Android manifest file
After that write this code on button click
startActivity(new intent(MainActivity.this,NextActivity.class));

You can do
Intent i = new Intent(classname.this , targetclass.class);
startActivity(i);

Android application crases when switching activity

I have a problem with an Android aplication. When I try to swich from main activity (PretvornikValut) to another one (Pretvornik) via buttun I get the "Unfortunately aplication stopped working" error. Can anyone help?
PretvornikValut.java
package pretvornik.valut;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
public class PretvornikValut extends Activity implements OnClickListener
{
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
View gumbPretvori = findViewById(R.id.gumb_pretvornik);
gumbPretvori.setOnClickListener(this);
View gumbTecaji = findViewById(R.id.gumb_tecaji);
gumbTecaji.setOnClickListener(this);
}
public void sendMessage(View view) {
Intent intent = new Intent(this, Pretvornik.class);
startActivity(intent);
}
public void onClick(View v) {
switch (v.getId()) {
case R.id.gumb_pretvornik:
Intent i = new Intent(this, Pretvornik.class);
//i.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(i);
break;
case R.id.gumb_tecaji:
Intent tecaj = new Intent(this, Tecaji.class);
tecaj.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(tecaj);
break;
}
}
}
Pretvornik java
package pretvornik.valut;
import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
/**
*
* #author FAKS
*/
public class Pretvornik extends Activity {
/**
* Called when the activity is first created.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.pretvornik);
}
}
main.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"
android:background="#99CCCC"
>
<Button
android:id="#+id/gumb_pretvornik"
android:layout_width="100dp"
android:layout_height="50dp"
android:layout_alignParentLeft="true"
android:layout_alignParentBottom="true"
android:text="Pretvornik"
/>
<Button
android:id="#+id/gumb_tecaji"
android:layout_width="100dp"
android:layout_height="50dp"
android:layout_toRightOf="#+id/OK"
android:layout_alignParentBottom="true"
android:text="Izpis tecajev"
/>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Izberi zeljeno opcijo"
/>
</LinearLayout>
pretvornik.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"
android:background="#99CCCC"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="glavni program"
/>
</LinearLayout>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="pretvornik.valut"
android:versionCode="1"
android:versionName="1.0">
<application android:label="#string/app_name" android:icon="#drawable/ic_launcher">
<activity android:name="PretvornikValut"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<activity
android:name="Pretvornik"
android:label="#string/Pretvornik_valut" >
<meta-data
android:name="PretvornikValut"
/>
</activity>
<activity
android:name="Tecaji"
android:label="#string/Izpis_tecajev" >
<meta-data
android:name="PretvornikValut"
/>
</activity>
</activity>
</application>
</manifest>

Change your manifest xml,
add action for your activities
action android:name="android.intent.action.ACTIVITY"
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="pretvornik.valut"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<application
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="PretvornikValut"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="Pretvornik"
android:label="#string/hello_world" >
<action android:name="android.intent.action.ACTIVITY" />
</activity>
<activity
android:name="Tecaji"
android:label="#string/hello_world" >
<action android:name="android.intent.action.ACTIVITY" />
</activity>
</application>
</manifest>