Eclipse Android配置问题

Question

I've been setting up my Android SDK and ADT Plugin in Eclipse this morning and my first couple of tests when building an android app have worked fine.

However now I'm starting to get a pop-up everytime I click on something saying AN ERROR HAS OCCURED - JAVA.NULLPOINTER.EXCEPTION .

I understand a nullpointer exception in Java is when something has been created but I haven't even typed in any code yet its just a standard mainactivity class created by the app creation wizard when you click new project.

The problems started when I ran the program and it seemed to have had an issue with Activity_mainlayout.out.xml or whatever its called.

Anyone got any ideas as to why this happening it was working before and I haven't begun to code my application.

Few details: Eclipse using the Android ADT Plugin and Android SDK with an Android Virtual Device for testing.

Thanks guys.

Ps I deleted the project in windows explorer and in Eclipse so got rid of it completely and any new project now is producing the same pop-up error.

---

This is the code for MainActivity

package wag.cymal.libraryportal.welshlibraries;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.LinearLayout;
import android.graphics.*;
import android.graphics.drawable.Drawable;

@SuppressWarnings("unused")
public class MainActivity extends Activity {

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

    LinearLayout ll = new LinearLayout(this);
    ll.setBackgroundResource(R.drawable.natlib); // background image
    this.setContentView(ll);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}

And the activity_main XML file:

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

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:padding="@dimen/padding_medium"
    android:text="@string/hello_world"
    tools:context=".MainActivity" />

Any ideas? :/

Answer 1

The 'sctivity_mainlayout.out.xml' is created when you try to run the aplication while you are in an xml file. As far I understand, the compiler tries to compile the xml file, and this generates the .out.xml file, which is not valid xml, and this causes an error.

Solution: delete the .out.xml file, and always when you run watch out that the editor has focus in java file (or none)...

Now if for some reason your eclipse is messed up, try running it with the option --clean (using the command line, or in the case of Windows, also "execute" option -> " c:\\mypathtoeclipse\\eclipse.exe --clean "). This makes eclipse itself to be rebuilt. In my case it has fixed several times some unexplainable, unexpected exceptions I got during workspace load.