+1 vote
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This question already has answers here:

How can I fix 'android.os.NetworkOnMainThreadException'? (64 answers)

Closed 7 years ago.

Im getting null pointer exception. This error seems a pretty usual one, but all the answers I found on the site were specific to a problem in others code which unfortunately I cant relate to in my code.

I'm a novice to android programming. Please help figure out the problem in this program. Here's the code.

Little bit of background on what Im trying to do. I'm just getting the http response from the google finance web service & set the http response to the textView component in the UI

package com.android.myexchange;

import android.app.Activity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.Spinner;

import android.widget.TextView;

import android.widget.Toast;

public class MyExchangeActivity extends Activity {

  private Spinner spinner1, spinner2;

  private Button btnSubmit;

  private EditText textbox;

  private TextView result;

  private TextView test;

  private static final String TAG = "MyApp";    

  /** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);     

    spinner1 = (Spinner) findViewById(R.id.SpinnerA);

    spinner2 = (Spinner) findViewById(R.id.SpinnerB);

    btnSubmit = (Button) findViewById(R.id.btnSubmit);

    textbox = (EditText) findViewById(R.id.textbox);

    result = (TextView) findViewById(R.id.resulttext);

    textbox.setText("Enter amount");

String testStr=HTTPRequestPoster.sendGetRequest("http://www.google.com/finance/converter",  "a=1&from=USD&to=INR");

    Log.i(TAG, "TEST");

    result.setText(testStr);

    addListenerOnButton();

}

private void addListenerOnButton() {

    btnSubmit.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {

        Toast.makeText(MyExchangeActivity.this,

                "OnClickListener : " +

                "\nSpinner 1 : "+ String.valueOf(spinner1.getSelectedItem()) +

                "\nSpinner 2 : "+ String.valueOf(spinner2.getSelectedItem()),

            Toast.LENGTH_SHORT).show();

        }

    });

}

}

Here's the manifest xml:

<uses-sdk android:minSdkVersion="14" />

<uses-permission android:name="android.permission.INTERNET"/>

<application

    android:icon="@drawable/ic_launcher"

    android:label="@string/app_name" >

    <activity

        android:label="@string/app_name"

        android:name=".MyExchangeActivity" >

        <intent-filter>

            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />

        </intent-filter>

    </activity>

</application>

</manifest>

Here's the log:

12-19 21:47:42.403: W/System.err(647): android.os.NetworkOnMainThreadException

12-19 21:47:42.403: W/System.err(647):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1084)

12-19 21:47:42.413: W/System.err(647):  at java.net.InetAddress.lookupHostByName(InetAddress.java:391)

12-19 21:47:42.413: W/System.err(647):  at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)

12-19 21:47:42.413: W/System.err(647):  at java.net.InetAddress.getAllByName(InetAddress.java:220)

12-19 21:47:42.413: W/System.err(647):  at libcore.net.http.HttpConnection.<init>(HttpConnection.java:71)

12-19 21:47:42.413: W/System.err(647):  at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)

12-19 21:47:42.423: W/System.err(647):  at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:351)

12-19 21:47:42.423: W/System.err(647):  at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:86)

12-19 21:47:42.423: W/System.err(647):  at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)

12-19 21:47:42.423: W/System.err(647):  at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308)

12-19 21:47:42.433: W/System.err(647):  at libcore.net.http.HttpEngine.connect(HttpEngine.java:303)

12-19 21:47:42.433: W/System.err(647):  at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282)

12-19 21:47:42.433: W/System.err(647):  at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232)

12-19 21:47:42.433: W/System.err(647):  at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:273)

12-19 21:47:42.433: W/System.err(647):  at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:168)

12-19 21:47:42.433: W/System.err(647):  at com.android.myexchange.HTTPRequestPoster.sendGetRequest(HTTPRequestPoster.java:43)

12-19 21:47:42.443: W/System.err(647):  at com.android.myexchange.MyExchangeActivity.onCreate(MyExchangeActivity.java:37)

12-19 21:47:42.443: W/System.err(647):  at android.app.Activity.performCreate(Activity.java:4465)

12-19 21:47:42.443: W/System.err(647):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)

12-19 21:47:42.453: W/System.err(647):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)

12-19 21:47:42.463: W/System.err(647):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)

12-19 21:47:42.473: W/System.err(647):  at android.app.ActivityThread.access$600(ActivityThread.java:122)

12-19 21:47:42.473: W/System.err(647):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)

12-19 21:47:42.473: W/System.err(647):  at android.os.Handler.dispatchMessage(Handler.java:99)

12-19 21:47:42.504: W/System.err(647):  at android.os.Looper.loop(Looper.java:137)

12-19 21:47:42.504: W/System.err(647):  at android.app.ActivityThread.main(ActivityThread.java:4340)

12-19 21:47:42.504: W/System.err(647):  at java.lang.reflect.Method.invokeNative(Native Method)

12-19 21:47:42.513: W/System.err(647):  at java.lang.reflect.Method.invoke(Method.java:511)

12-19 21:47:42.513: W/System.err(647):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)

12-19 21:47:42.513: W/System.err(647):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)

12-19 21:47:42.513: W/System.err(647):  at dalvik.system.NativeStart.main(Native Method)

12-19 21:47:42.513: I/MyApp(647): TEST

12-19 21:47:42.523: D/AndroidRuntime(647): Shutting down VM

12-19 21:47:42.523: W/dalvikvm(647): threadid=1: thread exiting with uncaught exception (group=0x409951f8)

12-19 21:47:42.543: E/AndroidRuntime(647): FATAL EXCEPTION: main

12-19 21:47:42.543: E/AndroidRuntime(647): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.myexchange/com.android.myexchange.MyExchangeActivity}: java.lang.NullPointerException

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.app.ActivityThread.access$600(ActivityThread.java:122)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.os.Handler.dispatchMessage(Handler.java:99)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.os.Looper.loop(Looper.java:137)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.app.ActivityThread.main(ActivityThread.java:4340)

12-19 21:47:42.543: E/AndroidRuntime(647):  at java.lang.reflect.Method.invokeNative(Native Method)

12-19 21:47:42.543: E/AndroidRuntime(647):  at java.lang.reflect.Method.invoke(Method.java:511)

12-19 21:47:42.543: E/AndroidRuntime(647):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)

12-19 21:47:42.543: E/AndroidRuntime(647):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)

12-19 21:47:42.543: E/AndroidRuntime(647):  at dalvik.system.NativeStart.main(Native Method)

12-19 21:47:42.543: E/AndroidRuntime(647): Caused by: java.lang.NullPointerException

12-19 21:47:42.543: E/AndroidRuntime(647):  at com.android.myexchange.MyExchangeActivity.onCreate(MyExchangeActivity.java:39)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.app.Activity.performCreate(Activity.java:4465)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)

12-19 21:47:42.543: E/AndroidRuntime(647):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)

12-19 21:47:42.543: E/AndroidRuntime(647):  ... 11 more

Here's the layout 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/plain_white_paper"

android:orientation="vertical" >

<LinearLayout

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:orientation="horizontal" >

    <Spinner

        android:id="@+id/SpinnerA"

        android:layout_width="150dp"

        android:layout_height="43dp"

        android:layout_margin="10dp"

        android:background="#8e99a4"

        android:dropDownWidth="150dp"

        android:entries="@array/currency"

        android:textColor="@android:color/black" />

    <EditText

        android:id="@+id/textbox"

        android:layout_width="135dp"

        android:layout_height="38dp"

        android:background="#8e99a4"

        android:cursorVisible="true"

        android:gravity="center_horizontal"

        android:inputType="number"

        android:text="@string/hello" >

        <requestFocus />

    </EditText>

</LinearLayout>

<LinearLayout

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:orientation="horizontal" >

    <Spinner

        android:id="@+id/SpinnerB"

        android:layout_width="150dp"

        android:layout_height="50dp"

        android:layout_margin="10dp"

        android:background="#8e99a4"

        android:dropDownWidth="150dp"

        android:entries="@array/currency" />

    <TextView

        android:id="@+id/resulttext"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_margin="10dp"

        android:layout_weight="0.68"

        android:background="#8e99a4"

        android:padding="25px"

        android:text="@string/hello" />

</LinearLayout>

<Button

    android:id="@+id/btnSubmit"

    android:layout_width="128dp"

    android:layout_height="wrap_content"

    android:layout_gravity="center_horizontal"

    android:layout_margin="10dp"

    android:text="Submit"

    android:textColor="#181f25" />

<TextView

    android:id="@+id/textView1"

    android:layout_width="match_parent"

    android:layout_height="wrap_content"

    android:layout_weight="0.93"

    android:text="TextView" />

</LinearLayout>

The exception occurs right after the log entry where I try to setText the http response text to TextView UI component. As far as I know the exception is occurring because result.setText(testStr) is having a porblem which I dont understand. The class HTTPRequestPost.java works perfectly fine. Ive tested it & it returns the httpresponse in string format. I can post code of HTTPRequestPost.java if you need it.

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1 Answer

0 votes
by
As you mentioned, The HTTPRequestPoster.sendGetRequest() returns null. It is because you need Internet access permission. Add the below line to manifest file:

<uses-permission android:name="android.permission.INTERNET" />

The arguments you have given for sendGetRequest() are perfectly fine.

Its just that your APK needs permission to access Internet.

EDIT :

In StrictMode, it blocks network access from UI thread. So you need to create a seperate thread (or AsyncTask) for network activity. See code below:

@Override

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);     

    .....

    new Thread(new Runnable() {

        @Override

        public void run() {

            String testStr=HTTPRequestPoster.sendGetRequest("http://www.google.com/finance/converter",  "a=1&from=USD&to=INR");

            Log.i(TAG, "TEST");

            result.setText(testStr);                

        }

    }).run();

/* String testStr=HTTPRequestPoster.sendGetRequest("http://www.google.com/finance/converter",  "a=1&from=USD&to=INR");

    Log.i(TAG, "TEST");

    result.setText(testStr); */

    addListenerOnButton();

}

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