这里我显示1个listview来自server.if我点击任何项目我想要一些程序发生...如果我在itemclick上放任何条件它显示我空指针异常... 这是我的代码：
public class SubMenu extends AppCompatActivity {
JSONObject jsonobject;
JSONArray jsonarray;
ListView listview;
ListViewAdapter adapter;
ProgressDialog mProgressDialog;
ArrayList<HashMap<String, String>> arraylist;
static String RANK = "id";
static String COUNTRY = "name";
private ProgressDialog pDialog;
String status="";
static String FLAG = "image";
Integer i = 1;
String _stringVal;
/* final int Pizza = 0; //should be equal to the index in your array.
final int Pasta = 1;
final int Lasagna = 2;
final int Salad =3 ;
final int Breakfast = 4;
final int Beverages= 5;
final int Soup = 6;
final int SpecialOffer =7;*/
private static String url_create_book = "http://cloud....com/broccoli/creatinfo.php";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sub_menu);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
String SelectedId = getIntent().getStringExtra("id");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// Get the view from listview_main.xml
// Execute DownloadJSON AsyncTask
new DownloadJSON().execute();
}
// DownloadJSON AsyncTask
private class DownloadJSON extends AsyncTask<Void, Void, Void> implements AdapterView.OnItemClickListener, AdapterView.OnItemSelectedListener {
protected Void doInBackground(Void... params) {
// Create an array
arraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
jsonarray = JsonFunctions
.getJSONfromURL("http://cloud.granddubai.com/broccoli/menu_typeitem.php?id=" + getIntent().getStringExtra("id"));
try {
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
map.put("name", jsonobject.getString("name"));
map.put("image", jsonobject.getString("image"));
// Set the JSON Objects into the array
arraylist.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void args) {
// Locate the listview in listview_main.xml
listview = (ListView) findViewById(R.id.list1);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(SubMenu.this, arraylist);
// Set the adapter to the ListView
listview.setAdapter(adapter);
listview.setOnItemClickListener(this);
// Close the progressdialog
// mProgressDialog.dismiss();
}
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long rowId) {
//Log.d("ANDROID", parent.getItemAtPosition(position).toString());
if ( parent.getItemAtPosition(position).toString().equals("Bianca Pizza"))
{
.....
}
else{
Toast.makeText(SubMenu.this, "hello", Toast.LENGTH_SHORT).show();
} @Override
public void onItemSelected(AdapterView<?> parent,
View view, int pos, long id) {
// Toast.makeText(SubMenu.this,"The planet is " + parent.getItemAtPosition(pos).toString(), Toast.LENGTH_LONG).show();
}
public void onNothingSelected(AdapterView parent) {
// Do nothing.
}
}
if（parent.getItemAtPosition（position）.toString（）。equals（＆＃34; Bian ca Pizza＆＃34;））...我在这里得到错误..如果我把条件取为空价值......其他工作正常......不知道它没有为条件带来价值。
异常：
FATAL EXCEPTION: main
Process: com.example.zeba.broccoli, PID: 32107
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at com.example.zeba.broccoli.SubMenu$DownloadJSON.onItemClick(SubMenu.java:161)
at android.widget.AdapterView.performItemClick(AdapterView.java:339)
at android.widget.AbsListView.performItemClick(AbsListView.java:1532)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3700)
at android.widget.AbsListView$3.run(AbsListView.java:5684)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6946)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
这是我的listviewAdapter：
public class ListViewAdapter extends BaseAdapter {
// Declare Variables
Context context;
LayoutInflater inflater;
ArrayList<HashMap<String, String>> data;
ImageLoader imageLoader;
HashMap<String, String> resultp = new HashMap<String, String>();
public ListViewAdapter(Context context,
ArrayList<HashMap<String, String>> arraylist) {
this.context = context;
data = arraylist;
imageLoader = new ImageLoader(context);
}
@Override
public int getCount() {
return data.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
public View getView(final int position, View convertView, ViewGroup parent) {
// Declare Variables
TextView id;
TextView name;
TextView population;
CircleImageView image;
inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View itemView = inflater.inflate(R.layout.list_item1, parent, false);
// Get the position
resultp = data.get(position);
// Locate the TextViews in listview_item.xml
// id = (TextView) itemView.findViewById(R.id.idq);
name = (TextView) itemView.findViewById(R.id.type1);
// Locate the ImageView in listview_item.xml
image = (CircleImageView) itemView.findViewById(R.id.subimg);
// icon = (ImageView) itemView.findViewById(R.id.arrow);
// Capture position and set results to the TextViews
// id.setText(resultp.get(SubMenu.RANK));
name.setText(resultp.get(SubMenu.COUNTRY));
// Capture position and set results to the ImageView
// Passes flag images URL into ImageLoader.class
imageLoader.DisplayImage(resultp.get(SubMenu.FLAG), image);
// imageLoader.DisplayImage(resultp.get(SubMenu.FLAG), icon);
// Capture ListView item click
/**itemView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// Get the position
resultp = data.get(position);
Intent intent = new Intent(context, SingleItemView.class);
// Pass all data rank
intent.putExtra("rank", resultp.get(MainActivity.RANK));
// Pass all data country
intent.putExtra("country", resultp.get(MainActivity.COUNTRY));
// Pass all data population
intent.putExtra("population",resultp.get(MainActivity.POPULATION));
// Pass all data flag
intent.putExtra("flag", resultp.get(MainActivity.FLAG));
// Start SingleItemView Class
context.startActivity(intent);
}
});*/
return itemView;
}
}
答案 0 :(得分：2)
您可以使用TextView提取Adapter Class，就像您在parentView中提取的那样匹配字符串值：
TextView name = (TextView) parent.findViewById(R.id.type1);
if ( name.getText.toString().equals("Bianca Pizza"))
{
.....
}