java Null pointer exception after onClick

1
votes

I am writing an app that sends an e-mail with multiple image as attachments. I followed this link : Android multiple email attachments using Intent to set up the Email intent and stuff .But the app force closes when I click on the send button and there seeems to be a Null Pointer Exception.

Here's the code for the two classes that are involved (only for the email part) :

PrevEmail.java :

   public class PrevEmail extends Activity{

Context context;
TextView tv,tvEmail,tvEmailAd,tvSubject,tvContent,tvLocation;
EditText etSubject,etContent,etLocation;
String subject,content,location;
Button send;
String btnSelected;
String[] imgPath;
Bundle extras;
ArrayList<Uri> uris;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.prevemail);
    intializeVar();
}

private void intializeVar() {
    // Links xml to java
    tv = (TextView) findViewById(R.id.tv);
    tvEmail = (TextView) findViewById(R.id.tvEmail);
    tvEmailAd = (TextView) findViewById(R.id.tvEmailAd);
    tvSubject = (TextView) findViewById(R.id.tvSubject);
    tvContent = (TextView) findViewById(R.id.tvContent);
    tvLocation = (TextView) findViewById(R.id.tvLocation);

    etSubject = (EditText) findViewById(R.id.Subject);
    etContent = (EditText) findViewById(R.id.Content);
    etLocation= (EditText) findViewById(R.id.Location);

    send = (Button) findViewById(R.id.bSend);



    extras = getIntent().getExtras();
    if(extras!=null){
        btnSelected=extras.getString("Button");
        imgPath=extras.getStringArray("Path");

        //Sets the E-mail field according to the value received by the Bundle.
        if(btnSelected.equalsIgnoreCase("case1")){
            tvEmailAd.setText("email_address");
        }else if(btnSelected.equalsIgnoreCase("case2")){
            tvEmailAd.setText("email_address");
        }else if(btnSelected.equalsIgnoreCase("case3")){
            tvEmailAd.setText("email_address");
        }else if(btnSelected.equalsIgnoreCase("case4")){
            tvEmailAd.setText("email_address");
        }

    }   



    send.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            convertEditTextToString();
            Intent emailIntent = new Intent(android.content.Intent.ACTION_SEND_MULTIPLE);
            emailIntent.setType("text/plain");
            emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL,"email_address");
            emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT,subject);
            emailIntent.putExtra(android.content.Intent.EXTRA_TEXT,content);

            uris = new ArrayList<Uri>();

            for(String file : imgPath) {
                File fileIn = new File(file);
                Uri u = Uri.fromFile(fileIn);
                uris.add(u);
            }

            emailIntent.putParcelableArrayListExtra(Intent.EXTRA_STREAM, uris);
            context.startActivity(Intent.createChooser(emailIntent, "Send mail..."));
        }
    });

}

    private void convertEditTextToString(){

        subject = etSubject.getText().toString();
        content = etContent.getText().toString();
        location= etLocation.getText().toString();
    }       
  }

Android manifest :

    <?xml version="1.0" encoding="utf-8"?>


<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="17" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.name.StartScreen"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>    
    </activity>
    <activity
        android:name="com.example.name.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="com.example.name.MAINACTIVITY" />

            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>
     <activity
         android:name="com.example.name.PrevEmail"
         android:label="@string/app_name">     
     </activity>
</application>

And the Logcat :

    12-02 21:44:48.180: W/dalvikvm(29329): threadid=1: thread exiting with uncaught   exception (group=0x40bc4498)
    12-02 21:44:48.180: E/test(29329): Exception
    12-02 21:44:48.200: E/AndroidRuntime(29329): FATAL EXCEPTION: main
    12-02 21:44:48.200: E/AndroidRuntime(29329): java.lang.NullPointerException
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at com.example.name.PrevEmail$1.onClick(PrevEmail.java:100)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at android.view.View.performClick(View.java:4106)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at  android.view.View$PerformClick.run(View.java:17150)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at android.os.Handler.handleCallback(Handler.java:615)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at android.os.Handler.dispatchMessage(Handler.java:92)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at android.os.Looper.loop(Looper.java:137)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at android.app.ActivityThread.main(ActivityThread.java:4792)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at java.lang.reflect.Method.invokeNative(Native Method)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at java.lang.reflect.Method.invoke(Method.java:511)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:808)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:575)
    12-02 21:44:48.200: E/AndroidRuntime(29329):    at dalvik.system.NativeStart.main(Native Method)
3
javaandroidnullpointerexception
I think that we don't need that much code to track an NPE. Please post the relevant parts only. - Adam Arold
Did you try debugging your code at the position where the null pointer is coming ? You should - Rahul Gupta
When you have a nullpointer, all we need to see is your logcat, and the code the logcat is pointing to. This is a bit much to sift through. - Chad Bingham

3 Answers

3
votes

You never initialize 

Context context;

So when doing context.startActivity(Intent.createChooser(emailIntent, "Send mail..."));, it throws a NPE.

Logcat messages are very helpful for debugging. This line :

at com.example.name.PrevEmail$1.onClick(PrevEmail.java:100)

indicates that something is'nt initialized correctly on the line 100 of your activity (inside the onClick method to be precise).

Try to learn from logcat, that will save you a lot of time.

2
votes

@ZouZou I believe has the right answer. BUT I see another potential NullPointer; You will force close when your editText are empty when you call this method:

   convertEditTextToString();

You will need to check for null on those first. What I did here was make your method return bool, and if the edit text in question are NOT null, then proceed. 

  @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        if(convertEditTextToString()){
        Intent emailIntent = new Intent(android.content.Intent.ACTION_SEND_MULTIPLE);
        emailIntent.setType("text/plain");
        emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL,"email_address");
        emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT,subject);
        emailIntent.putExtra(android.content.Intent.EXTRA_TEXT,content);

        uris = new ArrayList<Uri>();

        for(String file : imgPath) {
            File fileIn = new File(file);
            Uri u = Uri.fromFile(fileIn);
            uris.add(u);
        }

        emailIntent.putParcelableArrayListExtra(Intent.EXTRA_STREAM, uris);
        context.startActivity(Intent.createChooser(emailIntent, "Send mail..."));
    }
   }
 });



private boolean convertEditTextToString(){

    subject = etSubject.getText().toString();
    content = etContent.getText().toString();
    location= etLocation.getText().toString();
 if(!subject.equals("") && !content.equals("") && !location.equals(""){
         return true;
  } else {
       Toast.makeText(context, "Please fill out all edit text boxes", Toast.LENGTH_LONG).show();
       return false;
   }
}
1
votes
send.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        convertEditTextToString();
        Intent emailIntent = new Intent(android.content.Intent.ACTION_SEND_MULTIPLE);
        emailIntent.setType("text/plain");
        emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL,"email_address");
        emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT,subject);
        emailIntent.putExtra(android.content.Intent.EXTRA_TEXT,content);

        uris = new ArrayList<Uri>();

        for(String file : imgPath) {
            File fileIn = new File(file);
            Uri u = Uri.fromFile(fileIn);
            uris.add(u);
        }

        emailIntent.putParcelableArrayListExtra(Intent.EXTRA_STREAM, uris);
        context.startActivity(Intent.createChooser(emailIntent, "Send mail..."));
    }
});

Somewhere in this code, some value is coming null. Eclipse debugger is awesome. You should debug your code.

By doing that you will find the error and solution yourself only. Do tell us which is line 100 in this class also