getActionBar() return null 和 requestFeature() 出现在 ActionBarActivity class

Question

当我想在我的操作栏上添加一个应用程序图标时遇到了一些问题。

所以我有 ActionBarActivity class 在 onCreate()

中有以下代码

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
    setContentView(R.layout.activity_check_stock);

    if(this.getActionBar() != null){
        Log.d("ACTIONBAR_NOT_NULL", "ActionBar Not NULL");
        //getActionBar().setHomeButtonEnabled(true);
        //getActionBar().setDisplayHomeAsUpEnabled(true);
        //getActionBar().setDisplayUseLogoEnabled(true);
        //getActionBar().setDisplayOptions(getActionBar().DISPLAY_SHOW_HOME | getActionBar().DISPLAY_SHOW_TITLE);
        //getActionBar().setIcon(R.drawable.vanwellis_logo);
    }
    else{
        Log.d("ACTIONBAR_NULL","ActionBar NULL");
    }

    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mSectionsPagerAdapter);

}

由于我的 getActionBar() return 为空，所以我添加 getWindow().requestFeature(Window.FEATURE_ACTION_BAR); 但是这种方法仍然 return 一个错误，但是有了这个新的错误：

android.util.AndroidRuntimeException: requestFeature() must be called before adding content

所以我试着把 requestFeature() 放在 super.onCreate(savedInstanceState);

之前

结果是...getActionBar() return 再次为 null，但没有发生任何错误。

这是我的 style.xml 我不知道这是否适用于我的所有活动，但是给你...

<resources>

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
    <item name="android:actionBarStyle">@style/MyActionBar</item>
    <item name="drawerArrowStyle">@style/MyDrawerArrowToggle</item>

    <!-- Support library compatibility -->
    <item name="actionBarStyle">@style/MyActionBar</item>
</style>

<style name="MyActionBar" parent="Widget.AppCompat.Light.ActionBar.Solid.Inverse">
    <item name="android:titleTextStyle">@style/MyTitleTextStyle</item>
    <item name="android:background">@color/action_bar_background</item>

    <!-- Support library compatibility -->
    <item name="titleTextStyle">@style/MyTitleTextStyle</item>
    <item name="background">@color/action_bar_background</item>
</style>

<style name="MyDrawerArrowToggle" parent="Base.Widget.AppCompat.DrawerArrowToggle">
    <item name="color">@color/foreground</item>
</style>

<style name="MyTitleTextStyle" parent="@style/TextAppearance.AppCompat.Widget.ActionBar.Title">
    <item name="android:textColor">@color/foreground</item>
</style>

[更新] 所以这是我的全部Activityclass

package com.vanwellis.vinnomobile;

import java.util.Locale;

import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;

import com.vanwellis.vinnomobile.fragment.CheckStockFragment;


public class CheckStockActivity extends ActionBarActivity {

    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
     * may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */
    SectionsPagerAdapter mSectionsPagerAdapter;

    /**
     * The {@link ViewPager} that will host the section contents.
     */
    ViewPager mViewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_check_stock);

        if(this.getActionBar() != null){
            Log.d("ACTIONBAR_NOT_NULL", "ActionBar Not NULL");
            //getActionBar().setHomeButtonEnabled(true);
            //getActionBar().setDisplayHomeAsUpEnabled(true);
            //getActionBar().setDisplayUseLogoEnabled(true);
            //getActionBar().setDisplayOptions(getActionBar().DISPLAY_SHOW_HOME | getActionBar().DISPLAY_SHOW_TITLE);
            //getActionBar().setIcon(R.drawable.vanwellis_logo);
        }
        else{
            Log.d("ACTIONBAR_NULL","ActionBar NULL");
        }

        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_check_stock, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }


    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a CheckStockFragment (defined as a static inner class below).
            return CheckStockFragment.newInstance(position + 1);
        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            switch (position) {
                case 0:
                    return getString(R.string.title_section1).toUpperCase(l);
                case 1:
                    return getString(R.string.title_section2).toUpperCase(l);
                case 2:
                    return getString(R.string.title_section3).toUpperCase(l);
            }
            return null;
        }
    }

}

我担心 Widget.AppCompat.Light.ActionBar.Solid.Inverse 会生成无操作栏。

我在 gradle 应用程序属性中使用具有这些配置的 android studio :

android {
        compileSdkVersion 21
        buildToolsVersion "21.1.2"

        defaultConfig {
            applicationId "com.vanwellis.vinnomobile"
            minSdkVersion 15
            targetSdkVersion 21
            versionCode 1
            versionName "1.0"
        }
        buildTypes {
            release {
                minifyEnabled false
                proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            }
        }
    }

那么这里到底发生了什么？

Answer 1

如果您使用 Theme.AppCompat 主题，那么您必须使用 ActionBarActivity 扩展您的 activity 其他虎钳获取 null 操作栏

指数：

public class MyActivity extends ActionBarActivity {

}

谢谢

Answer 2

因为你的ActionBarActivity是从支持库中导入的...

import android.support.v7.app.ActionBarActivity;

...您需要使用 getSupportActionBar() 而不是 getActionBar()。