NullPointerException on setShareIntent using ActionBarSherlock

问题

I'm trying to use ActionBarSherlock + ShareActionProvider in a SherlockActivity. I've already checked this ( NullPointerException using ShareActionProvider + actionbarsherlock) but it doesn't solve my problem. I think the code is correct, but I keep getting FC and this logcat:

07-25 15:31:26.758: E/AndroidRuntime(911): FATAL EXCEPTION: main
07-25 15:31:26.758: E/AndroidRuntime(911): java.lang.NullPointerException
07-25 15:31:26.758: E/AndroidRuntime(911):  at com.corsalini.david.calcolopesi.ActCalcolo.onCreateOptionsMenu(ActCalcolo.java:162)
07-25 15:31:26.758: E/AndroidRuntime(911):  at com.actionbarsherlock.app.SherlockActivity.onCreatePanelMenu(SherlockActivity.java:173)
07-25 15:31:26.758: E/AndroidRuntime(911):  at com.actionbarsherlock.ActionBarSherlock.callbackCreateOptionsMenu(ActionBarSherlock.java:556)
07-25 15:31:26.758: E/AndroidRuntime(911):  at com.actionbarsherlock.internal.ActionBarSherlockCompat.preparePanel(ActionBarSherlockCompat.java:483)
07-25 15:31:26.758: E/AndroidRuntime(911):  at com.actionbarsherlock.internal.ActionBarSherlockCompat.dispatchInvalidateOptionsMenu(ActionBarSherlockCompat.java:273)
07-25 15:31:26.758: E/AndroidRuntime(911):  at com.actionbarsherlock.internal.ActionBarSherlockCompat$1.run(ActionBarSherlockCompat.java:988)
07-25 15:31:26.758: E/AndroidRuntime(911):  at android.os.Handler.handleCallback(Handler.java:587)
07-25 15:31:26.758: E/AndroidRuntime(911):  at android.os.Handler.dispatchMessage(Handler.java:92)
07-25 15:31:26.758: E/AndroidRuntime(911):  at android.os.Looper.loop(Looper.java:123)
07-25 15:31:26.758: E/AndroidRuntime(911):  at android.app.ActivityThread.main(ActivityThread.java:3683)
07-25 15:31:26.758: E/AndroidRuntime(911):  at java.lang.reflect.Method.invokeNative(Native Method)
07-25 15:31:26.758: E/AndroidRuntime(911):  at java.lang.reflect.Method.invoke(Method.java:507)
07-25 15:31:26.758: E/AndroidRuntime(911):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
07-25 15:31:26.758: E/AndroidRuntime(911):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
07-25 15:31:26.758: E/AndroidRuntime(911):  at dalvik.system.NativeStart.main(Native Method)

Here is the code:

public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getSupportMenuInflater();
    inflater.inflate(R.menu.menu_main, menu);
    MenuItem menuItem = menu.findItem(R.id.miShare);
    ShareActionProvider mShareActionProvider = (ShareActionProvider) menuItem.getActionProvider();
    // Set the default share intent
    Intent shareIntent = new Intent(Intent.ACTION_SEND);
    shareIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
    shareIntent.setType("text/plain");
    shareIntent.putExtra(Intent.EXTRA_TEXT, getString(R.string.share_text));
    shareIntent.putExtra(Intent.EXTRA_SUBJECT, getString(R.string.share_subject));
    mShareActionProvider.setShareIntent(shareIntent);  //Line 162
    return true;
}

And here is the xml for the menu:

<menu xmlns:android="http://schemas.android.com/apk/res/android" >
    <item
        android:id="@+id/miPref"
        android:icon="@drawable/ic_action_settings"
        android:showAsAction="ifRoom"
        android:title="@string/settings"
        android:visible="true" />
    <item
        android:id="@+id/miReset"
        android:icon="@drawable/ic_action_reset"
        android:showAsAction="ifRoom"
        android:title="@string/reset"
        android:visible="true" />
    <item
        android:id="@+id/miShare"
        android:actionProviderClass="android.widget.ShareActionProvider"
        android:showAsAction="ifRoom"
        android:title="@string/share" />
</menu>

EDIT 1:

I'm trying to add this line: mShareActionProvider.setShareHistoryFileName(ShareActionProvider.DEFAULT_SHARE_HISTORY_FILE_NAME);

And now the NullPointerException is here. Is it possible that there is no such file and so i get the exception?

EDIT 2: Do not take care of EDIT 1 I've found that the problem was in the XML. You have to use:

    android:actionProviderClass="com.actionbarsherlock.widget.ShareActionProvider"

but i was still using the original android widget. I have also included:

    menuItem.setActionProvider(mShareActionProvider);

in the activity, but i think it's redundant.

Now i've got two problems: 1. the app doesn't crash only if the "share" button doesn't show up in the action bar, if i try to put it on top of the list, the app crash and give the same logcat as the one posted here. 2. When i click "share" nothing happens.

回答1:

Notes

I have tried to duplicate your error and the only two ways I can cause mShareActionProvider to be null is to:

leave this out entirely: android:actionProviderClass=...
use the Android class: android:actionProviderClass="android.widget.ShareActionProvider"

As you discovered in EDIT 2 the appropriate ActionBarSherlock code is:

android:actionProviderClass="com.actionbarsherlock.widget.ShareActionProvider"

Suggestions

1) ... If I try to put (the menu item) on top of the list, the app crashes and gives the same logcat

Try creating a new menu XML file, save this as res/menu/temp_menu.xml:

<menu xmlns:android="http://schemas.android.com/apk/res/android" >
    <item
        android:id="@+id/miShare"
        android:actionProviderClass="com.actionbarsherlock.widget.ShareActionProvider"
        android:showAsAction="always"
        android:title="Share" />
</menu>

And load it with:

inflater.inflate(R.menu.temp_menu, menu);

2) If "share" is in the overflow menu nothing happens when I select it.

This is an ActionBarSherlock backwards compatibility quirk detailed here, Issue #455.

Null Pointer Exception

From a few of your comments, I want to clarify what exactly a NullPointerException is. When you tried adding this line:

mShareActionProvider.setShareHistoryFileName(ShareActionProvider.DEFAULT_SHARE_HISTORY_FILE_NAME);

You said:

And now the NullPointerException is here. Is it possible that there is no such file and so I get the exception?

The reason the NPE moved here is because mSharedActionProvider is still null. You cannot reference the concept of null.method() or in your case null.setShareHistoryFileName(), this is what a NPE is. In other words, you cannot ask nothing to do something. It doesn't matter here whether the file exists or not, the app crashes before this point.

You can prove this for yourself in the debugger or by adding a line like this:

ShareActionProvider mShareActionProvider = (ShareActionProvider) menuItem.getActionProvider();
Log.w("NullPointerException", "Is mShareActionProvider null: " + (mShareActionProvider == null));

Hope that helps!

来源：https://stackoverflow.com/questions/11653755/nullpointerexception-on-setshareintent-using-actionbarsherlock

标签

android

nullpointerexception

android-actionbar

actionbarsherlock

shareactionprovider