Question

我按照本教程：http://www.android4devs.com/2015/01/how-to-make-material-design-sliding-tabs.html?m=1制作了一个包含5个标签的布局。现在我想在第一个选项卡中为一个按钮放置一个OnLongClickListener，使其共享sound1。我在MainActivity.java中添加了这段代码：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    button1 = (Button) findViewById(R.id.button1);

    button1.setLongClickable(true);
    button1.setOnLongClickListener(new View.OnLongClickListener() {

        @Override
        public boolean onLongClick(View arg0) {
            Intent share = new Intent(Intent.ACTION_SEND);
            share.setType("audio/ogg");

            Uri uri = Uri.parse("android.resource://" + getPackageName()
                    + "/raw/" + R.raw.sound1);
            share.putExtra(Intent.EXTRA_STREAM, uri);
            startActivity(Intent.createChooser(share, "Share Sound File"));

            return true;
        }

    });

但这会让它在启动时崩溃，而logcat会说：

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setLongClickable(boolean)' on a null object reference

Answer 1

您正在使用片段。您应该在Fragment的onCreateView()或onViewCreated()回调

上执行此操作

public class Tab1 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v =inflater.inflate(R.layout.tab_1,container,false);
        button1 = (Button) v.findViewById(R.id.button1);
        button1.setLongClickable(true);
        ...
        return v;
    }
}

onLongClickListener布局中带有选项卡

1 个答案: