java - 滚动后的无序 RecycleView 列表
问题描述
如果我RecycleView
用鼠标滚轮滚动这个列表,我在列表中的项目看起来像是无序的。我不懂为什么?
我试图在单独的文件中创建单独的类CrimeAdapter extends RecyclerView.Adapter<CrimeAdapter.CrimeHolder>
,
class CrimeHolder extends RecyclerView.ViewHolder implements View.OnClickListener
但我做错了。不幸的是,我没有足够的经验。
我不知道如何在方法中编写正确的代码public void onClick(View v)
犯罪.java
package com.bignerdranch.android.criminalintent;
import java.util.Date;
import java.util.UUID;
public class Crime{
private UUID mId;
private String mTitle;
private Date mDate;
private boolean mSolved;
private boolean mRequiresPolice;
public Crime() {
// Generate unique identifier
this(UUID.randomUUID());
}
public Crime(UUID id) {
mId = id;
mDate = new Date();
}
public UUID getId() {
return mId;
}
public String getTitle() {
return mTitle;
}
public void setTitle(String title) {
mTitle = title;
}
public Date getDate() {
return mDate;
}
public void setDate(Date date) {
mDate = date;
}
public boolean isSolved() {
return mSolved;
}
public void setSolved(boolean solved) {
mSolved = solved;
}
public boolean isRequiresPolice() {
return mRequiresPolice;
}
public void setRequiresPolice(boolean requiresPolice) {
mRequiresPolice = requiresPolice;
}
}
犯罪实验室.java
package com.bignerdranch.android.criminalintent;
import android.content.Context;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.UUID;
public class CrimeLab {
private static CrimeLab sCrimeLab;
private List<Crime> mCrimes;
public static CrimeLab get(Context context) {
if (sCrimeLab == null) {
sCrimeLab = new CrimeLab(context);
}
return sCrimeLab;
}
private CrimeLab(Context context){
mCrimes = new ArrayList<>();
for (int i = 0; i < 100; i++) {
Crime crime = new Crime();
crime.setTitle("Crime #" + i);
crime.setSolved(i % 2 == 0);
if (i % 4 == 0 ) {crime.setRequiresPolice(true);}
else {crime.setRequiresPolice(false);}
mCrimes.add(crime);
}
}
public List<Crime> getCrimes() {
return mCrimes;
}
public Crime getCrime(UUID id){
for (Crime crime : mCrimes){
int rez = id.compareTo(crime.getId());
if (crime.getId().equals(id)){
return crime;
}
}
return null;
}
}
犯罪列表片段.java
package com.bignerdranch.android.criminalintent;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.text.format.DateFormat;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.LayoutRes;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import java.util.Date;
import java.util.List;
public class CrimeListFragment extends Fragment {
private static final int REQUEST_CRIME = 1;
private static final int NOT_REQUIRES_POLICE = 0;
private static final int REQUIRES_POLICE = 1;
private RecyclerView mCrimeRecyclerView;
private CrimeAdapter mAdapter;
private TextView mTitleTextView;
private TextView mDateTextView;
private ImageView mSolvedImageView;
private Button mButtonCallPolice;
private Crime mCrime;
private CharSequence mDateFormat;
private int layout;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_crime_list, container,
false);
mCrimeRecyclerView = (RecyclerView) view
.findViewById(R.id.crime_recycler_view);
mCrimeRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
updateUI();
return view;
}
private class CrimeHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public CrimeHolder(int layout, LayoutInflater inflater, ViewGroup parent ) {
super(inflater.inflate(layout, parent, false));
mTitleTextView = (TextView) itemView.findViewById(R.id.crime_title);
mDateTextView = (TextView) itemView.findViewById(R.id.crime_date);
mSolvedImageView = (ImageView) itemView.findViewById(R.id.crime_solved);
if (itemView.findViewById(R.id.call_police)!=null) {
mButtonCallPolice = (Button) itemView.findViewById(R.id.call_police);
}
itemView.setOnClickListener(this);
}
public void bind(Crime crime) {
mCrime = crime;
mTitleTextView.setText(mCrime.getTitle());
mDateFormat = DateFormat.format("EEE, MMM dd, yyyy", mCrime.getDate());
mDateTextView.setText(mDateFormat);
mSolvedImageView.setVisibility(mCrime.isSolved() ? View.VISIBLE :
View.GONE);
if(mCrime.isRequiresPolice()){
mButtonCallPolice.setEnabled(true);
}
}
@Override
public void onClick(View view) {
Intent intent = CrimePagerActivity.newIntent(getActivity(),
CrimeLab.get(requireActivity()).getCrimes().get((getAdapterPosition())).getId());
startActivityForResult(intent, REQUEST_CRIME);
}
}
private class CrimeAdapter extends RecyclerView.Adapter<CrimeHolder> {
private List<Crime> mCrimes;
public CrimeAdapter(List<Crime> crimes) {
mCrimes = crimes;
}
@Override
public CrimeHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
if (viewType==1) { layout = R.layout.list_item_crime_police;}
else { layout = R.layout.list_item_crime; }
return new CrimeHolder (layout, layoutInflater, parent);
}
@Override
public void onBindViewHolder(CrimeHolder holder, int position) {
Crime crime = mCrimes.get(position);
holder.bind(crime);
}
@Override
public int getItemCount() {
return mCrimes.size();
}
public int getItemViewType(int position) {
Crime crime = mCrimes.get(position);
return (crime.isRequiresPolice()) ? 1 : 0;
}
}
@Override
public void onResume() {
super.onResume();
updateUI();
}
private void updateUI() {
CrimeLab crimeLab = CrimeLab.get(getActivity());
List<Crime> crimes = crimeLab.getCrimes();
if (mAdapter == null) {
mAdapter = new CrimeAdapter(crimes);
mCrimeRecyclerView.setAdapter(mAdapter);
} else {
mAdapter.notifyDataSetChanged();
}
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQUEST_CRIME) {
// Обработка результата
}
}
public void returnResult() {
getActivity().setResult(Activity.RESULT_OK, null);
}
}
CrimePagerActivity.java
package com.bignerdranch.android.criminalintent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentStatePagerAdapter;
import androidx.viewpager.widget.ViewPager;
import java.util.List;
import java.util.UUID;
public class CrimePagerActivity extends AppCompatActivity {
private static final String EXTRA_CRIME_ID = "com.bignerdranch.android.criminalintent.crime_id";
private ViewPager mViewPager;
private List<Crime> mCrimes;
MyAdapter mAdapter;
public static Intent newIntent(Context packageContext, UUID crimeId) {
Intent intent = new Intent(packageContext, CrimePagerActivity.class);
intent.putExtra(EXTRA_CRIME_ID, crimeId);
return intent;
}
@Override
protected void onCreate( Bundle savedInstanceState ) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_crime_pager);
UUID crimeId = (UUID) getIntent().getSerializableExtra(EXTRA_CRIME_ID);
mViewPager = (ViewPager) findViewById(R.id.crime_view_pager);
mCrimes = CrimeLab.get(this).getCrimes();
mAdapter = new MyAdapter(getSupportFragmentManager(),mCrimes);
mViewPager.setAdapter(mAdapter);
for (int i = 0; i < mCrimes.size(); i++) {
if (mCrimes.get(i).getId().equals(crimeId)) {
mViewPager.setCurrentItem(i);
break;
}
}
}
public static class MyAdapter extends FragmentStatePagerAdapter {
private List<Crime> mCrimesCopy;
public MyAdapter(FragmentManager fm, List<Crime> mCrimesParametr) {
//super(fm);
super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
this.mCrimesCopy = mCrimesParametr;
}
@Override
public int getCount() {
return mCrimesCopy.size();
}
@Override
public Fragment getItem(int position) {
Crime crime = mCrimesCopy.get(position);
return CrimeFragment.newInstance(crime.getId());
}
}
}
fragment_crime_list.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/crime_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
片段犯罪.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="16dp"
android:orientation="vertical">
<TextView
style="?android:listSeparatorTextViewStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/crime_title_label"/>
<EditText
android:id="@+id/crime_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/crime_title_hint"
android:inputType=""
android:autofillHints="" />
<TextView
style="?android:listSeparatorTextViewStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/crime_details_label"/>
<Button
android:id="@+id/crime_date"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
<CheckBox
android:id="@+id/crime_solved"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/crime_solved_label"/>
</LinearLayout>
list_item_crime_police.xml
<?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:id="@+id/linearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="@+id/crime_title"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="8dp"
android:text="@string/crime_title"
android:textColor="@android:color/black"
android:textSize="18sp"
app:layout_constraintEnd_toStartOf="@+id/crime_solved"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/crime_date"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:text="@string/crime_date"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/crime_solved" />
<Button
android:id="@+id/call_police"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:layout_marginBottom="8dp"
android:text="@string/call_police"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/crime_date" />
<ImageView
android:id="@+id/crime_solved"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="16dp"
android:contentDescription="@string/todo"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/ic_solved" />
</androidx.constraintlayout.widget.ConstraintLayout>
list_item_crime.xml
<?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:id="@+id/linearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="@+id/crime_title"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="8dp"
android:text="@string/crime_title"
android:textColor="@android:color/black"
android:textSize="18sp"
app:layout_constraintEnd_toStartOf="@+id/crime_solved"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/crime_date"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:text="@string/crime_date"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/crime_solved" />
<ImageView
android:id="@+id/crime_solved"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="16dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/ic_solved"
android:contentDescription="@string/todo" />
</androidx.constraintlayout.widget.ConstraintLayout>
activity_crime_pager.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.viewpager.widget.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/crime_view_pager"
android:layout_width="match_parent"
android:layout_height="match_parent">
</androidx.viewpager.widget.ViewPager>
活动片段.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
解决方案
我认为 中的项目RecyclerView
是无序的,因为您的或布局文件views
中存在的引用被声明为类成员而不是类中的类成员:list_item_crime_police.xml
list_item_crime.xml
CrimeListFragment
CrimeHolder
public class CrimeListFragment extends Fragment {
// your other views and variables related declarations
// these are problematic declaration that keeps on being reused
private TextView mTitleTextView;
private TextView mDateTextView;
private ImageView mSolvedImageView;
private Button mButtonCallPolice;
// your other declarations
// your other code
}
这就是为什么,相同的view
实例,如mTitleTextView
, mDateTextView
, mSolvedImageView
,mButtonCallPolice
等被重复用于每个CrimeHolder
实例,导致列表中的项目无序。现在,为了解决这个问题,您可以简单地将这些行移动到代码中CrimeHolder
作为类变量,这将确保每个新CrimeHolder
实例都将具有上述视图的单独实例:
private class CrimeHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
// declare all of them here so there will be unique instances of these views for unique viewholder
private TextView mTitleTextView;
private TextView mDateTextView;
private ImageView mSolvedImageView;
private Button mButtonCallPolice;
public CrimeHolder(int layout, LayoutInflater inflater, ViewGroup parent ) {
View itemView = inflater.inflate(layout, parent, false));
super(itemView);
mTitleTextView = (TextView) itemView.findViewById(R.id.crime_title);
mDateTextView = (TextView) itemView.findViewById(R.id.crime_date);
mSolvedImageView = (ImageView) itemView.findViewById(R.id.crime_solved);
if (itemView.findViewById(R.id.call_police)!=null) {
mButtonCallPolice = (Button) itemView.findViewById(R.id.call_police);
}
itemView.setOnClickListener(this);
}
public void bind(Crime crime) {
mCrime = crime;
mTitleTextView.setText(mCrime.getTitle());
mDateFormat = DateFormat.format("EEE, MMM dd, yyyy", mCrime.getDate());
mDateTextView.setText(mDateFormat);
mSolvedImageView.setVisibility(mCrime.isSolved() ? View.VISIBLE :
View.GONE);
if(mCrime.isRequiresPolice()){
mButtonCallPolice.setEnabled(true);
}
}
@Override
public void onClick(View view) {
Intent intent = CrimePagerActivity.newIntent(getActivity(),
CrimeLab.get(requireActivity()).getCrimes().get((getAdapterPosition())).getId());
startActivityForResult(intent, REQUEST_CRIME);
}
}
它解决了我的问题,我希望它也能解决你的问题。
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