Question

我正在尝试在我的代码中使用getJSON和parseJSON，并且getJSON正常工作但解析不行。我得到例外：

java.lang.NullPointerException: Attempt to invoke virtual method 'org.json.JSONObject org.json.JSONArray.getJSONObject(int)' on a null object reference

在MainActivity中我有：

        public void onCellLocationChanged(CellLocation lokacija) {
        super.onCellLocationChanged(lokacija);
        location = (GsmCellLocation) Phone.getCellLocation();
        textCellId.setText(String.valueOf(location.getCid() % 65536));
        textCellLac.setText(String.valueOf(location.getLac()));
        String JSON_URL_string=JSON_URL + "?cellid=" + String.valueOf(location.getCid()%65636);
        getJSON(JSON_URL_string);
        ParseJSON();
    }

getJSON返回如下内容：

{"result":[{"cellname":"BG_ACB1","celllat":"44.81125","celllon":"20.39933","celldir":"0","cellattr":"gsm900"},{"cellname":"SOMB5W1","celllat":"45.783055","celllon":"19.120833","celldir":"100","cellattr":"umts900"}]}

在看到getJSON后，我调用了ParseJSON：

    private void ParseJSON() {
        Intent intent = new Intent(MainActivity.this,ParseJSON.class);
        intent.putExtra(MY_JSON,textCellNameSakriven.getText().toString());
        startActivity(intent);
    }

这是一个ParseJSON类。如果我运行没有ParseJSON的代码，它可以正常工作：

public class ParseJSON extends ActionBarActivity {

    private String myJSONString;

    private static final String JSON_ARRAY ="result";
    private static final String CELLNAME = "cellname";

    private JSONArray users = null;

    private int TRACK = 0;

    private TextView textCellName;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Intent intent = getIntent();
        myJSONString = intent.getStringExtra(MainActivity.MY_JSON);

        textCellName=(TextView) findViewById(R.id.textCellName);
        extractJSON();
        showData();
    }

    private void extractJSON(){
        try {
            JSONObject jsonObject = new JSONObject(myJSONString);
            users = jsonObject.getJSONArray(JSON_ARRAY);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    private void showData(){
        try {
            JSONObject jsonObject = users.getJSONObject(TRACK);

            textCellName.setText(jsonObject.getString(CELLNAME));

        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
 }

最后，这是一个日志：

FATAL EXCEPTION: main
 Process: com.zelenigrad.bsavkovic.myapplication, PID: 9862
 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.zelenigrad.bsavkovic.myapplication/com.zelenigrad.bsavkovic.myapplication.ParseJSON}: java.lang.NullPointerException: Attempt to invoke virtual method 'org.json.JSONObject org.json.JSONArray.getJSONObject(int)' on a null object reference
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2305)
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2365)
     at android.app.ActivityThread.access$800(ActivityThread.java:148)
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1283)
     at android.os.Handler.dispatchMessage(Handler.java:102)
     at android.os.Looper.loop(Looper.java:135)
     at android.app.ActivityThread.main(ActivityThread.java:5272)
     at java.lang.reflect.Method.invoke(Native Method)
     at java.lang.reflect.Method.invoke(Method.java:372)
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:909)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:704)
  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'org.json.JSONObject org.json.JSONArray.getJSONObject(int)' on a null object reference
     at com.zelenigrad.bsavkovic.myapplication.ParseJSON.showData(ParseJSON.java:59)
     at com.zelenigrad.bsavkovic.myapplication.ParseJSON.onCreate(ParseJSON.java:43)
     at android.app.Activity.performCreate(Activity.java:5977)
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2258)
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2365) 
     at android.app.ActivityThread.access$800(ActivityThread.java:148) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1283) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:135) 
     at android.app.ActivityThread.main(ActivityThread.java:5272) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at java.lang.reflect.Method.invoke(Method.java:372) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:909) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:704)

感谢您的努力。

RGDS

Answer 1

你不能使用这个

JSONObject jsonObject = users.getJSONObject(TRACK);

在你的响应中没有像这样的json对象，它给你NullPointerException。

，对象名称必须为String always。您正在使用int值TRACK。

getJSON有效但parseJSON不行

1 个答案: