Error Java.Lang.NullPointer Exception on Android Twitter OAuth-Collection of common programming errors
i have some problem, i want to make my application OAuth with twitter account
This is my Main.xml file
And this is my Main.java File
package com.test.twitteroauth;
import oauth.signpost.OAuth;
import oauth.signpost.commonshttp.CommonsHttpOAuthConsumer;
import oauth.signpost.commonshttp.CommonsHttpOAuthProvider;
import oauth.signpost.exception.OAuthCommunicationException;
import oauth.signpost.exception.OAuthExpectationFailedException;
import oauth.signpost.exception.OAuthMessageSignerException;
import oauth.signpost.exception.OAuthNotAuthorizedException;
import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.app.Dialog;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageButton;
public class MainActivity extends Activity {
private static final String CONSUMER_KEY = "CONSUMER KEY GOES HERE";
private static final String CONSUMER_SECRET = "CONSUMER SECRET GOES HERE";
private static String ACCESS_KEY = null;
private static String ACCESS_SECRET = null;
private static final String REQUEST_URL = "http://twitter.com/oauth/request_token";
private static final String ACCESS_TOKEN_URL = "http://twitter.com/oauth/access_token";
private static final String AUTH_URL = "http://twitter.com/oauth/authorize";
private static final String CALLBACK_URL = "OauthTwitter://twitt";
private static final String PREFERENCE_FILE = "twitter_oauth.prefs";
private static CommonsHttpOAuthConsumer consumer = new CommonsHttpOAuthConsumer(CONSUMER_KEY, CONSUMER_SECRET);
private static CommonsHttpOAuthProvider provider = new CommonsHttpOAuthProvider(REQUEST_URL, ACCESS_TOKEN_URL, AUTH_URL);
@Override
public void onCreate(Bundle savedInstanceState) {
ImageButton btnTwitterConnect = (ImageButton) findViewById(R.id.btnTwitterConnect);
btnTwitterConnect.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
try {
String authURL = provider.retrieveRequestToken(consumer, CALLBACK_URL);
Log.d("OAuthTwitter", authURL);
startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(authURL)));
} catch (OAuthMessageSignerException e) {
e.printStackTrace();
} catch (OAuthNotAuthorizedException e) {
e.printStackTrace();
} catch (OAuthExpectationFailedException e) {
e.printStackTrace();
} catch (OAuthCommunicationException e) {
e.printStackTrace();
}
}
});
}
@Override
public void onResume() {
super.onResume();
Uri uri = this.getIntent().getData();
if (uri != null && uri.toString().startsWith(CALLBACK_URL)) {
Log.d("OAuthTwitter", uri.toString());
String verifier = uri.getQueryParameter(OAuth.OAUTH_VERIFIER);
Log.d("OAuthTwitter", verifier);
try {
provider.retrieveAccessToken(consumer, verifier);
ACCESS_KEY = consumer.getToken();
ACCESS_SECRET = consumer.getTokenSecret();
Log.d("OAuthTwitter", ACCESS_KEY);
Log.d("OAuthTwitter", ACCESS_SECRET);
} catch (OAuthMessageSignerException e) {
e.printStackTrace();
} catch (OAuthNotAuthorizedException e) {
e.printStackTrace();
} catch (OAuthExpectationFailedException e) {
e.printStackTrace();
} catch (OAuthCommunicationException e) {
e.printStackTrace();
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
I just followed the tutorial here: http://blog.copyninja.info/2010/09/android-oauth-authentication-with.html
But the android application is always Crashed
LogCat Details:
09-08 19:11:13.754: D/AndroidRuntime(566): Shutting down VM
09-08 19:11:13.754: W/dalvikvm(566): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
09-08 19:11:13.785: E/AndroidRuntime(566): FATAL EXCEPTION: main
09-08 19:11:13.785: E/AndroidRuntime(566): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.test.twitteroauth/com.test.twitteroauth.MainActivity}: java.lang.NullPointerException
09-08 19:11:13.785: E/AndroidRuntime(566): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
09-08 19:11:13.785: E/AndroidRuntime(566): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
09-08 19:11:13.785: E/AndroidRuntime(566): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
09-08 19:11:13.785: E/AndroidRuntime(566): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
09-08 19:11:13.785: E/AndroidRuntime(566): at android.os.Handler.dispatchMessage(Handler.java:99)
09-08 19:11:13.785: E/AndroidRuntime(566): at android.os.Looper.loop(Looper.java:123)
09-08 19:11:13.785: E/AndroidRuntime(566): at android.app.ActivityThread.main(ActivityThread.java:4627)
09-08 19:11:13.785: E/AndroidRuntime(566): at java.lang.reflect.Method.invokeNative(Native Method)
09-08 19:11:13.785: E/AndroidRuntime(566): at java.lang.reflect.Method.invoke(Method.java:521)
09-08 19:11:13.785: E/AndroidRuntime(566): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-08 19:11:13.785: E/AndroidRuntime(566): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-08 19:11:13.785: E/AndroidRuntime(566): at dalvik.system.NativeStart.main(Native Method)
09-08 19:11:13.785: E/AndroidRuntime(566): Caused by: java.lang.NullPointerException
09-08 19:11:13.785: E/AndroidRuntime(566): at com.test.twitteroauth.MainActivity.onCreate(MainActivity.java:44)
09-08 19:11:13.785: E/AndroidRuntime(566): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-08 19:11:13.785: E/AndroidRuntime(566): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
09-08 19:11:13.785: E/AndroidRuntime(566): ... 11 more
I know it’s caused by java.Lang.NullPointerException but where is the errors?
Thank you
(Android 2.2, Eclipse 3.7, Java JDK 1.7)
-
In addition to the
setContentView(...), you should callsuper.onCreate(savedInstanceState);above it, otherwise you’ll end up with aSuperNotCalledException@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(...); // ... } -
Please Add
setcontentview(R.layout.main)line beforeImageButton btnTwitterConnect = (ImageButton) findViewById(R.id.btnTwitterConnect);, it will solve your problem. -
You need to call
setContentView(layoutID)and pass in the layout the button belongs too before you callfindViewById(viewId)