Jak obsługiwać NullPointerException w systemie Android?

Question

Jan 18, 2014, 12:03 AM

Jak obsługiwać NullPointerException w systemie Android?

01-18 02:08:05.271: E/AndroidRuntime(24688): FATAL EXCEPTION: main
01-18 02:08:05.271: E/AndroidRuntime(24688): java.lang.NullPointerException
01-18 02:08:05.271: E/AndroidRuntime(24688):    at com.example.tava.EchangingMessage$LoadData.onPostExecute(EchangingMessage.java:178)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at com.example.tava.EchangingMessage$LoadData.onPostExecute(EchangingMessage.java:1)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at android.os.AsyncTask.finish(AsyncTask.java:602)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at android.os.AsyncTask.access$600(AsyncTask.java:156)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at android.os.Looper.loop(Looper.java:154)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at android.app.ActivityThread.main(ActivityThread.java:4945)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at java.lang.reflect.Method.invokeNative(Native Method)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at java.lang.reflect.Method.invoke(Method.java:511)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-18 02:08:05.271: E/AndroidRuntime(24688):    at dalvik.system.NativeStart.main(Native Method)

A to jest mój kod aktywności kodu:

public class EchangingMessage extends Activity implements OnClickListener {

    private ProgressDialog pDialog;
    JSONParser jParser = new JSONParser();
    ArrayList<HashMap<String, String>> DaftarRS;
    EditText textToSend;

    ArrayList<HashMap<String, String>> arraylist;

    private static String url_daftar_rs = "http://192.168.137.1/www/Android_Login_Secure/detailMessage.php";
    private static String url_daftar_rs1 = "http://192.168.137.1/www/Android_Login_Secure/myFriends.php";

    public static final String TAG_SUCCESS = "success";
    public static final String TAG_DAFTAR_RS = "daftar_rs";
    public static final String TAG_ID_RS = "id_rs";
    public static final String TAG_NAMA_RS = "username";
    public static final String TAG_LINK_IMAGE_RS = "image";
    public static final String TAG_MESSAGE_RS = "messageText";
    public static final String TAG_TIME_RS = "sendAt";
    public static final String TAG_SEEN_RS = "readStatus";

    JSONArray daftar_rs = null;

    ListAdapterUserOnile adapterFirends;

    ImageView showOnline;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.exchange_message);
arraylist = new ArrayList<HashMap<String, String>>();
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub

        switch (v.getId()) {

        case R.id.userOnline:
            userOnlineWindow();
            break;

        }

    }

    private void userOnlineWindow() {
        // TODO Auto-generated method stub

        LayoutInflater layoutInflater = (LayoutInflater) getBaseContext()
                .getSystemService(LAYOUT_INFLATER_SERVICE);
        View popupView = layoutInflater.inflate(R.layout.popup, null);
        final PopupWindow popupWindow = new PopupWindow(popupView,
                LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);

        Button btnDismiss = (Button) popupView.findViewById(R.id.dismiss);
        btnDismiss.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                popupWindow.dismiss();
            }
        });

        popupWindow.showAsDropDown(showOnline, -190, -90);

        new LoadData().execute();

        popupWindow.setFocusable(true);
        popupWindow.update();
    }

    class LoadData extends AsyncTask<String, String, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(EchangingMessage.this);
            pDialog.setMessage("Loading Information...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(false);
            pDialog.show();
        }

        @Override
        protected String doInBackground(String... arg0) {

            List<NameValuePair> params1 = new ArrayList<NameValuePair>();

            params1.add(new BasicNameValuePair("me", "52"));

            JSONObject json = jParser.makeHttpRequest(url_daftar_rs1, "POST",
                    params1);

            try {

                int success = json.getInt(TAG_SUCCESS);
                Log.i("success :", "" + success);

                if (success == 1) {

                    daftar_rs = json.getJSONArray(TAG_DAFTAR_RS);
                    for (int i = 0; i < daftar_rs.length(); i++) {
                        JSONObject c = daftar_rs.getJSONObject(i);
                        String id_rs = c.getString(TAG_ID_RS);
                        String nama_rs = c.getString(TAG_NAMA_RS);
                        String link_image_rs = c.getString(TAG_LINK_IMAGE_RS);

                        HashMap<String, String> map = new HashMap<String, String>();

                        map.put(TAG_ID_RS, id_rs);
                        map.put(TAG_NAMA_RS, nama_rs);
                        map.put(TAG_LINK_IMAGE_RS,
                                "http://192.168.137.1/www/Android_Login_Secure/Images/upload/big/"
                                        + link_image_rs);

                        arraylist.add(map);

                    }
                } else {

                }
            } catch (Exception e) {
                Log.e("Error", "COnnection:" + e.toString());
            }
            return null;
        }

        protected void onPostExecute(String file_url) {
            pDialog.dismiss();



        ListView listUserOnline = (ListView) findViewById(R.id.listOfUserOnline);


            adapterFirends = new ListAdapterUserOnile(EchangingMessage.this,
                    arraylist);

            listUserOnline.setAdapter(adapterFirends);

        }
    }

}

Stworzyłem tę aplikację, ale gdy klikam górny przycisk, otrzymałem ten błąd i to jest okno wyskakujące, a to jest połączenie z php

proszę, jak poradzić sobie z tym błędem, co mam zrobić?

i to mój plik EchangeMesssage.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
   android:background="@drawable/backgroudnformain"
    android:orientation="vertical" >
    <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:background="#99cc00"
        android:gravity="center"
        >

        <ImageView
            android:id="@+id/userOnline"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:src="@drawable/userimages" />

    </LinearLayout>

    <LinearLayout
        android:id="@+id/bottom_write_bar"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:background="@drawable/message_bar" >

        <EditText
            android:id="@+id/messageToSend"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_margin="5sp"
            android:layout_weight="1"
            android:background="@drawable/message_field"
            android:hint="Write here"
            android:padding="5sp"
            android:textColor="@color/textFieldColor" />

        <Button
            android:id="@+id/sendButton"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_margin="5sp"
            android:background="@drawable/send_button"
            android:onClick="sendMessage"
            android:paddingBottom="5sp"
            android:paddingLeft="15sp"
            android:paddingRight="15sp"
            android:paddingTop="5sp"
            android:text="Send"
            android:textColor="#FFF" />

    </LinearLayout>

    <ListView
        android:id="@+id/listSend"
        android:layout_width="fill_parent"
        android:layout_height="0dip"
        android:layout_marginTop="40dp"
        android:layout_above="@id/bottom_write_bar"
        android:layout_alignParentTop="true"
        android:cacheColorHint="#00000000"
        android:divider="#00000000"
        android:stackFromBottom="true"
        android:clickable="false"
        android:scrollbars="none"
         android:transcriptMode="alwaysScroll"
        android:listSelector="#00000000" >
    </ListView>


        <TextView
            android:id="@+id/you_id"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Large Text"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:visibility="gone" />

        <TextView
            android:id="@+id/me_id"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Large Text"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:visibility="gone" />


</RelativeLayout>

a to jest mój plik popup.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@drawable/windowwww"
    android:orientation="vertical" >

    <Button
        android:id="@+id/dismiss"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="240dp"
        android:layout_marginTop="60dp"
        android:text="EXIT" />

    <ListView
        android:id="@+id/listOfUserOnline"
        android:layout_width="match_parent"
        android:layout_height="330dp"
        android:layout_marginTop="30dp" >
    </ListView>

</LinearLayout>

A to jest moja klasa ListAdapter:

public class ListAdapterUserOnile extends BaseAdapter {

    public String POST_TEXT;
    private Activity activity;
    private ArrayList<HashMap<String, String>> data;
    private static LayoutInflater inflater = null;
    public ImageLoader imageLoader;
    public final static String you_id=null;

    int count = 0; 

    public ListAdapterUserOnile(Activity a, ArrayList<HashMap<String, String>> d) {
        activity = a;
        data = d;
        inflater = (LayoutInflater) activity
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        imageLoader = new ImageLoader(activity.getApplicationContext());
    }

    public int getCount() {
        // TODO Auto-generated method stub
        return data.size();
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        View vi = convertView;
        if (convertView == null) {
            vi = inflater.inflate(R.layout.item_list_friends, null);
        }

        TextView name_rs = (TextView) vi.findViewById(R.id.myFriendUsername);


        ImageView thumb_image = (ImageView) vi
                .findViewById(R.id.myFriendImage);


        TextView status = (TextView) vi.findViewById(R.id.status);

        ImageView on=(ImageView) vi.findViewById(R.id.online);
        ImageView off=(ImageView) vi.findViewById(R.id.offline);

        HashMap<String, String> daftar_rs = new HashMap<String, String>();
        daftar_rs = data.get(position);
        final int getPosition = position;
        name_rs.setText(daftar_rs.get(EchangingMessage.TAG_NAMA_RS));







        Log.e("IMage", daftar_rs.get(EchangingMessage.TAG_LINK_IMAGE_RS));

        imageLoader.DisplayImage(daftar_rs.get(EchangingMessage.TAG_LINK_IMAGE_RS),
                thumb_image);

        if (status.getText().toString().equals("1")) {

            off.setVisibility(View.INVISIBLE);
            on.setVisibility(View.VISIBLE);
            status.setVisibility(View.INVISIBLE);

        }
        else
        { 
            off.setVisibility(View.VISIBLE);
            on.setVisibility(View.INVISIBLE);
            status.setVisibility(View.INVISIBLE);
        }




        vi.setOnClickListener(new OnClickListener() {



            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                Toast.makeText(
                        activity,
                        "  You click"
                                + data.get(getPosition)
                                        .get(MyFriends.TAG_ID_RS).toString(),
                        Toast.LENGTH_SHORT).show();

                Intent i=new Intent(activity,EchangingMessage.class);
                i.putExtra(you_id, data.get(getPosition)
                                        .get(MyFriends.TAG_ID_RS).toString());
                activity.startActivity(i);


            }
        });

        return vi;

    }

}