在Android中单击按钮时出现NullPointerException

Question

我真的陷入了我的应用程序中的这个问题,这会导致点击按钮后崩溃.

我有一个单独的"Comment"对象类(CommentLab类,在一个arrayList中保存注释),一个CommentListFragment,它有我的注释的listView,以及PostCommentFragment,用于在CommentLab中向arrayList添加新的注释.

我向我添加了一个OptionMenu CommentListFragment,当我点击optoinMenu中的New Comment项时,我希望它启动CommentListFragment类,我可以在其中编辑和添加新注释.

以下是协同工作的部分内容:

在CommentListFragment中:

// method to add an option menu to the fragment
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    super.onCreateOptionsMenu(menu, inflater);
    inflater.inflate(R.menu.fragment_comment_list, menu);
}

// method to indicate what to do when an item is selected on the menu(which,what)
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()){
        case R.id.menu_item_new_comment:
            Comment comment = new Comment();
            CommentLab.get(getActivity()).addComment(comment);
            Intent i = new Intent(getActivity(), PostCommentActivity.class);
            i.putExtra(PostCommentFragment.EXTRA_COMMENT, comment.getId());
            startActivity(i);
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

PostCommentActivity(PostCommentFragment的托管活动):

public class PostCommentActivity extends SingleFragmentActivity{

@Override
protected Fragment createFragment() {
    UUID commentId = (UUID)getIntent().getSerializableExtra(PostCommentFragment.EXTRA_COMMENT);
    return PostCommentFragment.newInstance(commentId);
}

}

PostCommentFragment:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    UUID commentId = (UUID)getArguments().getSerializable(EXTRA_COMMENT);
    mComment = CommentLab.get(getActivity()).getComment(commentId);
}

    @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_post_comment, container, false);
    mCommentEditText = (EditText) v.findViewById(R.id.title_edit_text);
    mCommentEditText = (EditText) v.findViewById(R.id.comment_edit_text);
    mDateTextView = (TextView) v.findViewById(R.id.date_text_view);
    mDateTextView.setText(mComment.getDate().toString());
    mPostButton = (Button) v.findViewById(R.id.post_button);

    mPostButton.setOnClickListener( new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String title = mTitleEditText.getText().toString();
            String comment = mCommentEditText.getText().toString();
            mComment.setTitle(title);
            mComment.setComment(comment);
        }
    });

    return v;
}

当我单击Post按钮时PostCommentFragment,应用程序崩溃...这里是logcat:

08-01 00:39:29.720    7442-7442/com.example.ashl7.E/AndroidRuntime? FATAL EXCEPTION: main
    java.lang.NullPointerException
            at com.example.ashl7.PostCommentFragment$1.onClick(PostCommentFragment.java:46)
            at android.view.View.performClick(View.java:3534)
            at android.view.View$PerformClick.run(View.java:14263)
            at android.os.Handler.handleCallback(Handler.java:605)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4441)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
            at dalvik.system.NativeStart.main(Native Method)

有人能解决这个问题吗？

Answer 1

你做了一个复制粘贴错误.您将分配给mCommentEditText两次,并且从不分配给mTitleEditText.