如何以编程方式更改 ActionBar 中的 MenuItem 图标 [英] How to change MenuItem icon in ActionBar programmatically

问题描述

如何以编程方式更改 ActionBar 中的 MenuItem 图标?我尝试使用

How to change MenuItem icon in ActionBar programmatically? I tried to use

MenuItem menuItem = (MenuItem)findViewById(R.id.action_settings);
menuItem.setIcon(getResources().getDrawable(R.drawable.ic_launcher))

但它不起作用.这是我的代码:

but it doesn't work. This is my code:

主活动

package com.test;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;

public class MainActivity extends ActionBarActivity {
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button)findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MenuItem menuItem = (MenuItem)findViewById(R.id.action_settings);
                menuItem.setIcon(getResources().getDrawable(R.drawable.ic_launcher));
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

main.xml

<menu
    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"
    tools:context=".MainActivity" >

    <item
        android:icon="@drawable/action_settings"
        android:id="@+id/action_settings"
        android:title="@string/action_settings"
        android:orderInCategory="100"
        app:showAsAction="always"/>
</menu>

activity_main

activity_main

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="fill_parent"
    android:layout_width="fill_parent">
    <Button
        android:id="@+id/button"
        android:text="Set icon"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

这是我运行后的异常:

MenuItem menuItem = (MenuItem)findViewById(R.id.action_settings);


11-09 19:52:40.471    1735-1735/com.test E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.ClassCastException: android.support.v7.internal.view.menu.ActionMenuItemView
            at com.test.MainActivity$1.onClick(MainActivity.java:19)
            at android.view.View.performClick(View.java:2485)
            at android.view.View$PerformClick.run(View.java:9080)
            at android.os.Handler.handleCallback(Handler.java:587)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:123)
            at android.app.ActivityThread.main(ActivityThread.java:3683)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:507)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
            at dalvik.system.NativeStart.main(Native Method)

推荐答案

您不能在 onCreate() 中的菜单项上使用 findViewById() 因为菜单布局还没有充气.您可以创建一个全局菜单变量并在 onCreateOptionsMenu() 中对其进行初始化，然后在您的 onClick() 中使用它.

You can't use findViewById() on menu items in onCreate() because the menu layout isn't inflated yet. You could create a global Menu variable and initialize it in the onCreateOptionsMenu() and then use it in your onClick().

private Menu menu;

在你的 onCreateOptionsMenu()

this.menu = menu;

在按钮的onClick() 方法中

menu.getItem(0).setIcon(ContextCompat.getDrawable(this, R.drawable.ic_launcher));

这篇关于如何以编程方式更改 ActionBar 中的 MenuItem 图标的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！