在Android开发中读取通讯录时出现错误

Question

I'm new to android development. I'm developing in eclipse and java. I'm trying to read contacts and do some string manupulation like substring() or contains (). i did the following steps,

1. Permission added ( )

2. Code to read contacts :

    Cursor people=getContentResolver().query(ContactsContract.Contacts.CONTENT_URI, null, null, null, null); while(people.moveToNext()) { int id=people.getColumnIndex(PhoneLookup.DISPLAY_NAME); String name= people.getString(id); if(name!="") { edittext1.setText(name.substring(2,3)); } } 

Here i'm getting error because of substring. I'm getting error if i use any string class methods. But if assign some hardcoded value in name,then i'm not getting any error. ie.

       String name= "John";  // people.getString(id);

Error messages :

08-19 22:13:03.467: E/AndroidRuntime(4265): FATAL EXCEPTION: main
08-19 22:13:03.467: E/AndroidRuntime(4265): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1111, result=-1, data=Intent { (has extras) }} to activity {com.ravi.vrs/com.ravi.vrs.Voice}: java.lang.NullPointerException
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.app.ActivityThread.deliverResults(ActivityThread.java:2553)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.app.ActivityThread.handleSendResult(ActivityThread.java:2595)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.app.ActivityThread.access$2000(ActivityThread.java:121)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:973)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.os.Looper.loop(Looper.java:130)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.app.ActivityThread.main(ActivityThread.java:3701)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at java.lang.reflect.Method.invokeNative(Native Method)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at java.lang.reflect.Method.invoke(Method.java:507)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at dalvik.system.NativeStart.main(Native Method)
08-19 22:13:03.467: E/AndroidRuntime(4265): Caused by: java.lang.NullPointerException
08-19 22:13:03.467: E/AndroidRuntime(4265):     at com.ravi.vrs.Voice.onActivityResult(Voice.java:71)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.app.Activity.dispatchActivityResult(Activity.java:3908)
08-19 22:13:03.467: E/AndroidRuntime(4265):     at android.app.ActivityThread.deliverResults(ActivityThread.java:2549)
08-19 22:13:03.467: E/AndroidRuntime(4265):     ... 11 more

Could anyone please guide me how to fix this issue ?

Answer 1

I'm assuming that the code fragment you posted is from the onActivityResult method of class Voice . The problem is probably due to a contact not having a defined DISPLAY_NAME , in which case name will be set to null . You are not checking for a null value for name . Change your code from this:

if (name!="")

to:

if (name != null && name.length() > 0)

You should also be protecting against exceptions when you call getString . From the docs for Cursor.getString :

The result and whether this method throws an exception when the column value is null or the column type is not a string type is implementation-defined.

Answer 2

I would suggest you to write the result of people.getString(1) to logcat, because I guess it's null. Look at ResultInfo{who=null, ...}

Cheers