Question

我正在为我的应用创建一种登录系统，我让它工作到用户可以添加其详细信息并从列表中选择它们的位置。

用户将其信息输入UserInput类，然后将此信息存储在Firebase数据库中。然后，数据显示在ListView项中，但首先通过CustomAdapter类。这堂课是我遇到问题的地方。

目前，用户可以通过setOnClickListener（）与此列表视图进行交互。当选择列表中的项目时，我让程序显示Toast并显示没问题。我现在要弄清楚的是如何获取它以便当用户点击listview项目（包括其名称和详细信息）时，它会立即将它们带到名为Menu_Activity.java的主菜单活动

消息Gradle Build

Error:(71, 44) error: no suitable constructor found for Intent(<anonymous OnClickListener>,Class<Menu_Activity>)
constructor Intent.Intent(String,Uri) is not applicable
(argument mismatch; <anonymous OnClickListener> cannot be converted to String)
constructor Intent.Intent(Context,Class<?>) is not applicable
(argument mismatch; <anonymous OnClickListener> cannot be converted to Context)
error:cannot find symbol method startActivity(Intent)

CustomAdapter.java

package uk.ac.napier.newsreader.Details_UI;

import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;

import uk.ac.napier.newsreader.Home_Screen_Activity;
import uk.ac.napier.newsreader.Menu_Activity;
import uk.ac.napier.newsreader.R;
import uk.ac.napier.newsreader.Details_UserInput.User;
import uk.ac.napier.newsreader.Routes_Activity;

/**
 * Created by MarkB on 14/03/2017.
 */

public class CustomAdapter extends BaseAdapter {
    Context c;
    ArrayList<User> users;

    public CustomAdapter (Context c, ArrayList<User> users) {
        this.c = c;
        this.users = users;
    }

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

    @Override
    public Object getItem(int position) {
        return users.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView==null)
        {
            convertView = LayoutInflater.from(c).inflate(R.layout.model,parent,false);
        }

        TextView nameTxt = (TextView) convertView.findViewById(R.id.nameTxt);
        TextView ageTxt = (TextView) convertView.findViewById(R.id.ageTxt);
        TextView weightTxt = (TextView) convertView.findViewById(R.id.weightTxt);

        final User u = (User) this.getItem(position);

        nameTxt.setText(u.getName());
        ageTxt.setText(u.getAge());
        weightTxt.setText(u.getWeight());

        //ONITEMCLICK
        convertView.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                //Toast.makeText(c,u.getName(), Toast.LENGTH_SHORT).show();

                Intent startMenuActivity = new Intent(this, Menu_Activity.class);
                startActivity(startMenuActivity);
            }
        });

        return convertView;
    }
}

使用＆＃34;（this，Menu_Activity.class）创建Intent时会出现问题;＆＃34;标记错误说

Cannot resolve constructor 'Intent(anonymous android.view.View.OnClickListener, java.lang.Class<uk.ac.napier.newsreader.Menu_Activity>)'

Answer 1

Intent startMenuActivity = new Intent(c, Menu_Activity.class);

此处c是您的上下文变量。

说明：

您应该将活动上下文作为第一个参数传递。

Answer 2

这是我在我的一个申请中使用的。

 LocationAdapter adapter = new LocationAdapter(getApplicationContext(), R.layout.row, result);
                //set the locationList (listview) to use adapter initialised above
                locationList.setAdapter(adapter);
                //Set up onClickListner
                locationList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                        //get the position of the row. So which row was clicked
                        LocationModel locationModel = result.get(position);
                        //initialise intent, this click event takes the user to locationDetails Activity
                        Intent intent = new Intent(ListActivity.this, LocationDetails.class);
                        //passing extra value. in this case passing of locationModel
                        intent.putExtra("locationModel", new Gson().toJson(locationModel));
                        //start activity
                        startActivity(intent);
                    }
                });

Answer 3

在适配器类中“this”不会返回类对象。使用列表对象

设置OnItemClickListener

 listview.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Intent startMenuActivity = new Intent(MyActivity.this, Menu_Activity.class);
            startActivity(startMenuActivity);
        }
    });

Answer 4

改变这个：

//ONITEMCLICK
        convertView.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                Intent startMenuActivity = new Intent(this, Menu_Activity.class);
                startActivity(startMenuActivity);
            }
        });

为此：

//ONITEMCLICK
        convertView.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                Intent startMenuActivity = new Intent(c, Menu_Activity.class);
                startActivity(startMenuActivity);
            }
        });

性差异：

Intent startMenuActivity = new Intent（ this ，Menu_Activity.class）;

Intent startMenuActivity = new Intent（ c ，Menu_Activity.class）;

<强>记住：

当您将此“说”为匿名类时，您将引用她（匿名对象类），而不是您的“主类”。

查看更多Anonymous Classes - Oracle Doc

单击ListViewItem时移动到新活动

4 个答案: