在alertDialog中使用自旋器时出现空指针异常

Question

这就是我写的代码：

// create a view in dialog box
final View fileView = getLayoutInflater().inflate(R.layout.filename, null);
String[] array_spinner = new String[5];
array_spinner[0]="1";
array_spinner[1]="2";
array_spinner[2]="3";
array_spinner[3]="4";
array_spinner[4]="5";

Spinner s = (Spinner) findViewById(R.id.sp_CAT);
ArrayAdapter adapter = new ArrayAdapter(this,
android.R.layout.simple_spinner_item, array_spinner);
s.setAdapter(adapter);
s.setSelection(2);

//Spinner mCAT = (Spinner) findViewById(R.id.sp_CAT);
//ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
//fileView.getContext(), R.array.a_CAT, android.R.layout.simple_spinner_item);
//adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
//mCAT.setAdapter(adapter);

EditText mSID = (EditText) fileView.findViewById(R.id.et_SID);
EditText mSCD = (EditText) fileView.findViewById(R.id.et_SCD);
EditText mNUM = (EditText) fileView.findViewById(R.id.et_NUM);
final String tSID=mSID.getText().toString();
final String tSCD=mSCD.getText().toString();
final String tNUM=mNUM.getText().toString();

// show dialog box
new AlertDialog.Builder(CameraActivity3.this).setTitle("Set FileName")
  .setView(fileView)
  .setPositiveButton("OK", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {

      Toast.makeText(CameraActivity3.this, tSID+tSCD+tNUM, Toast.LENGTH_SHORT).show();

    }// public void onClick
  }) // setPositiveButton
  .setNegativeButton("Cancel", null).show();

但是，我正在接收一个空指针异常。经过一些测试(注释掉一些行)，它似乎与spinner适配器有关。我出什么问题了吗？

Answer 1

用这个：

Spinner s = (Spinner) fileView.findViewById(R.id.sp_CAT);

Answer 2

在代码行下面写

Spinner s = (Spinner) fileView.findViewById(R.id.sp_CAT);

而不是

Spinner s = (Spinner) findViewById(R.id.sp_CAT);

Answer 3

对于将来使用DialogFragment构建AlertDialog的人来说，不能只在ArrayAdapter中使用this。我的解决办法如下：

AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    LayoutInflater inflater = getActivity().getLayoutInflater();
    View myView = inflater.inflate(R.layout.program_num_spinner_popup, null);

    builder.setView(myView);

    programNumbers = (Spinner) myView.findViewById(R.id.prog_num_spinner_list);
    ArrayAdapter<CharSequence> numbersAdapter = ArrayAdapter.createFromResource(this.getActivity(), R.array.program_numbers, android.R.layout.simple_spinner_item);
    numbersAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    programNumbers.setAdapter(numbersAdapter);

我将this替换为this.getActivity()，并结合Zaz的答案和Dipak的答案(这是相同的)。