java - Android - 我想从另一个 Activity 或类中调用 getText()

Question

完成注册需要三个步骤，在不同的类和方法中从另一个 Activity 读取所有字符串。 启动项目时出现一些错误!

class1(RegisterActivity.java)

public class RegisterActivity extends AppCompatActivity {

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_register);

            Next = (Button)findViewById(R.id.next);
            Fname = (EditText)findViewById(R.id.fname);
            Lname = (EditText)findViewById(R.id.lname);

            Next.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    fname = Fname.getText().toString().trim();
                    lname = Lname.getText().toString().trim();

                    Intent intent = new Intent(RegisterActivity.this,RegisterStepTwoActivity.class);
                    startActivity(intent);
                    finish();

                }
            });

        }
    }

class2(RegisterStepTwoActivity)

public class RegisterStepTwoActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register_step_two);

        overridePendingTransition(R.anim.animation,R.anim.animation2);

        Day = (Spinner)findViewById(R.id.spinner_dates);
        Month = (Spinner)findViewById(R.id.spinner_months);
        Year = (Spinner)findViewById(R.id.spinner_years);
        Male = (RadioButton) findViewById(R.id.male);
        Female = (RadioButton) findViewById(R.id.female);
        RG = (RadioGroup)findViewById(R.id.rg);
        Next = (Button)findViewById(R.id.next_s_two);

        Next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                day = Day.getSelectedItem().toString().trim();
                month = Month.getSelectedItem().toString().trim();
                year = Year.getSelectedItem().toString().trim();

                int id = RG.getCheckedRadioButtonId();
                Male = (RadioButton)findViewById(id);
                Female = (RadioButton)findViewById(id);

                gender = ((RadioButton) findViewById(id)).getText().toString().trim();

                Male.getText();
                Female.getText();

                Intent intent = new Intent(RegisterStepTwoActivity.this,RegisterStepThreeActivity.class);
                startActivity(intent);
                finish();

            }
        });

    }
}

在这里，我想调用所有的class3(RegisterStepThreeActivity)

public class RegisterStepThreeActivity extends AppCompatActivity {

    EditText E_mail , Password;
    Button Complete;
    String email , password;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register_step_three);

        overridePendingTransition(R.anim.animation,R.anim.animation2);
        Complete = (Button) findViewById(R.id.complete);
        E_mail = (EditText) findViewById(R.id.email);
        Password = (EditText) findViewById(R.id.password);

        Complete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                email = E_mail.getText().toString().trim();
                password = Password.getText().toString().trim();

                RegisterActivity reg = new RegisterActivity();
                RegisterStepTwoActivity regtwo = new RegisterStepTwoActivity();

                if (!regtwo.day.isEmpty() && !regtwo.month.isEmpty() && !regtwo.year.isEmpty() && !regtwo.gender.isEmpty() &&
                    !reg.fname.equals(reg.Fname) && !reg.lname.isEmpty() && !email.isEmpty() && !password.isEmpty()) {

                    registerUser(reg.fname, reg.lname, regtwo.day, regtwo.month, regtwo.year, regtwo.gender, email, password);

                }

                else {
                    Snackbar.make(v, "Please enter your datalist", Snackbar.LENGTH_LONG).setAction("Action", null).show();
                }
            }
        });
    }

方法registerUser不能应用所有字符串! 错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.isEmpty()' on a null object reference

Answer 1

在您的 Intent 声明下尝试放置此代码

intent.putExtra("data", whatever you are trying to parse);

当您想要在下一个 Activity 写入时检索该数据时

Intent intent = getIntent();
String whatever=intent.getStringExtra("data");

现在您可以按照您喜欢的方式使用字符串。