Question

public class MainActivity extends Activity{

Spinner spinner;
String values[];


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

    StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
            .detectAll()
            .penaltyLog()
            .penaltyDialog()
            .build());

    StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder().detectAll()
            .penaltyLog()
            .build());

    TextView wid = (TextView) findViewById(R.id.wid);
    TextView name = (TextView) findViewById(R.id.name);
    TextView url = (TextView) findViewById(R.id.url);

    JSONObject json = null;
    String str = "";
    HttpResponse response;
    HttpClient myClient = new DefaultHttpClient();
    HttpPost myConnection = new HttpPost("http://egcrm.cloudapp.net/operations/index.php/dcapi/gettrucktypes");
    //http://demos.tricksofit.com/files/json.php

    try {
        response = myClient.execute(myConnection);
        str = EntityUtils.toString(response.getEntity(), "UTF-8");

    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        JSONArray jArray = new JSONArray(str);
        for (int i=0; i < jArray.length();i++){
        json = jArray.getJSONObject(i);

        wid.setText(json.getString("Key"));
        name.setText(json.getString("Value"));
        // url.setText(json.getString("url"));
            String shiva=new String();
            shiva=json.getString("Value");
            values=new String[jArray.length()];
            values[i]=shiva;
    }

    }

    catch ( JSONException e) {
        e.printStackTrace();
    }
spinner=(Spinner)findViewById(R.id.spinner);
        ArrayAdapter<String> aa=new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,values);
        aa.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(aa);
    }

}

logcat的：

01-26 11：56：12.799 19322-19322 / com.example.sai.lasttry E / AndroidRuntime：致命异常：主要处理：com.example.sai.lasttry，PID：19322 java.lang.NullPointerException：尝试调用虚方法＆＃39; java.lang.String java.lang.Object.toString（）＆＃39;在null对象上参考在 android.widget.ArrayAdapter.createViewFromResource（ArrayAdapter.java:394）在android.widget.ArrayAdapter.getView（ArrayAdapter.java:362）在android.widget.AbsSpinner.onMeasure（AbsSpinner.java:197）在android.widget.Spinner.onMeasure（Spinner.java:507）在android.view.View.measure（View.java:17430）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5463）在 android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1436）在 android.widget.LinearLayout.measureHorizontal（LinearLayout.java:1083）在android.widget.LinearLayout.onMeasure（LinearLayout.java:615）在android.view.View.measure（View.java:17430）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5463）在android.widget.FrameLayout.onMeasure（FrameLayout.java:430）在android.view.View.measure（View.java:17430）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5463）在 android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1436）在android.widget.LinearLayout.measureVertical（LinearLayout.java:722）在android.widget.LinearLayout.onMeasure（LinearLayout.java:613）在android.view.View.measure（View.java:17430）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5463）在android.widget.FrameLayout.onMeasure（FrameLayout.java:430）在 com.android.internal.policy.impl.PhoneWindow $ DecorView.onMeasure（PhoneWindow.java:2560）在android.view.View.measure（View.java:17430）在android.view.ViewRootImpl.performMeasure（ViewRootImpl.java:2001）在android.view.ViewRootImpl.measureHierarchy（ViewRootImpl.java:1166）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:1372）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1054）在 android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:5779）在 android.view.Choreographer $ CallbackRecord.run（Choreographer.java:767）在android.view.Choreographer.doCallbacks（Choreographer.java:580）在android.view.Choreographer.doFrame（Choreographer.java:550）在 android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:753）在android.os.Handler.handleCallback（Handler.java:739）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:135）在android.app.ActivityThread.main（ActivityThread.java:5221） at java.lang.reflect.Method.invoke（Native Method）在java.lang.reflect.Method.invoke（Method.java:372）在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:899）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:694）

Answer 1

根本原因：循环中的新String []

values=new String[jArray.length()];

Answer 2

我认为您的错误就在这一行

str = EntityUtils.toString(response.getEntity(), "UTF-8");

似乎你试图让数据不发布，所以这样做

HttpGet httpGet = new HttpGet("http://egcrm.cloudapp.net/operations/index.php/dcapi/gettrucktypes");
HttpResponse httpResponse = new DefaultHttpClient()
                    .execute(httpGet);

然后获取

之类的字符串

String result = EntityUtils.toString(httpResponse.getEntity(),
                "utf-8");

Answer 3

错误是因为这些行：

values=new String[jArray.length()];
values[i]=shiva;

这是因为values数组没有填满，它给出了NullPointerException。尝试调试并检查jArray.length()中的内容并确保它填满您的值数组。

我得到一个nullpointer异常

3 个答案: