Question

我创造了一个包含多个片段的活动。当在片段内部单击按钮（图像）时，片段将被替换为新片段。这很好用。其中一个图像/按钮是打开添加页面的“添加”按钮。在这个片段中有几个EditTexts和一个按钮'Insert'。

按“插入”按钮时，必须检索Edittext值。这是它出错的地方。

这是我的代码（我排除了似乎没有必要的代码）： MainActicity.java：

public class MainActivity extends AppCompatActivity {
    FragmentTransaction fragmentTransaction;
    EditText etDistancesInsertDays;

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

        etDistancesInsertDays = (EditText)findViewById(R.id.etDistancesInsertDays);

        // On create display home page (HomeFragment)
        Fragment frRecords = new RecordsFragment();
        fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.add(R.id.main_container, frRecords);
        fragmentTransaction.commit();


    }


    public void openDistancesInsert(){
        fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.main_container, new DistanceInsertFragment());
        fragmentTransaction.commit();
        getSupportActionBar().setTitle(getString(R.string.frTitleDistanceInsert));
    }


    public void switchFragment(View view){
        switch (view.getId()) {
            case R.id.btnInsertDistance:

                // Trial 1
                EditText etText = (EditText)findViewById(R.id.etDistancesInsertDays);
                String strDays = etDistancesInsertDays.getText().toString();
                // Caused by: java.lang.NullPointerException
                Toast.makeText(MainActivity.this, "Days: "+strDays, Toast.LENGTH_LONG).show();

                // Trial 2
                Fragment frInsert;
                frInsert = getSupportFragmentManager().findFragmentById(R.id.frDistanceInsert);
                View frViewInsert;
                frViewInsert = frInsert.getView();
                // Caused by: java.lang.NullPointerException
                EditText etText = (EditText)frViewInsert.findViewById(R.id.etDistancesInsertDays);
                String strDays = etDistancesInsertDays.getText().toString();
                Toast.makeText(MainActivity.this, "Days: "+strDays, Toast.LENGTH_LONG).show();

                break;
        }
    }

}

我的DistanceInsertFragment.java

public class DistanceInsertFragment extends Fragment {
    EditText etDistancesInsertDays, etDistancesInsertMonths, etDistancesInsertYears;

    public DistanceInsertFragment() {
        // Required empty public constructor
    }


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

        View frViewInsert = inflater.inflate(R.layout.fragment_distance_insert, container, false);


        // Set current dat in text field:
        Calendar c = Calendar.getInstance();
        String strDayOfMonth = Integer.toString(c.get(Calendar.DAY_OF_MONTH));
        String strMonthOfYear = Integer.toString(c.get(Calendar.MONTH)+1);
        String strYear = Integer.toString(c.get(Calendar.YEAR));
        etDistancesInsertDays = (EditText)frViewInsert.findViewById(R.id.etDistancesInsertDays);
        etDistancesInsertMonths = (EditText)frViewInsert.findViewById(R.id.etDistancesInsertMonths);
        etDistancesInsertYears = (EditText)frViewInsert.findViewById(R.id.etDistancesInsertYears);
        etDistancesInsertDays.setText(strDayOfMonth);
        etDistancesInsertMonths.setText(strMonthOfYear);
        etDistancesInsertYears.setText(strYear);

        return frViewInsert;
    }
}

试验1和试验2都给出了错误“引起：java.lang.NullPointerException”。虽然我不确定用它是什么意思..

Answer 1

代码不应该是：

EditText etText = (EditText)findViewById(R.id.etDistancesInsertDays);
String strDays = etText.getText().toString();

在这里，您将从EditText获取文本，在您尝试从id etDistancesInsertDays中检索的代码中

通过onClick

1 个答案: