我是Android开发的新手。我正在开发eclipse和java。我正在尝试读取联系人并执行一些字符串操作,如substring()或contains()。我做了以下步骤,
阅读联系人的代码:
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));
}
}
这里我因为子字符串而收到错误。如果我使用任何字符串类方法,我会收到错误。但是如果在名称中分配一些硬编码值,那么我没有收到任何错误。即
String name= "John"; // people.getString(id);
错误讯息:
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
有人可以指导我如何解决这个问题吗?
答案 0 :(得分:0)
我假设您发布的代码片段来自类onActivityResult
的{{1}}方法。问题可能是由于联系人未定义Voice
,因此DISPLAY_NAME
将设置为name
。您没有检查null
的空值。从这个改变您的代码:
name
为:
if (name!="")
当您致电if (name != null && name.length() > 0)
时,您还应该防范异常。来自the docs for Cursor.getString
:
结果以及当列值为null或列类型不是字符串类型时此方法是否抛出异常是实现定义的。
答案 1 :(得分:0)
我建议你把people.getString(1)
的结果写入logcat,因为我猜它是空的。
看看ResultInfo{who=null, ...}
干杯