Question

我正在尝试向我的应用添加一些菜单。这是我的代码：

java代码：

package com.example.excercise;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import java.util.Date;
import java.util.Random;

public class MainActivity extends AppCompatActivity {

    TextView my_text;
    Button button;


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

        my_text=findViewById(R.id.textView);

        my_text.setText(new Date().toString());

        button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Random random=new Random();
                my_text.setTextColor(Color.rgb(random.nextInt(256),random.nextInt(256),random.nextInt(256)));

            }
        });

        button.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View view) {

                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                startActivity(intent);
                return true;
            }
        });


    }

    @Override
    protected void onResume() {
        super.onResume();

        Toast.makeText(this, "MainActivity: OnResume()", Toast.LENGTH_SHORT).show();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.main_menu,menu);
        return super.onCreateOptionsMenu(menu);


    }
}

main_menu xml：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android">

<item android:title="Item1"/>
<item android:title="Item2"/>
<item android:title="Item3"/>
<item
    android:id="@+id/app_bar_search"
    android:icon="@drawable/ic_search_black_24dp"
    android:title="Search"

    app:actionViewClass="android.widget.SearchView"/>
<item android:title="Item4">
    <menu>
        <item android:title="SubItem1"
            android:onClick="itemClick"/>
        <item android:title="SubItem2"/>
    </menu>
</item>

我在logcat中以红色显示此消息：

2019-07-14 02：49：18.148 6160-6160 / com.example.excercise E / AndroidRuntime：致命异常：main 流程：com.example.execercise，PID：6160 android.view.InflateException：无法解析com.example.excercise.MainActivity类中的菜单项onClick处理程序itemClick 在androidx.appcompat.view.SupportMenuInflater $ InflatedOnMenuItemClickListener。（SupportMenuInflater.java:254）在androidx.appcompat.view.SupportMenuInflater $ MenuState.setItem（SupportMenuInflater.java:482）在androidx.appcompat.view.SupportMenuInflater $ MenuState.addItem（SupportMenuInflater.java:530）在androidx.appcompat.view.SupportMenuInflater.parseMenu（SupportMenuInflater.java:206）在androidx.appcompat.view.SupportMenuInflater.parseMenu（SupportMenuInflater.java:184）在androidx.appcompat.view.SupportMenuInflater.inflate（SupportMenuInflater.java:128）在com.example.excercise.MainActivity.onCreateOptionsMenu（MainActivity.java:69）在android.app.Activity.onCreatePanelMenu（Activity.java:4055）在androidx.fragment.app.FragmentActivity.onCreatePanelMenu（FragmentActivity.java:378）在androidx.appcompat.view.WindowCallbackWrapper.onCreatePanelMenu（WindowCallbackWrapper.java:94）在androidx.appcompat.app.AppCompatDelegateImpl $ AppCompatWindowCallback.onCreatePanelMenu（AppCompatDelegateImpl.java:2549）在androidx.appcompat.app.AppCompatDelegateImpl.preparePanel（AppCompatDelegateImpl.java:1589）在androidx.appcompat.app.AppCompatDelegateImpl.doInvalidatePanelMenu（AppCompatDelegateImpl.java:1869）在androidx.appcompat.app.AppCompatDelegateImpl $ 2.run（AppCompatDelegateImpl.java:230）在android.os.Handler.handleCallback（Handler.java:883）在android.os.Handler.dispatchMessage（Handler.java:100）在android.os.Looper.loop（Looper.java:214）在android.app.ActivityThread.main（ActivityThread.java:7319）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:492）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:934）引起原因：java.lang.NoSuchMethodException：com.example.excercise.MainActivity.itemClick [接口 android.view.MenuItem] 在java.lang.Class.getMethod（Class.java:2072）在java.lang.Class.getMethod（Class.java:1693）在androidx.appcompat.view.SupportMenuInflater $ InflatedOnMenuItemClickListener。（SupportMenuInflater.java:250）在androidx.appcompat.view.SupportMenuInflater $ MenuState.setItem（SupportMenuInflater.java:482）
        at androidx.appcompat.view.SupportMenuInflater$MenuState.addItem(SupportMenuInflater.java:530)

        at androidx.appcompat.view.SupportMenuInflater.parseMenu(SupportMenuInflater.java:206)

        at androidx.appcompat.view.SupportMenuInflater.parseMenu(SupportMenuInflater.java:184)

        at androidx.appcompat.view.SupportMenuInflater.inflate(SupportMenuInflater.java:128)

        at com.example.excercise.MainActivity.onCreateOptionsMenu(MainActivity.java:69)

        at android.app.Activity.onCreatePanelMenu(Activity.java:4055) 
        at androidx.fragment.app.FragmentActivity.onCreatePanelMenu(FragmentActivity.java:378)

        at androidx.appcompat.view.WindowCallbackWrapper.onCreatePanelMenu(WindowCallbackWrapper.java:94)

        at androidx.appcompat.app.AppCompatDelegateImpl$AppCompatWindowCallback.onCreatePanelMenu(AppCompatDelegateImpl.java:2549)

        at androidx.appcompat.app.AppCompatDelegateImpl.preparePanel(AppCompatDelegateImpl.java:1589)

        at androidx.appcompat.app.AppCompatDelegateImpl.doInvalidatePanelMenu(AppCompatDelegateImpl.java:1869)

        at androidx.appcompat.app.AppCompatDelegateImpl$2.run(AppCompatDelegateImpl.java:230)

        at android.os.Handler.handleCallback(Handler.java:883) 
        at android.os.Handler.dispatchMessage(Handler.java:100) 
        at android.os.Looper.loop(Looper.java:214) 
        at android.app.ActivityThread.main(ActivityThread.java:7319) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)

        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:934)

问题出在哪里，我该如何解决？我应该在红色消息引用的所有Java类中添加我，出现“无法解析R符号”错误。

Answer 1

在您的main_menu.xml中向 item 元素

添加一个ID

<?xml version="1.0" encoding="utf-8"?>
<item android id="@+id/item1" 
   android:title="Item1"/>
<item android id="@+id/item2" 
   android:title="Item2"/>
<item android id="@+id/item3" 
   android:title="Item3"/>

在您的MainActivity.java中，添加 onOptionsItemSelected 方法

@Override
public boolean onCreateOptionsMenu(Menu menu) {
  getMenuInflater().inflate(R.menu.main_menu,menu);
  return super.onCreateOptionsMenu(menu);
}

public boolean onOptionsItemSelected(MenuItem item) {
//respond to menu item selection
switch (item.getItemId()) {
  case R.id.item1:
    Toast.makeText(this, "You clicked on item 1", Toast.LENGTH_SHORT).show();
    return true;
  case R.id.item2:
    Toast.makeText(this, "You clicked on item 1", Toast.LENGTH_SHORT).show();
    return true;
  default:
    return super.onOptionsItemSelected(item);
  }
}

最后解决无法解决R符号错误 ...您尚未将R类导入到Java文件中。执行此操作有两个步骤

第一步

单击R符号，您应该看到一个红色灯泡...单击那个红色灯泡...您将看到一个显示导入类的弹出窗口...单击导入

或第二步

单击R符号...然后按 Alt + Enter

我希望这对您有帮助...

在向应用程序添加菜单时遇到问题

1 个答案: