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java - 无法在我的列表视图中添加删除功能

问题描述

所以我想添加一个选项来删除列表中的特定条目，所以我在列表的适配器中添加了一个图像视图。但是由于某种原因，当我现在尝试在我的应用程序中创建列表时，它崩溃了。这是错误行：

java.lang.ClassCastException: android.widget.LinearLayout 不能转换为 android.widget.ImageView

这是我的列表适配器的代码：

package com.example.taskmasterv3;

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

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import java.util.ArrayList;

public class SubtaskAdapter extends ArrayAdapter<subtask> {

private final Context context;
private ArrayList<subtask> values;


public SubtaskAdapter(Context context, ArrayList<subtask> list) {

    //since your are using custom view,pass zero and inflate the custom view by overriding getview

    super(context, 0 , list);
    this.context = context;
    this.values = list;
}



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

    //check if its null, if so inflate it, else simply reuse it
    if (convertView == null) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.subtask_item, parent, false);
    }

    //use convertView to refer the childviews to populate it with data
    TextView tvSubtaskName = convertView.findViewById(R.id.tvSubtaskName);
    ImageView ivPri = convertView.findViewById(R.id.ivPri);
    ImageView ivTime = convertView.findViewById(R.id.ivTime);
    ImageView ivDelete = convertView.findViewById(R.id.ivDelete);

    tvSubtaskName.setText(values.get(position).getSubtaskName());

    if (values.get(position).isPriHigh()) {
        ivPri.setImageResource(R.drawable.priority_high);
    } else if (values.get(position).isPriMed()) {
        ivPri.setImageResource(R.drawable.priority_med);
    } else if (values.get(position).isPriLow()) {
        ivPri.setImageResource(R.drawable.priority_low);
    }

    if (values.get(position).isTimeMore()) {
        ivTime.setImageResource(R.drawable.time_symbol_more);
    } else if (values.get(position).isTimeMed()) {
        ivTime.setImageResource(R.drawable.time_symbol_med);
    } else if (values.get(position).isTimeLess()) {
        ivTime.setImageResource(R.drawable.time_symbol_less);
    }


    // Delete button for subtasks

    ivDelete.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            values.remove(position);
            notifyDataSetChanged();
        }
    });

    //return the view you inflated
    return convertView;
}




//to keep adding the new subtasks try the following
public void addANewSubTask(subtask newSubTask){
    ArrayList<subtask> newvalues = new ArrayList<>(this.values);
    newvalues.add(newSubTask);
    this.values = newvalues;
    notifyDataSetChanged();

}


}

这是列表项的 xml 代码：

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/ivDelete"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    android:layout_margin="16dp"
    android:background="@color/white"
    android:clickable="true"
    android:orientation="horizontal"

     >

    <ImageView
    android:id="@+id/imageView"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_weight="1"
    android:clickable="true"
    app:srcCompat="@drawable/delete" />

    <TextView
    android:id="@+id/tvSubtaskName"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:layout_weight="3"
    android:fontFamily="@font/roboto"
    android:gravity="center_horizontal"
    android:text="subtask_name"
    android:textColor="@color/black"
    android:textSize="15sp" />

    <ImageView
    android:id="@+id/ivPri"
    android:layout_width="0dp"
    android:layout_height="32dp"
    android:layout_gravity="center"
    android:layout_weight="1"
    app:srcCompat="@drawable/priority_high" />

    <ImageView
    android:id="@+id/ivTime"
    android:layout_width="0dp"
    android:layout_height="32dp"
    android:layout_gravity="center"
    android:layout_weight="1"
    app:srcCompat="@drawable/time_symbol_more" />
</LinearLayout>

标签： javaandroidandroid-layoutlistview

解决方案

您正在尝试将 a 引用LinearLayout为ImageView.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/ivDelete"
...

ImageView ivDelete = convertView.findViewById(R.id.ivDelete);

你看到这里的id了吗？

只需将最后一行替换为以下内容：

LinearLayout ivDelete = convertView.findViewById(R.id.ivDelete);

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