Question

I have an activity that shows a game screen. One of the UI elements is a score box. The score box is basically a Table Layout with four rows. All the rows are the same here is the xml representing one row.

<TableRow
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/farkle_image"
        android:src="@drawable/icon"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_weight="1" />
    <TextView
        android:id="@+id/name_text"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:text="Name" />
    <TextView
        android:id="@+id/temp_score_text"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:text="Temp Score" />
    <TextView
        android:id="@+id/score_text"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:text="Score" />
</TableRow>

Each row then has imageview , a textview representing the player name, and two other textviews representing various scores.

Here is what I do in the layout used by the activity:

<TableLayout
        android:id="@+id/score_box"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_below="@+id/score_button">

        <include
            layout="@layout/score_box_row"
            android:id="@+id/row_1" />

        <include
            layout="@layout/score_box_row"
            android:id="@+id/row_2"
            android:layout_below="@+id/row_1" />

        <include
            layout="@layout/score_box_row"
            android:id="@+id/row_3"
            android:layout_below="@+id/row_2" />

        <include
            android:id="@+id/row_4"
            layout="@layout/score_box_row"
            android:layout_below="@+id/row_3" />

    </TableLayout>

The game can be played with 2 to 4 players so what I had in mind was to set the Visibility of the Rows without respective player to View.GONE .

The only problem is that I cannot “find” the rows. findViewById() returns null. This method is called from onCreate() right after setContentView()

private void initializeArrays() {

        TableLayout table = (TableLayout) findViewById(R.id.score_box);
        Log.w(getClass().getName(), "Child Count: " + table.getChildCount());

        rows = ArrayList<TableRow>();    
        rows.add((TableRow) findViewById(R.id.row_1)); //Line 95
        rows.add((TableRow) findViewById(R.id.row_2));
        rows.add((TableRow) findViewById(R.id.row_3));
        rows.add((TableRow) findViewById(R.id.row_4));

        letters[0] = R.drawable.f;
        letters[1] = R.drawable.a;
        letters[2] = R.drawable.r;
        letters[3] = R.drawable.k;
        letters[4] = R.drawable.l;
        letters[5] = R.drawable.e;

    }

I always get a NullPointerException at runtime. The TableRows are there because table.getChildCount() returns 4. I’m not sure what is wrong.

Is this a bug with android or a bug with eclipse?

EDIT: As requested here is the stack:

06-14 15:59:40.437: WARN/dalvikvm(1587): threadid=1: thread exiting with uncaught exception (group=0x40015560)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587): FATAL EXCEPTION: main
06-14 15:59:40.441: ERROR/AndroidRuntime(1587): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mikgonz.farkle/com.mikgonz.farkle.ui.GameScreen}: java.lang.NullPointerException
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1768)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.app.ActivityThread.access$1500(ActivityThread.java:123)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.os.Looper.loop(Looper.java:130)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.app.ActivityThread.main(ActivityThread.java:3835)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at java.lang.reflect.Method.invokeNative(Native Method)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at java.lang.reflect.Method.invoke(Method.java:507)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at dalvik.system.NativeStart.main(Native Method)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587): Caused by: java.lang.NullPointerException
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at com.mikgonz.farkle.ui.GameScreen.initializeArrays(GameScreen.java:95)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at com.mikgonz.farkle.ui.GameScreen.onCreate(GameScreen.java:48)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722)
06-14 15:59:40.441: ERROR/AndroidRuntime(1587):     ... 11 more

Answer 1

First, it looks like that should be

rows = new ArrayList<TableRow>();

I’m surprised that that line compiled at all, if it did.

Also, and this would be a silly error, make sure that the score_box_row layout file actually exists and defines a layout properly.