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我的代码有问题....当一个实例化项目时它会导致 NULL，我真的不知道是什么问题。有人可以帮忙吗？这种情况下的常见错误是什么？

public class DisplayActivity extends SherlockFragmentActivity {
    final static int NUM_ITEMS = 9;
    private final String TAG="links";
    String keyword; 
    MyAdapter mAdapter;
    ViewPager mPager;
    static ArrayAdapter<String> adapter;
    static View v;
    static ListView tv;
    static ArrayList<ArrayList<String>> items=new ArrayList<ArrayList<String>>();
    searchTask exec;    

    static String sites[]={"http://www.record.pt/","http://www.dn.pt/inicio","http://www.jn.pt",
        "http://www.publico.pt/?fullsite=true","http://www.abola.pt/?m=1",
        "http://www.economico.sapo.pt/?version=desktop&redirect=/","http://www.ojogo.pt",
        "http://www.expresso.sapo.pt","http://www.jornaldenegocios.pt","http://www.cmjornal.xl.pt"
};

@Override
public void onBackPressed(){
    android.os.Process.killProcess(android.os.Process.myPid());
    //DisplayActivity.this.finish();
}

@SuppressLint( "NewApi")
@Override
protected void onCreate(Bundle savedInstanceState){
    ActionBar actionBar = getSupportActionBar();

    actionBar.setDisplayHomeAsUpEnabled(true);
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    //getWindow().setWindowAnimations(17432586);
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_display);

    searchTask exec=new searchTask();
    exec.execute(sites);

    mPager = (ViewPager)findViewById(R.id.pager);

    mAdapter=new MyAdapter();  

    mPager.setAdapter(mAdapter);

    Intent intent = getIntent();
    keyword =intent.getStringExtra(MainActivity.EXTRA_INPUTKEY);
    keyword.toLowerCase();




    //Make sure we're running on Honeycomb or higher to use ActionBar APIs
    //if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
    //Show the Up button in the action bar.
    //  getActionBar().setDisplayHomeAsUpEnabled(true);
    //}

}   

public static class MyAdapter extends PagerAdapter {
    @Override
    public void destroyItem(View collection, int position, Object view) {
        //Util.Log("destroying" + position);
        ((ViewPager) collection).removeView((View) view);
    }

    @Override
    public Object instantiateItem(View collection, int position) {
        LayoutInflater inflater = (LayoutInflater) collection.getContext()
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View page=inflater.inflate(R.layout.activity_display_list, null);

        ListView tv=(ListView) page.findViewById(android.R.id.list);
        tv.setAdapter(adapter);
        if (items.get(position).size() > 0){ 
            for(int i=0; i < items.get(position).size();i++){
                adapter.add(items.get(position).get(i));
            }
        }
        ((ViewPager) collection).addView(page, position);
        adapter.notifyDataSetChanged();
        return page;

    }

    public MyAdapter() {
        super();
    }

    @Override
    public int getCount() {
        return NUM_ITEMS;
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == ((View) object);
    }
}

//***********************Fazer o add das listas aqui***************************

//Creates a new Task to execute the various getHtmlCode
public class searchTask extends AsyncTask<String, Elements, Elements> {
    int number=0;
    @Override
    protected Elements doInBackground(String... params) {
        Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
        for(int i=0 ; i < params.length;i++){
            Elements aux=getHtmlCode(params[i]);
            publishProgress(aux);
        }
        return null;
    }

    protected void onProgressUpdate(Elements... elem) {
        int index=0;
        ArrayList<String> aux=new ArrayList<String>();

        for(Element link:elem[0]){
            if(link.text().toLowerCase().contains(keyword)){                        
                aux.add(index, link.text());
                index++;
            }
        }
        items.add(number, aux);
        number++;
    }

    protected void onPostExecute(Elements aux){
         //adapter.add("---------END---------");
         //adapter.notifyDataSetChanged();
    }
}


//parsing the html
public Elements getHtmlCode(String url) {
    try {
        Document doc = Jsoup.connect(url).get();
        Elements content=doc.select("a[href]");
        return content;
    } 
    catch (IOException e) {
        DisplayActivity.this.finish();
        Log.e(TAG, "Failed to load HTML code", e);
        // Also tell the user that something went wrong (keep it simple,
        // no stacktraces):
        //Toast.makeText(this, "Failed to load HTML code",
        //      Toast.LENGTH_SHORT).show(); 
    }
    return null;
}

}

09-09 21:02:38.239: E/AndroidRuntime(19656): FATAL EXCEPTION: main
09-09 21:02:38.239: E/AndroidRuntime(19656): java.lang.NullPointerException
09-09 21:02:38.239: E/AndroidRuntime(19656):    at com.newsfinder.DisplayActivity$MyAdapter.instantiateItem(DisplayActivity.java:109)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.support.v4.view.PagerAdapter.instantiateItem(PagerAdapter.java:110)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:649)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.support.v4.view.ViewPager.populate(ViewPager.java:783)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1016)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.View.measure(View.java:8313)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:581)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:365)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.View.measure(View.java:8313)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.View.measure(View.java:8313)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.View.measure(View.java:8313)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.View.measure(View.java:8313)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.View.measure(View.java:8313)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.ViewRoot.performTraversals(ViewRoot.java:845)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.view.ViewRoot.handleMessage(ViewRoot.java:1866)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.os.Looper.loop(Looper.java:130)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at android.app.ActivityThread.main(ActivityThread.java:3687)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at java.lang.reflect.Method.invokeNative(Native Method)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at java.lang.reflect.Method.invoke(Method.java:507)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
09-09 21:02:38.239: E/AndroidRuntime(19656):    at dalvik.system.NativeStart.main(Native Method)
4

2 回答 2

0

哪一行是109？

LayoutInflater inflater = (LayoutInflater) collection.getContext()
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

我想就是这个。如果它是一个新的视图集合 

public Object instantiateItem(View collection, int position) {

将为 null 而不是使用

collection.getContext()

我会设置一个全局变量

private Context mContext;

然后在 onCreate()

mContext = 这个；

于 2013-09-09T21:43:27.943 回答
0

你有

View page=inflater.inflate(R.layout.activity_display_list, null);

    ListView tv=(ListView) page.findViewById(android.R.id.list);

你正在使用你自己的布局，但使用 android.R.id.list 一个你想要的 android id

R.id.list
于 2013-09-10T00:06:04.110 回答