javascript - 查询 list 上的空指针异常

Question

我正在尝试在我的应用程序中设置应用程序内结算。我在 alpha 测试中有它。我不断从所有测试人员那里收到使用相同 logcat 的崩溃报告，如下所示:

java.lang.RuntimeException: Unable to start activity  
ComponentInfo{autonote.six.padc.autonote/autonote.six.padc.autonote.SaveScreen}:     
java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2305)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2359)
at android.app.ActivityThread.access$700(ActivityThread.java:165)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1326)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5455)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at autonote.six.padc.autonote.SaveScreen.onCreate(SaveScreen.java:59)
at android.app.Activity.performCreate(Activity.java:5372)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
... 11 more

这似乎是一个简单的解决方案，只需转到第 59 行，对吗？错误的。当我去那里时，抛出异常的行是:

 mHelper.queryInventoryAsync(mGotInventoryListener);

这就是我失去它的地方。以下是我的代码的相关部分:

public class SaveScreen extends ActionBarActivity {
Button EMAIL_NOTES;
IabHelper mHelper;
String UPGRADE_CODE = "upgrade_autonote";
public static int VERSION_NUMBER = 534985739;
boolean mIsPremium;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_savescreen);
    //Query Inventory to see if user is premium
    IabHelper.QueryInventoryFinishedListener mGotInventoryListener
            = new IabHelper.QueryInventoryFinishedListener() {
        public void onQueryInventoryFinished(IabResult result,
                                             Inventory inventory) {

            if (result.isFailure()) {
                // handle error here
            }
            else {
                // does the user have the premium upgrade?
                mIsPremium = inventory.hasPurchase(UPGRADE_CODE);
                VERSION_NUMBER = 434975736;
            }
        }
    };
    mHelper.queryInventoryAsync(mGotInventoryListener);
    //^^^^^^^^^^^^^^^null pointer^^^^^^^^^^^^^^^^^^^^^^^^


    EMAIL_NOTES.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(VERSION_NUMBER == 534985736){
                Toast.makeText(getBaseContext(), "You must upgrade to unlock this feature", Toast.LENGTH_LONG).show();

            }else if(VERSION_NUMBER == 434975739){
                Intent EMAIL_NOTES = new Intent(getBaseContext(), Email_Notes.class);
                EMAIL_NOTES.putExtra("serialized",cNotes_serialized);
                EMAIL_NOTES.putExtra("class_Name", cName);
                startActivity(EMAIL_NOTES);



            }
        }
    });

}任何想法如何解决这个问题？作为记录，我已经进去购买了产品。表示购买成功。谢谢大家!

Answer 1

这里:

mHelper.queryInventoryAsync(mGotInventoryListener);

NPE 因为 mHelper 是 null。

通过使用当前 Acitivty 上下文和公钥调用 IabHelper 构造函数来初始化 mHelper 对象:

mHelper = new IabHelper(this, base64EncodedPublicKey);

有关什么是 base64EncodedPublicKey 的更多信息？，请参阅:

Preparing Your In-app Billing Application