Question

我试图创建一个自定义适配器来在列表视图中显示来自ArrayList的信息，但它似乎拒绝了一个ArrayList，而只是要求一个数组。这是我错误的代码：

的ArrayList

public ArrayList<Ing> IngList = new ArrayList<>();

public ArrayList<Ing> get(){

    return this.IngList;

}

对象类

public class Ing {





int init;

double value;

String name;

String unit;

String quantity;

public String getName() { return name; }

public void setName(String name) { this.name = name;}

public double getValue(){ return value; }

public void setValue(double value){ this.value = value; }

public int getInit(){ return init; }

public void setInit(int init){ this.init = init; }

public String getUnit(){ return unit; }

public void setUnit(String unit){ this.unit = unit; }

public String getQuantity(){ return quantity; }

public void setQuantity(String quantity){ this.quantity = quantity; }


Ing(String name, double value, int init, String unit, String quantity) {
    this.name = name;
    this.value = value;
    this.init = init;
    this.unit = unit;
    this.quantity = quantity;
}


}

ListAdapter

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import java.util.ArrayList;

public class ListAdapter extends ArrayAdapter<Ing> {

private Context context;

private Ing[] values = null;

public static Kitchen kitchen = new Kitchen();

public ListAdapter(Context context, int textViewResourceId, Ing[] values) {
    super(context, textViewResourceId, values);
    this.context = context;
    this.values = values;
}

public int getCount(){
    return values.length;
}

public Ing getItem(int position){
    return values[position];
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    if (convertView == null) {

        convertView = LayoutInflater.from(getContext()).inflate(R.layout.row_layout, parent, false);

    }

    TextView name = (TextView) convertView.findViewById(R.id.name);
    TextView value = (TextView) convertView.findViewById(R.id.value);
    TextView unit = (TextView) convertView.findViewById(R.id.unit);

    name.setText(kitchen.IngList.get(position).getName());
    value.setText(kitchen.IngList.get(position).getQuantity());
    unit.setText(kitchen.IngList.get(position).getUnit());

    return convertView;

}


}

分配适配器

final ListAdapter adapter = new ListAdapter(getContext(), 
R.layout.row_layout, IngList);
//error is in line above
    final ListView listView = (ListView) root.findViewById(R.id.list);
    listView.setAdapter(adapter);

行布局

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="10dp"
android:paddingTop="10dp"
android:paddingRight="10dp">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/name"
    android:text="Name"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:layout_alignParentTop="true"
    android:ellipsize="end"
    android:maxLines="1"
    android:layout_marginBottom="2dp"
    android:layout_marginLeft="10dp"/>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/value"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:layout_alignParentTop="true"
    android:maxLines="1"
    android:layout_toEndOf="@+id/name"
    android:layout_toRightOf="@+id/name"
    android:text="Value"
    android:layout_marginLeft="50dp"
    android:layout_marginBottom="2dp"
    android:ellipsize="end"/>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/unit"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:layout_alignParentTop="true"
    android:maxLines="1"
    android:layout_toEndOf="@+id/value"
    android:layout_toRightOf="@+id/value"
    android:text="Unit"
    android:layout_marginLeft="5dp"
    android:layout_marginBottom="2dp"
    android:ellipsize="end"/>

很抱歉，如果我发布了超过我需要的内容。我还提前道歉，因为在组织代码方面有点愚蠢。万分感谢能找到错误的人。

Answer 1

您的修改后的ListAdapter

public class ListAdapter extends ArrayAdapter<Ing> {

private Context context;

private ArrayList<Ing> values = new ArrayList<>();

public static Kitchen kitchen = new Kitchen();

public ListAdapter(Context context, int textViewResourceId, ArrayList<Ing> values) {
    super(context, textViewResourceId, values);
    this.context = context;
    this.values = values;
}

public int getCount(){
    return values.size();
}

public Ing getItem(int position){
    return values.get(position);
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    if (convertView == null) {

        convertView = LayoutInflater.from(getContext()).inflate(R.layout.row_layout, parent, false);

    }

    TextView name = (TextView) convertView.findViewById(R.id.name);
    TextView value = (TextView) convertView.findViewById(R.id.value);
    TextView unit = (TextView) convertView.findViewById(R.id.unit);

    name.setText(kitchen.IngList.get(position).getName());
    value.setText(kitchen.IngList.get(position).getQuantity());
    unit.setText(kitchen.IngList.get(position).getUnit());

    return convertView;

}


}

我也不明白为什么你使用kitchen.IngList获取ArrayList来填充你的列表。您可以使用values代替kitchen.IngList

Answer 2

就像@ mark-keen和@ mike-m所说的那样，你的适配器构造函数期待Array，但你给它ArrayList。

使用以下命令创建适配器：

public ArrayList<Ing> IngList = new ArrayList<>();
...
final ListAdapter adapter = new ListAdapter(getContext(), R.layout.row_layout, IngList);

但是你的Adapter构造函数只接受Array：

public class ListAdapter extends ArrayAdapter<Ing> {
  ...
  private Ing[] values = null;

  public ListAdapter(Context context, int textViewResourceId, Ing[] values) {
    ...
  }
}

因此，您需要更改构造函数以接受ArrayList作为其参数。像这样：

public class ListAdapter extends ArrayAdapter<Ing> {

  private Context context;

  // don't need to create object for values 
  // because it depends on the parameter value.
  private ArrayList<Ing> values; 
  ...

  public ListAdapter(Context context, int textViewResourceId, ArrayList<Ing> values) {
    super(context, textViewResourceId, values);
    this.context = context;
    this.values = values;
  }

  ...
}

为什么我的自定义适配器拒绝ArrayList？

2 个答案: