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Android Studio: Session 'MainActivity': error, but there is no error

Hi I have been racking my brain for hours, did research online but nobody seems to have an answer. My emulator was running my code no problem then I ran it again and I get "Session 'MainActivity': error". I looked through this main activity about 10 times but there is no error sign anywhere and it looks like it should be working fine, I mean it was working before no problem. So I'm not sure if there really is a problem I don't see that Android Studio is not pointing out properly or if this is a different problem all together.
Any help would be greatly appreciated. Thank you.
package tekvision.codedecrypter;
import android.content.Context;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.Toast;
import gameInfo.GameDatabase;
public class MainActivity extends ActionBarActivity {
//Runs before the application is created
private Button mCampaignButton;
private final Context context = this;
//When the application is created
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Instantiate a GameDatabase object (this activity)
final GameDatabase gDB = new GameDatabase(context);
gDB.fillGameDatabase();
//Keeps screen on so it doesn't fall asleep
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
//Finding button by button id after application is created
mCampaignButton = (Button)findViewById(R.id.campaignButtonID);
//Checks if the campaign button is clicked
mCampaignButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String ans = gDB.getAnswer("Ancient",1);
//Toast pop up message
Toast toast = Toast.makeText(getApplicationContext(),
ans ,
Toast.LENGTH_SHORT);
toast.show();
//Intent to go from main activity to campaign Level Select Activity
final Intent intent = new Intent(MainActivity.this, CampaignSelectLevel.class);
startActivity(intent);
}
});
}
}

Try rebuilding and cleaning your project.
Build > Rebuild Project
and
Build > Clean Project

tried exporting my app the process failed and ended up giving me errors in my code

hey i am new to android development. i tried exporting my app the process failed because of some minor errors and then i got errors all over my code. it was working perfectly fine with no errors before attempting to export.
check these two pics of the xml files where the errors popped up
main activity file: http://postimg.org/image/4gwdipnap/
second activity file: http://postimg.org/image/vuy1ryba3/
I didn't have any of these errors before trying to export the project.
heres the code for both of the files
main activity page
package youngadults.camden;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.view.View.OnClickListener;
public class FrontPage extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.front_page);
findViewById(R.id.uyounadults).setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent myIntent = new Intent(FrontPage.this, youngadultsp.class);
myIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(myIntent);
}
});
}
}
second activity page
package youngadults.camden;
import android.app.Activity;
import android.os.Bundle;
public class youngadultsp extends Activity
{
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.youngadultsp_1);
}
}

You need to set Android API level, do you use Android Studio or Eclipse?
For Eclipse edit your Manifest file (19 is example):
<uses-sdk android:minSdkVersion="19" />
For Android Studio
Right click the App directory
Select "Open Module Setting" at the bottom
Under Modules select app
Set 'Compile Sdk version' as you want

shipp-sliding-menu android slider error

I am trying to implement facebook like slider, and i am planning to user below opensource code
https://github.com/leonardosalles/shipp-sliding-menu
but after i integrate, i created a sample activity
as per the code guide, in the
PrincipalActivity.java
//intent = new Intent(this, MyNewActivity2.class);
if it try giving my class, i get below error
cannot find symbol constructor Intent(,java.lang.Class)
here is my activity class
import android.app.Activity;
import android.os.Bundle;
public class SampleFirstTest extends Activity
{
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
please Help me to resolve the issue, i am new to android..

add SampleFirstTest in your AndroidManifest.xml

How to prevent double tap (bug?) on Android JB WebView?

I'm trying to port a Flash based game to Android.
I've ported it successfully (WebView), but now, the problem is that when I do a short click (short tap) somewhere in the game, it does 2 clicks (double tap), and when I do a long click (long tap) it does a short click (short tap).This is really annoying, specially when it does double fire instead of one fire. I've tried with the touch screen and a mouse; both had the same issue, so the input isn't the problem.
After reading a lot of stuff I think it must be a bug(?) on Andriod (4.x+ I think) WebView.
I hope you can help me to invert those things or to prevent those double taps as soon as possible.
Here is the code of the MainActivity.java:
package usr.sh.raul.dofus;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
import android.webkit.WebView;
#SuppressLint("SetJavaScriptEnabled")
public class MainActivity extends Activity
{
WebView mWebView;
/** Called when the activity is first created. */
#SuppressLint("SdCardPath")
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_main);
mWebView = (WebView) findViewById(R.id.webview);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setPluginsEnabled(true);
mWebView.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);
mWebView.setBackgroundColor(Color.parseColor("#000000"));
mWebView.loadUrl("file:///sdcard/Android/data/usr.sh.raul.dofus/data/loader.swf");
}
}
Thank you in advance and sorry for my bad english.

Android App Runtime Error

I have 2 classes for an Android project.
The first class is the Activity and the second class is just a OnClickListener which implements the interface.
If I run the project on my phone I always get an runtime error.
Also I got the message:
The specified activity does not exist! Getting the launcher activity.
Here are my two classes
SendActivity
package kops.sms;
//import android.R;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.widget.Button;
public class SendActivity extends Activity {
Button buttonSend= (Button) findViewById(R.id.buttonSend);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_send);
buttonSend.setOnClickListener(new ButtonListener());
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.send, menu);
return true;
}
}
and the ButtonListener
package kops.sms;
import android.view.View;
import android.view.View.OnClickListener;
public class ButtonListener implements OnClickListener {
#Override
public void onClick(View v)
{
}
}
I don´t know what is wrong...
I look forward to your replies! :)

You cannot call findViewById() until after you call setContentView(). Please move:
Button buttonSend= (Button) findViewById(R.id.buttonSend);
to after:
setContentView(R.layout.activity_send);
and before:
buttonSend.setOnClickListener(new ButtonListener());
Also, in the future, please use LogCat (e.g., in the DDMS perspective in Eclipse) to examine the Java stack trace associated with your crashes. You would have been told about your NullPointerException, and that may have helped you to fix your problem.

Be sure that your Activity is declared in your manifest. Also, change your onCreate()
public class SendActivity extends Activity {
Button buttonSend;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_send);
buttonSend = (Button) findViewById(R.id.buttonSend);
buttonSend.setOnClickListener(new ButtonListener());
}
You can't call a View such as a Button before you call setContentView() as it exists in your Layout and you haven't inflated your Layout until you call setContentViewe().
If these don't fix your problem then please post Logcat
Edit
Unless I missed it, you need to have all of your Activitys in your manifest. Something like:
<activity
android:name="your.package.name.SendActivity"
// activity attributes such as config changes, lable, etc...
</activity>
Logcat
Logcat output can be one of the most important pieces to determining a crash. It lists what the error was and a line number with activity where the problem occurred. If using Eclipse,
Window-->Show View-->Other-->Android-->Logcat
If you copy/paste the Logcat using coding brackets, it makes getting help much easier. You can also set filters for the logs so you don't get every single message and it is much more manageable. For example, I have a filter with: Filter Name: Runtime, by Log Tag: AndroidRuntime, by Log Level: error. This gives me only error messages for runtime errors/crashes. These filters are on the left side of the logcat view. Hope this helps