import java.util.ArrayList;
// list of item with checkbox. the value i want to parse
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.SparseBooleanArray;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Button;
import android.widget.AdapterView.OnItemClickListener;
public class Item extends Activity implements OnClickListener {
String [] builder;
Button button;
ListView listView;
String [] array = new String[] {"Baby Cot ", "Bouncer", "Bottle", "Blanket", "Stroller", "Toy", "Walker", "Thermal Bag", "Storage Bag", "Diaper", "Pacifier", "Potty", "Baby Bath" , "Baby CD", "Baby Book", "Car Seat", "Teethers", "Cooler Bag", "High Chair", "Apparel"};
private ArrayList<String> checked;
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.main1);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_checked, array);
listView = (ListView) findViewById(R.id.list);
listView.setAdapter(adapter);
listView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
button = (Button) findViewById (R.id.testbutton);
button.setOnClickListener(this);
}
@Override
public void onClick(View v) {
SparseBooleanArray positions = listView.getCheckedItemPositions();
for (int index = 0; index <array.length; index++){
if (positions.get (index) == true)
{
checked.add(array [index]);
}
}
Intent i = new Intent(this, AndroidJSONParsingActivity.class);
// Bundle b = new Bundle();
i.putStringArrayListExtra("Item", checked);
startActivity(i);
}
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
}
}
package com.example.searching2;
// value of checkbox pass to this activity
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class AndroidJSONParsingActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> shopList;
// url to get all products list
private static String url="http://10.0.2.2/fyp/item.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_SHOP = "shop";
private static final String TAG_ITEM = "Item";
private static final String TAG_ID = "Id";
private static final String TAG_SHOP_ID = "Shop_id";
private static final String TAG_SHOP_NAME = "Shop_Name";
// products JSONArray
JSONArray shop = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Hashmap for ListView
shopList = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadShop().execute();
// Get listview
ListView lv = getListView();
// on seleting single product
// launching Edit Product Screen
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String Item = ((TextView) view.findViewById(R.id.Item)).getText().toString();
// Starting new intent
ArrayList<String> getChecked;
Bundle extras = getIntent().getExtras();
if (extras!= null)
{
getChecked = extras.getStringArrayList("Item");
}
}
});
}
/**
* Background Async Task to Load all product by making HTTP Request
* */
class LoadShop extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AndroidJSONParsingActivity.this);
pDialog.setMessage("Loading shop. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url, "POST", params);
// Check your log cat for JSON reponse
Log.d("All Shop: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
shop = json.getJSONArray(TAG_SHOP);
// looping through All Products
for (int i = 0; i < shop.length(); i++) {
JSONObject s = shop.getJSONObject(i);
// Storing each json item in variable
String Id = s.getString(TAG_ID);
String Shop_id = s.getString(TAG_SHOP_ID);
String Shop_Name = s.getString(TAG_SHOP_NAME);
String Item = s.getString(TAG_ITEM);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, Id);
map.put(TAG_SHOP_ID, Shop_id);
map.put(TAG_SHOP_NAME,Shop_Name );
map.put(TAG_ITEM, Item);
// adding HashList to ArrayList
shopList.add(map);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(AndroidJSONParsingActivity.this, shopList, R.layout.list_item,
new String [] {TAG_ID, TAG_SHOP_ID, TAG_SHOP_NAME, TAG_ITEM},
new int [] {R.id.Id, R.id.Shop_id, R.id.Shop_Name, R.id.Item});
setListAdapter(adapter);
}
});
}
}
}
我想将复选框中的项目列表传递给android JSON活动。然后，android JSON将调用PHP文件以根据用户勾选复选框
来检索数据11-10 21:41:07.542: E/AndroidRuntime(3273): FATAL EXCEPTION: main
11-10 21:41:07.542: E/AndroidRuntime(3273): java.lang.NullPointerException
11-10 21:41:07.542: E/AndroidRuntime(3273): at com.example.searching2.Item.onClick(Item.java:54)
11-10 21:41:07.542: E/AndroidRuntime(3273): at android.view.View.performClick(View.java:4204)
11-10 21:41:07.542: E/AndroidRuntime(3273): at android.view.View$PerformClick.run(View.java:17355)
11-10 21:41:07.542: E/AndroidRuntime(3273): at android.os.Handler.handleCallback(Handler.java:725)
11-10 21:41:07.542: E/AndroidRuntime(3273): at android.os.Handler.dispatchMessage(Handler.java:92)
11-10 21:41:07.542: E/AndroidRuntime(3273): at android.os.Looper.loop(Looper.java:137)
11-10 21:41:07.542: E/AndroidRuntime(3273): at android.app.ActivityThread.main(ActivityThread.java:5041)
11-10 21:41:07.542: E/AndroidRuntime(3273): at java.lang.reflect.Method.invokeNative(Native Method)
11-10 21:41:07.542: E/AndroidRuntime(3273): at java.lang.reflect.Method.invoke(Method.java:511)
11-10 21:41:07.542: E/AndroidRuntime(3273): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
11-10 21:41:07.542: E/AndroidRuntime(3273): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
11-10 21:41:07.542: E/AndroidRuntime(3273): at dalvik.system.NativeStart.main(Native Method)
11-10 21:41:15.473: E/Trace(3310): error opening trace file: No such file or directory (2)
// LOGCAT ERROR FULL
仍然有NullPointerException
答案 0 :(得分：2)
checked成员永远不会被初始化，因此您有空指针异常。
更改
ListView listView;
private ArrayList<String> checked;
到
ListView listView = new ListView( /* whatever it takes to create object */);
private ArrayList<String> checked = new ArrayList<String>();
在跟踪运行时错误时，堆栈跟踪至关重要。在堆栈跟踪中打印的检查行，您知道哪行代码会导致问题。