我一直犯错误。不兼容的类型：ArrayList无法转换为ArrayList

Question

package com.example.helpresponse;

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.List;


//Note that you can implement more than one interfaces, that's one of its beauty.
public class ShowStudentDetailsActivity extends AppCompatActivity implements HandleClick {
    private DatabaseReference databaseReference;

    ProgressDialog progressDialog;

    private ArrayList<StudentDetails> list = new ArrayList<>();

    private RecyclerView recyclerView;
    private TargetDataAdapter adapter;

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

        initRecyclerView();
        initProgressDialog("Loading Data from Firebase Database");

        progressDialog.show();

        databaseReference = FirebaseDatabase.getInstance().getReference("Police").child("Chats");

        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {

                for (DataSnapshot dataSnapshot : snapshot.getChildren()) {

                    StudentDetails studentDetails = dataSnapshot.getValue(StudentDetails.class);

                    list.add(studentDetails);
                }

                adapter = new TargetDataAdapter(list,this);
                recyclerView.setAdapter(adapter);

                progressDialog.dismiss();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

                progressDialog.dismiss();

            }
        });
    }

    private void initProgressDialog(String msg){
        progressDialog = new ProgressDialog(this);
        progressDialog.setMessage(msg);
    }

    private void initRecyclerView(){
        recyclerView = findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
    }

    @Override
    public void onItemClick(int index){
        Intent intent = new Intent(this, MapsActivity.class);
        int myData = index;
        intent.putExtra("myDataKey", myData);
        startActivity(intent);
    }
}

package com.example.helpresponse;

public class AndroidTargets {
    public String FIELD1;
    public Long FIELD2;
    public String FIELD3;
}

package com.example.helpresponse;

import android.content.Context;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.Locale;

public class TargetDataAdapter extends RecyclerView.Adapter<TargetDataAdapter.TargetViewHolder> {

    private ArrayList<AndroidTargets> targetsArrayList;
    private HandleClick mHandleClick;

    /*Note that the constructor now take two params which helps us get ride of setmHandleClick() method.*/
    public TargetDataAdapter(ArrayList<AndroidTargets> mTargetData, HandleClick handleClick) {
        targetsArrayList = mTargetData;
        mHandleClick = handleClick;
    }

    @NonNull
    @Override
    public TargetViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.target_row, viewGroup, false);
        return new TargetViewHolder(v);
    }

    /* There is an interesting way to make below code neater by abstracting it back to the Activity incharge, let me know if you want that...priority now is to focus on fixing your issue. */
    @Override
    public void onBindViewHolder(@NonNull TargetViewHolder viewHolder, int i) {
        viewHolder.androidTargetName.setText(targetsArrayList.get(i).FIELD1);
        viewHolder.androidTargetNumber.setText(String.format(Locale.getDefault(), "API Level: %d", targetsArrayList.get(i).FIELD2));
        viewHolder.androidTargetShortName.setText(targetsArrayList.get(i).FIELD3);
        viewHolder.myClickableView.setClickable(true);

        viewHolder.myClickableView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mHandleClick.onItemClick(i);
            }
        });
    }

    @Override
    public int getItemCount() {
        if (targetsArrayList == null)
            return 0;
        return targetsArrayList.size();
    }

    public static class TargetViewHolder extends RecyclerView.ViewHolder {
        protected TextView androidTargetName;
        protected TextView androidTargetNumber;
        protected TextView androidTargetShortName;
        protected LinearLayout myClickableView;


        public TargetViewHolder(@NonNull View itemView) {

            super(itemView);
            myClickableView = itemView.findViewById(R.id.linearLayout);
            androidTargetShortName = itemView.findViewById(R.id.textView2);
            androidTargetName = itemView.findViewById(R.id.textView3);
            androidTargetNumber = itemView.findViewById(R.id.textView4);

        }

        public interface IHomeSelector {
            void onCategorySelected(int postion);
        }
    }
}

package com.example.helpresponse;

/**
 * Created by Juned on 7/25/2017.
 */

public class StudentDetails {


    private String name;
   public String message;
    public String latitude;
    public String longitude;

    public StudentDetails() {
        // This is default constructor.
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public String getLatitude() {
        return latitude;
    }

    public void setLatitude(String latitude) {
        this.latitude = latitude;
    }

    public String getLongitude() {
        return longitude;
    }

    public void setLongitude(String longitude) {
        this.longitude = longitude;
    }

    public String getStudentName() {

        return name;
    }

    public void setStudentName(String name) {

        this.name = name;
    }

}

Answer 1

您得到该错误是因为您传入了以下代码行：

adapter = new TargetDataAdapter(list,this);

对于TargetDataAdapter构造函数来说，列表，它声明为ArrayList 类型，而在适配器中，该列表的类型为ArrayList ，因此出现错误。要解决这个问题，您应该传递一个相同数据类型的列表，更准确地说，是ArrayList 类型的列表。因此，列表中的所有对象都必须是androidtargets类型，而不是studentdetails类型。

如果要显示StudentDetails对象列表，则需要创建另一个接受StudentDetails类型列表的适配器。