Android 应用程序在片段中的按钮单击实现后崩溃
我的应用程序包含导航抽屉。其中有一个项目片段。在这个片段中,我尝试实现三个按钮点击事件来打开3个活动。但是,每当我单击导航抽屉中的片段时,应用程序就会因nullPointerAcception崩溃。调试后,它会显示包含onClickListener的以下代码的问题:Android 应用程序在片段中的按钮单击实现后崩溃,android,android-fragments,nullpointerexception,android-button,Android,Android Fragments,Nullpointerexception,Android Button,我的应用程序包含导航抽屉。其中有一个项目片段。在这个片段中,我尝试实现三个按钮点击事件来打开3个活动。但是,每当我单击导航抽屉中的片段时,应用程序就会因nullPointerAcception崩溃。调试后,它会显示包含onClickListener的以下代码的问题: itemButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(Vie
itemButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent itemIntent=new Intent(getActivity(),ItemsActivity.class);
startActivity(itemIntent);
}
});
这是我的片段代码
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
/**
* A simple {@link Fragment} subclass.
*/
public class ItemsFragment extends Fragment {
Button itemButton;
Button categoryButton;
Button discountButton;
public ItemsFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
itemButton=(Button) container.findViewById(R.id.items_button);
categoryButton=(Button) container.findViewById(R.id.category_button);
discountButton=(Button) container.findViewById(R.id.discount_button);
itemButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent itemIntent=new Intent(getActivity(),ItemsActivity.class);
startActivity(itemIntent);
}
});
setHasOptionsMenu(false);
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_items, container, false);
}
}
//Logcat错误
E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException
at com.soumya.possystem.ItemsFragment.onCreateView(ItemsFragment.java:36)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2080)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1108)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1290)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1677)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:536)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
在展开视图和已创建视图之前,您正在尝试查找控件的实例,并在
onCreateView
另一种方法是在onViewCreated
或onActivityCreated
中获取实例(findviewById
)
第二个问题是,您试图从容器中获取控件的对象,而不是需要从视图中获取的对象
View v=inflater.inflate(R.layout.fragment_items, container, false);
在下面,我保留了带有更改的代码
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
/**
* A simple {@link Fragment} subclass.
*/
public class ItemsFragment extends Fragment {
Button itemButton;
Button categoryButton;
Button discountButton;
public ItemsFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v=inflater.inflate(R.layout.fragment_items, container, false);
//check in place of container here you need to use inflated view (`v`) instance
itemButton=(Button) v.findViewById(R.id.items_button);
categoryButton=(Button) v.findViewById(R.id.category_button);
discountButton=(Button) v.findViewById(R.id.discount_button);
itemButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent itemIntent=new Intent(getActivity(),ItemsActivity.class);
startActivity(itemIntent);
}
});
setHasOptionsMenu(false);
// Inflate the layout for this fragment
return v;
}
}
在展开视图和已创建视图之前,您正在尝试查找控件的实例,并在onCreateView
另一种方法是在onViewCreated
或onActivityCreated
中获取实例(findviewById
)
第二个问题是,您试图从容器中获取控件的对象,而不是需要从视图中获取的对象
View v=inflater.inflate(R.layout.fragment_items, container, false);
在下面,我保留了带有更改的代码
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
/**
* A simple {@link Fragment} subclass.
*/
public class ItemsFragment extends Fragment {
Button itemButton;
Button categoryButton;
Button discountButton;
public ItemsFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v=inflater.inflate(R.layout.fragment_items, container, false);
//check in place of container here you need to use inflated view (`v`) instance
itemButton=(Button) v.findViewById(R.id.items_button);
categoryButton=(Button) v.findViewById(R.id.category_button);
discountButton=(Button) v.findViewById(R.id.discount_button);
itemButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent itemIntent=new Intent(getActivity(),ItemsActivity.class);
startActivity(itemIntent);
}
});
setHasOptionsMenu(false);
// Inflate the layout for this fragment
return v;
}
}
您必须根据要求初始化视图:
所以你必须做
View=充气机。充气(R.layout.YOUR_布局,容器,false)代码>
然后
itemButton=(按钮)view.findViewById(R.id.items\u按钮)代码>您必须根据要求初始化视图:
所以你必须做
View=充气机。充气(R.layout.YOUR_布局,容器,false)代码>
然后
itemButton=(按钮)view.findViewById(R.id.items\u按钮)代码>试试这个
View rootView = inflater.inflate(R.layout.fragment_id, container, false);
itemButton=(Button) container.findViewById(R.id.items_button);
categoryButton=(Button) container.findViewById(R.id.category_button);
discountButton=(Button) container.findViewById(R.id.discount_button);
.
.
.
return rootView;
试试这个
View rootView = inflater.inflate(R.layout.fragment_id, container, false);
itemButton=(Button) container.findViewById(R.id.items_button);
categoryButton=(Button) container.findViewById(R.id.category_button);
discountButton=(Button) container.findViewById(R.id.discount_button);
.
.
.
return rootView;
试试这个:
public class ItemsFragment extends Fragment {
Button itemButton;
Button categoryButton;
Button discountButton;
public ItemsFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v=inflater.inflate(R.layout.fragment_items, container, false);
setHasOptionsMenu(false);
return v;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
itemButton=(Button) view.findViewById(R.id.items_button);
categoryButton=(Button) view.findViewById(R.id.category_button);
discountButton=(Button) view.findViewById(R.id.discount_button);
itemButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent itemIntent=new Intent(getActivity(),ItemsActivity.class);
startActivity(itemIntent);
}
});
}
}
试试这个:
public class ItemsFragment extends Fragment {
Button itemButton;
Button categoryButton;
Button discountButton;
public ItemsFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v=inflater.inflate(R.layout.fragment_items, container, false);
setHasOptionsMenu(false);
return v;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
itemButton=(Button) view.findViewById(R.id.items_button);
categoryButton=(Button) view.findViewById(R.id.category_button);
discountButton=(Button) view.findViewById(R.id.discount_button);
itemButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent itemIntent=new Intent(getActivity(),ItemsActivity.class);
startActivity(itemIntent);
}
});
}
}
什么是异常?请发布来自logcat的异常堆栈跟踪。可能是重复的我正在添加logcat@Code学徒它是nullPointerException@VivekMishrawhat is exception?请发布来自logcat的异常堆栈跟踪。可能是重复的我正在添加logcat@Code学徒它是nullPointerException@VivekMishracan you指定未指定的特定代码working@jiteshmohite请检查我保留的代码和注释,它们正好位于NullPointerException giving Crashc的位置。您可以在不存在的位置指定特定代码吗working@jiteshmohite请检查我保留的代码和注释,NullPointerException giving crashi建议您保留解释这个问题。因此,用户可以理解问题。我建议您保留对问题的解释。所以用户可以理解这个问题