java - 字符串比较期间出现空指针异常

Question

当将类引用传递给时，我收到java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“boolean java.lang.String.equals(java.lang.Object)”一个方法。导致错误的行是:

if (!contactData.getContactNo().equals("")){

更多代码:

方法调用:

recContDBHelper.insertRecord(new ContactData("", number, date)); <--Exception here

调用的方法:

 public void insertRecord(ContactData contactData) {
        String name = "";
        if (!contactData.getContactNo().equals("")) { <--exception here
            name = CommonServices.getContactDisplayNameByNumber(contactData.getContactNo(), context);
            if (name.equalsIgnoreCase("")) {
                name = contactData.getContactNo();
            }
        }
    }

上述代码中contactData.getContactNo()返回类型为String。

异常(exception)是:

04-12 18:21:40.153: E/AndroidRuntime(27924): FATAL EXCEPTION: main
04-12 18:21:40.153: E/AndroidRuntime(27924): Process: com.stackoverflow.ranjith.androidprojdel, PID: 27924
04-12 18:21:40.153: E/AndroidRuntime(27924): java.lang.RuntimeException: Unable to start receiver com.stackoverflow.ranjith.androidprojdel.PhoneCallreceiver: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
04-12 18:21:40.153: E/AndroidRuntime(27924):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2586)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at android.app.ActivityThread.access$1700(ActivityThread.java:144)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1355)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at android.os.Handler.dispatchMessage(Handler.java:102)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at android.os.Looper.loop(Looper.java:135)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at android.app.ActivityThread.main(ActivityThread.java:5221)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at java.lang.reflect.Method.invoke(Native Method)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at java.lang.reflect.Method.invoke(Method.java:372)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
04-12 18:21:40.153: E/AndroidRuntime(27924): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
04-12 18:21:40.153: E/AndroidRuntime(27924):    at com.stackoverflow.ranjith.androidprojdel.recentlyContacted.RecContDBHelper.insertRecord(RecContDBHelper.java:57)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at com.stackoverflow.ranjith.androidprojdel.PhoneCallreceiver.onReceive(PhoneCallreceiver.java:93)
04-12 18:21:40.153: E/AndroidRuntime(27924):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2579)
04-12 18:21:40.153: E/AndroidRuntime(27924):    ... 9 more

ContactData 类:

public class ContactData {
    private String contact_name;
    private String ph_no;
    private String time_call;

    public ContactData(String contact_name, String ph_no, String time_call) {
        this.contact_name = contact_name;
        this.ph_no = ph_no;
        this.time_call = time_call;
    }

    public ContactData(String contact_name, String ph_no) {
        this.contact_name = contact_name;
        this.ph_no = ph_no;
    }

    public String getContactNo() {
        return this.ph_no;
    }
}

Answer 1

试试这个

if (contactData.getContactNo() != null && !contactDate.getContactNo().isEmpty()) {
    // your code here
}

似乎 contactData.getContactNo() 返回 null。