java - 带有全局变量的 TextView

Question

我只是在 Textview 对象上调用全局变量并将其打印出来，但出现以下错误

如何才能正常运行下面的代码？

p.s.textread_buf 是全局变量。

<小时/>

日志猫

E/AndroidRuntime:致命异常:main 进程:com.example.sentence_app，PID:26177

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

    at com.example.sentence_app.senten_check_example_mean.onCreateView(senten_check_example_mean.java:40)

<小时/>

//错误代码

public class senten_check_example_mean extends Fragment {

    public static senten_check_example_mean newInstance(){

        return new senten_check_example_mean();

    }

    public senten_check_example_mean() {
        // Required empty public constructor
    }

    Button return_sentence_check_button;

    TextView textView_name ;
    TextView textView_mean ;
    TextView textView_example ;

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        textView_name =(TextView) ((MainActivity)getActivity()).findViewById(R.id.text_read_name);
        textView_mean =(TextView) ((MainActivity)getActivity()).findViewById(R.id.text_read_mean);
        textView_example =(TextView) ((MainActivity)getActivity()).findViewById(R.id.text_read_example);

        textView_name.setText(((MyApplication) getActivity().getApplicationContext()).textread_buf.getSentence_name());
        textView_mean.setText(((MyApplication) getActivity().getApplicationContext()).textread_buf.getSentence_example());
        textView_example.setText(((MyApplication) getActivity().getApplicationContext()).textread_buf.getSentence_mean());

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

}

//textread.class

package com.example.sentence_app;

import java.util.LinkedList;

import java.util.Queue;

import java.util.Stack;

public class textread {

    String sentence_name;
    String sentence_example;
    Queue<String> sentence_mean;

    textread(){

    }

    textread(String temp){
        String []cs = temp.split("\\|");
        this.setSentence_name(cs[0]);
        this.setSentence_mean(cs[1]);
        this.setSentence_example(cs[2]);
    }

    public String getSentence_example() {
        return sentence_example;
    }

    public String getSentence_mean() {
        return sentence_mean.peek();
    }

    public String getSentence_name() {
        return sentence_name;
    }


}

Answer 1

这个问题最终将作为空指针异常的重复问题被关闭。但是，如果这些 TextView 像平常一样位于您的 fragment 布局内，那么请尝试重构您的 fragment onCreateView，如下所示:

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_senten_check_example_mean, container, false);

        textView_name =(TextView) view.findViewById(R.id.text_read_name);
        textView_mean =(TextView) view.findViewById(R.id.text_read_mean);
        textView_example =(TextView) view.findViewById(R.id.text_read_example);

        textView_name.setText(((MyApplication) getActivity().getApplicationContext()).textread_buf.getSentence_name());
        textView_mean.setText(((MyApplication) getActivity().getApplicationContext()).textread_buf.getSentence_example());
        textView_example.setText(((MyApplication) getActivity().getApplicationContext()).textread_buf.getSentence_mean());

        return view;
    }

您需要首先膨胀布局 View ，然后在该膨胀布局中找到您的 View 。在 Activity 中查找这些 View 不会返回任何内容。