片段 return 空值指针上的按钮并使应用程序崩溃

Question

我试图在片段中使用一个按钮，但是当我尝试实例化它时，按钮 returns 成为空指针并使应用程序崩溃。这是我的代码：

Questionario.xml

     <?xml version="1.0" encoding="utf-8"?>
        <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:layout_width="match_parent" android:layout_height="match_parent"
            android:background="@color/Branco"
            android:id="@+id/Questionario">

            <ScrollView
                android:layout_width="match_parent"
                android:layout_height="fill_parent">
                <RelativeLayout
                    android:layout_width="match_parent"
                    android:layout_height="match_parent">

                    <TextView
                        android:id="@+id/Titulo1Quest"
                        android:layout_width="match_parent"
                        android:layout_height="50sp"
                        android:text="É membro do XV?"
                        android:layout_marginBottom="1sp"
                        android:layout_alignParentTop="true"
                        android:textSize="25sp"
                        android:padding="10sp"
                        android:textColor="@color/AzulPadrao"/>

                    <RadioGroup
                        android:layout_width="match_parent"
                        android:layout_height="30sp"
                        android:layout_below="@+id/Titulo1Quest"
                        android:orientation="horizontal"
                        android:gravity="center"
                        android:layout_marginTop="1sp"
                        android:id="@+id/RadioGroup1">
                    <RadioButton
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_below="@+id/Titulo1Quest"
                        android:text="Sim"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:gravity="center"
                        android:id="@+id/Rd1"
                        android:textSize="20sp"
                        android:textColor="@color/AzulPadrao"/>

                    <RadioButton
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_below="@+id/Titulo1Quest"
                        android:layout_toRightOf="@+id/Rd1"
                        android:text="Não"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:id="@+id/Rd2"
                        android:textSize="20sp"
                        android:textColor="@color/AzulPadrao"/>
                    </RadioGroup>

                    <View
                        android:layout_width="match_parent"
                        android:layout_height="1dp"
                        android:background="@color/Vermelho"
                        android:layout_below="@+id/RadioGroup1"
                        android:layout_margin="10sp"
                        android:id="@+id/Sep1"/>

                    <TextView
                        android:id="@+id/Titulo2Quest"
                        android:layout_width="match_parent"
                        android:layout_height="50sp"
                        android:text="Participa de quais ministérios?"
                        android:layout_marginBottom="1sp"
                        android:textSize="25sp"
                        android:padding="10sp"
                        android:textColor="@color/AzulPadrao"
                        android:layout_below="@+id/Sep1"/>

                    <GridLayout
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_below="@+id/Titulo2Quest"
                        android:columnCount="2"
                        android:layout_marginBottom="15sp"
                        android:id="@+id/gridLayout">
                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Teatro"
                        android:id="@+id/cbTeatro"
                        android:layout_below="@+id/Titulo2Quest"
                        android:textColor="@color/AzulPadrao"
                        android:layout_alignParentLeft="true"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Infantil"
                        android:id="@+id/cbInfantil"
                        android:layout_below="@+id/Titulo2Quest"
                        android:textColor="@color/AzulPadrao"
                        android:layout_centerHorizontal="true"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Adolescente"
                        android:layout_weight="1"
                        android:layout_gravity="start"
                        android:id="@+id/cbAdolescente"
                        android:layout_below="@+id/cbTeatro"
                        android:textColor="@color/AzulPadrao"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Jovens"
                        android:id="@+id/cbJovens"
                        android:layout_below="@+id/cbInfantil"
                        android:textColor="@color/AzulPadrao"
                        android:layout_centerHorizontal="true"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Casados"
                        android:id="@+id/cbCasados"
                        android:layout_below="@+id/cbAdolescente"
                        android:textColor="@color/AzulPadrao"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Missões"
                        android:id="@+id/cbMissoes"
                        android:layout_below="@+id/cbJovens"
                        android:textColor="@color/AzulPadrao"
                        android:layout_centerHorizontal="true"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Diáconos"
                        android:id="@+id/cbDiaconos"
                        android:layout_below="@+id/cbCasados"
                        android:textColor="@color/AzulPadrao"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Mulheres"
                        android:id="@+id/cbMulheres"
                        android:layout_below="@+id/cbMissoes"
                        android:textColor="@color/AzulPadrao"
                        android:layout_centerHorizontal="true"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Dança"
                        android:id="@+id/cbDança"
                        android:textColor="@color/AzulPadrao"
                        android:layout_below="@+id/cbDiaconos"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    <CheckBox
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Louvor"
                        android:id="@+id/cbLouvor"
                        android:textColor="@color/AzulPadrao"
                        android:layout_alignParentBottom="true"
                        android:layout_centerHorizontal="true"
                        android:layout_marginLeft="10sp"
                        android:layout_marginRight="10sp"
                        android:textSize="20sp"/>

                    </GridLayout>

                    <View
                        android:layout_width="match_parent"
                        android:layout_height="1dp"
                        android:background="@color/Vermelho"
                        android:id="@+id/Sep2"
                        android:layout_below="@id/gridLayout"
                        android:layout_margin="10sp"/>

                    <Button
                        android:id="@+id/btQuestionario"
                        android:layout_width="fill_parent"
                        android:layout_height="wrap_content"
                        android:background="@color/AzulPadrao"
                        android:text="OK"
                        android:layout_marginTop="10sp"
                        android:textColor="@android:color/white"
                        android:layout_below="@id/Sep2"
                        android:layout_marginLeft="40sp"
                        android:layout_marginRight="40sp"
                        android:clickable="true"/>


                </RelativeLayout>

            </ScrollView>

        </FrameLayout>

Canais.java

package igparadaxv.igbparadaxv.Parse;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

import igparadaxv.igbparadaxv.Home.homeActivity;
import igparadaxv.igbparadaxv.R;


public class Canais extends Fragment {

    ArrayList<String> canais;
    RadioButton sim;
    RadioButton nao;
    CheckBox teatro;
    CheckBox adolescente;
    CheckBox casados;
    CheckBox danca;
    CheckBox diaconos;
    CheckBox infantil;
    CheckBox jovens;
    CheckBox louvor;
    CheckBox missoes;
    CheckBox mulheres;
    Button ok;

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

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ok = (Button)getActivity().findViewById(R.id.btQuestionario);

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

            }
        });



        /*Radio Buttons*/
        sim = (RadioButton) getActivity().findViewById(R.id.Rd1);
        nao = (RadioButton) getActivity().findViewById(R.id.Rd2);

        /*Check box*/

        teatro = (CheckBox) getActivity().findViewById(R.id.cbTeatro);
        adolescente = (CheckBox) getActivity().findViewById(R.id.cbAdolescente);
        casados = (CheckBox) getActivity().findViewById(R.id.cbCasados);
        danca = (CheckBox) getActivity().findViewById(R.id.cbDança);
        diaconos = (CheckBox) getActivity().findViewById(R.id.cbDiaconos);
        infantil = (CheckBox) getActivity().findViewById(R.id.cbInfantil);
        jovens = (CheckBox) getActivity().findViewById(R.id.cbJovens);
        louvor = (CheckBox) getActivity().findViewById(R.id.cbLouvor);
        missoes = (CheckBox) getActivity().findViewById(R.id.cbMissoes);
        mulheres = (CheckBox) getActivity().findViewById(R.id.cbMulheres);

        RadioGroup radioGroup = (RadioGroup) getActivity().findViewById(R.id.RadioGroup1);

        radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {

                if(checkedId == sim.getId()){
                    teatro.setEnabled(true);
                    adolescente.setEnabled(true);
                    casados.setEnabled(true);
                    danca.setEnabled(true);
                    diaconos.setEnabled(true);
                    infantil.setEnabled(true);
                    jovens.setEnabled(true);
                    louvor.setEnabled(true);
                    missoes.setEnabled(true);
                    mulheres.setEnabled(true);

                }else{
                    teatro.setEnabled(false);
                    adolescente.setEnabled(false);
                    casados.setEnabled(false);
                    danca.setEnabled(false);
                    diaconos.setEnabled(false);
                    infantil.setEnabled(false);
                    jovens.setEnabled(false);
                    louvor.setEnabled(false);
                    missoes.setEnabled(false);
                    mulheres.setEnabled(false);
                }
            }
        });

    }

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

        return inflater.inflate(R.layout.questionario, container, false);
    }

    public void canais()
    {
        if(teatro.isChecked())
        {
            canais.add("Teatro");
        }
        if(adolescente.isChecked())
        {
            canais.add("Adolescente");
        }
        if(casados.isChecked())
        {
            canais.add("Casados");
        }
        if(danca.isChecked())
        {
            canais.add("Danca");
        }
        if(diaconos.isChecked())
        {
            canais.add("Diaconos");
        }
        if(infantil.isChecked())
        {
            canais.add("Infantil");
        }
        if(jovens.isChecked())
        {
            canais.add("Jovens");
        }
        if(louvor.isChecked())
        {
            canais.add("Louvor");
        }
        if(missoes.isChecked())
        {
            canais.add("Missoes");
        }
        if(mulheres.isChecked())
        {
            canais.add("Louvor");
        }

        ParseUtils.subscribeMultipleChannels(canais);

        home();


    }

    private void home() {

        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.remove(this);
        Intent intent = new Intent(getActivity(),homeActivity.class);
        startActivity(intent);
    }


}

我有另一部分代码将按钮用于片段，但仅在这个特定部分不起作用。

Answer 1

the button returns a null pointer and crash the application

如 Fragment 中所见，onCreate 方法在 onCreateView 之前被调用，目前 Fragment 屏幕的视图是 return 来自 onCreateView 使用以下行：

return inflater.inflate(R.layout.questionario, container, false);

这就是为什么在向 Button 添加点击侦听器时得到 NullPointerException 的原因。

不使用 onCreate 方法，而是使用 onCreateView 或 onViewCreated 从片段布局访问视图，片段布局是 return 来自 onCreateView.

就像在 onCreateView 方法中访问按钮一样：

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view =inflater.inflate(R.layout.questionario, container, false);
        ok = (Button)view.findViewById(R.id.btQuestionario);
        // add click listener for Button here
        // do same for accessing other Views
        return view;
    }

片段 return 空值指针上的按钮并使应用程序崩溃

Button on fragment return null value pointer and crash the app

java

android

button

android-fragments