应用无法启动活动componentinfo（Android）

Question

i have a problem with my app. I am trying to open a second activity but it is getting this error

04-22 13:39:50.634: E/AndroidRuntime(1016): FATAL EXCEPTION: main
    04-22 13:39:50.634: E/AndroidRuntime(1016): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.finale/com.example.finale.EmployeeActivity}: java.lang.NullPointerException
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.os.Handler.dispatchMessage(Handler.java:99)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.os.Looper.loop(Looper.java:137)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.app.ActivityThread.main(ActivityThread.java:4424)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at java.lang.reflect.Method.invokeNative(Native Method)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at java.lang.reflect.Method.invoke(Method.java:511)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at dalvik.system.NativeStart.main(Native Method)
    04-22 13:39:50.634: E/AndroidRuntime(1016): Caused by: java.lang.NullPointerException
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at com.example.finale.EmployeeActivity.onCreate(EmployeeActivity.java:35)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.app.Activity.performCreate(Activity.java:4465)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
    04-22 13:39:50.634: E/AndroidRuntime(1016):     ... 11 more

My mainactivity is this

package com.example.finale;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.text.Editable;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.os.Build;

public class MainActivity extends ActionBarActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final EditText textfeld1 = (EditText) findViewById(R.id.editText1);
    final EditText textfeld2 = (EditText) findViewById(R.id.editText2);     
    final Button login = (Button) findViewById(R.id.button1);

    login.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {           

            if(textfeld1.getText().toString().equals("employee") && textfeld2.getText().toString().equals("123"))
            {
                Intent intent = new Intent(MainActivity.this, EmployeeActivity.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;
}

@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.activity_main, container,
                false);
        return rootView;
    }
}

}

And this is my second Activity

package com.example.finale;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.os.Build;

public class EmployeeActivity extends ActionBarActivity {

int temp = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);     

    final Button button2 = (Button) findViewById(R.id.Button01);
    final Button button3 = (Button) findViewById(R.id.Button02);
    final Button button4 = (Button) findViewById(R.id.Button03);
    final Button button5 = (Button) findViewById(R.id.Button04);
    final EditText EditText1 = (EditText) findViewById(R.id.EditText01);
    final EditText EditText2 = (EditText) findViewById(R.id.EditText02);
    final EditText EditText3 = (EditText) findViewById(R.id.EditText03);
    final EditText EditText4 = (EditText) findViewById(R.id.EditText04);
    final EditText EditText5 = (EditText) findViewById(R.id.EditText05);
    final EditText EditText6 = (EditText) findViewById(R.id.EditText06);

     button2.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                EditText1.setVisibility(View.VISIBLE);
                EditText2.setVisibility(View.VISIBLE);
                button3.setVisibility(View.VISIBLE);                                    

                //Spalte 2 löschen
                if(button2.getText().equals("-"))
                {
                    if(temp == 3)
                    {
                        EditText1.setText(EditText3.getText());
                        EditText2.setText(EditText4.getText());
                        EditText3.setText(EditText5.getText());
                        EditText4.setText(EditText6.getText());
                        EditText5.setVisibility(View.INVISIBLE);
                        EditText6.setVisibility(View.INVISIBLE);
                        button4.setText("+");

                    }

                    if(temp == 2)
                    {
                        EditText1.setText(EditText3.getText());
                        EditText2.setText(EditText4.getText());
                        EditText3.setVisibility(View.INVISIBLE);
                        EditText4.setVisibility(View.INVISIBLE);
                        button3.setText("+");   
                        button4.setVisibility(View.INVISIBLE);
                    }

                    if(temp == 1)
                    {
                        EditText1.setVisibility(View.INVISIBLE);
                        EditText2.setVisibility(View.INVISIBLE);
                        button2.setText("+");
                        button3.setVisibility(View.INVISIBLE);
                        button4.setVisibility(View.INVISIBLE);
                    }


                    temp--; 
                }

                else
                {
                    button2.setText("-");   
                    temp++;
                    EditText1.setText("");
                    EditText2.setText("");                      
                }

            }
        });

        button3.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                EditText3.setVisibility(View.VISIBLE);
                EditText4.setVisibility(View.VISIBLE);
                button4.setVisibility(View.VISIBLE);



                if(button3.getText().equals("-"))
                {
                    if(temp == 3)
                    {
                        EditText3.setText(EditText5.getText());
                        EditText4.setText(EditText6.getText());
                        EditText5.setVisibility(View.INVISIBLE);
                        EditText6.setVisibility(View.INVISIBLE);
                        button4.setText("+");
                    }
                    if(temp == 2)
                    {
                        EditText3.setVisibility(View.INVISIBLE);
                        EditText4.setVisibility(View.INVISIBLE);
                        button4.setVisibility(View.INVISIBLE);
                        button3.setText("+");
                    }
                    temp--;                     
                }
                else
                {
                    button3.setText("-");
                    temp++;
                    EditText3.setText("");
                    EditText4.setText("");
                }

            }
        });

        button4.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                EditText5.setVisibility(View.VISIBLE);                  
                EditText6.setVisibility(View.VISIBLE);                    

                if(button4.getText().equals("-"))
                {
                    EditText5.setVisibility(View.INVISIBLE);
                    EditText6.setVisibility(View.INVISIBLE);
                    button4.setText("+");
                    temp--;

                }

                else
                {
                    temp++;
                    button4.setText("-");
                    EditText5.setText("");
                    EditText6.setText("");
                }

            }
        });

        button5.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                //VERSENDEN
            }
        });



}

public void ActivityEintragen()
{       



}

@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.activity_main,
                container, false);
        return rootView;
}
}

}

My Manifest

    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.finale"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.finale.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.finale.EmployeeActivity"
            android:label="@string/title_activity_employee" >            
        </activity>
    </application>

I tried so many things but the error happens everytime. Does someone know a solution?

Answer 1

You're setting the same layout activity_main in both activities. In EmployeeActivity you should probably have something else in setContentView() . Attempting to findViewById() the buttons from activity_main layout results in null s and calling setOnClickListener() method on null causes the NPE that crashes your app.