在空对象上调用 findViewById。哪个不为空

Question

所以我有一个设置片段，其中包含设置。

在第22行，我有一个findview，它找到一个textview。直到今天，它都创造了奇迹(没有改变任何事情)。现在我想它也会失败的其他发现，但由于它崩溃在这个，我们永远不会知道。

为什么?

XML文件:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/textView3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#a8a4a1"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="ACCOUNT"
android:textColor="#2b2a29"
android:textSize="15dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/SettingsFragmentAccountSettings"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="Account Settings"
android:textColor="#2b2a29"
android:textSize="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/textView3" />
<TextView
android:id="@+id/textView4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="12dp"
android:background="#a8a4a1"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="THEME"
android:textColor="@color/black"
android:textSize="15dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/SettingsFragmentAccountSettings" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="Dark Mode"
android:textColor="@color/black"
android:textSize="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/textView4" />
<Switch
android:id="@+id/SettingsFragmentDarkModeSwitch"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="52dp"
android:scaleX="1.25"
android:scaleY="1.25"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.94"
app:layout_constraintStart_toEndOf="@+id/textView2"
app:layout_constraintTop_toBottomOf="@+id/SettingsFragmentAccountSettings" />
<TextView
android:id="@+id/r"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:background="#a8a4a1"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="OTHER"
android:textColor="@color/black"
android:textSize="15dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/SettingsFragmentDarkModeSwitch" />
<TextView
android:id="@+id/SettingsFragmentFAQ"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="FAQ"
android:textColor="@color/black"
android:textSize="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/r" />
<TextView
android:id="@+id/SettingsFragmentSupport"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="Support"
android:textColor="@color/black"
android:textSize="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/SettingsFragmentFAQ" />
<TextView
android:id="@+id/SettingsFragmentPolicy"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="Content Policy &amp; EULA"
android:textColor="@color/black"
android:textSize="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/SettingsFragmentSupport" />
<TextView
android:id="@+id/SettingsFragmentUSerAgreement"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="User Agreement"
android:textColor="@color/black"
android:textSize="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/SettingsFragmentPolicy" />
<TextView
android:id="@+id/SettingsFragmentBugReport"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="Report A Bug"
android:textColor="@color/black"
android:textSize="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/SettingsFragmentUSerAgreement" />
<TextView
android:id="@+id/Build"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:background="#a8a4a1"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:text="BUILD INFORMATION"
android:textColor="@color/black"
android:textSize="15dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/SettingsFragmentBugReport" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="12dp"
android:text="1.0.0"
android:textSize="15dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.042"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/Build" />
</androidx.constraintlayout.widget.ConstraintLayout>

片段代码:

package com.example.create4me;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CompoundButton;
import android.widget.Switch;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class Settings extends Fragment {
TextView accSettings, FAQ, BugReport, Policy, UserAgg, Support;
Switch darkModeSwitch;
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState){
accSettings = (TextView) getView().findViewById(R.id.SettingsFragmentAccountSettings);  <--- This one
FAQ = (TextView) getView().findViewById(R.id.SettingsFragmentFAQ);
BugReport = (TextView) getView().findViewById(R.id.SettingsFragmentBugReport);
Policy = (TextView) getView().findViewById(R.id.SettingsFragmentPolicy);
UserAgg = (TextView) getView().findViewById(R.id.SettingsFragmentUSerAgreement);
Support = (TextView) getView().findViewById(R.id.SettingsFragmentSupport);
darkModeSwitch = (Switch) getView().findViewById(R.id.SettingsFragmentDarkModeSwitch);
accSettings.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(getContext(), AccountSettings.class);
startActivity(intent);
}
});
BugReport.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(getContext(), BugReport.class);
startActivity(intent);
}
});
FAQ.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
alertDiag();
}
});
Policy.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
alertDiag();
}
});
UserAgg.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
alertDiag();
}
});
Support.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
alertDiag();
}
});
darkModeSwitch.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
/*
In here, put 0 into MySqli DB if the isChecked value = False.
Put 1 into MySqli DB if the isChecked value = 1.
*/
}
});
return inflater.inflate(R.layout.settings, container, false);
}
void alertDiag(){
new AlertDialog.Builder(getContext())
.setTitle("Well here we are")
.setMessage("Normally, the user by now would've gone into a website explaining the content of the pressed TextView.n"
+ "Since we do not have a website or a domain, we show this AlertDialog. Sorry for the turnout!")
.setNegativeButton(android.R.string.no, null)
.show();
}
}

Answer 1

你需要在onCreateView的第一行做:

View view = inflater.inflate(R.layout.settings, container, false);

然后为每个findViewById:

view.findViewById(R.id.your_view);

您在最后而不是第一个对视图进行充气。

然后在onCreateView()的末尾:

return view;

Answer 2

请尝试以下方法初始化并在oncreateview中返回

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

View view =  inflater.inflate(R.layout.settings, container, false);

//Init all here like 
accSettings = (TextView) view. findViewById(R.id.SettingsFragmentAccountSettings)

//and then return like
return view;
}

希望对你有帮助