Java 尝试调用虚拟方法'；void ListView.setAdapter（ListAdapter）和#x27；关于空对象引用

我试图在每个列表视图项中显示一个图像和文本。我读了一些教程，但还是看不懂

当我尝试打开TagsActivity时，出现以下错误：

尝试调用虚拟方法“void” android.widget.ListView.setAdapter（android.widget.ListAdapter）“”在 空对象引用

在这方面：

this.tagList.setAdapter(adapter);

TagsActivity.java

public class TagsActivity extends AppCompatActivity {
public ListView tagList;
final List<Tag> tags = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.activity_main);

    tags.add(new Tag("Black & White"));
    tags.add(new Tag("Geometric"));

    this.tagList = (ListView) this.findViewById(R.id.list_tags);
    LazyAdapter adapter = new LazyAdapter(this, this.tags);
    this.tagList.setAdapter(adapter);
}
}

public class Tag {
private String title;

public Tag(String title) {
    super();
    this.title = title;
}

public String getTitle() {
    return this.title;
}

public void setTitle(String title) {
    this.title = title;
}
}

public class LazyAdapter extends BaseAdapter {
private LayoutInflater inflater;
private List<Tag> tags;

public LazyAdapter(Activity activity, List<Tag> tags) {
    this.inflater = (LayoutInflater) activity.getSystemService(
            Context.LAYOUT_INFLATER_SERVICE);
    this.tags = tags;
}

@Override
public int getCount() {
    return this.tags.size();
}

@Override
public Tag getItem(int position) {
    return this.tags.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView (int position, View convertView, ViewGroup parent) {
    View row;
    row = this.inflater.inflate(R.layout.list_item, null);

    TextView textView = (TextView) row.findViewById(R.id.title);
    ImageView imageView = (ImageView) row.findViewById(R.id.icon);

    Tag tag = this.tags.get(position);

    textView.setText(tag.getTitle());
    imageView.setImageResource(R.drawable.icon);

    return row;
}
}

View row;
row = this.inflater.inflate(R.layout.list_item, null);

JazyAdapter.java

public class TagsActivity extends AppCompatActivity {
public ListView tagList;
final List<Tag> tags = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.activity_main);

    tags.add(new Tag("Black & White"));
    tags.add(new Tag("Geometric"));

    this.tagList = (ListView) this.findViewById(R.id.list_tags);
    LazyAdapter adapter = new LazyAdapter(this, this.tags);
    this.tagList.setAdapter(adapter);
}
}

public class Tag {
private String title;

public Tag(String title) {
    super();
    this.title = title;
}

public String getTitle() {
    return this.title;
}

public void setTitle(String title) {
    this.title = title;
}
}

public class LazyAdapter extends BaseAdapter {
private LayoutInflater inflater;
private List<Tag> tags;

public LazyAdapter(Activity activity, List<Tag> tags) {
    this.inflater = (LayoutInflater) activity.getSystemService(
            Context.LAYOUT_INFLATER_SERVICE);
    this.tags = tags;
}

@Override
public int getCount() {
    return this.tags.size();
}

@Override
public Tag getItem(int position) {
    return this.tags.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView (int position, View convertView, ViewGroup parent) {
    View row;
    row = this.inflater.inflate(R.layout.list_item, null);

    TextView textView = (TextView) row.findViewById(R.id.title);
    ImageView imageView = (ImageView) row.findViewById(R.id.icon);

    Tag tag = this.tags.get(position);

    textView.setText(tag.getTitle());
    imageView.setImageResource(R.drawable.icon);

    return row;
}
}

View row;
row = this.inflater.inflate(R.layout.list_item, null);

公共类LazyAdapter扩展了BaseAdapter{
私人充气机；
私有列表标签；
公共LazyAdapter（活动、列表标记）{
this.inflater=（LayoutInflater）activity.getSystemService(
上下文。布局（充气机和服务）；
this.tags=标签；
}
@凌驾
public int getCount（）{
返回此.tags.size（）；
}
@凌驾
公共标记getItem（int位置）{
返回此.tags.get（位置）；
}
@凌驾
公共长getItemId（int位置）{
返回位置；
}
@凌驾
公共视图getView（int位置、视图转换视图、视图组父视图）{
查看行；
行=此.充气器.充气（R.layout.list_项，空）；
TextView TextView=（TextView）row.findViewById（R.id.title）；
ImageView ImageView=（ImageView）row.findViewById（R.id.icon）；
Tag Tag=this.tags.get（位置）；
setText（tag.getTitle（））；
setImageResource（R.drawable.icon）；
返回行；
}
}

list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="15dp"
android:background="@drawable/border_bottom">

<LinearLayout
    android:id="@+id/thumb"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:padding="2dp"
    android:layout_marginRight="5dp"
    android:layout_alignParentLeft="true">
    <ImageView
        android:id="@+id/icon"
        android:layout_width="35dp"
        android:layout_height="35dp"
        android:layout_marginBottom="5dp"
        android:layout_marginLeft="5dp"
        android:layout_marginRight="5dp"
        android:layout_marginTop="5dp"
        android:src="@drawable/icon" />
</LinearLayout>

<TextView
    android:id="@+id/title"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/thumb"
    android:layout_toRightOf="@+id/thumb"
    android:layout_toEndOf="@+id/thumb"
    android:layout_centerVertical="true"
    android:textStyle="bold"
    android:textSize="24sp"
    android:text="Black &amp; White"
    android:paddingTop="5dp"/>

<ImageView
    android:layout_width="20dp"
    android:layout_height="20dp"
    android:layout_margin="15dp"
    android:layout_alignParentRight="true"
    android:layout_centerVertical="true"
    android:src="@drawable/arrow_right"/>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="{relativePackage}.${activityClass}" >

<ListView
    android:id="@+id/list_tags"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
</RelativeLayout>

activity_tags.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="15dp"
android:background="@drawable/border_bottom">

<LinearLayout
    android:id="@+id/thumb"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:padding="2dp"
    android:layout_marginRight="5dp"
    android:layout_alignParentLeft="true">
    <ImageView
        android:id="@+id/icon"
        android:layout_width="35dp"
        android:layout_height="35dp"
        android:layout_marginBottom="5dp"
        android:layout_marginLeft="5dp"
        android:layout_marginRight="5dp"
        android:layout_marginTop="5dp"
        android:src="@drawable/icon" />
</LinearLayout>

<TextView
    android:id="@+id/title"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/thumb"
    android:layout_toRightOf="@+id/thumb"
    android:layout_toEndOf="@+id/thumb"
    android:layout_centerVertical="true"
    android:textStyle="bold"
    android:textSize="24sp"
    android:text="Black &amp; White"
    android:paddingTop="5dp"/>

<ImageView
    android:layout_width="20dp"
    android:layout_height="20dp"
    android:layout_margin="15dp"
    android:layout_alignParentRight="true"
    android:layout_centerVertical="true"
    android:src="@drawable/arrow_right"/>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="{relativePackage}.${activityClass}" >

<ListView
    android:id="@+id/list_tags"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
</RelativeLayout>

---

如何解决此问题？

this.setContentView（R.layout.activity\u main）应该是
this.setContentView（R.layout.activity_标记）
此.setContentView（R.layout.activity\u main）应该是
this.setContentView（R.layout.activity_标记）
由于“查看行”为空，因此出现此错误。只需在您的LazyLoader.java

public class TagsActivity extends AppCompatActivity {
public ListView tagList;
final List<Tag> tags = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.activity_main);

    tags.add(new Tag("Black & White"));
    tags.add(new Tag("Geometric"));

    this.tagList = (ListView) this.findViewById(R.id.list_tags);
    LazyAdapter adapter = new LazyAdapter(this, this.tags);
    this.tagList.setAdapter(adapter);
}
}

public class Tag {
private String title;

public Tag(String title) {
    super();
    this.title = title;
}

public String getTitle() {
    return this.title;
}

public void setTitle(String title) {
    this.title = title;
}
}

public class LazyAdapter extends BaseAdapter {
private LayoutInflater inflater;
private List<Tag> tags;

public LazyAdapter(Activity activity, List<Tag> tags) {
    this.inflater = (LayoutInflater) activity.getSystemService(
            Context.LAYOUT_INFLATER_SERVICE);
    this.tags = tags;
}

@Override
public int getCount() {
    return this.tags.size();
}

@Override
public Tag getItem(int position) {
    return this.tags.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView (int position, View convertView, ViewGroup parent) {
    View row;
    row = this.inflater.inflate(R.layout.list_item, null);

    TextView textView = (TextView) row.findViewById(R.id.title);
    ImageView imageView = (ImageView) row.findViewById(R.id.icon);

    Tag tag = this.tags.get(position);

    textView.setText(tag.getTitle());
    imageView.setImageResource(R.drawable.icon);

    return row;
}
}

View row;
row = this.inflater.inflate(R.layout.list_item, null);

与：

由于“视图行”为空，因此出现此错误。只需在您的LazyLoader.java

public class TagsActivity extends AppCompatActivity {
public ListView tagList;
final List<Tag> tags = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.activity_main);

    tags.add(new Tag("Black & White"));
    tags.add(new Tag("Geometric"));

    this.tagList = (ListView) this.findViewById(R.id.list_tags);
    LazyAdapter adapter = new LazyAdapter(this, this.tags);
    this.tagList.setAdapter(adapter);
}
}

public class Tag {
private String title;

public Tag(String title) {
    super();
    this.title = title;
}

public String getTitle() {
    return this.title;
}

public void setTitle(String title) {
    this.title = title;
}
}

public class LazyAdapter extends BaseAdapter {
private LayoutInflater inflater;
private List<Tag> tags;

public LazyAdapter(Activity activity, List<Tag> tags) {
    this.inflater = (LayoutInflater) activity.getSystemService(
            Context.LAYOUT_INFLATER_SERVICE);
    this.tags = tags;
}

@Override
public int getCount() {
    return this.tags.size();
}

@Override
public Tag getItem(int position) {
    return this.tags.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView (int position, View convertView, ViewGroup parent) {
    View row;
    row = this.inflater.inflate(R.layout.list_item, null);

    TextView textView = (TextView) row.findViewById(R.id.title);
    ImageView imageView = (ImageView) row.findViewById(R.id.icon);

    Tag tag = this.tags.get(position);

    textView.setText(tag.getTitle());
    imageView.setImageResource(R.drawable.icon);

    return row;
}
}

View row;
row = this.inflater.inflate(R.layout.list_item, null);

与：

谢谢，我想那是个错误，但我还是犯了同样的错误（谢谢，我想这是一个错误，但我仍然会遇到同样的错误。）（你可能不想只发布一个类，你可能想澄清为什么这会解决问题中提出的问题。这样海报可以从中学习，以及未来的用户。因为我的英语非常差=（与仅仅发布一个类不同，你可能想澄清为什么这可以解决问题中提出的问题。这样，海报可以从中学习，也可以向未来的用户学习。因为我的英语很差=(