Question

我无法实例化活动组件信息：mainactivity：NullPointerException 我的第一个屏幕是一个启动屏幕，它将数据传递给主要活动。主要活动将数据传递给它的片段。此数据用于加载微调器下拉列表。互联网访问是在片段中完成的，之前的代码正在运行。因此，当每次选择片段时，从服务器检索数据以加载下拉列表。但现在我只是使用异步任务在初始启动屏幕中从服务器获取数据，并通过意图将其传递给主要活动。使用getDepartment（）等函数，片段可以访问字符串。

    FragmentTab1.java
    @Override
    public SherlockFragmentActivity getSherlockActivity() {
        return super.getSherlockActivity();
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // Get the view from fragmenttab1.xml
        View view = inflater.inflate(R.layout.fragmenttab1, container, false);




        final Spinner spinner1 = (Spinner) view.findViewById(R.id.Spinner1);
          // Spinner click listener
      spinner1.setOnItemSelectedListener(this);
       // Spinner Drop down elements
      List<String> categories = new ArrayList<String>();
      categories.add("select");


      StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
      StrictMode.setThreadPolicy(policy);
        //MainActivity x=new MainActivity();



        try {
            // dept_response = CustomHttpClient.executeHttpPost("http://10.0.2.2/android_db/ppf4_dept.php",response_Parameters);
            //dept_response = CustomHttpClient.executeHttpPost("http://webdev1.tifr.res.in/~PFproj/pplf/ppf4_dept.php",response_Parameters,FragmentTab1.this.getActivity());
            String dept_result=((MainActivity)this.getActivity()).getDepartment();
        JSONArray jArray = new JSONArray(dept_result);
          for(int i=0;i<jArray.length();i++){
                JSONObject json_data = jArray.getJSONObject(i);


                //categories.add(json_data.getString("dept"));}
                categories.add(json_data.getString("PF_dept"));}


        }
        catch(JSONException e){
            Log.e("log_tag", "Error parsing data "+e.toString());
    }
        catch (Exception e) {
             Log.e("log_tag","Error in http connection!!" + e.toString());     
            }




        // Creating adapter for spinner
        ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this.getActivity(), android.R.layout.simple_spinner_item, categories);
        // Drop down layout style - list view with radio button
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        // attaching data adapter to spinner
        spinner1.setAdapter(dataAdapter);



        final Spinner spinner2 = (Spinner) view.findViewById(R.id.Spinner2);
          // Spinner click listener
      spinner2.setOnItemSelectedListener(this);
      // Spinner Drop down elements
      List<String> categories2 = new ArrayList<String>();
      categories2.add("select");

     // ArrayList<NameValuePair> response_Parameters = new ArrayList<NameValuePair>();

        try {
             //role_response = CustomHttpClient.executeHttpPost("http://10.0.2.2/android_db/ppf4_role.php",response_Parameters);
            //role_response = CustomHttpClient.executeHttpPost("http://webdev1.tifr.res.in/~PFproj/pplf/ppf4_role.php",response_Parameters,FragmentTab1.this.getActivity());
            String role_result=((MainActivity)this.getActivity()).getRole();

        JSONArray jArray = new JSONArray(role_result);
          for(int i=0;i<jArray.length();i++){
                JSONObject json_data = jArray.getJSONObject(i);


                categories2.add(json_data.getString("role"));}

        }
        catch(JSONException e){
          Log.e("log_tag", "Error parsing data "+e.toString());
  }
        catch (Exception e) {
             Log.e("log_tag","Error in http connection!!" + e.toString());     
            }


      // Creating adapter for spinner
        ArrayAdapter<String> dataAdapter2 = new ArrayAdapter<String>(this.getActivity(), android.R.layout.simple_spinner_item, categories2);
        // Drop down layout style - list view with radio button
        dataAdapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        // attaching data adapter to spinner
        spinner2.setAdapter(dataAdapter2);




        //spinner3
        final Spinner spinner3 = (Spinner) view.findViewById(R.id.Spinner3);
          // Spinner click listener
      spinner3.setOnItemSelectedListener(this);
      // Spinner Drop down elements
      List<String> categories3 = new ArrayList<String>();
      categories3.add("select");

      String desig_response = null;
        try {
             //desig_response = CustomHttpClient.executeHttpPost("http://10.0.2.2/android_db/ppf4_desig.php",response_Parameters);
            //desig_response = CustomHttpClient.executeHttpPost("http://webdev1.tifr.res.in/~PFproj/pplf/ppf4_desig.php",response_Parameters,FragmentTab1.this.getActivity());
            String desig_result=((MainActivity)this.getActivity()).getDesignation();

        JSONArray jArray = new JSONArray(desig_result);
          for(int i=0;i<jArray.length();i++){
                JSONObject json_data = jArray.getJSONObject(i);

               // String name=json_data.getString("dept");
                categories3.add(json_data.getString("designation"));}

        }
        catch(JSONException e){
        Log.e("log_tag", "Error parsing data "+e.toString());
}
        catch (Exception e) {
             Log.e("log_tag","Error in http connection!!" + e.toString());     
            }

      // Creating adapter for spinner
        ArrayAdapter<String> dataAdapter3 = new ArrayAdapter<String>(this.getActivity(), android.R.layout.simple_spinner_item, categories3);
        // Drop down layout style - list view with radio button
        dataAdapter3.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        // attaching data adapter to spinner
        spinner3.setAdapter(dataAdapter3);

MainActivity

    public class MainActivity extends SherlockFragmentActivity implements
    SearchView.OnQueryTextListener, SearchView.OnSuggestionListener {
//***********************************************************************************************************

// start of actionbarsherlock tabnavigation
// Declare Variables
ActionBar mActionBar;
ViewPager mPager;
Tab tab;
DBController controller = new DBController(this);
Intent i = getIntent();
String dept_response = i.getExtras().getString("dept_response");
String role_response = i.getExtras().getString("role_response");
String desig_response = i.getExtras().getString("desig_response");
public String getDepartment(){
       return this.dept_response;
     }
public String getRole(){
       return this.role_response;
     }
public String getDesignation(){
       return this.desig_response;
     }


ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>();

@Override
protected void onCreate(Bundle savedInstanceState) {

logcat的：

01-28 22:24:09.623: D/AndroidRuntime(1123): Shutting down VM
01-28 22:24:09.623: W/dalvikvm(1123): threadid=1: thread exiting with uncaught exception (group=0x40015560)
01-28 22:24:09.663: E/AndroidRuntime(1123): FATAL EXCEPTION: main
01-28 22:24:09.663: E/AndroidRuntime(1123): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.tab/com.example.tab.MainActivity}: java.lang.NullPointerException
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.os.Looper.loop(Looper.java:123)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.app.ActivityThread.main(ActivityThread.java:3683)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at java.lang.reflect.Method.invokeNative(Native Method)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at java.lang.reflect.Method.invoke(Method.java:507)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at dalvik.system.NativeStart.main(Native Method)
01-28 22:24:09.663: E/AndroidRuntime(1123): Caused by: java.lang.NullPointerException
01-28 22:24:09.663: E/AndroidRuntime(1123):     at com.example.tab.MainActivity.<init>(MainActivity.java:49)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at java.lang.Class.newInstanceImpl(Native Method)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at java.lang.Class.newInstance(Class.java:1409)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
01-28 22:24:09.663: E/AndroidRuntime(1123):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561)
01-28 22:24:09.663: E/AndroidRuntime(1123):     ... 11 more
01-28 22:24:15.943: I/Process(1123): Sending signal. PID: 1123 SIG: 9

Answer 1

Intent i = getIntent();返回null。在调用Activity之前，您无法使用onCreate的任何方法，因为尚未设置信息。

移动

DBController controller = new DBController(this);
Intent i = getIntent();
String dept_response = i.getExtras().getString("dept_response");
String role_response = i.getExtras().getString("role_response");
String desig_response = i.getExtras().getString("desig_response");

进入onCreate，因为它无法正常工作。

无法实例化活动组件信息：nullpointerexception

1 个答案: