Android 3.0中奇怪的NullPointerException

我不知道为什么相同的代码在Android 2.3上运行正常，但当涉及到Android 3.1平板电脑时，它会抛出NullPointerException…下面是代码：

public class CalleeButton extends Button implements OnClickListener, AddressAware {
private AddressText mAddress;
private OnClickListener externalClickListener;
public void setExternalClickListener(OnClickListener e) {externalClickListener = e;}
public void setAddressWidget(AddressText a) {a=mAddress;}

//set Uri SipUri ,so we can initialize the mAddress inside calleebutton --smartclassroom
//because every calleebutton will have one sip account/ext. this will replace the information for original mAddress --smartclassroom
public void setSip(String StudentName,String SipUri, AddressText a)
{
    Log.i("CalleeButton-35");
    super.setText(StudentName);
    //mAddress.setText(SipUri);
    Log.i("CalleeButton-38");
    mAddress.setContactAddress(SipUri, StudentName);
    Log.i("CalleeButton-40");
    setAddressWidget(a);
    Log.i("CalleeButton-42");

}

public CalleeButton(Context context, AttributeSet attrs) {
    super(context, attrs);
    setOnClickListener(this);

    //must use this line or you got null pointer exception...smartclassroom
    Log.i("CalleeButton-50");
    mAddress = new AddressText(context, attrs);
    //mAddress = null;
    Log.i("CalleeButton-52");
}

public void onClick(View v) {
    try {
        if (!LinphoneManager.getInstance().acceptCallIfIncomingPending()) {
            if (mAddress.getText().length() >0) { 
            LinphoneManager.getInstance().newOutgoingCall(mAddress);
                //add new action here
                /*******************************************************/
                /*******************************************************/
            }
        }
    } catch (LinphoneCoreException e) {
        LinphoneManager.getInstance().terminateCall();
        onWrongDestinationAddress();
    };

    if (externalClickListener != null) externalClickListener.onClick(v);
}


protected void onWrongDestinationAddress() {
    Toast toast = Toast.makeText(getContext()
            ,String.format(getResources().getString(R.string.warning_wrong_destination_address),mAddress.getText().toString())
            ,Toast.LENGTH_LONG);
    toast.show();
}


}

事实上，我曾经在Android 2.3平台上遇到过NullPointerException，但在添加以下内容之后：

mAddress = new AddressText(context, attrs);

然后，它可以顺利编译和运行…直到我尝试在android 3.1平板电脑上安装相同的程序…很奇怪，不是吗？请让我知道我在这方面犯了什么错误，提前谢谢！logcat的错误MSG为：

04-25 23:58:13.308: ERROR/AndroidRuntime(6728): FATAL EXCEPTION: main
04-25 23:58:13.308: ERROR/AndroidRuntime(6728): java.lang.RuntimeException: Unable to start activity ComponentInfo{org.linphone/org.linphone.LinphoneActivity}: java.lang.RuntimeException: Unable to start activity ComponentInfo{org.linphone/org.linphone.DialerActivity}: java.lang.NullPointerException
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1751)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1767)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread.access$1500(ActivityThread.java:122)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1005)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.os.Looper.loop(Looper.java:132)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread.main(ActivityThread.java:4028)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at java.lang.reflect.Method.invokeNative(Native Method)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at java.lang.reflect.Method.invoke(Method.java:491)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:844)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at dalvik.system.NativeStart.main(Native Method)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{org.linphone/org.linphone.DialerActivity}: java.lang.NullPointerException
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1751)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread.startActivityNow(ActivityThread.java:1592)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:130)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:342)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:676)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.widget.TabHost.setCurrentTab(TabHost.java:345)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.widget.TabHost.setCurrentTabByTag(TabHost.java:282)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at org.linphone.LinphoneActivity.gotToDialer(LinphoneActivity.java:481)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at org.linphone.LinphoneActivity.fillTabHost(LinphoneActivity.java:207)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at org.linphone.LinphoneActivity.onCreate(LinphoneActivity.java:126)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1715)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     ... 11 more
04-25 23:58:13.308: ERROR/AndroidRuntime(6728): Caused by: java.lang.NullPointerException
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at org.linphone.DialerActivity.onCreate(DialerActivity.java:128)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1715)
04-25 23:58:13.308: ERROR/AndroidRuntime(6728):     ... 22 more 

根据我的意见，logcat msgs告诉了我该功能：

    mCallee1.setSip("Jack","sip:xxx@xxx.xxx.xxx.xxx",mAddress);

---

在DaileActivity.java中（您可以在这里将其视为主函数）导致了NullPointerExcetion，然后我将代码跟踪到CalleeButton.java，但仍然无法找到导致null指针异常的点

在该行上设置断点（

setSip（）

），并检查mCallee1和mAddress变量。一个应该是空的。那将是你的问题。然后只需追溯它并找出它没有被实例化的原因——或者如果null是变量的有效状态，只需在调用

setSip（）

之前检查它是否为null

在设置了异常断点之后，我使用eclipse进行调试。我发现变量mCallee1的值为null。我不知道为什么。。。mCallee1的变量类型（称为CallButton）与mCall的变量类型（称为CallButton）非常相似。我尝试了许多不同的方法试图绕过它，但值仍然是相同的，null…在您遇到此问题的代码中进行编辑。发布的内容中没有任何涉及

mCallee1

变量的内容。我找到了！！！这是因为我的布局问题。我的android 3.0平板电脑只使用横向布局，我忽略了初始化这些xml布局文件。