尝试在android中使用json Parsing将数据从服务器添加到listView时获取空指针异常
我正在尝试从php获取数据&希望将其放在一个简单的listView而不是TextView中。当我使用TextView数据显示时，但当我使用在ListView中放置数据时，我只会得到空指针异常。 请建议我并说明我的错误。 代码如下：尝试在android中使用json Parsing将数据从服务器添加到listView时获取空指针异常,android,json,android-listview,nullpointerexception,Android,Json,Android Listview,Nullpointerexception,我正在尝试从php获取数据&希望将其放在一个简单的listView而不是TextView中。当我使用TextView数据显示时，但当我使用在ListView中放置数据时，我只会得到空指针异常。 请建议我并说明我的错误。 代码如下： package cse.project.medical; import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamRea
package cse.project.medical;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONObject;
import android.annotation.TargetApi;
import android.app.ActionBar;
import android.app.Activity;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.os.StrictMode;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public class Patient_biodata extends Activity {
String pat_name, total_title;
ListView listView;
// TextView profile_show;
Button update;
ArrayAdapter<String > adapter;
String[] arr;
protected void onCreate(Bundle savedInstanceState) {
Log.e("ni", "doc biodata has started");
super.onCreate(savedInstanceState);
setContentView(R.layout.patient_biodata);
StrictMode.enableDefaults();
ActionBar action_bar = getActionBar();
Intent i = getIntent();
// getting attached intent data
pat_name = i.getStringExtra("person_name");
total_title = "Hello...." + pat_name;
action_bar.setTitle(total_title);
// profile_show = (TextView) findViewById(R.id.show_profile);
update = (Button) findViewById(R.id.update_btn);
listView = (ListView) findViewById(R.id.listView2);
get_all_information_of_a_user();
update.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
alert_update_method();
}
});
}
protected void alert_update_method() {
// TODO Auto-generated method stub
}
protected void get_all_information_of_a_user() {
String result = "";
InputStream isr = null;
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("pat_name", pat_name));
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(
"http://192.168.56.1/imp/JSON/json_pat_biodata.php");
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
isr = entity.getContent();
Log.e("connection", "connection success");
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
// profile_show.setText("Couldn't connect to database");
}
// convert response to string
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
isr, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
isr.close();
result = sb.toString();
Log.e("connection", "convertion success");
Log.e("result", result);
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
// parse json data
try {
//String s = "";
JSONArray jArray = new JSONArray(result);
for (int i = 0; i < jArray.length(); i++) {
JSONObject json = jArray.getJSONObject(i);
arr[0] = json.getString("p_name");
arr[1] = json.getString("p_age");
arr[2] = json.getString("p_gender");
arr[3] = json.getString("p_address");
arr[4] = json.getString("p_mobile");
arr[5] = json.getString("p_email");
arr[6] = json.getString("p_nationality");
arr[7] = json.getString("p_username");
}
Log.e("before", "adapter");
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
Patient_biodata.this, android.R.layout.simple_list_item_1,
arr);
listView.setAdapter(adapter);
Log.e("after", "adapter");
// profile_show.setText(s);
} catch (Exception e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
}
}
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ScrollView
android:id="@+id/scrollView1"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="5dp" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_weight="3"
android:text="Your Profile"
android:textSize="20sp"
android:textStyle="italic" />
<Button
android:id="@+id/update_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Update" />
</LinearLayout>
</LinearLayout>
</ScrollView>
<ListView
android:id="@+id/listView2"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
<?php
$host='localhost';
$uname='root';
$pwd='';
$db="hospital";
$con = mysql_connect($host,$uname,$pwd) or die("connection failed");
mysql_select_db($db,$con) or die("db selection failed");
$name = $_POST['pat_name'];
$find_pat_id = "select p_name,p_age,p_gender,p_address,p_mobile,p_email,p_nationality,p_username from current_patient where p_username = '$name'";
$p_id_run = mysql_query($find_pat_id);
if(mysql_num_rows($p_id_run)>0)
{
while($row=mysql_fetch_assoc($p_id_run))
{
$flag[]=$row;
}
print(json_encode($flag));
}
mysql_close($con);
?>
看起来你的主要问题是你没有初始化你的arr数组，也就是说你从来没有做过arr=newstring[8]； 这可能是你的NPE的原因 但是，看起来您只是从JSON结果中给适配器一条记录 您可能需要创建一个自定义适配器，并为simple_list_item_1.xml中的每个项目创建一个TextView 但是，为了让您走上正确的道路，请先尝试以下方法：
// parse json data
try {
//String s = "";
JSONArray jArray = new JSONArray(result);
arr = new String[jArray.length()]; //initialize your array
for (int i = 0; i < jArray.length(); i++) {
JSONObject json = jArray.getJSONObject(i);
StringBuffer buff = new StringBuffer();
buff.append(json.getString("p_name") + " ");
buff.append(json.getString("p_age") + " ");
buff.append(json.getString("p_gender") + " ");
buff.append(json.getString("p_address") + " ");
buff.append(json.getString("p_mobile") + " ");
buff.append(json.getString("p_email") + " ");
buff.append(json.getString("p_nationality") + " ");
buff.append(json.getString("p_username");
arr[i] = buff.toString();
}
Log.e("before", "adapter");
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
Patient_biodata.this, android.R.layout.simple_list_item_1,
arr);
listView.setAdapter(adapter);
Log.e("after", "adapter");
// profile_show.setText(s);
} catch (Exception e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
您可以发布stacktrace吗？请发布您的简单列表项目。您的项目xml中只有一个文本视图？您希望数据如何显示？发布堆栈跟踪，以及XML布局是否为R.layout.patient_biodata？我想是的。