我将AsyncTask类的值传递给addValue方法，并从getValue方法获取值。这里addValue运行良好，但getValue以某种方式无法获取值并在我点击图片时在我的应用中返回Java.lang.nullPointerException
package com.example.mobile_e_commerce;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.ResourceBundle;
import org.ksoap2.SoapEnvelope;
import org.ksoap2.serialization.PropertyInfo;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.transport.HttpTransportSE;
import com.example.mobile_e_commerce.dummy.ProductInfo.ProductItem;
import android.app.Activity;
import android.app.Fragment;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;
import android.widget.Toast;
//include soap passing here
public class ProductCollection extends Activity {
public final static String EXTRA_MESSAGE = "com.example.mobile_e_commerce.product_name";
private static final ResourceBundle rb = ResourceBundle.getBundle("com.example.mobile_e_commerce.webserviceurl");
public static Map<String, ProductItem> ITEM_MAP = new HashMap<String, ProductItem>();
//Class involve asynctask(background running)//
public class objectTransfer extends AsyncTask<Void,Void,Void>{
这里列出了web服务网址和soap操作，但我已经测试过，并且还返回了值。
private final String NAMESPACE = rb.getString("WSDLTargetNamespace");
private final String SoapURL = rb.getString("SoapAddress");
private final String SOAP_ACTION = rb.getString("SoapAction");
private final String METHOD_NAME = rb.getString("OperationName");
private final String SOAP_ACTION2 = rb.getString("SoapAction2");
private final String METHOD_NAME2 = rb.getString("OperationName2");
private final String SOAP_ACTION3 = rb.getString("SoapAction3");
private final String METHOD_NAME3 = rb.getString("OperationName3");
private final String SOAP_ACTION4 = rb.getString("SoapAction4");
private final String METHOD_NAME4 = rb.getString("OperationName4");
private final String SOAP_ACTION5 = rb.getString("SoapAction5");
private final String METHOD_NAME5 = rb.getString("OperationName5");
private final String SOAP_ACTION6 = rb.getString("SoapAction6");//image location
private final String METHOD_NAME6 = rb.getString("OperationName6");//image location
private final String SOAP_ACTION7 = rb.getString("SoapAction7");
private final String METHOD_NAME7 = rb.getString("OperationName7");
//private Activity activity = new Activity();
// ImageView imageView = (ImageView)getActivity().findViewById(R.id.productImgDisplay);
/**
* A map of sample (dummy) items, by ID.
*/
// private File file = new File(Integer.toString(R.drawable.search));
private String[] valuePass = new String[100];
private int i;
PropertyInfo pi = new PropertyInfo();
private int n =0;
PropertyInfo getInfo = new PropertyInfo();
// private int number = 0;
@Override
protected Void doInBackground(Void... arg0) {
try
{
//get the no of the product
Object response2 = null;
SoapObject request2 = new SoapObject(NAMESPACE,METHOD_NAME5);
SoapSerializationEnvelope envelope2 = new SoapSerializationEnvelope(SoapEnvelope.VER11);
envelope2.dotNet = true;
envelope2.setOutputSoapObject(request2);
HttpTransportSE httpTransport2 = new HttpTransportSE(SoapURL);
httpTransport2.call(SOAP_ACTION5, envelope2);
response2 = envelope2.getResponse();
i = Integer.parseInt(response2.toString());
try
{
//get the name of the product
Object response = null;
while(n < i)
{
SoapObject request = new SoapObject(NAMESPACE,METHOD_NAME);
SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
envelope.dotNet = true;
request.addProperty("number", n);
envelope.setOutputSoapObject(request);
HttpTransportSE httpTransport = new HttpTransportSE(SoapURL);
httpTransport.call(SOAP_ACTION, envelope);
response = envelope.getResponse();
//imageurl equal to byte type image data,will add to WS later
valuePass[n] = response.toString();
// Log.e("Value", valuePass[n]);
n++;
addValue(new ProductItem(Integer.toString(n) ,valuePass[n]));
}
}
catch (Exception exception)
{
exception.printStackTrace();
Log.e("Apps Error", exception.toString());
}
}
catch (Exception exception)
{
exception.printStackTrace();
Log.e("Apps Error", exception.toString());
}
return null;
}
}
addValue方法应该可以正常工作，可以包含在上面的onBackground方法中。我将在稍后尝试查看。
public void addValue(ProductItem Item)
{
ITEM_MAP.put(Item.id, Item);
}
getValue方法基于我稍后将在onCreate方法中输入的String值
public String getValue(String id)
{ ProductItem value;
try{
value = ITEM_MAP.get(id);//check here later
Log.e("Value: ", value.toString());
return "";
}
catch(Exception ee)
{
ee.printStackTrace();
}
return "";
}
这是初始化变量的类，将在我的保存和检索值中使用，就像刚才提到的那样：名称和id。
public static class ProductItem {//Instantiation of variable
public String name;
public String id;
public ProductItem(String id,String name) {
this.id = id;
this.name = name;
}
}
/////*****////////
可以忽略MOBILE_OS，因为它仅用于检测图像的测试目的
static final String[] MOBILE_OS = new String[] {
"Samsung Galaxy S III 16GB", "Samsung Galaxy S IV Zoom","Samsung Galaxy Note 8.0 16GB", "Blackberry" };
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final Intent intent = new Intent(this,ProductCollectionDetails.class);
setContentView(R.layout.activity_product_collection);
GridView gridview = (GridView) findViewById(R.id.productGridView);
gridview.setAdapter(new ImageAdapter(this,MOBILE_OS));
gridview.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
// Toast.makeText(ProductCollection.this, "" + MOBILE_OS[position], Toast.LENGTH_SHORT).show();
// Log.e("Item map value", ITEM_MAP.get(position).toString());
// for (Map.Entry<String,ProductItem> entry : ITEM_MAP.entrySet()) {
此处调用getValue方法。
getValue(Integer.toString(position));
// }
// if((MOBILE_OS[position]).toString()== ITEM_MAP.get(position).toString())
// {
//intent.putExtra(EXTRA_MESSAGE,(MOBILE_OS[position]).toString());
//startActivity(intent);
// }
}
});
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
onResume和onPause方法仅用于调用AsyncTask并清除HashMap
@Override
protected void onResume()
{
super.onResume();
(new objectTransfer()).execute(null,null,null);
//Log.e("Task Running", "AsyncTask");
}
@Override
protected void onPause()
{
super.onPause();
ITEM_MAP.clear();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.product_collection, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(
R.layout.fragment_product_collection, container, false);
return rootView;
}
}
}
来自我日食的logcat：
04-17 14:14:55.820: D/dalvikvm(14073): GC_FOR_ALLOC freed 124K, 27% free 6530K/8899K, paused 0ms
04-17 14:14:55.820: I/dalvikvm-heap(14073): Grow heap (frag case) to 10.931MB for 2524908-byte allocation
04-17 14:14:55.890: D/dalvikvm(14073): GC_CONCURRENT freed 1K, 22% free 8995K/11395K, paused 0ms+0ms
04-17 14:14:56.020: D/dalvikvm(14073): GC_FOR_ALLOC freed 2468K, 40% free 7629K/12547K, paused 0ms
04-17 14:14:56.140: I/PGA(14073): New SOCKET connection: bile_e_commerce (pid 14073, tid 14073)
04-17 14:14:59.960: D/dalvikvm(14073): GC_CONCURRENT freed 1259K, 34% free 8402K/12547K, paused 0ms+0ms
04-17 14:15:00.100: E/dalvikvm(14073): No JIT support for bytecode f0 at offsetPC 0
04-17 14:15:00.100: E/dalvikvm(14073): JIT implementation not found
04-17 14:15:00.100: I/dalvikvm(14073): codeGenBasicBlockJit returns negative number
04-17 14:15:00.100: E/dalvikvm(14073): No JIT support for bytecode f0 at offsetPC 0
04-17 14:15:00.100: E/dalvikvm(14073): JIT implementation not found
04-17 14:15:00.100: I/dalvikvm(14073): codeGenBasicBlockJit returns negative number
04-17 14:15:00.160: D/dalvikvm(14073): GC_FOR_ALLOC freed 540K, 24% free 9553K/12547K, paused 10ms
04-17 14:15:00.210: D/dalvikvm(14073): GC_FOR_ALLOC freed 1172K, 32% free 9056K/13315K, paused 10ms
04-17 14:15:00.210: I/dalvikvm-heap(14073): Grow heap (frag case) to 15.110MB for 4320012-byte allocation
04-17 14:15:00.310: D/dalvikvm(14073): GC_FOR_ALLOC freed <1K, 25% free 13274K/17539K, paused 90ms
04-17 14:15:00.330: D/dalvikvm(14073): GC_CONCURRENT freed 0K, 25% free 13274K/17539K, paused 0ms+0ms
04-17 14:15:00.350: D/dalvikvm(14073): GC_FOR_ALLOC freed 2K, 25% free 13282K/17539K, paused 0ms
04-17 14:15:00.360: I/dalvikvm-heap(14073): Grow heap (frag case) to 16.948MB for 1920012-byte allocation
04-17 14:15:00.370: D/dalvikvm(14073): GC_FOR_ALLOC freed <1K, 23% free 15156K/19459K, paused 10ms
04-17 14:15:00.390: D/dalvikvm(14073): GC_FOR_ALLOC freed 4221K, 44% free 10943K/19459K, paused 0ms
04-17 14:15:00.400: I/dalvikvm-heap(14073): Grow heap (frag case) to 14.978MB for 2250012-byte allocation
04-17 14:15:00.440: D/dalvikvm(14073): GC_CONCURRENT freed <1K, 33% free 13140K/19459K, paused 0ms+0ms
04-17 14:15:01.050: D/dalvikvm(14073): GC_CONCURRENT freed 3141K, 39% free 11952K/19459K, paused 0ms+0ms
04-17 14:15:04.030: W/System.err(14073): java.lang.NullPointerException
04-17 14:15:04.030: W/System.err(14073): at com.example.mobile_e_commerce.ProductCollection.getValue(ProductCollection.java:162)
04-17 14:15:04.030: W/System.err(14073): at com.example.mobile_e_commerce.ProductCollection$1.onItemClick(ProductCollection.java:202)
04-17 14:15:04.040: W/System.err(14073): at android.widget.AdapterView.performItemClick(AdapterView.java:292)
04-17 14:15:04.040: W/System.err(14073): at android.widget.AbsListView.performItemClick(AbsListView.java:1058)
04-17 14:15:04.040: W/System.err(14073): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2514)
04-17 14:15:04.040: W/System.err(14073): at android.widget.AbsListView$1.run(AbsListView.java:3168)
04-17 14:15:04.040: W/System.err(14073): at android.os.Handler.handleCallback(Handler.java:605)
04-17 14:15:04.040: W/System.err(14073): at android.os.Handler.dispatchMessage(Handler.java:92)
04-17 14:15:04.040: W/System.err(14073): at android.os.Looper.loop(Looper.java:137)
04-17 14:15:04.040: W/System.err(14073): at android.app.ActivityThread.main(ActivityThread.java:4424)
04-17 14:15:04.040: W/System.err(14073): at java.lang.reflect.Method.invokeNative(Native Method)
04-17 14:15:04.040: W/System.err(14073): at java.lang.reflect.Method.invoke(Method.java:511)
04-17 14:15:04.040: W/System.err(14073): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:825)
04-17 14:15:04.040: W/System.err(14073): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:592)
04-17 14:15:04.040: W/System.err(14073): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
检查你的getValue（）方法
试试这个
public String getValue(String id)
{
ProductItem value;
try{
if(ITEM_MAP != null )
value = ITEM_MAP.get(id.trim());//check here later
if(value != null){
Log.e("Value: ", value.toString());
}
return "";
}
catch(Exception ee)
{
ee.printStackTrace();
}
return "";
}