Android List View populating null pointer exception

Question

I am trying to populate a simple list view with the values in a string array using the following code ,it throws a null pointer exception.The list is fetched from the previous ctivity that stats this and the list is valid i have checked it containns string values

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Bundle extras = getIntent().getExtras(); 
        final ListView listview = (ListView) findViewById(R.id.listview);
        List<Map<String, String>> deptList = new ArrayList<Map<String,String>>();

        if (extras != null) {

            deplist = extras.getStringArray("deparments");
            Log.w("Got","List");

            }
         ArrayAdapter<String> adapter = new ArrayAdapter<String>(Home.this,
                  android.R.layout.simple_list_item_1, android.R.id.text1, deplist);
         listview.setAdapter(adapter); 


        setContentView(R.layout.home);

here is the stack trace

10-06 02:39:33.002: D/dalvikvm(1409): GC_FOR_ALLOC freed 59K, 7% free 2541K/2720K, paused 139ms, total 141ms
10-06 02:39:33.102: I/dalvikvm-heap(1409): Grow heap (frag case) to 4.058MB for 1536016-byte allocation
10-06 02:39:33.152: D/dalvikvm(1409): GC_FOR_ALLOC freed <1K, 5% free 4041K/4224K, paused 48ms, total 48ms
10-06 02:39:33.642: D/gralloc_goldfish(1409): Emulator without GPU emulation detected.
10-06 02:39:35.952: W/Got(1409): List
10-06 02:39:36.092: D/AndroidRuntime(1409): Shutting down VM
10-06 02:39:36.092: W/dalvikvm(1409): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
10-06 02:39:36.372: E/AndroidRuntime(1409): FATAL EXCEPTION: main
10-06 02:39:36.372: E/AndroidRuntime(1409): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.usa/com.example.usa.Home}: java.lang.NullPointerException
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.os.Looper.loop(Looper.java:137)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.app.ActivityThread.main(ActivityThread.java:5103)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at java.lang.reflect.Method.invokeNative(Native Method)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at java.lang.reflect.Method.invoke(Method.java:525)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at dalvik.system.NativeStart.main(Native Method)
10-06 02:39:36.372: E/AndroidRuntime(1409): Caused by: java.lang.NullPointerException
10-06 02:39:36.372: E/AndroidRuntime(1409):     at com.example.usa.Home.onCreate(Home.java:51)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.app.Activity.performCreate(Activity.java:5133)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
10-06 02:39:36.372: E/AndroidRuntime(1409):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
10-06 02:39:36.372: E/AndroidRuntime(1409):     ... 11 more

bclymer · Accepted Answer · 2013-10-06 06:47:39Z

2

You are calling

final ListView listview = (ListView) findViewById(R.id.listview);

before

setContentView(R.layout.home);

Which doesn't make sense. findViewById() finds the view in the currently inflated view. But you haven't inflated a view until 10 lines later with setContentView(). Put setContentView() on the beginning of onCreate().

answered Oct 6, 2013 at 6:47

bclymer

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