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POSimple App Crashes on Launch
 

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    <p>Hello stackoverflow community,</p> <p>I recently began learning and coding android applications. For my first app, I decided to create a simple app where you press a button (when you go to the bathroom) and the count goes up in an editable text field. There is also a reset button. On launch in an emulator, it opens to where I can see the app title but then crashes unexpectedly. Code is below, please help:</p> <p>MainActivity.java:</p> <pre><code>package com.CPTech.bathroomtracker; import android.os.Bundle; import android.app.Activity; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; public class MainActivity extends Activity { private int TOTAL_TRIPS = 0; private EditText tripsNumberEditText; Button bathroomTripButton; Button resetButton; protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); tripsNumberEditText.setText(TOTAL_TRIPS); bathroomTripButton = (Button) findViewById(R.id.bathroomTripButton); bathroomTripButton.setOnClickListener(bathroomTripButtonListener); resetButton = (Button) findViewById(R.id.resetButton); resetButton.setOnClickListener(resetButtonListener); tripsNumberEditText = (EditText) findViewById(R.id.tripsNumberEditText); } public OnClickListener bathroomTripButtonListener = new OnClickListener(){ @Override public void onClick(View v) { TOTAL_TRIPS++; tripsNumberEditText.setText(TOTAL_TRIPS); } }; public OnClickListener resetButtonListener = new OnClickListener(){ @Override public void onClick(View v) { TOTAL_TRIPS = 0; tripsNumberEditText.setText(TOTAL_TRIPS); } }; @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; } } </code></pre> <p>MainActivity.xml:</p> <pre><code>&lt;TableLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/TableLayout1" 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" android:background="@color/dark_blue" tools:context=".MainActivity" &gt; &lt;TableRow android:id="@+id/tableRow1" android:layout_width="wrap_content" android:layout_height="wrap_content" &gt; &lt;Button android:id="@+id/bathroomTripButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:background="@color/ash_grey" android:layout_marginTop="30dp" android:text="@string/bathroom_trip_button" /&gt; &lt;/TableRow&gt; &lt;TableRow android:id="@+id/tableRow2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="30dp" &gt; &lt;TextView android:id="@+id/todayTripsTextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:layout_marginLeft="20dp" android:text="@string/today_trips" android:textAppearance="?android:attr/textAppearanceLarge" android:textSize="16pt" /&gt; &lt;/TableRow&gt; &lt;TableRow android:id="@+id/tableRow3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="25dp" &gt; &lt;EditText android:id="@+id/tripsNumberEditText" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:layout_marginLeft="20dp" android:textColor="@color/white" android:textSize="20pt" android:background="@color/davy_grey" android:ems="2" &gt; &lt;requestFocus /&gt; &lt;/EditText&gt; &lt;/TableRow&gt; &lt;TableRow android:id="@+id/tableRow4" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="75dp" &gt; &lt;Button android:id="@+id/resetButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:background="@color/ash_grey" android:text="@string/reset_count" /&gt; &lt;/TableRow&gt; &lt;/TableLayout&gt; </code></pre> <p>Logcat:</p> <pre><code>10-23 10:43:13.230: D/AndroidRuntime(837): Shutting down VM 10-23 10:43:13.230: W/dalvikvm(837): threadid=1: thread exiting with uncaught exception (group=0x41465700) 10-23 10:43:13.340: E/AndroidRuntime(837): FATAL EXCEPTION: main 10-23 10:43:13.340: E/AndroidRuntime(837): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.CPTech.bathroomtracker/com.CPTech.bathroomtracker.MainActivity}: java.lang.NullPointerException 10-23 10:43:13.340: E/AndroidRuntime(837): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.app.ActivityThread.access$600(ActivityThread.java:141) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.os.Handler.dispatchMessage(Handler.java:99) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.os.Looper.loop(Looper.java:137) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.app.ActivityThread.main(ActivityThread.java:5103) 10-23 10:43:13.340: E/AndroidRuntime(837): at java.lang.reflect.Method.invokeNative(Native Method) 10-23 10:43:13.340: E/AndroidRuntime(837): at java.lang.reflect.Method.invoke(Method.java:525) 10-23 10:43:13.340: E/AndroidRuntime(837): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 10-23 10:43:13.340: E/AndroidRuntime(837): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 10-23 10:43:13.340: E/AndroidRuntime(837): at dalvik.system.NativeStart.main(Native Method) 10-23 10:43:13.340: E/AndroidRuntime(837): Caused by: java.lang.NullPointerException 10-23 10:43:13.340: E/AndroidRuntime(837): at com.CPTech.bathroomtracker.MainActivity.onCreate(MainActivity.java:23) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.app.Activity.performCreate(Activity.java:5133) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 10-23 10:43:13.340: E/AndroidRuntime(837): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175) 10-23 10:43:13.340: E/AndroidRuntime(837): ... 11 more </code></pre>
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    1. USTechmaster37
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    1. COWhat is in this line MainActivity.java:23
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    2. CO`10-23 10:43:13.340: E/AndroidRuntime(837): Caused by: java.lang.NullPointerException 10-23 10:43:13.340: E/AndroidRuntime(837): at com.CPTech.bathroomtracker.MainActivity.onCreate(MainActivity.java:23)` is the key to tracking down the problem.
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      1. USnhgrif
    3. CONote that storing a total in an Activity object member variable isn't going to be very useful, as it will be cleared every time the Activity is recreated, such as if the process needs to be removed from the background to provide resources for other apps, or even something as simple as rotating the orientation of the phone if you haven't configured the Manifest to ignore orientation changes.
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      1. POSimple App Crashes on Launch
      1. USChris Stratton
 

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