Question

im really desperate right now, ive tried everything.

Everytime i run my app this it force closes. It shows this in the logcat.

04-02 21:26:33.079: E/AndroidRuntime(18013): FATAL EXCEPTION: main
04-02 21:26:33.079: E/AndroidRuntime(18013): java.lang.RuntimeException: Unable to            start activity ComponentInfo{com.pxr.tutorial.xmltest/com.pxr.tutorial.xmltest.Main}:    java.lang.NullPointerException
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.app.ActivityThread.access$600(ActivityThread.java:123)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.os.Looper.loop(Looper.java:137)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.app.ActivityThread.main(ActivityThread.java:4424)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at java.lang.reflect.Method.invokeNative(Native Method)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at java.lang.reflect.Method.invoke(Method.java:511)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at dalvik.system.NativeStart.main(Native Method)
04-02 21:26:33.079: E/AndroidRuntime(18013): Caused by: java.lang.NullPointerException
04-02 21:26:33.079: E/AndroidRuntime(18013):    at com.pxr.tutorial.xmltest.Main.onCreate(Main.java:41)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.app.Activity.performCreate(Activity.java:4465)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
04-02 21:26:33.079: E/AndroidRuntime(18013):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
04-02 21:26:33.079: E/AndroidRuntime(18013):    ... 11 more

Main.java

public class Main extends ListActivity {
private AdView adView;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.listplaceholder);

    LinearLayout layout = (LinearLayout)findViewById(R.layout.main);
    adView = new AdView(this, AdSize.BANNER, "here i put my id with the quotes");
    layout.addView(adView);
    AdRequest adRequest = new AdRequest();
    adRequest.setTesting(true);
    adView.loadAd(adRequest);

Manifest:

<activity
            android:name="com.google.ads.AdActivity"
            android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"/>

Main.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads"

listplaceholder.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">    

    <ListView
        android:id="@id/android:list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:drawSelectorOnTop="false" />

    <TextView
        android:id="@id/android:empty"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="No data"/>

</LinearLayout>

Yes i imported the libaries and i changed build target. I also changed lib to libs.

Please help me 🙁

Answer 1

Since you stated that

layout.addView(adView);

throws the NullPointerException, it’s most likely that

findViewById(R.layout.main);

returned null and layout keeps that in the lines below. And that’s actually the case here. You use R.layout.main, which is a layout reference. You need an ID though, hence findViewById() – so in this case it will never work.

So to get this working, you need two things:

First, you need to assign an id to a LinearLayout. I guess the intended one is the outer one in listplaceholder.xml, and it has no id yet. Add an android:id xml attribute, it should look like this in the end:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/container">

Second, change the above findViewById() statement to look for the correct id

findViewById(R.id.container);

This should result in a properly assigned layout inside layout.