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))

但是它不起作用. 这是我的代码:

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

MainActivity

MainActivity

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>

这是我跑步后遇到的异常:

This is the exception that i've had after running:

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()，因为菜单布局尚未膨胀.您可以创建一个全局Menu变量，然后在onCreateOptionsMenu()中对其进行初始化，然后在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;

在您的onCreateOptionsMenu()

In your onCreateOptionsMenu()

this.menu = menu;

在按钮的onClick()方法中

In your button's onClick() method

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！