从 MapView 通过 MainActivity 启动 Intent 时出现空指针异常？

Question

我的应用程序中有一个 MapView。单击覆盖项时，会弹出一个气泡，其中包含有关该地点的信息。单击该图标时，用户应该转到另一个活动。

我首先使用以下方法将控件从

BalloonItemizedOverlay<OverlayItem>.MapBalloonItemizedOverlay.onBalloonTap(int index, OverlayItem item)

方法内部发送到 MainActivity 页面：

MainActivityObject.gotoMethod();

ie

@Override
public boolean onBalloonTap(int index, OverlayItem item)
{
   MainActivityObject.gotoMethod();
    return true;
}

然后在该方法中我编码：

try
    {
    Intent goIntent = new Intent(MainActivity.this, NextActivity.class);
    startActivity(goIntent);
    }
    catch(Exception e)
    {
        e.printStackTrace();
    }

但是我收到以下空指针异常错误：

09-19 16:02:56.707: WARN/System.err(2454): java.lang.NullPointerException
09-19 16:02:56.717: WARN/System.err(2454):     at android.content.ContextWrapper.getPackageName(ContextWrapper.java:120)
09-19 16:02:56.717: WARN/System.err(2454):     at android.content.ComponentName.<init>(ComponentName.java:75)
09-19 16:02:56.717: WARN/System.err(2454):     at android.content.Intent.<init>(Intent.java:2678)
09-19 16:02:56.717: WARN/System.err(2454):     at towerCo.Android.Main.MapsActivity.showDetailpage(MapsActivity.java:897)
09-19 16:02:56.717: WARN/System.err(2454):     at towerCo.Android.MapOverLays.MapBalloonItemizedOverlay.onBalloonTap(MapBalloonItemizedOverlay.java:55)
09-19 16:02:56.717: WARN/System.err(2454):     at mapViewBalloon.BalloonItemizedOverlay$1.onTouch(BalloonItemizedOverlay.java:169)
09-19 16:02:56.717: WARN/System.err(2454):     at android.view.View.dispatchTouchEvent(View.java:3762)
09-19 16:02:56.727: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:897)
09-19 16:02:56.727: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.727: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.727: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.727: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.727: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.727: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.727: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.727: WARN/System.err(2454):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1671)
09-19 16:02:56.727: WARN/System.err(2454):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
09-19 16:02:56.727: WARN/System.err(2454):     at android.app.Activity.dispatchTouchEvent(Activity.java:2086)
09-19 16:02:56.738: WARN/System.err(2454):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1655)
09-19 16:02:56.738: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.738: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.738: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.738: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.738: WARN/System.err(2454):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
09-19 16:02:56.738: WARN/System.err(2454):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1671)
09-19 16:02:56.747: WARN/System.err(2454):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
09-19 16:02:56.747: WARN/System.err(2454):     at android.app.Activity.dispatchTouchEvent(Activity.java:2086)
09-19 16:02:56.747: WARN/System.err(2454):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1655)
09-19 16:02:56.747: WARN/System.err(2454):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1785)
09-19 16:02:56.747: WARN/System.err(2454):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-19 16:02:56.747: WARN/System.err(2454):     at android.os.Looper.loop(Looper.java:123)
09-19 16:02:56.747: WARN/System.err(2454):     at android.app.ActivityThread.main(ActivityThread.java:4627)
09-19 16:02:56.747: WARN/System.err(2454):     at java.lang.reflect.Method.invokeNative(Native Method)
09-19 16:02:56.747: WARN/System.err(2454):     at java.lang.reflect.Method.invoke(Method.java:521)
09-19 16:02:56.747: WARN/System.err(2454):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-19 16:02:56.747: WARN/System.err(2454):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-19 16:02:56.747: WARN/System.err(2454):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

我想我在另一篇文章中找到了答案。我将在这里为其他人重新发布：

Mapview 在单击 baloonOverlay 时启动新活动

将其替换

MainActivity MainActivityObject = new MainActivity (); 
sub.startCustomActivity(); 

为：

Intent Details = new Intent(context, Tab.class); 
context.startActivity(Details); 

因此，我们基本上必须使用从传入覆盖类的 MapView 中获取的上下文变量来启动我们的活动。

感谢大家早些时候对我的帮助。赞赏！