Question

findViewById can’t retrieve a button and a radiusBar even though their id exists. code crashes when initiating saveButton or radiusBar.

acticity:

    private Button saveButton;
    private EditText titleText;
    private SeekBar radiusBar;
    private TextView radiusValue;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        titleText = (EditText) findViewById(R.id.title);
        radiusValue = (TextView) findViewById(R.id.radiusValue);
        saveButton = (Button) findViewById(R.id.confirm);
    radiusBar = (SeekBar) findViewById(R.id.radiusBar);

xml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:padding="3dp"
    android:text="@string/title"
    android:textColor="#00ffff"
    android:textSize="20sp"
    android:textStyle="bold" />

<EditText
    android:id="@+id/title"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:padding="3dp" >

    <requestFocus />
</EditText>

<TextView
    android:id="@+id/myLocationText"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:padding="3dp"
    android:text="@string/hello"
    android:textColor="#ffffff"
    android:textSize="15sp" />

<com.google.android.maps.MapView
    android:id="@+id/myMapView"
    android:layout_width="fill_parent"
    android:layout_height="300dp"
    android:apiKey="my google maps api key"
    android:clickable="true"
    android:enabled="true"
    android:padding="5dp" >
</com.google.android.maps.MapView>

<RelativeLayout
    android:id="@+id/relativeLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <TextView
        android:id="@+id/radiusText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:paddingLeft="3dip"
        android:paddingRight="3dip"
        android:text="@string/proximity"
        android:textColor="#00ffff"
        android:textSize="20sp"
        android:textStyle="bold" />

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_toRightOf="@+id/radiusText" >

        <TextView
            android:id="@+id/radiusValue"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:paddingLeft="3dip"
            android:paddingRight="3dip"
            android:text="@string/radius"
            android:textColor="#00ffff"
            android:textSize="20sp"
            android:textStyle="bold" />
    </LinearLayout>

    <SeekBar
        android:id="@+id/radiusBar"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/radiusText"
        android:max="1000"
        android:padding="5dip"
        android:soundEffectsEnabled="true" />

    <Button
        android:id="@+id/confirm"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/radiusBar"
        android:padding="3dp"
        android:text="@string/confirm"
        android:textSize="20sp" />
</RelativeLayout>

i am new at android. even though i used old school comment out way or ddms i couldn’t find why this is happening. thanks for the help.

Answer 1

When you say “crash”, you should go on to say “… and this is the log output with the error message”. Anyway, the resource IDs certainly exist, as your code compiles. However, a common build system error with Android is that your resource IDs can be wrong after you reorder some XML. I think you’ll find that the error is a ClassCastException. The solution: clean your repo (e.g., with ant clean, or some button/menu in Eclipse) and recompile everything from scratch.