解析JSON对象的AsyncTask＃3错误。 String无法转换为JSONObject
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有人可以告诉我我的错误是什么吗？我从androidHive.info下载了这段代码。我一直在收到“解析数据错误的错误。也有人能告诉我如何找出错误在哪一行？
public class NewProductActivity extends Activity {
// Progress Dialog
private ProgressDialog pDialog;
JSONParser jsonParser = new JSONParser();
EditText inputName;
EditText inputPrice;
EditText inputDesc;
// url to create new product
private static String url_create_product = "http://xxx.xxx.xxx.xxx/include/create_product.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_product);
// Edit Text
inputName = (EditText) findViewById(R.id.inputName);
inputPrice = (EditText) findViewById(R.id.inputPrice);
inputDesc = (EditText) findViewById(R.id.inputDesc);
// Create button
Button btnCreateProduct = (Button) findViewById(R.id.btnCreateProduct);
// button click event
btnCreateProduct.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
// creating new product in background thread
new CreateNewProduct().execute();
}
});
}
/**
* Background Async Task to Create new product
* */
class CreateNewProduct extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(NewProductActivity.this);
pDialog.setMessage("Creating Product..");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* Creating product
* */
protected String doInBackground(String... args) {
String name = inputName.getText().toString();
String price = inputPrice.getText().toString();
String description = inputDesc.getText().toString();
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("name", name));
params.add(new BasicNameValuePair("price", price));
params.add(new BasicNameValuePair("description", description));
// getting JSON Object
// Note that create product url accepts POST method
JSONObject json = jsonParser.makeHttpRequest(url_create_product,
"POST", params);
// check log cat fro response
Log.d("Create Response", json.toString());
// check for success tag
try {
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// successfully created product
Intent i = new Intent(getApplicationContext(), AllProductsActivity.class);
startActivity(i);
// closing this screen
finish();
} else {
// failed to create product
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once done
pDialog.dismiss();
}
}
}
这是我的logcat
01-26 18:14:35.366: D/dalvikvm(12395): GC_CONCURRENT freed 72K, 52% free 2619K/5379K, external 1529K/2026K, paused 8ms+2ms
01-26 18:14:36.296: E/JSON Parser(12395): Error parsing data org.json.JSONException: Value Unknown of type java.lang.String cannot be converted to JSONObject
01-26 18:14:36.296: W/dalvikvm(12395): threadid=9: thread exiting with uncaught exception (group=0x2aac8560)
01-26 18:14:36.306: E/AndroidRuntime(12395): FATAL EXCEPTION: AsyncTask #1
01-26 18:14:36.306: E/AndroidRuntime(12395): java.lang.RuntimeException: An error occured while executing doInBackground()
01-26 18:14:36.306: E/AndroidRuntime(12395): at android.os.AsyncTask$3.done(AsyncTask.java:200)
01-26 18:14:36.306: E/AndroidRuntime(12395): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
01-26 18:14:36.306: E/AndroidRuntime(12395): at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
01-26 18:14:36.306: E/AndroidRuntime(12395): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
01-26 18:14:36.306: E/AndroidRuntime(12395): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
01-26 18:14:36.306: E/AndroidRuntime(12395): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
01-26 18:14:36.306: E/AndroidRuntime(12395): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
01-26 18:14:36.306: E/AndroidRuntime(12395): at java.lang.Thread.run(Thread.java:1019)
01-26 18:14:36.306: E/AndroidRuntime(12395): Caused by: java.lang.NullPointerException
01-26 18:14:36.306: E/AndroidRuntime(12395): at com.example.androidhive.AllProductsActivity$LoadAllProducts.doInBackground(AllProductsActivity.java:129)
01-26 18:14:36.306: E/AndroidRuntime(12395): at com.example.androidhive.AllProductsActivity$LoadAllProducts.doInBackground(AllProductsActivity.java:1)
01-26 18:14:36.306: E/AndroidRuntime(12395): at android.os.AsyncTask$2.call(AsyncTask.java:185)
01-26 18:14:36.306: E/AndroidRuntime(12395): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
01-26 18:14:36.306: E/AndroidRuntime(12395): ... 4 more
01-26 18:14:36.566: E/WindowManager(12395): Activity com.example.androidhive.AllProductsActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@2afca938 that was originally added here
01-26 18:14:36.566: E/WindowManager(12395): android.view.WindowLeaked: Activity com.example.androidhive.AllProductsActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@2afca938 that was originally added here
01-26 18:14:36.566: E/WindowManager(12395): at android.view.ViewRoot.<init>(ViewRoot.java:265)
01-26 18:14:36.566: E/WindowManager(12395): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
01-26 18:14:36.566: E/WindowManager(12395): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
01-26 18:14:36.566: E/WindowManager(12395): at android.view.Window$LocalWindowManager.addView(Window.java:424)
01-26 18:14:36.566: E/WindowManager(12395): at android.app.Dialog.show(Dialog.java:241)
01-26 18:14:36.566: E/WindowManager(12395): at com.example.androidhive.AllProductsActivity$LoadAllProducts.onPreExecute(AllProductsActivity.java:116)
01-26 18:14:36.566: E/WindowManager(12395): at android.os.AsyncTask.execute(AsyncTask.java:391)
01-26 18:14:36.566: E/WindowManager(12395): at com.example.androidhive.AllProductsActivity.onCreate(AllProductsActivity.java:57)
01-26 18:14:36.566: E/WindowManager(12395): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-26 18:14:36.566: E/WindowManager(12395): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1623)
01-26 18:14:36.566: E/WindowManager(12395): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1675)
01-26 18:14:36.566: E/WindowManager(12395): at android.app.ActivityThread.access$1500(ActivityThread.java:121)
01-26 18:14:36.566: E/WindowManager(12395): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943)
01-26 18:14:36.566: E/WindowManager(12395): at android.os.Handler.dispatchMessage(Handler.java:99)
01-26 18:14:36.566: E/WindowManager(12395): at android.os.Looper.loop(Looper.java:123)
01-26 18:14:36.566: E/WindowManager(12395): at android.app.ActivityThread.main(ActivityThread.java:3701)
01-26 18:14:36.566: E/WindowManager(12395): at java.lang.reflect.Method.invokeNative(Native Method)
01-26 18:14:36.566: E/WindowManager(12395): at java.lang.reflect.Method.invoke(Method.java:507)
01-26 18:14:36.566: E/WindowManager(12395): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:862)
01-26 18:14:36.566: E/WindowManager(12395): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
01-26 18:14:36.566: E/WindowManager(12395): at dalvik.system.NativeStart.main(Native Method)
01-26 18:16:02.626: I/Process(12395): Sending signal. PID: 12395 SIG: 9
谢谢！
编辑：这是AllProductsActivity.java的代码：
public class AllProductsActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList;
// url to get all products list
private static String url_all_products = "http://xxx.xxx.xxx.xxx/include/get_all_products.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "products";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
// products JSONArray
JSONArray products = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_products);
// Hashmap for ListView
productsList = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadAllProducts().execute();
// Get listview
ListView lv = getListView();
// on seleting single product
// launching Edit Product Screen
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String pid = ((TextView) view.findViewById(R.id.pid)).getText()
.toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(),
EditProductActivity.class);
// sending pid to next activity
in.putExtra(TAG_PID, pid);
// starting new activity and expecting some response back
startActivityForResult(in, 100);
}
});
}
// Response from Edit Product Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user edited/deleted product
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all product by making HTTP Request
* */
class LoadAllProducts extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AllProductsActivity.this);
pDialog.setMessage("Loading products. 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_all_products, "GET", params);
// Check your log cat for JSON reponse
Log.d("All Products: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_PID, id);
map.put(TAG_NAME, name);
// adding HashList to ArrayList
productsList.add(map);
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getApplicationContext(),
NewProductActivity.class);
// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} 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(
AllProductsActivity.this, productsList,
R.layout.list_item, new String[] { TAG_PID,
TAG_NAME},
new int[] { R.id.pid, R.id.name });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
答案
首先，将您的方法包装在一个
try{
} catch(Throwable t) { Log.e("MyActivity", t.getMessage(), t); }
您应该更容易阅读堆栈跟踪。
要使此代码工作，您需要在Web服务器上使用“include / get_all_products.php”。然后，您需要使用服务器的IP地址更新url_all_products中定义的URL。你做过这个吗？
内部JSON解析器可用于少量数据。对于更多数据，像GSON这样的东西可以节省你的理智。
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