在解析JSON数据时，我在主异常中发现了错误Error parsing Data。
然而，我的错误No Data Found没有被JSONException捕获，这让我认为数据库正在被成功读取，
我的服务器上有一个php文件：
<?php
mysql_connect("database_ip","database_username","database_password");
mysql_select_db("database_name");
$sql=mysql_query("select * from table");
while($row=mysql_fetch_assoc($sql))
$output[]=$row;
print(json_encode($output));// this will print the output in json
mysql_close();
?>
在线导航到php文件将显示预期的JSON数据：
[{"KEY_ROWID":"1","KEY_NAME":"Andrew","KEY_SCORE":"100","KEY_DATE":"0000-00-00 00:00:00"},{"KEY_ROWID":"2","KEY_NAME":"Peter","KEY_SCORE":"5000","KEY_DATE":"2013-11-29 10:58:21"}]
在Android中，我使用Async任务来读取数据：
class Task extends AsyncTask<String, String, Void> {
InputStream is = null;
String result = "";
@Override
protected Void doInBackground(String... params) {
// TODO Auto-generated method stub
String url_select = "http://mywebsite.com/myphpfile.php";
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url_select);
ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
try {
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
// read content
is = httpEntity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
try {
BufferedReader br = new BufferedReader(
new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = "";
while ((line = br.readLine()) != null) {
sb.append(line + "'n");
}
is.close();
result = sb.toString();
} catch (Exception e) {
// TODO: handle exception
Log.e("log_tag", "Error converting result " + e.toString());
}
return null;
}
protected void onPostExecute(Void v) {
try {
JSONArray Jarray = new JSONArray(result);
for (int i = 0; i < Jarray.length(); i++) {
JSONObject Jasonobject = Jarray.getJSONObject(i);
text = (TextView) findViewById(R.id.textView1);
// get an output on the screen
String name = Jasonobject.getString("KEY_NAME");
text.append(name + "'n");
}
}
catch (JSONException e1) {
Toast.makeText(getBaseContext(), "NO Data Found",
Toast.LENGTH_LONG).show();
}
catch (Exception e) {
// TODO: handle exception
Log.e("log_tag", "Error parsing data " + e.toString());
}
}
}
在我的活动onCreate中，我实例化异步类：
new Task().execute();
关于分析数据时出错的原因，有什么建议吗？
感谢
注意：使用println（）输出变量"result"会将Json输出到logcat，如预期
形成您的代码：
...
catch (Exception e) {
// TODO: handle exception
Log.e("log_tag", "Error parsing data " + e.toString());
}
问题是它可能不是Json异常，而是任何异常。在实践中，不建议捕获类型Exception。我们应该只捕获Exception类的特定子类型。在我们的例子中，findViewById抛出：NullPointerException。所以，首先将其更改为NullPointerException（除了JSONException之外），然后再次运行程序。
我会把Error parsing data改成通用的。
假设我们在findViewById上没有异常，并且我们的text不是null。
尝试使用Handler更新主线程（又名GUI）：
private Handler mHandler = null;
...
mHandler = new Handler();
...
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
try {
text = (TextView) findViewById(R.id.textView1);
JSONArray Jarray = new JSONArray(result);
for (int i = 0; i < Jarray.length(); i++) {
JSONObject Jasonobject = Jarray.getJSONObject(i);
// get an output on the screen
String name = Jasonobject.getString("KEY_NAME");
text.append(name + "'n");
}
}
catch (JSONException e1) {
Toast.makeText(getBaseContext(), "NO Data Found",
Toast.LENGTH_LONG).show();
}
catch (NullPointerException e) {
// TODO: handle exception
Log.e("log_tag", "Error " + e.toString());
}
}
}, 100); // dummy delay
附带说明：
放在循环for 外部的行text = (TextView) findViewById(R.id.textView1);
Dud i将您的json粘贴到assets文件夹中的本地文件中，并尝试检索它。它运行良好。这是我的密码。我不能使用你的代码，因为url在我这边不起作用。无论如何，这是我的代码：-
package com.example.test;
import java.io.InputStream;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
public class MainActivity extends Activity {
static InputStream is = null;
static JSONObject jObj = null;
String jsonString;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Making HTTP request
// String url = "http://api.worldbank.org/countries/ir?format=json";
String url = "http://10.0.2.2/andApp/artikel.php";
JSONParser jParser = new JSONParser();
// Getting JSON from URL
// JSONArray json = jParser.getJSONFromUrl(url);
// JSONObject json = jParser.getJSONFromUrl1(url);
// JSONObject json = null;
JSONArray json = null;
try {
InputStream is = getAssets().open("json1.json");
int size = is.available();
byte[] buffer = new byte[size];
is.read(buffer);
is.close();
jsonString = new String(buffer, "UTF-8");
// json = new JSONObject(jsonString);
json = new JSONArray(jsonString);
} catch (Exception e) {
e.printStackTrace();
}
try {
JSONArray json2 = json;
// .getJSONArray("artikel");
for (int i = 0; i < json2.length(); i++) {
JSONObject c = json2.getJSONObject(i);
// Storing JSON item in a Variable
String name = c.optString("KEY_ROWID", "");
String capitalCity = c.optString("KEY_NAME", "");
String score = c.optString("KEY_SCORE", "");
String date = c.optString("KEY_DATE", "");
}
} catch (JSONException e) {
e.printStackTrace();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}