问题描述
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。
这篇关于试图findViewById NullPointerException异常时，抛出的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！