空指针异常 - 获取价值的EditText [英] Null Pointer Exception - Getting EditText Value

问题描述

这是我在这里的第一个问题，我会提前道歉，如果我没有问这个问题非常好。我已经看了看我像我的问题其他问题，但我还没有找到一个很好的解决方案，以满足什么在我的程序怎么回事。

This is my first question on here I will apologize in advance if I didn't ask this question very well. I have looked at my other questions similar to my problem, but I have not found a good solution to satisfy what is going on in my program.

所以我的问题是，我试图分配一个值到一个叫做变量， NUM1 从我的EditText 字段所谓 num1TextField ，但我没有任何运气至今。

So my problem is I am trying to assign a value to a variable called, num1 from my EditText field called, num1TextField, but I am not having any luck so far.

这引发异常我的Java文件内的段是：

The segment inside my java file that throws the exception is:

EditText num1Field = (EditText)v.findViewById(R.id.num1TextField);
num1 = num1Field.getText().toString();

我AP preciate提前这个问题的每一个贡献。

I appreciate every contribution to this problem in advance.

下面是我的 fragment_compute.xml 文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="14dp"
    android:text="@string/compute_activity"
    android:textAppearance="?android:attr/textAppearanceLarge" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/textView1"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="44dp"
    android:text="@string/num_1"
    android:textAppearance="?android:attr/textAppearanceMedium" />

<EditText
    android:id="@+id/num1TextField"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/textView2"
    android:layout_centerHorizontal="true"
    android:ems="10"
    android:inputType="number"
    android:gravity="center" >

    <requestFocus />
</EditText>

<EditText
    android:id="@+id/num2TextField"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/num1TextField"
    android:layout_below="@+id/textView3"
    android:ems="10"
    android:inputType="number"
    android:layout_centerHorizontal="true"
    android:gravity="center" >
</EditText>

<TextView
    android:id="@+id/textView4"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/num2TextField"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="22dp"
    android:text="@string/result"
    android:textAppearance="?android:attr/textAppearanceMedium" />

<TextView
    android:id="@+id/textView3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/num1TextField"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="22dp"
    android:text="@string/num_2"
    android:textAppearance="?android:attr/textAppearanceMedium" />

<TextView
    android:id="@+id/result"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/textView4"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="22dp" />

<Button
    android:id="@+id/compute_multiply"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignRight="@+id/num2TextField"
    android:layout_below="@+id/result"
    android:layout_marginTop="40dp"
    android:text="@string/multiply" />

<Button
    android:id="@+id/compute_add"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/compute_multiply"
    android:layout_alignBottom="@+id/compute_multiply"
    android:layout_alignLeft="@+id/num2TextField"
    android:text="@string/add" />

</RelativeLayout>

---

下面是我的 ComputeFragment.java code：

public class ComputeFragment extends Fragment {

    String num1;
    String num2;

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_compute, parent, false);

        // Add Button
        Button addButton = (Button)v.findViewById(R.id.compute_add);
        addButton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // ERROR STARTS HERE!
                EditText num1Field = (EditText)v.findViewById(R.id.num1TextField);
                num1 = num1Field.getText().toString(); // Null Pointer Exception is thrown here!

                EditText num2Field = (EditText)v.findViewById(R.id.num2TextField);
                num2 = num2Field.getText().toString();
                // ERROR ENDS HERE!

                Intent i = new Intent(getActivity(), AddActivity.class);
                i.putExtra("x", num1);
                i.putExtra("y", num2);
                startActivityForResult(i,0);
            }
        });

        return v; 
    }
}

---

感谢大家，有一个愉快的一天！

---

Thank you all and have a nice day!

推荐答案

在参数v 的EditText num1Field =（EditText上）v.findViewById（R.id.num1TextField）; 是按钮，而不是整个视图。

The parameter v in EditText num1Field = (EditText)v.findViewById(R.id.num1TextField); is your button, not the whole view.

您应声明的变量 onCreateView ：

final EditText num1Field = (EditText)v.findViewById(R.id.num1TextField);

和使用它的onClick

num1 = num1Field.getText().toString();

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