我有以下活动：

public class MainActivity extends ActionBarActivity {

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

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new StartFragment())
                .commit();
    }

    Button login = (Button) findViewById(R.id.loginButton);

    login.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {

            Intent intent = new Intent(MainActivity.this,LoginActivity.class);
            startActivity(intent);
        }
    });

}

我收到了NPE，当我尝试调用 findViewByID 为 R.id.loginButton ，和我猜测这是因为 loginButton 是在一个独立的片段，我有如下：

I get a NPE when I try to invoke findViewByID for R.id.loginButton, and I'm guessing this is because loginButton is within a separate Fragment, which I have as:

public static class StartFragment extends Fragment {

    public StartFragment() {
    }
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        return inflater.inflate(R.layout.fragment_main, container, false);

    }
}

不过，我不确定如何解决这个问题，让我可以找到loginButton ID。我还没有与之前的片段，让我意识到我可能会使用它们/不正确执行它们。 fragment_main 包含几个按钮的的LinearLayout 和 activity_main 有什么，但一个的FrameLayout 。

However, I am unsure of how to fix this so that I can find the loginButton ID. I haven't worked with fragments before, so I realize I may be using them/implementing them incorrectly. fragment_main contains a few buttons in a LinearLayout, and activity_main has nothing but a single FrameLayout.

推荐答案

写code，从片段初始化按钮监守你的按钮是为碎片布局不进活动的布局。的

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_main, container,
            false);
    Button login = (Button) rootView.findViewById(R.id.loginButton);
    login.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {

            Intent intent = new Intent(MainActivity.this,
                    LoginActivity.class);
            startActivity(intent);
        }
    });

    return rootView;
}

和从的onCreate 删除活动。