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基本上我有一個Android應用程序和一個MySQL數據庫，我使用PHP嘗試使用它來填充ListView。現在，出於某種原因，下面的代碼似乎崩潰和logcat的說，有一個與窗口管理器的一個問題當試圖從數據庫中獲取值時，Android應用程序崩潰引用WindowManager錯誤
的代碼是：
AllComediansActivity.java：
package com.example.connecttest;
public class AllComediansActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String,String>> comedianList;
// url to get all comedian names
private static String url_all_comedians = "http://localhost/connect/get_all_comedians.php";
//JSON Node Names
private static final String TAG_SUCCESS = "success";
private static final String TAG_COMEDIAN = "comedian";
private static final String TAG_PID = "id";
private static final String TAG_NAME = "name";
// products JSONArray
JSONArray comedians = null;
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.all_comedians);
//Hashmap for ListView
comedianList = new ArrayList<HashMap<String, String>>();
//Loading comedians in background thread
new LoadAllComedians().execute();
// Get Listview
ListView lv = getListView();
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.id)).getText().toString();
//
}
});
}
class LoadAllComedians extends AsyncTask<String, String, String>{
// Before Starting background thread show Progress Dialog
protected void onPreExecute(){
super.onPreExecute();
pDialog = new ProgressDialog(AllComediansActivity.this);
pDialog.setMessage("Loading products. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// Getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_comedians, "GET", params);
//Check log cat for JSON response
Log.d("All Comedians: ", json.toString());
try{
//Checking for SUCCESS TAG in JSON
int success = json.getInt(TAG_SUCCESS);
if(success == 1){
// Comedians found
// Getting Array of Comedians
comedians = json.getJSONArray(TAG_COMEDIAN);
// Looping through All Comedians
for(int i = 0; i < comedians.length(); i++){
JSONObject c = comedians.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
comedianList.add(map);
}
} else {
// no products found
// Launch Add New Comedian Activity
Intent i = new Intent(getApplicationContext(), NewComedianActivity.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 comedians
pDialog.dismiss();
// Updating UI from Background Thread
runOnUiThread(new Runnable(){
public void run(){
// Updating JSON data into ListView
ListAdapter adapter = new SimpleAdapter(AllComediansActivity.this, comedianList, R.layout.list_item, new String[] {TAG_PID, TAG_NAME}, new int[] {R.id.id,R.id.name});
setListAdapter(adapter);
}
});
}
}
}
我有正確的進口只是刪除他們爲了簡潔起見。它引用
的JSONParser是：
JSONParser.java：
package com.example.connecttest;
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 method
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;
}
}
當我瀏覽到它在瀏覽器中的PHP文件返回以下信息：
{"comedian":[{"id":"1","name":"Mike Coombes","address":"Test","email":"[email protected]","tel":"xxxxxxxx"},{"id":"2","name":"Test","address":"Test","email":"[email protected]","tel":"xxxxxxx"}],"success":1}
所以我的PHP正確地查詢數據庫並使用JSON返回它。
現在調試程序表明，它似乎變得儘可能的下面一行：
JSONObject json = jParser.makeHttpRequest(url_all_comedians, "GET", params);
之前談到脫膠，我一直在拉我的頭髮幾個小時試圖讓這項工作過，但無濟於事，我想知道人們是否可以幫助我解決這個問題！
至於問我logcat的錯誤是：
03-21 05:57:10.319: E/Buffer Error(3500): Error converting result java.lang.NullPointerException: lock == null
03-21 05:57:10.319: E/JSON Parser(3500): Error parsing data org.json.JSONException: End of input at character 0 of
03-21 05:57:10.329: E/AndroidRuntime(3500): FATAL EXCEPTION: AsyncTask #1
03-21 05:57:10.329: E/AndroidRuntime(3500): java.lang.RuntimeException: An error occured while executing doInBackground()
03-21 05:57:10.329: E/AndroidRuntime(3500): at android.os.AsyncTask$3.done(AsyncTask.java:299)
03-21 05:57:10.329: E/AndroidRuntime(3500): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
03-21 05:57:10.329: E/AndroidRuntime(3500): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
03-21 05:57:10.329: E/AndroidRuntime(3500): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
03-21 05:57:10.329: E/AndroidRuntime(3500): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
03-21 05:57:10.329: E/AndroidRuntime(3500): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
03-21 05:57:10.329: E/AndroidRuntime(3500): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
03-21 05:57:10.329: E/AndroidRuntime(3500): at java.lang.Thread.run(Thread.java:856)
03-21 05:57:10.329: E/AndroidRuntime(3500): Caused by: java.lang.NullPointerException
03-21 05:57:10.329: E/AndroidRuntime(3500): at com.example.connecttest.AllComediansActivity$LoadAllComedians.doInBackground(AllComediansActivity.java:93)
03-21 05:57:10.329: E/AndroidRuntime(3500): at com.example.connecttest.AllComediansActivity$LoadAllComedians.doInBackground(AllComediansActivity.java:1)
03-21 05:57:10.329: E/AndroidRuntime(3500): at android.os.AsyncTask$2.call(AsyncTask.java:287)
03-21 05:57:10.329: E/AndroidRuntime(3500): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
03-21 05:57:10.329: E/AndroidRuntime(3500): ... 4 more
發佈您的logcat錯誤。 – rajeshwaran 2013-03-21 05:50:31
@Coombes：看到[這個例子]（http：//veerasundar.com/blog/2011/09/making-get-and-post-requests-in-android-application/）都是http get-post請求，因爲你沒有從服務器獲得結果 – 2013-03-21 06:04:31