Java 在微调器NullPointerException中添加赋值
就像我之前的帖子： 但现在，我试图在FragA的微调器中赋值，并将其添加到FragB的int中。与前一篇文章一样，金额将在FragC上。这是我的密码： FragAJava 在微调器NullPointerException中添加赋值,java,android,android-fragments,nullpointerexception,android-spinner,Java,Android,Android Fragments,Nullpointerexception,Android Spinner,就像我之前的帖子： 但现在，我试图在FragA的微调器中赋值，并将其添加到FragB的int中。与前一篇文章一样，金额将在FragC上。这是我的密码： FragA public class FragA extends Fragment{ Spinner spinner1; String s1; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,
public class FragA extends Fragment{
Spinner spinner1;
String s1;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
spinner1 = (Spinner) getActivity().findViewById(R.id.spinner1);
spinner1.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1,
int arg2, long arg3) {
s1 = spinner1.getSelectedItem().toString();
getInt(s1);
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
}
});
return inflater.inflate(R.layout.fraga, container, false);
}
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
ArrayAdapter<CharSequence> adapter_a = ArrayAdapter.createFromResource(getActivity(), R.array.spinner1,android.R.layout.simple_spinner_item );
spinner1.setAdapter(adapter_a);
}
public int getInt(String s1) {
int a = 0;
if(s1.equals("Hello")) {
a = 5;
}
else if(s1.equals("Hi")) {
a = 10;
}
return a;
}
}
public class MainActivity extends FragmentActivity {
ViewPager viewPager = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager)findViewById(R.id.pager);
FragmentManager fragmentManager = getSupportFragmentManager();
viewPager.setAdapter(new MyAdapter(fragmentManager));
}
public class MyAdapter extends FragmentStatePagerAdapter {
public MyAdapter (FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = null;
if (i == 0)
{
fragment = new FragA();
}
if (i == 1)
{
fragment = new FragB();
}
if (i == 2)
{
fragment = new FragC();
}
return fragment;
}
@Override
public int getCount() {
return 3;
}
}
public String sum() {
FragA FragA = new FragA();
FragB FragB = new FragB();
return Integer.valueOf(FragA.getInt() + FragB.getInt());
}
}
public class FragC extends Fragment{
Button button;
TextView textView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragc, container, false);
textView = (TextView)v.findViewById(R.id.textview);
button = (Button)v.findViewById(R.id.button);
button.setOnClickListener(Click);
return v;
}
OnClickListener Click = new OnClickListener() {
@Override
public void onClick(View v) {
textView.setText(((MainActivity)getActivity()).sum());
}
};
}
spinner1=（Spinner）getActivity（）。findViewById（R.id.spinner1）
换成
Spinner spinner1 = (Spinner) getView().findViewById(R.id.spinner1);
将该行放在onCreateView中
spinner1 = (Spinner) getActivity().findViewById(R.id.spinner1);
AsonActivityCreated
方法总是在onCreateView
之前调用，并且当您尝试初始化微调器时，它无法获取视图
在onCreateView
编辑：
通过为微调器实现setonItemClickListener
，尝试获取所选项目，如下所示：
String s1;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
spinner1 = (Spinner) getActivity().findViewById(R.id.spinner1);
spinner1 .setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1,
int arg2, long arg3) {
s1 = spinner1.getSelectedItem().toString();
getInt(s1);
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
});
return inflater.inflate(R.layout.fraga, container, false);
}
试试这个
在onCreateView
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fraga, container, false);
spinner1 = (Spinner) view.findViewById(R.id.spinner1);
ArrayAdapter<CharSequence> adapter_a = ArrayAdapter.createFromResource(getActivity(), R.array.spinner1,android.R.layout.simple_spinner_item );
spinner1.setAdapter(adapter_a);
return view;
}
@覆盖
创建视图上的公共视图（布局、充气机、视图组容器、，
Bundle savedInstanceState）{
视图=充气机。充气（R.layout.fraga，容器，假）；
spinner1=（Spinner）view.findViewById（R.id.spinner1）；
ArrayAdapter_a=ArrayAdapter.createFromResource（getActivity（），R.array.spinner1，android.R.layout.simple_微调器_项）；
喷丝头1.固定接头（接头a）；
返回视图；
}
示例：
public class FragA extends Fragment{
Spinner spinner1;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fraga, container, false);
spinner1 = (Spinner) view.findViewById(R.id.spinner1);
ArrayAdapter<CharSequence> adapter_a = ArrayAdapter.createFromResource(getActivity(), R.array.spinner1,android.R.layout.simple_spinner_item );
spinner1.setAdapter(adapter_a);
return view;
}
public int getInt() {
int a = 0;
String s1 = spinner1.getSelectedItem().toString();
if(s1.equals("Hello")) {
a = 5;
}
else if(s1.equals("Hi")) {
a = 10;
}
return a;
}
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
}
公共类FragA扩展片段{
喷丝器喷丝器1；
@凌驾
创建视图上的公共视图（布局、充气机、视图组容器、，
Bundle savedInstanceState）{
视图=充气机。充气（R.layout.fraga，容器，假）；
spinner1=（Spinner）view.findViewById（R.id.spinner1）；
ArrayAdapter_a=ArrayAdapter.createFromResource（getActivity（），R.array.spinner1，android.R.layout.simple_微调器_项）；
喷丝头1.固定接头（接头a）；
返回视图；
}
公共int getInt（）{
int a=0；
字符串s1=喷丝头1.getSelectedItem（）.toString（）；
如果（s1等于（“你好”））{
a=5；
}
else如果（s1等于（“Hi”））{
a=10；
}
返回a；
}
已创建ActivityState上的公共无效（Bundle savedInstanceState）{
super.onActivityCreated（savedInstanceState）；
}
}
FragA.java中第18行有什么？@Tamanna-String s1=spinner1.getSelectedItem（）.toString（）；spinner1为null或spinner1.getSelectedItem（）为null您无法通过实例化该类来访问视图（Spinner）。我的意思是FragA-FragA=new-FragA（）不包含微调器实例。只有当前面的片段返回null时，才能访问视图exception@SathishKumar-那我该怎么办？我仍然在“String s1=spinner1.getSelectedItem（）.toString（）；”处得到NullPointerException…@user2942600也在onCreateView
中执行setadapter，就像我的编辑一样。@user2942600我检查了它，它正在工作。正确地在创建的活动中输入条目设置entiers已经晚了。在设置条目之前，我们将调用spinner1.getSelectedItem（）.toString（）
，以使空指针。是。“字符串s1=spinner1.getSelectedItem（）.toString（）；”的NullPointerException“@user2942600是fraga
布局中的spinner1
。仍在“字符串s1=spinner1.getSelectedItem（）.toString（）；“我在MainActivity上出错”返回整数。toString（fraga.getInt（）+FragB.getInt（））；”上显示“FragA类型中的方法getInt（）不适用于参数（）”@user2942600像这样尝试“返回Integer.valueOf（FragA.getInt（）+FragB.getInt（））；“
如果要返回字符串
，请将返回类型更改为字符串
类似返回字符串.valueOf（FragA.getInt（）+FragB.getInt（））；
或者如果只想返回Integer
，则需要将sum
方法的返回类型更改为String
例如public int sum（）{……
当我将其更改为“return Integer.valueOf（FragA.getInt（）+FragB.getInt（））；”或“return String.valueOf（FragA.getInt（）+FragB.getInt（））”；getInt（）处出现错误，表示“FragA类型中的方法getInt（）不适用于参数（）
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fraga, container, false);
spinner1 = (Spinner) view.findViewById(R.id.spinner1);
ArrayAdapter<CharSequence> adapter_a = ArrayAdapter.createFromResource(getActivity(), R.array.spinner1,android.R.layout.simple_spinner_item );
spinner1.setAdapter(adapter_a);
return view;
}
public class FragA extends Fragment{
Spinner spinner1;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fraga, container, false);
spinner1 = (Spinner) view.findViewById(R.id.spinner1);
ArrayAdapter<CharSequence> adapter_a = ArrayAdapter.createFromResource(getActivity(), R.array.spinner1,android.R.layout.simple_spinner_item );
spinner1.setAdapter(adapter_a);
return view;
}
public int getInt() {
int a = 0;
String s1 = spinner1.getSelectedItem().toString();
if(s1.equals("Hello")) {
a = 5;
}
else if(s1.equals("Hi")) {
a = 10;
}
return a;
}
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
}