Question

所以我正在转换我的应用程序，经过大量研究后我决定将我的活动转换为碎片。这是成功的，但现在稍微更难的部分来实现从我的Activity到片段的代码。所以我使用了getView（）。和getActivity（）。解决问题，一切都很好。如下所示...

public class HomeFragment extends Fragment {  

  public static HomeFragment newInstance(String title) {

      HomeFragment homeFragment = new HomeFragment();
      Bundle bundle = new Bundle();
      bundle.putString("title", title);
      homeFragment.setArguments(bundle);
      return homeFragment;
  }

  @Override  
  public void onCreate(Bundle savedInstanceState) {  
      super.onCreate(savedInstanceState);  
  }  

  @Override  
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {          
      View view = inflater.inflate(R.layout.fragment_activity_home, container, false);  

        // Time function - Displays timeview on Card
        final boolean keepRunning = true;
        Thread thread = new Thread(){
            @Override
            public void run(){

                while(keepRunning){

                    // Make the thread wait half a second (if you're only showing time up to seconds, it doesn't need to be updating constantly)
                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        Toast.makeText(getActivity().getApplicationContext(), "Default Signature Fail", Toast.LENGTH_LONG).show();
                        e.printStackTrace();
                    }

                    getActivity().runOnUiThread(new Runnable(){
                        @Override
                        public void run(){
                            TextView time = (TextView) getView().findViewById(R.id.time);
                            time.setText(DateUtils.formatDateTime(getActivity().getBaseContext(), System.currentTimeMillis(),DateUtils.FORMAT_SHOW_TIME | DateUtils.FORMAT_12HOUR));
                        }
                    });
                }
            }
        };

        thread.start();

        // Date function - Displays dateview on Card
        final boolean keepRunning1 = true;
        Thread thread_two = new Thread(){
            @Override
            public void run(){

                while(keepRunning1){

                    // Make the thread wait half a second. If you want...
                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        Toast.makeText(getActivity().getApplicationContext(), "Default Signature Fail", Toast.LENGTH_LONG).show();
                        e.printStackTrace();
                    }

                    getActivity().runOnUiThread(new Runnable(){
                        @Override
                        public void run(){
                            TextView date = (TextView) getView().findViewById(R.id.date);
                            date.setText(DateUtils.formatDateTime(getActivity().getBaseContext(), System.currentTimeMillis(),DateUtils.FORMAT_SHOW_WEEKDAY | DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_SHOW_YEAR));
                        }
                    });
                }
            }
        };

        thread_two.start();
      return view;  
    }  
}

运行应用程序时，它会显示应用程序大约2秒，然后强制关闭，所以我检查了日志中是否有任何错误。这就出现了 -

05-20 16:54:17.213: E/AndroidRuntime(26473): java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
05-20 16:54:17.213: E/AndroidRuntime(26473):    at com.activelauncher.fragments.HomeFragment$1$1.run(HomeFragment.java:54)

我对片段相当陌生我有更多使用活动的经验，所以我不知道这里有什么问题。所以我检查第54行，就是这一行 -

time.setText(DateUtils.formatDateTime(getActivity().getBaseContext(), System.currentTimeMillis(),DateUtils.FORMAT_SHOW_TIME | DateUtils.FORMAT_12HOUR));

但是我没有看到任何问题或错误？有什么我想念的吗？感谢您阅读本文。

Answer 1

更改此

TextView time = (TextView) getView().findViewById(R.id.time);

到

TextView time = (TextView) view.findViewById(R.id.time);

并做出最后的

final View view;

Simailarly

TextView date = (TextView) view.findViewById(R.id.date);

Answer 2

试试这个..

改变这个..

TextView time = (TextView) getView().findViewById(R.id.time);
time.setText(DateUtils.formatDateTime(getActivity().getBaseContext(), System.currentTimeMillis(),DateUtils.FORMAT_SHOW_TIME | DateUtils.FORMAT_12HOUR));

到

TextView time = (TextView) view.findViewById(R.id.time);
time.setText(""+DateUtils.formatDateTime(getActivity().getBaseContext(), System.currentTimeMillis(),DateUtils.FORMAT_SHOW_TIME | DateUtils.FORMAT_12HOUR));

以及

TextView date = (TextView) view.findViewById(R.id.date);
date.setText(""+DateUtils.formatDateTime(getActivity().getBaseContext(), System.currentTimeMillis(),DateUtils.FORMAT_SHOW_WEEKDAY | DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_SHOW_YEAR));

片段类中的错误

2 个答案: