【例2-6】上下文菜单应用示例

上下文菜单类似于电脑右键菜单，长按2秒视图对象，就会弹出一个浮动菜单。

教学视频

布局文件activity_contextmenu.xml的源代码

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

<androidx.constraintlayout.widget.ConstraintLayout 

    xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".ContextMenuActivity">

    <TextView

        android:id="@+id/txt"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="上下文菜单示例"

        android:textSize="24sp"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.432"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toTopOf="parent"

        app:layout_constraintVertical_bias="0.204" />

    <ImageView

        android:id="@+id/imageView2"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.439"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toTopOf="parent"

        app:layout_constraintVertical_bias="0.549"

        app:srcCompat="@drawable/flower" />

</androidx.constraintlayout.widget.ConstraintLayout>

控制文件ContextMenuActivity.java源代码

package com.example.chap02;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import android.view.ContextMenu;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.widget.ImageView;

import android.widget.TextView;

import android.view.ContextMenu;

import android.view.ContextMenu.ContextMenuInfo;

public class ContextMenuActivity extends AppCompatActivity {

    TextView txt;

    ImageView img;

    private static final int item1 = Menu.FIRST;

    private static final int item2 = Menu.FIRST+1;

    private static final int item3 = Menu.FIRST+2;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_contextmenu);

        txt = (TextView)findViewById(R.id.txt);

        img = (ImageView)findViewById(R.id.imageView2);

        registerForContextMenu(img);

        registerForContextMenu(txt);

    }

    @Override

    public void onCreateContextMenu(ContextMenu menu, View view, ContextMenuInfo menuinfo){

        menu.add(0,item1,0,"复制");

        menu.add(0,item2,0,"收藏");

        menu.add(0,item3,0,"提醒");

    }

    @Override

    public boolean onContextItemSelected(MenuItem item){

        switch (item.getItemId()){

            case item1:

                break;

            case item2:

                break;

            case item3:

                break;

        }

        return true;

    }

}

打开项目配置文件AndroidManifest.xml，配置要启动的Activity类名

        <activity android:name=".ContextMenuActivity  ">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>