android - 为什么项目上下文菜单没有显示在 ListView 中

Question

我正在为 ListView 中的每个项目开发一个带有上下文菜单的 ListView ；但是，当单击某个项目时，上下文菜单不会显示。我在菜单目录下创建了一个 list_menu.xml 文件，并且我正在使用自定义适配器。自定义适配器 xml 文件由图像和 TextView 组成。最终，我想在单击图像时显示菜单，但现在，我想在单击列表项时显示菜单。但是没有任何反应。如何显示上下文菜单？谢谢 主xml

package org.pctechtips.menulistview;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    ArrayList hosts;
    String ipAdd = "192.168.10.";

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

        hosts = new ArrayList<String>();
        for(int i = 0; i < 255; i++) {
            hosts.add(ipAdd+i);
        }

        ListView list = (ListView) findViewById(R.id.list);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.list_item, R.id.ip_address, hosts);
        list.setAdapter(adapter);
        registerForContextMenu(list);

    }

    /*
    * Infating the menu for toolbar
    */
    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate(R.menu.list_menu, menu);
    }
}

适配器

package org.pctechtips.menulistview;

import android.content.Context;
import android.support.annotation.NonNull;
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 java.util.ArrayList;

import static org.pctechtips.menulistview.R.drawable.computer_48_dp;

/**
 * Created by George on 8/8/2017.
 */

public class ListAdapter extends ArrayAdapter<String>{
    public ListAdapter(Context context, int num, ArrayList<String> hosts) {
        super(context, 0, hosts);
    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // Get the data item for this position
        String item = getItem(position);

        // Check if an existing view is being reused, otherwise inflate the view
        if (convertView == null) {
            convertView = LayoutInflater.from(getContext()).inflate(R.layout.list_item, parent, false);
        }

        ImageView iconImgView = (ImageView) convertView.findViewById(R.id.host_icon);
        TextView ipAddTxtView = (TextView) convertView.findViewById(R.id.ip_address);


        iconImgView.setImageResource(R.drawable.computer_48_dp);
        ipAddTxtView.setText(item);

        return convertView;
    }
}

list_item xml 文件(适配器)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <LinearLayout
        android:id="@+id/text_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <ImageView
            android:id="@+id/host_icon"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="0.20"
            android:padding="7dp"
            android:src="@drawable/computer_48_dp"/>

        <TextView
            android:id="@+id/ip_address"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.80"
            android:textSize="18dp"
            tools:text="192.168.10.100"
            />

    </LinearLayout>
</LinearLayout>

list_menu.xml 文件

 <!-- listview menu for host scan options eg:
         change hostname, icon, notification etc -->
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">

<!-- Settings, should always be in the overflow -->
<item android:id="@+id/change_icon"
    android:title="change icon"
    />

<item android:id="@+id/set_hostname"
    android:title="set hostname"
    />

<itme android:id="@+id/notifications"
    android:title="notifications"
     />

</menu>

Answer 1

上下文菜单在长按列表项而不是短按时起作用。如果您希望它在短按时起作用，请执行如下所示的 onListItemClick 方法

public void onListItemClick(ListView l, View v, int position, long id){
  list.showContextMenuForChild(v);   
}

如果你想在其他元素上打开相同的按钮，你可以这样做 -

public void onButtonClickEvent(View sender)
{
    registerForContextMenu(sender); 
    openContextMenu(sender);
    unregisterForContextMenu(sender);
}

否则你也可以使用PopupMenu

在 ListView 项中添加布局为-

<ImageButton
   android:layout_width="wrap_content" 
   android:layout_height="wrap_content" 
   android:src="@drawable/ic_overflow_holo_dark"
   android:contentDescription="@string/descr_overflow_button"
   android:onClick="showPopup" />

然后按如下所示实现您的 showPopup 方法 -

public void showPopup(View v) {
     PopupMenu popup = new PopupMenu(this, v);
     MenuInflater inflater = popup.getMenuInflater();
     inflater.inflate(R.menu.actions, popup.getMenu());
     popup.show();
 }