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我是新來的Android和JSON和我試圖檢索雅虎氣象服務的一些JSON數據，並.setText在我的三個textviews在我的XML相關數據的JSON對象Android JSONObject結果始終爲空？
這是在那裏我得到了休息查詢（點擊測試，你會得到休息查詢）：
https://developer.yahoo.com/yql/console/#h=select+*+from+weather.forecast+where+woeid%3D2502265
錯誤：
12-22 19:39:10.745 31404-31431/eggy.com.jsontest E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
Process: eggy.com.jsontest, PID: 31404
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:300)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
Caused by: java.lang.NullPointerException
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
at org.json.JSONTokener.nextValue(JSONTokener.java:94)
at org.json.JSONObject.<init>(JSONObject.java:155)
at org.json.JSONObject.<init>(JSONObject.java:172)
at eggy.com.jsontest.MainActivity$MyAsyncTask.doInBackground(MainActivity.java:81)
at eggy.com.jsontest.MainActivity$MyAsyncTask.doInBackground(MainActivity.java:41)
at android.os.AsyncTask$2.call(AsyncTask.java:288)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
代碼：
public class MainActivity extends ActionBarActivity {
private static String yahooWeatherInfo =
"https://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20weather.forecast%20where%20woeid%3D2502265&format=json&diagnostics=true&callback=";
private static String chill = "";
private static String direction = "";
private static String speed = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new MyAsyncTask().execute();
}
private class MyAsyncTask extends AsyncTask<String,String,String> {
@Override
protected String doInBackground(String... params) {
DefaultHttpClient httpclient = new DefaultHttpClient(new BasicHttpParams());
HttpPost httppost = new HttpPost(yahooWeatherInfo);
// Depends on your web service
httppost.setHeader("Content-type", "application/json");
InputStream inputStream = null;
String result = null;
try {
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
inputStream = entity.getContent();
// json is UTF-8 by default
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
{
sb.append(line + "\n");
}
result = sb.toString();
} catch (Exception e) {
// Oops
}
finally {
try{
if(inputStream != null)
inputStream.close();
}catch(Exception squish){
}
}
try {
JSONObject jObject = new JSONObject(result);
JSONObject queryObject = jObject.getJSONObject("query");
JSONObject windObject = queryObject.getJSONObject("wind");
chill = windObject.getString("chill");
direction = windObject.getString("direction");
speed = windObject.getString("speed");
} catch(JSONException e) {
}
return null;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
TextView line1 = (TextView) findViewById(R.id.line1);
TextView line2 = (TextView) findViewById(R.id.line2);
TextView line3 = (TextView) findViewById(R.id.line3);
line1.setText("Chill " + chill);
line2.setText("Direction " + direction);
line3.setText("Speed " + speed);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
錯誤總是在：
JSONObject jObject = new JSONObject(result);
也許我用錯了查詢，我不能完全肯定。
謝謝你的幫助。
你檢查什麼結果，當執行涉及到該行？ –
那麼，如果您的HTTP請求有任何問題，結果將爲空。嘗試從null分析JSONObject將是一個問題。您是否嘗試檢查運行時的結果？ –
嗨，大家好，我嘗試記錄結果，但我甚至得到一個空指針異常 - 由於：java.lang.NullPointerException：println需要一條消息。我認爲沒有任何問題。 – Adz