Question

I am building this app and I can’t make it work. Here is the code and if you find the problem please post the solution.

This is the Main Activity

package in.isuru.caf;

//imports imported here. removed to simplify the code.

public class MainList extends ListActivity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    final String[] main_items_array = getResources().getStringArray(R.array.main_items);
    setListAdapter(new ArrayAdapter<String>(MainList.this, android.R.layout.simple_list_item_1, main_items_array));

    final ListView lv = getListView();
    lv.setTextFilterEnabled(true);

    lv.setOnItemClickListener(new OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
          // When clicked, show a toast with the TextView text
          String selectedFromList = (String) (lv.getItemAtPosition(position));
          Toast.makeText(getApplicationContext(), selectedFromList, Toast.LENGTH_SHORT).show();

          if(selectedFromList.contains("Top 20 Questions")){
                Intent mainIntent = new Intent(MainList.this, in.isuru.caf.Top20Questions.class);
                startActivity(mainIntent);
          }

        }
      });

  }
}

This is the second activity.

package in.isuru.caf;

import in.isuru.caf.R;
import android.app.Activity;
import android.os.Bundle;
import android.webkit.WebView;

public class Top20Questions extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);

    WebView myWebView = (WebView) findViewById(R.id.webview);
    myWebView.loadUrl("http://www.forums.catholic.com/forumdisplay.php?f=4&daysprune=-1&order=desc&sort=views");

    setContentView(R.layout.top_20_questions);
}

}

This is the AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="in.isuru.caf"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk android:minSdkVersion="8" />

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
    <activity
        android:label="@string/app_name"
        android:name=".MainList" >
        <intent-filter >
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".Top20Questions"></activity>


</application>

</manifest>

And I am getting this error.

01-21 12:18:44.231: E/AndroidRuntime(1767): 
java.lang.RuntimeException: Unable to start activity
ComponentInfo{in.isuru.caf/in.isuru.caf.Top20Questions}: 
java.lang.NullPointerException

Answer 1

You must call the setContentView() method before trying to access any resources.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.top_20_questions);

    WebView myWebView = (WebView) findViewById(R.id.webview);
    ...
    ...
}