java - 在 fragment 之间传递变量数据时出现 NullPointerException

Question

我有 2 个带有变量数据的 java 类(NewCard 和 inputText)，我想将它们传递给第三个类(FinalSubmit)。我已经对如何完成此操作进行了一些研究，并且我认为我已经完成了我应该做的所有事情，但是当目标类尝试获取数据时，应用程序由于 NullPointerException 而崩溃。以下是这 3 个类的 onCreateView 方法。

新卡:

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

    View view = inflater.inflate(R.layout.fragment_new_card, container, false);
    ImageButton blueBtn = view.findViewById(R.id.blueButton);
    ImageButton greenBtn = view.findViewById(R.id.greenButton);
    ImageButton redBtn = view.findViewById(R.id.redButton);


    blueBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            cardNumber = 1;
            FinalSubmit fragment = new FinalSubmit();
            Bundle bundle = new Bundle();
            bundle.putInt("dataPointOne", cardNumber);
            fragment.setArguments(bundle);

            Toast.makeText(getContext(), "Blue", Toast.LENGTH_SHORT).show();
            inputText fragment4 = new inputText();
            FragmentTransaction ft4 = getFragmentManager().beginTransaction();
            ft4.replace(R.id.frameLayout, fragment4, "FragmentName");
            ft4.commit();

        }
    });
    greenBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            cardNumber = 2;
            inputText finalSubmit = new inputText();
            Bundle bundle = new Bundle();
            bundle.putInt("dataPointOne", cardNumber);
            finalSubmit.setArguments(bundle);

            Toast.makeText(getContext(), "Green", Toast.LENGTH_SHORT).show();
            inputText fragment4 = new inputText();
            FragmentTransaction ft4 = getFragmentManager().beginTransaction();
            ft4.replace(R.id.frameLayout, fragment4, "FragmentName");
            ft4.commit();

        }
    });
    redBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            cardNumber = 3;
            FinalSubmit fragment = new FinalSubmit();
            Bundle bundle = new Bundle();
            bundle.putInt("dataPointOne", cardNumber);
            fragment.setArguments(bundle);

            Toast.makeText(getContext(), "Red", Toast.LENGTH_SHORT).show();
            inputText fragment4 = new inputText();
            FragmentTransaction ft4 = getFragmentManager().beginTransaction();
            ft4.replace(R.id.frameLayout, fragment4, "FragmentName");
            ft4.commit();

        }
    });


    return view;
}

处理数据传递的部分是

FinalSubmit fragment = new FinalSubmit();
        Bundle bundle = new Bundle();
        bundle.putInt("dataPointOne", cardNumber);
        fragment.setArguments(bundle);

输入文本

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

    View view = inflater.inflate(R.layout.fragment_input_text, container, false);

    final EditText editText = (EditText) view.findViewById(R.id.text);

    String cardText = editText.getText().toString();

    Button submit = view.findViewById(R.id.submit);

    submit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            Toast.makeText(getContext(), editText.getText().toString(), Toast.LENGTH_SHORT).show();
            FinalSubmit finalSubmit = new FinalSubmit();
            Bundle bundle = new Bundle();
            bundle.putString("dataPointTwo", editText.getText().toString());
            finalSubmit.setArguments(bundle);

            recordAudio fragment5 = new recordAudio();
            FragmentTransaction ft5 = getFragmentManager().beginTransaction();
            ft5.replace(R.id.frameLayout, fragment5, "FragmentName");
            ft5.commit();

        }
    });



    return view;
}

数据传递部分:

FinalSubmit finalSubmit = new FinalSubmit();
            Bundle bundle = new Bundle();
            bundle.putString("dataPointTwo", editText.getText().toString());
            finalSubmit.setArguments(bundle);

最终提交:

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

    final TextView info = view.findViewById(R.id.info);
    Button finalSubmit = view.findViewById(R.id.finalS);




    finalSubmit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Bundle bundle = getArguments();
            int cardNumber = bundle.getInt("dataPointOne", 0);
            String inputText = bundle.getString("dataPointTwo", "");
            info.setText(cardNumber+" "+inputText);//+inputText);
        }
    });

    return view;
}

尝试获取此处的数据时发生异常:

Bundle bundle = getArguments();
            int cardNumber = bundle.getInt("dataPointOne", 0);
            String inputText = bundle.getString("dataPointTwo", "");

日志猫:

06-15 12:53:44.064 16325-16325/com.parrotcards.kyle.parrotcards E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.parrotcards.kyle.parrotcards, PID: 16325
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String, int)' on a null object reference
    at com.parrotcards.kyle.parrotcards.FinalSubmit$1.onClick(FinalSubmit.java:42)
    at android.view.View.performClick(View.java:4785)
    at android.view.View$PerformClick.run(View.java:19884)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5343)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)

根据我的研究，我应该做对所有事情，所以如果有人能指出我在这里做错了什么，我将非常感激。谢谢一百万!

Answer 1

你的问题在这里，你创建一个 FinalSubmit ，其中包含一个 Int 值

但是在这里，您创建一个新的并设置一个字符串值.. 因此，您需要将包含 Int 值的包传递给您的 inputText，然后向其中添加 String 值。尝试使用sharedPreference，如下所示:

 blueBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                cardNumber = 1;
                FinalSubmit fragment = new FinalSubmit();
                Toast.makeText(getContext(), "Blue", Toast.LENGTH_SHORT).show();
                getContext().getSharedPreferences("pref",0)
                        .edit().putInt("int",cardNumber).apply();
                FragmentTransaction ft4 = getFragmentManager().beginTransaction();
                ft4.replace(R.id.frameLayout, fragment4, "FragmentName");
                ft4.commit();

            }
        });

并提取它

finalSubmit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int cardNumber= getContext().getSharedPreferences("pref",0)
                        .getInt("int",0);


            }
        });

与字符串值相同)