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Getting error when changing other activity's TextView

I'm a beginner at Android and Java and I have an error when trying to change an other activity's TextView. I've created MainActivity, and another one (PlayerNames).
I've set PlayerNames to be the Launcher activity, maybe the error is that, I don't know. I post the error and the code:
FATAL EXCEPTION: main
Process: com.example.android.mapamundi, PID: 1423
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.android.mapamundi/com.example.android.mapamundi.PlayerNames}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference
at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:68)
at android.support.v7.app.AppCompatDelegateImplV7.<init>(AppCompatDelegateImplV7.java:146)
at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:28)
at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:41)
at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:190)
at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:172)
at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:512)
at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:184)
at com.example.android.mapamundi.PlayerNames.<init>(PlayerNames.java:12)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
MAINACTIVITY.JAVA
Well, on MainActivity I only cast the TextViews with public static TextView tv1, so I don't post it
PLAYERNAMES.JAVA
public class PlayerNames extends AppCompatActivity implements View.OnClickListener {
Button accept = (Button) findViewById(R.id.changeNames);
EditText playerInput1 = (EditText) findViewById(R.id.PlayerNameInput1);
EditText playerInput2 = (EditText) findViewById(R.id.PlayerNameInput2);
EditText playerInput3 = (EditText) findViewById(R.id.PlayerNameInput3);
EditText playerInput4 = (EditText) findViewById(R.id.PlayerNameInput4);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_player_names);
accept.setOnClickListener(this);
}
#Override
public void onClick(View view) {
switch (view.getId()){
case (R.id.changeNames):
MainActivity.playerName1.setText(playerInput1.toString());
MainActivity.playerName2.setText(playerInput2.toString());
MainActivity.playerName3.setText(playerInput3.toString());
MainActivity.playerName4.setText(playerInput4.toString());
Intent intent = new Intent(PlayerNames.this, MainActivity.class);
startActivity(intent);
}
}
}
I post AndroidManifest.xml, just in case I have an error or something that causes the error
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="com.example.android.mapamundi.MainActivity" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity android:name=".PlayerNames">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
Can someone please tell me what am I doing wrong? TKS!!

You are calling findViewById() to early, before your activity is fully created. It cannot be in a field initialiser. It has to be in (or after) onCreate(). And also after setContentView(), because you first have to set the content of your activity, before you can try to find views inside of it.

Android App Emulator Issue

I have created a project in Android Studio:
package com.example.apps.newapplication;
Java code:
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.RelativeLayout;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
RelativeLayout DakotasLayout = new RelativeLayout(this);
Button redButton = new Button(this);
DakotasLayout.addView(redButton);
setContentView(DakotasLayout);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
#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);
}
}
Manifest.xml code:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.app.newapplication">
<application>
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
The problem is my app shuts down every time I launch it in the emulator.
I'm not sure what's wrong in my java file. It might be my manifest file that's wrong, but I'm not sure.
Here's the logcat:
Error Logs:
01-13 18:24:51.244 4486-4486/? I/art: Not late-enabling -Xcheck:jni (already on)
01-13 18:24:51.328 4486-4494/? I/art: Debugger is no longer active
01-13 18:24:51.369 4486-4494/? W/art: Suspending all threads took: 41.636ms
01-13 18:24:51.373 4486-4486/? W/System: ClassLoader referenced unknown path: /data/app/com.example.apps.newapplication-2/lib/x86
01-13 18:24:51.423 4486-4486/? D/AndroidRuntime: Shutting down VM
01-13 18:24:51.424 4486-4486/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.apps.newapplication, PID: 4486
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.apps.newapplication/com.example.apps.newapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.support.v7.widget.Toolbar.getTitle()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.support.v7.widget.Toolbar.getTitle()' on a null object reference
at android.support.v7.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:98)
at android.support.v7.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:91)
at android.support.v7.app.ToolbarActionBar.<init>(ToolbarActionBar.java:73)
at android.support.v7.app.AppCompatDelegateImplV7.setSupportActionBar(AppCompatDelegateImplV7.java:205)
at android.support.v7.app.AppCompatActivity.setSupportActionBar(AppCompatActivity.java:99)
at com.example.apps.newapplication.MainActivity.onCreate(MainActivity.java:28)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
01-13 18:25:03.649 4486-4494/com.example.apps.newapplication W/art: Suspending all threads took: 60.192ms
01-13 18:25:22.653 4486-4494/com.example.apps.newapplication W/art: Suspending all threads took: 44.409ms
01-13 18:25:29.152 4486-4494/com.example.apps.newapplication W/art: Suspending all threads took: 24.137ms

The problem is you are not setting a valid layout for what your activity is expecting. Your layout needs to have in it a defined view for each call to findViewById(...); you have. The view's ID will match what you pass into the method.
Currently you are only setting your content view to a relative layout with a button so you are likely getting a NullPointerException when you lookup other views using findViewById(...); and later try to use them.
Look inside your res/layout directory for a valid layout file and use that as your content view instead since this looks like a template to begin with.
setContentView(R.layout.activity_main);

Switch Activity Android Studio

i so tired for trying switch activity in Android Studio, i know maybe this question is too repeated, but please help me,after i start my project ,get error a lot
, this is my MainActivity
package com.example.satan.custommm;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.content.Intent;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private Button btt1;
private EditText et1;
private EditText et2;
private TextView tv1;
private TextView tv2;
private TextView tv4;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
run();
btt1 = (Button) findViewById(R.id.button);
et1 = (EditText) findViewById(R.id.editText);
et2 = (EditText) findViewById(R.id.editText2);
tv1 = (TextView) findViewById(R.id.textView);
tv2 = (TextView) findViewById(R.id.textView2);
tv4 = (TextView) findViewById(R.id.textView4);
}
public void run() {
btt1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (et1.getText().toString().equals("admin") && et2.getText().toString().equals("admin")) {
Intent i = new Intent(MainActivity.this, Main2Activity.class);
startActivity(i);
} else {
tv4.setText("Wrong Username/Password!");
}
}
});
}
#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);
}
}
and this is my manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.satan.custommm" >
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".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=".Main2Activity"
android:label="#string/app_name" >
</activity>
</application>
</manifest>
and after start the project , i get this errors :
09-02 21:09:05.998 26875-26875/? I/art﹕ Not late-enabling -Xcheck:jni (already on)
09-02 21:09:06.049 26875-26882/? E/art﹕ Failed sending reply to debugger: Broken pipe
09-02 21:09:06.049 26875-26882/? I/art﹕ Debugger is no longer active
09-02 21:09:06.205 26875-26887/? I/art﹕ Background sticky concurrent mark sweep GC freed 2736(226KB) AllocSpace objects, 0(0B) LOS objects, 0% free, 13MB/13MB, paused 11.436ms total 32.643ms
09-02 21:09:06.339 26875-26875/? D/AndroidRuntime﹕ Shutting down VM
09-02 21:09:06.339 26875-26875/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.satan.custommm, PID: 26875
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.satan.custommm/com.example.satan.custommm.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.satan.custommm.MainActivity.run(MainActivity.java:42)
at com.example.satan.custommm.MainActivity.onCreate(MainActivity.java:28)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
and sorry for my bad english

You have a java.lang.NullPointerException because you are calling
btt1.setOnClickListener
before initializing the btt1 object. Then you are calling a method on a null obj (btt1 = null).
Change your onCreate method
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btt1 = (Button) findViewById(R.id.button);
et1 = (EditText) findViewById(R.id.editText);
et2 = (EditText) findViewById(R.id.editText2);
tv1 = (TextView) findViewById(R.id.textView);
tv2 = (TextView) findViewById(R.id.textView2);
tv4 = (TextView) findViewById(R.id.textView4);
// move this line
run();
}

Initialize your views before calling the run() method

NullPointer Exception on setAdapter()

This is my first android app and all i'm trying to do is basically create a list with some sample data. I get the "Unfortunately Sunshine has stopped" error on my phone when i run it.
If i remove this line of code, the app runs -
lstview.setAdapter(mForecastAdapter);
Also When i remove this line of code and run the app i get a calendar of all years but i have not used a calendar anywhere in my code! Any idea why this happens?
Here is my MainActivity.java -
public class MainActivity extends ActionBarActivity {
#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.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);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
private ArrayAdapter<String> mForecastAdapter;
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
String[] forecastArray;
forecastArray = new String[]{
"Today - Sunny 88/63",
"Tomorrow - Foggy - 70/40",
"Thursday",
"Friday",
"Saturday",
"Sunday"
};
List<String> weekForecast = new ArrayList<String>(Arrays.asList(forecastArray));
mForecastAdapter = new
ArrayAdapter<String>(
getActivity(),
R.layout.list_item_forecast,
R.id.list_item_forecast_textview,
weekForecast);
ListView lstview = (ListView) rootView.findViewById(R.id.listview_forecast);
lstview.setAdapter(mForecastAdapter);
return rootView;
}
}
}
list_item_forecast.xml -
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="?android:attr/listPreferredItemHeight"
android:gravity="center_vertical"
android:id="#+id/list_item_forecast_textview"
>
</TextView>
fragment_main.xml -
<FrameLayout 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:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context=".MainActivity$PlaceholderFragment">
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/listview_forecast"></ListView>
</FrameLayout>
AndroidManifest.xml -
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.prashanth.sunshine" >
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".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>
This is a really simple program and i have looked everywhere and none of the solutions seem to work. So -
Why do i get an infinite calendar on my app when i remove this line of code?
lstview.setAdapter(mForecastAdapter);
Why does the app not run with that line?
BTW here is the logcat -
06-17 11:34:32.121 32380-32380/com.example.prashanth.sunshine I/Timeline﹕ Timeline: Activity_idle id: android.os.BinderProxy#1689948 time:428069386
06-17 11:36:28.478 641-641/com.example.prashanth.sunshine D/AndroidRuntime﹕ Shutting down VM
06-17 11:36:28.479 641-641/com.example.prashanth.sunshine E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.prashanth.sunshine, PID: 641
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.prashanth.sunshine/com.example.prashanth.sunshine.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2354)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.access$900(ActivityThread.java:153)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1319)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5291)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:931)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:726)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at com.example.prashanth.sunshine.MainActivity$PlaceholderFragment.onCreateView(MainActivity.java:90)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:953)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1136)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1499)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:548)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1236)
at android.app.Activity.performStart(Activity.java:6062)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2317)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416)
            at android.app.ActivityThread.access$900(ActivityThread.java:153)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1319)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5291)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:931)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:726)
06-17 11:42:14.846 1437-1437/com.example.prashanth.sunshine I/art﹕ Late-enabling -Xcheck:jni
06-17 11:42:15.308 1437-1437/com.example.prashanth.sunshine D/AndroidRuntime﹕ Shutting down VM
06-17 11:42:15.312 1437-1437/com.example.prashanth.sunshine E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.prashanth.sunshine, PID: 1437
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.prashanth.sunshine/com.example.prashanth.sunshine.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2354)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.access$900(ActivityThread.java:153)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1319)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5291)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:931)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:726)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at com.example.prashanth.sunshine.MainActivity$PlaceholderFragment.onCreateView(MainActivity.java:91)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:953)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1136)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1499)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:548)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1236)
at android.app.Activity.performStart(Activity.java:6062)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2317)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416)
            at android.app.ActivityThread.access$900(ActivityThread.java:153)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1319)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5291)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:931)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:726)
06-17 11:51:54.224 2292-2292/com.example.prashanth.sunshine D/AndroidRuntime﹕ Shutting down VM
06-17 11:51:54.225 2292-2292/com.example.prashanth.sunshine E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.prashanth.sunshine, PID: 2292
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.prashanth.sunshine/com.example.prashanth.sunshine.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2354)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.access$900(ActivityThread.java:153)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1319)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5291)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:931)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:726)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at com.example.prashanth.sunshine.MainActivity$PlaceholderFragment.onCreateView(MainActivity.java:91)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:953)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1136)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1499)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:548)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1236)
at android.app.Activity.performStart(Activity.java:6062)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2317)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416)
            at android.app.ActivityThread.access$900(ActivityThread.java:153)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1319)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5291)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:931)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:726)
06-17 11:51:56.581 2292-2292/com.example.prashanth.sunshine I/Process﹕ Sending signal. PID: 2292 SIG: 9
EDIT : Activity_main.xml
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:id="#+id/container"
android:layout_width="match_parent" android:layout_height="match_parent"
tools:context=".MainActivity" tools:ignore="MergeRootFrame" />
Thanks in Advance!

I changed certain bits of your code, and it seems to be working. I believe it's the problem with wrong imports of AppCompat library. Below is the entire MainActivity code.
import android.app.Fragment;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
private ArrayAdapter<String> mForecastAdapter;
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
String[] forecastArray;
forecastArray = new String[]{
"Today - Sunny 88/63",
"Tomorrow - Foggy - 70/40",
"Day After - Life",
"Kidney",
"Saturday",
"Sunday"
};
List<String> weekForecast = new ArrayList<String>(Arrays.asList(forecastArray));
mForecastAdapter = new
ArrayAdapter<String>(
getActivity(),
R.layout.list_item_forecast,
weekForecast);
ListView lstview = (ListView) rootView.findViewById(R.id.listview_forecast);
lstview.setAdapter(mForecastAdapter);
return rootView;
}
}
}
Is this the output you are looking for

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo, all activities are registered in AndroidManifest.xml, dont know whats wrong

I'm new to Android and i'm trying to run an app (simple test app), but get this error(. I have registered all my activities in AndroidManifest.xml and i'm using Android Studio 1.0.2
Here is the logcat of an app:
01-03 20:34:24.128 17300-17300/com.example.temur.sherlocked D/AndroidRuntime﹕ Shutting down VM
01-03 20:34:24.134 17300-17300/com.example.temur.sherlocked E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.temur.sherlocked, PID: 17300
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.temur.sherlocked/com.example.temur.sherlocked.MainActivity}: java.lang.InstantiationException: com.example.temur.sherlocked.MainActivity
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2124)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
at android.app.ActivityThread.access$800(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5086)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
Caused by: java.lang.InstantiationException: com.example.temur.sherlocked.MainActivity
at java.lang.Class.newInstance(Class.java:1561)
at android.app.Instrumentation.newActivity(Instrumentation.java:1084)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2115)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
            at android.app.ActivityThread.access$800(ActivityThread.java:139)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5086)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1559)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1084)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2115)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
            at android.app.ActivityThread.access$800(ActivityThread.java:139)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5086)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:1892)
at com.example.temur.sherlocked.MainActivity.<init>(MainActivity.java:43)
            at java.lang.reflect.Constructor.newInstance(Native Method)
            at java.lang.Class.newInstance(Class.java:1559)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1084)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2115)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
            at android.app.ActivityThread.access$800(ActivityThread.java:139)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5086)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
Code of MainActivity
package com.example.temur.sherlocked;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
#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.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);
}
TextView infoTextView = (TextView)findViewById(R.id.textViewAnswer);
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data){
super.onActivityResult(requestCode,resultCode,data);
if (requestCode==CHOOSE_THIEF){
if (resultCode==RESULT_OK){
String thiefName = data.getStringExtra(SecondActivity.THIEF);
infoTextView.setText(thiefName);
}else {
infoTextView.setText("");
}
}
}
static final private int CHOOSE_THIEF = 0;
public void onClick(View view) {
Intent questionIntent = new Intent(MainActivity.this, SecondActivity.class);
startActivityForResult(questionIntent,CHOOSE_THIEF);
}
}
Help me please :)

If you read other Stack Overflow questions, you will notice that well-written questions include the source code that is crashing (in your case, MainActivity) in addition to the stack trace.
In this case, I can tell just from the stack trace that you are calling findViewById() on your MainActivity too soon. This cannot be done until after your call to setContentView().
In particular, you appear to be calling findViewById() in the initializer of data member. Do not call inherited methods on Activity until after super.onCreate(), unless specifically directed otherwise.