Java NullPointerException onCreate-android微调器

我的应用程序中的微调器有问题

微调器应该将所选项目传递给SQlite DB并保存数据

但到目前为止，每次我按下寄存器按钮，它都会抛出javaNullPointerException错误

这是我的班级：

public class RegisterMember extends Activity implements OnItemSelectedListener{
DbAdapter dbAdapter;
EditText txtName;
EditText txtPassword;
EditText txtPasswordConf;
EditText txtEmail;
EditText txtEmailConf;
EditText txtSchool;
Button btnJoin;
//Button btnRegister;

private String[] state= {"USB","Stanford","Harvard","UCV","USM","Tor vergata", "La Sapienza"};
Spinner spinner_school;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_members_register);
    System.out.println(state.length);
    spinner_school = (Spinner) findViewById(R.id.spinner_school);
    ArrayAdapter<String> adapter_state = new ArrayAdapter<String>(this,
    android.R.layout.simple_spinner_item, state);
    adapter_state
    .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner_school.setAdapter(adapter_state);
    spinner_school.setOnItemSelectedListener(this);
    //btnRegister = (Button) findViewById(R.id.btn_reg);

    dbAdapter = new DbAdapter(this);
    dbAdapter.open();

    btnJoin.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
            imm.hideSoftInputFromWindow(txtName.getWindowToken(), 0);
            imm.hideSoftInputFromWindow(txtPassword.getWindowToken(), 0);
            imm.hideSoftInputFromWindow(txtPasswordConf.getWindowToken(), 0);
            imm.hideSoftInputFromWindow(txtEmail.getWindowToken(), 0);
            imm.hideSoftInputFromWindow(txtEmailConf.getWindowToken(), 0);
            //imm.hideSoftInputFromWindow(txtSchool.getWindowToken(), 0);
            //imm.hideSoftInputFromWindow(spinner_school.getWindowToken(), 0);
            try {

                String name = txtName.getText().toString();
                String password = txtPassword.getText().toString();
                String passwordconf = txtPasswordConf.getText().toString();
                String email = txtEmail.getText().toString();
                String emailconf = txtEmailConf.getText().toString();
                //String school = txtSchool.getText().toString();
                String school = spinner_school.getSelectedItem().toString();
                long i = dbAdapter.register(name, password, email, school);
                if(i != -1)
                    Toast.makeText(RegisterMember.this, "You have successfully registered",Toast.LENGTH_LONG).show();
                else {
                    if(!passwordconf.equals(password))
                    {
                        Toast.makeText(getApplicationContext(), "Password Does Not Matches", Toast.LENGTH_LONG).show();
                    }
                    if(!emailconf.equals(email))
                    {
                        Toast.makeText(getApplicationContext(), "Email Does Not Matches", Toast.LENGTH_LONG).show();
                    }

                }

            } catch (SQLException e) {
                Toast.makeText(RegisterMember.this, "Some problem occurred",
                        Toast.LENGTH_LONG).show();

            }

        }
    });
}
public void onItemSelected(AdapterView<?> parent, View view, int position,
                           long id) {
    spinner_school.setSelection(position);
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
    // TODO Auto-generated method stub

    }
}

有什么想法吗？我已经看过了很多例子，但我还是不明白这一点

提前谢谢

重复编辑

不，复制并不能解决我的问题，因为这里涉及SQLite，这是一个简单的方法问题，谢谢

第二次编辑

这就是btnJoin.setOnClickListener新OnClickListener{方法现在的样子，同样的错误：

btnJoin.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
            imm.hideSoftInputFromWindow(txtName.getWindowToken(), 0);
            imm.hideSoftInputFromWindow(txtPassword.getWindowToken(), 0);
            imm.hideSoftInputFromWindow(txtPasswordConf.getWindowToken(), 0);
            imm.hideSoftInputFromWindow(txtEmail.getWindowToken(), 0);
            imm.hideSoftInputFromWindow(txtEmailConf.getWindowToken(), 0);
            //imm.hideSoftInputFromWindow(txtSchool.getWindowToken(), 0);
            //imm.hideSoftInputFromWindow(spinner_school.getWindowToken(), 0);
            try {

                txtName = (EditText) findViewById(R.id.et_user);
                String name = txtName.getText().toString();
                txtPassword = (EditText) findViewById(R.id.et_pw_reg);
                String password = txtPassword.getText().toString();
                txtPasswordConf = (EditText) findViewById(R.id.et_pw_conf);
                String passwordconf = txtPasswordConf.getText().toString();
                txtEmail = (EditText) findViewById(R.id.et_email_reg);
                String email = txtEmail.getText().toString();
                txtEmailConf = (EditText) findViewById(R.id.et_email_conf);
                String emailconf = txtEmailConf.getText().toString();
                //String school = txtSchool.getText().toString();
                spinner_school = (Spinner) findViewById(R.id.spinner_school);
                String school = spinner_school.getSelectedItem().toString();
                long i = dbAdapter.register(name, password, email, school);
                if(i != -1)
                    Toast.makeText(RegisterMember.this, "You have successfully registered",Toast.LENGTH_LONG).show();
                else {
                    if(!passwordconf.equals(password))
                    {
                        Toast.makeText(getApplicationContext(), "Password Does Not Matches", Toast.LENGTH_LONG).show();
                    }
                    if(!emailconf.equals(email))
                    {
                        Toast.makeText(getApplicationContext(), "Email Does Not Matches", Toast.LENGTH_LONG).show();
                    }

                }

            } catch (SQLException e) {
                Toast.makeText(RegisterMember.this, "Some problem occurred",
                        Toast.LENGTH_LONG).show();

            }

        }
    });

---

您尚未为btnJoin分配任何值。这导致了异常

编辑1-如何解决问题

要解决此问题以及单击该按钮时可能出现的其他问题，请在setContentViewR.layout.activity\u members\u register之后向onCreate方法添加以下行：

只要布局文件中有类似的内容：

...
<EditText android:id="@+id/register_member_name" ... />
...
<EditText android:id="@+id/register_member_password" ... />
...
<EditText android:id="@+id/register_member_password_confirm" ... />
...
<EditText android:id="@+id/register_member_email" ... />
...
<EditText android:id="@+id/register_member_email_confirm" ... />
...
<EditText android:id="@+id/register_member_school" ... />
...
<Button android:id="@+id/register_member_button_join" ... />
...

---

其中register\u member\u name、register\u member\u password、register\u password\u confirm、register\u member\u email、register\u member\u email\u confirm、register\u member\u school和register\u member\u button\u join是小部件ID。您不必完全使用这些名称。只要您在布局文件和java实现中使用相同的值ion，一切都会好起来的。

你应该在onClick方法中尝试一下

 spinner_school = (Spinner) findViewById(R.id.spinner_school);
  String school = spinner_school.getSelectedItem().toString();

---

请将findviewByid放入所有小部件中

我认为您忘记了从您的视图中查找并放大小部件。因此，当您调用 txtName.getText.toString； 它抛出nullPointerException，因为您的txtName仍然为null

要解决此问题，您需要在尝试访问代码中的所有小部件之前将其膨胀。因此，在调用setContentView之后，您需要：

txtName = (EditText) findViewById(R.id.the_id_of_the_widget)

用于所有小部件

编辑：您仍然得到相同的错误，因为您仍然没有膨胀按钮

加：

---

在调用setOnClickListener之前。

您的问题就在这里：

 Caused by: java.lang.NullPointerException
        at com.kkoci.shairlook.RegisterMember.onCreate(RegisterMember.java:57)

---

查看RegisterMember.java的第57行，您正在尝试访问一些未初始化的变量。看不到行号，因此我无法进一步帮助您…哪一行是您的第57行？

尝试了，没有成功：您的代码中应该有null，这就是错误出现的原因。

 spinner_school = (Spinner) findViewById(R.id.spinner_school);
  String school = spinner_school.getSelectedItem().toString();

txtName = (EditText) findViewById(R.id.the_id_of_the_widget)

 btnJoin = (Button) findViewById(...)

 Caused by: java.lang.NullPointerException
        at com.kkoci.shairlook.RegisterMember.onCreate(RegisterMember.java:57)