问题描述

Listvew 中 textview 和 checkbox 的问题

我想创建一个listview，包含textview 和 checkbox。我创建好了 listview，也可以捕捉listview item select，但是当我想捕捉 checkbox 的select和unselect时，获得null pointer exception异常。如何给checkbox创建setOnCheckedChangeListener()？

public class LocationActivity extends Activity{@Overrideprotected void onCreate(Bundle savedInstanceState) {    // TODO Auto-generated method stub    super.onCreate(savedInstanceState);    setContentView(R.layout.locationmain);    ListView listview = (ListView) findViewById(R.id.listView1);    String selectQuery = ""SELECT  * FROM "" +     DatabaseHandler.TABLE_LOCATIONLABLES;    SQLiteDatabase db = new DatabaseHandler(this).getReadableDatabase();    Cursor cursor = db.rawQuery(selectQuery null);    final List<String> locLables = new ArrayList<String>();    if(cursor != null){        if (cursor.moveToFirst()) {            do {                locLables.add(cursor.getString(1));            } while (cursor.moveToNext());        }    }    //String[] locLables = new String[] {""Home""University""Office""};    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this R.layout.locationmain_entryR.id.textView12 locLables);    //cb gives a null pointer exception    CheckBox cb = (CheckBox) listview.findViewById(R.id.checkBox12);    cb.setOnCheckedChangeListener(new OnCheckedChangeListener() {        @Override        public void onCheckedChanged(CompoundButton buttonView boolean isChecked) {            // TODO Auto-generated method stub            if(isChecked){                System.out.println(""selected"");            }else if(!isChecked){                System.out.println(""not selected"");            }        }    });         listview.setAdapter(adapter);    listview.setOnItemClickListener(new OnItemClickListener() {        @Override        public void onItemClick(AdapterView<?> arg0 View arg1 int arg2                long arg3) {            // TODO Auto-generated method stub            Toast.makeText(getApplicationContext() locLables.get(arg2) Toast.LENGTH_SHORT).show();        }    });}

解决方案

你可以保持独立的 adpater 类，那样就可以实现

public class bsAdapter extends BaseAdapter {   Activity cntx;   public bsAdapter(Activity context)   {     // TODO Auto-generated constructor stub     this.cntx=context;   }   public int getCount()   {     // TODO Auto-generated method stub     return listview_arr.length;   }  public Object getItem(int position)  {     // TODO Auto-generated method stub     return listview_arr[position];  }  public long getItemId(int position)  {     // TODO Auto-generated method stub     return listview_array.length;  }  public View getView(final int position View convertView ViewGroup parent)  {     View row=null;    LayoutInflater inflater=cntx.getLayoutInflater();    row=inflater.inflate(R.layout.search_list_item null);    TextView tv=(TextView)row.findViewById(R.id.title);    CheckBox cb=(CheckBox)row.findViewById(R.id.cb01);    tv.setText(listview_arr[position]);    cb.setOnClickListener(new OnClickListener(){    public void onClick(View v) {    if(cb.ischecked)    {       //ur code    }    else //ur code    }  });  return row;  } }

解决方案二：
你的CheckBox cb = (CheckBox) listview.findViewById(R.id.checkBox12); 是不是要放到listview.setAdapter(adapter);后面