php - Android 应用程序 - JSON - PHP - localhost --> 通过从 php 脚本获取数据出现 NullPointerException

Question

我现在正在处理我的 Android 应用程序项目，但 listView 出现问题 下面是代码和 LogCat - 错误消息； 我的数据库存储在本地主机，我使用 php 脚本来获取 mysql 数据库

主要 - 应用程序的 Activity

public class PlanActivity extends Activity {
String url = "http://10.0.2.2/phpBusplan/phpConnect.php";
InputStream is;
ArrayList<String> results = new ArrayList<String>();
JSONObject json_data;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.planlayout);

    RadioGroup rgZeit = (RadioGroup) findViewById(R.id.rgZeiten);
}

这里我从php脚本获取数据

public void getData() {

    String result = "";
     ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();

    // http post
        try{
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost(url);
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            is = entity.getContent();
            }catch(Exception e){
                Log.e("log_tag", "Fehler bei der http Verbindung "+e.toString());
            }

        // convert response to string
        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();
            result=sb.toString();
            }catch(Exception e){
                Log.e("log_tag", "Error converting result "+e.toString());
            }

        // parse json data
        try{
            JSONArray jArray = new JSONArray(result);
            for(int i=1;i<jArray.length();i++){
                json_data = jArray.getJSONObject(i);
                results.add((String) json_data.get("IDHaltestelle") + " "+ json_data.get("HaltestelleName"));
            } 
                filllist();
            }
            catch(JSONException e){
                Log.e("log_tag", "Error parsing data "+e.toString());
            }

    }
    public <T> void filllist() {
        ListView listStart = (ListView) findViewById(android.R.id.list);
        ListAdapter adapter = new ArrayAdapter<T>(getApplicationContext(), android.R.layout.simple_list_item_1);

        listStart.setAdapter(adapter);;
    }`

日志 - 猫消息

10-07 17:43:39.557: E/AndroidRuntime(702): FATAL EXCEPTION: main
10-07 17:43:39.557: E/AndroidRuntime(702): java.lang.RuntimeException: Unable to start activity ComponentInfo{at.atn.android/at.atn.android.MainActivity}:java.lang.RuntimeException: Unable to start activity ComponentInfo{at.atn.android/at.atn.android.PlanActivity}: java.lang.NullPointerException
10-07 17:43:39.557: E/AndroidRuntime(702):  at.android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.os.Looper.loop(Looper.java:123)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.ActivityThread.main(ActivityThread.java:3683)
10-07 17:43:39.557: E/AndroidRuntime(702):  at java.lang.reflect.Method.invokeNative(Native Method)
10-07 17:43:39.557: E/AndroidRuntime(702):  at java.lang.reflect.Method.invoke(Method.java:507)
10-07 17:43:39.557: E/AndroidRuntime(702):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-07 17:43:39.557: E/AndroidRuntime(702):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-07 17:43:39.557: E/AndroidRuntime(702):  at dalvik.system.NativeStart.main(Native Method)
10-07 17:43:39.557: E/AndroidRuntime(702): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{at.atn.android/at.atn.android.PlanActivity}: java.lang.NullPointerException
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.ActivityThread.startActivityNow(ActivityThread.java:1487)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:654)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.widget.TabHost.setCurrentTab(TabHost.java:326)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.widget.TabHost.addTab(TabHost.java:216)
10-07 17:43:39.557: E/AndroidRuntime(702):  at at.atn.android.MainActivity.onCreate(MainActivity.java:38)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
10-07 17:43:39.557: E/AndroidRuntime(702):  ... 11 more
10-07 17:43:39.557: E/AndroidRuntime(702): Caused by: java.lang.NullPointerException
10-07 17:43:39.557: E/AndroidRuntime(702):  at at.atn.android.PlanActivity.filllist(PlanActivity.java:143)
10-07 17:43:39.557: E/AndroidRuntime(702):  at at.atn.android.PlanActivity.getData(PlanActivity.java:132)
10-07 17:43:39.557: E/AndroidRuntime(702):  at at.atn.android.PlanActivity.onCreate(PlanActivity.java:51)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-07 17:43:39.557: E/AndroidRuntime(702):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
10-07 17:43:39.557: E/AndroidRuntime(702):  ... 20 more

php - 脚本(名称:phpConnect.php)

<?php
$host = "localhost"; 
$username = "XXXXX"; 
$password = "XXXXX"; 
$db_name = "XXXXX"; 

mysql_connect($host,$username,$password);
mysql_select_db($db_name);

$q=mysql_query("SELECT * FROM haltestelle");
while($e=mysql_fetch_assoc($q))
    $output[]=$e;

print(json_encode($output));

mysql_close();
?>

json - 来自 php 脚本的数据

[{"IDHaltestelle":"1","HaltestelleName":"Schwarzenberg"},{"IDHaltestelle":"2","HaltestelleName":"Ulrichsberg"},{"IDHaltestelle":"3","HaltestelleName":"Aigen"},{"IDHaltestelle":"4","HaltestelleName":"Rohrbach"},{"IDHaltestelle":"5","HaltestelleName":"St. Owald"},{"IDHaltestelle":"6","HaltestelleName":"St. Stefan"},{"IDHaltestelle":"7","HaltestelleName":"Afiesl"},{"IDHaltestelle":"8","HaltestelleName":"Guglwald"},{"IDHaltestelle":"9","HaltestelleName":"Bad Leonfelden"},{"IDHaltestelle":"10","HaltestelleName":null},{"IDHaltestelle":"11","HaltestelleName":"Helfenberg"},{"IDHaltestelle":"12","HaltestelleName":"Haslach"},{"IDHaltestelle":"13","HaltestelleName":"Peilstein"},{"IDHaltestelle":"14","HaltestelleName":"Kollerschlag"},{"IDHaltestelle":"15","HaltestelleName":"Julbach"},{"IDHaltestelle":"16","HaltestelleName":"Nebelberg Ost"},{"IDHaltestelle":"17","HaltestelleName":"Sarleinsbach"},{"IDHaltestelle":"18","HaltestelleName":"HTL Neufelden"},{"IDHaltestelle":"19","HaltestelleName":"Niederwaldkirchen"},{"IDHaltestelle":"20","HaltestelleName":"St. Peter"},{"IDHaltestelle":"21","HaltestelleName":"St. Johann"},{"IDHaltestelle":"22","HaltestelleName":"St, Veit"},{"IDHaltestelle":"23","HaltestelleName":"Oberneukirchen"},{"IDHaltestelle":"24","HaltestelleName":"Herzogsdorf"},{"IDHaltestelle":"25","HaltestelleName":"St, Martin"},{"IDHaltestelle":"26","HaltestelleName":"Gramastetten"},{"IDHaltestelle":"27","HaltestelleName":"Linz Hauptbahnhof"},{"IDHaltestelle":"28","HaltestelleName":null},{"IDHaltestelle":"29","HaltestelleName":"Ottensheim"},{"IDHaltestelle":"30","HaltestelleName":"Walding"},{"IDHaltestelle":"31","HaltestelleName":"Gerling B127"},{"IDHaltestelle":"32","HaltestelleName":"Feldkirchen"},{"IDHaltestelle":"33","HaltestelleName":"Landshaag"},{"IDHaltestelle":"34","HaltestelleName":"Aschach Bahnhof"},{"IDHaltestelle":"35","HaltestelleName":"Hartkirchen"},{"IDHaltestelle":"36","HaltestelleName":"Eferding"},{"IDHaltestelle":"37","HaltestelleName":"Haibach"},{"IDHaltestelle":"38","HaltestelleName":"Kirchberg ob der Donau"},{"IDHaltestelle":"39","HaltestelleName":null},{"IDHaltestelle":"40","HaltestelleName":"Lembach"},{"IDHaltestelle":"41","HaltestelleName":"Niederkappel"},{"IDHaltestelle":"42","HaltestelleName":"Pfarrkirchen"},{"IDHaltestelle":"43","HaltestelleName":"Hofkirchen"},{"IDHaltestelle":"44","HaltestelleName":"Neustift"},{"IDHaltestelle":"45","HaltestelleName":"Oberkappel"},{"IDHaltestelle":"46","HaltestelleName":"Niederranna"},{"IDHaltestelle":"47","HaltestelleName":"Waldkirchen"},{"IDHaltestelle":"48","HaltestelleName":"Neukirchen"},{"IDHaltestelle":"49","HaltestelleName":"Peuerbach"}]

希望你能帮助我 谢谢!

Answer 1

试试这个:

ArrayAdapter<String> arrayAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, results);

我认为您误解了如何使用 ArrayAdapter 的方式。看看这个真的很棒TUTORIAL