我正在尝试将我的Android应用程序连接到外部数据库。我的phpmyadmin数据库中有一个表'产品'。当我尝试在我的应用中打开活动AllProductsActivity时，它会粉碎并显示错误。
我已经使用调试模式来运行应用程序并发现它在运行到第129行上的代码Log.d("All Products: ", json.toString());和JSONObject json的值时将会死机为空 。
我是新手写的应用程序，我现在真的感到绝望。如果你能提供帮助，那将会很感激。谢谢大家。
仅供参考：该计划首先转到AllProductsActivity.java，然后调用JSONParser.java和EditProductActivity.java。 AllProductsActivity.java的布局为list_item.xml，EditProductActivity.java的布局为edit_product.xml。用户可以选择list_item中的选项，然后转到相关页面。
以下是错误：
03-17 17:17:54.003 1821-1821/com.google.andriod.gms.example.hongkongmedicalapp I/Choreographer﹕ Skipped 70 frames!
The application may be doing too much work on its main thread.
03-17 17:17:54.963 1821-1835/com.google.andriod.gms.example.hongkongmedicalapp E/JSON Parser﹕ Error parsing data org.json.JSONException: End of input at character 0 of
03-17 17:17:54.963 1821-1835/com.google.andriod.gms.example.hongkongmedicalapp W/dalvikvm﹕ threadid=11: thread exiting with uncaught exception (group=0x40a71930)
03-17 17:17:55.203 1821-1835/com.google.andriod.gms.example.hongkongmedicalapp E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:299)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
at java.util.concurrent.FutureTask.run(FutureTask.java:239)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
at java.lang.Thread.run(Thread.java:856)
Caused by: java.lang.NullPointerException
at com.google.andriod.gms.example.hongkongmedicalapp.AllProductsActivity$LoadAllProducts.doInBackground(AllProductsActivity.java:129)
at com.google.andriod.gms.example.hongkongmedicalapp.AllProductsActivity$LoadAllProducts.doInBackground(AllProductsActivity.java:102)
at android.os.AsyncTask$2.call(AsyncTask.java:287)
at java.util.concurrent.FutureTask.run(FutureTask.java:234)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
at java.lang.Thread.run(Thread.java:856)
03-17 17:17:56.093 1821-1821/com.google.andriod.gms.example.hongkongmedicalapp I/Choreographer﹕ Skipped 57 frames! The application may be doing too much work on its
03-17 17:17:56.473 1821-1821/com.google.andriod.gms.example.hongkongmedicalapp I/Choreographer﹕ Skipped 33 frames! The application may be doing too much work on its main thread.
03-17 17:17:57.173 1821-1821/com.google.andriod.gms.example.hongkongmedicalapp I/Choreographer﹕ Skipped 73 frames! The application may be doing too much work on its main thread.
03-17 17:17:58.083 1821-1821/com.google.andriod.gms.example.hongkongmedicalapp E/WindowManager﹕ Activity com.google.andriod.gms.example.hongkongmedicalapp.AllProductsActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{40db1fe0 V.E..... R.....ID 0,0-729,192} that was originally added here
android.view.WindowLeaked: Activity com.google.andriod.gms.example.hongkongmedicalapp.AllProductsActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{40db1fe0 V.E..... R.....ID 0,0-729,192} that was originally added here
at android.view.ViewRootImpl.<init>(ViewRootImpl.java:354)
at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:216)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
at android.app.Dialog.show(Dialog.java:281)
at com.google.andriod.gms.example.hongkongmedicalapp.AllProductsActivity$LoadAllProducts.onPreExecute(AllProductsActivity.java:114)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
at android.os.AsyncTask.execute(AsyncTask.java:534)
at com.google.andriod.gms.example.hongkongmedicalapp.AllProductsActivity.onCreate(AllProductsActivity.java:57)
at android.app.Activity.performCreate(Activity.java:5104)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
以下是AllProductActivity.Java的代码：
package com.google.andriod.gms.example.hongkongmedicalapp;
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;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
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://101.78.175.101:21280/android_connect/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() {
@Override
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
//When I use debug mode, I find the program dead on this line and the value of JSONObject json is null
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 {
}
} 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);
}
});
}
}
}
以下是EditProductActivity.java的代码
package com.google.andriod.gms.example.hongkongmedicalapp;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.StrictMode;
import android.util.Log;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
public class EditProductActivity extends Activity {
TextView txtName;
TextView txtPrice;
TextView txtDesc;
TextView txtUses;
TextView txtSide;
TextView txtPrecau;
TextView txtinterac;
TextView txtoverdose;
String pid;
// Progress Dialog
private ProgressDialog pDialog;
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCT = "product";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
private static final String TAG_PRICE = "price";
private static final String TAG_DESCRIPTION = "description";
private static final String TAG_USES = "uses";
private static final String TAG_SIDEEFFECTS = "sideeffects";
private static final String TAG_PRECAUTIONS= "precauctions";
private static final String TAG_INTERACTIONS = "interactions";
private static final String TAG_OVERDOSE = "overdose";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.edit_product);
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
// getting product details from intent
Intent i = getIntent();
// getting product id (pid) from intent
pid = i.getStringExtra(TAG_PID);
// Getting complete product details in background thread
GetProductDetails dproductdetail = new GetProductDetails();
dproductdetail.execute();
}
/**
* Background Async Task to Get complete product details
* */
class GetProductDetails extends AsyncTask<String, String, String> {
// JSON parser class
JSONParser jsonParser = new JSONParser();
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(EditProductActivity.this);
pDialog.setMessage("Loading product details. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* Getting product details in background thread
* */
protected String doInBackground(String... params) {
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
// Check for success tag
int success;
try {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("pid", pid));
// getting product details by making HTTP request
// Note that product details url will use GET request
JSONObject json = jsonParser.makeHttpRequest("http://101.78.175.101:21280/android_connect/get_product_details.php", "GET", params);
// check your log for json response
Log.d("Single Product Details", json.toString());
// json success tag
success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// successfully received product details
JSONArray productObj = json.getJSONArray(TAG_PRODUCT); // JSON Array
// get first product object from JSON Array
JSONObject product = productObj.getJSONObject(0);
// product with this pid found
// Edit Text
txtName = (TextView) findViewById(R.id.inputName);
txtPrice = (TextView) findViewById(R.id.inputPrice);
txtDesc = (TextView) findViewById(R.id.inputDesc);
txtUses = (TextView) findViewById(R.id.inputuses);
txtSide = (TextView) findViewById(R.id.inputsideeffects);
txtPrecau = (TextView) findViewById(R.id.inputprecautions);
txtinterac= (TextView) findViewById(R.id.inputinteractions);
txtoverdose = (TextView) findViewById(R.id.inputoverdose);
// display product data in EditText
txtName.setText(product.getString(TAG_NAME));
txtPrice.setText(product.getString(TAG_PRICE));
txtDesc.setText(product.getString(TAG_DESCRIPTION));
txtUses.setText(product.getString(TAG_USES));
txtSide.setText(product.getString(TAG_SIDEEFFECTS));
txtPrecau.setText(product.getString(TAG_PRECAUTIONS));
txtinterac.setText(product.getString(TAG_INTERACTIONS));
txtoverdose .setText(product.getString(TAG_OVERDOSE));
}else{
// product with pid not found
}
} 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 got all details
pDialog.dismiss();
}
}
}
以下是JSONParser.java的代码
package com.google.andriod.gms.example.hongkongmedicalapp;
import android.util.Log;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,List<NameValuePair> params) {
// Making HTTP request
try {
// check for request method
if(method == "POST"){
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}else if(method == "GET"){
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
我的php脚本get_product_details：
<?php
/*
* Following code will get single product details
* A product is identified by product id (pid)
*/
// array for JSON response
$response = array();
// include db connect class
require_once __DIR__ . '/db_connect.php';
// connecting to db
$db = new DB_CONNECT();
// check for post data
if (isset($_GET["pid"])) {
$pid = $_GET['pid'];
// get a product from products table
$result = mysql_query("SELECT *FROM products WHERE pid = $pid");
if (!empty($result)) {
// check for empty result
if (mysql_num_rows($result) > 0) {
$result = mysql_fetch_array($result);
$products = array();
$products["pid"] = $result["pid"];
$products["name"] = $result["name"];
$products["price"] = $result["price"];
$products["description"] = $result["description"];
$products["uses"] = $result["uses"];
$products["sideeffects"] = $result["sideeffects"];
$products["precauctions"] = $result["precauctions"];
$products["interactions"] = $result["interactions"];
$products["overdose"] = $result["overdose"];
$products["created_at"] = $result["created_at"];
$products["updated_at"] = $result["updated_at"];
// success
$response["success"] = 1;
// user node
$response["products"] = array();
array_push($response["products"], $products);
// echoing JSON response
echo json_encode($response);
} else {
// no product found
$response["success"] = 0;
$response["message"] = "No product found";
// echo no users JSON
echo json_encode($response);
}
} else {
// no product found
$response["success"] = 0;
$response["message"] = "No product found";
// echo no users JSON
echo json_encode($response);
}
} else {
// required field is missing
$response["success"] = 0;
$response["message"] = "Required field(s) is missing";
// echoing JSON response
echo json_encode($response);
}
?>
答案 0 :(得分：0)
我认为错误的主要原因是你的服务器没有返回json。
我尝试在浏览器中打开http://101.78.175.101:21280/android_connect/get_all_products.php，不幸的是，我有一个空页。
对于有效的JSON，它应该至少返回{}。
您可以使用此热门工具http://jsonlint.com/
手动验证JSON所以，首先，你必须让你的服务器返回有效的JSON，然后我们可以看看其他一切是否正常工作。