Question

我关注如何使用标签制作滑动视图this tutorial。我使用的是Android Studio 1.2.2。

我的所有类都与示例代码中的类相同。当我运行应用程序时，我得到NullPointerException并且应用程序崩溃了。在调试模式下，我发现getActionBar()返回null。

经过一番研究，我发现了两个问题的解决方案：

在getWindow().requestFeature(Window.FEATURE_ACTION_BAR);

setContentView

Use one Theme.AppCompat个主题

由于我已经使用了来自Theme.AppCompat的主题，我尝试了第一个解决方案，但它也没有用。然后我开始围绕不同的主题，我发现应用程序正在使用ThemeOverlay中的主题，但如果我正确理解this answer，我不应该使用ThemeOverlay作为一般应用程序主题。

无论我是否应将ThemeOvarlay用于一般主题，我都希望将其与Theme.AppCompat.Light一起使用。

经过一些调试后，我发现在Activity.java中的方法initWindowDecorActionBar中，由于某种原因，执行window.getDecorView();之后的第一行是方法中的最后一行。我不知道如何解释这种行为，我所知道的是window.getDecorView();的下一步将我带到方法的最后一行，mActionBar = new WindowDecorActionBar(this);上的断点不会破坏执行。

private void initWindowDecorActionBar() {
        Window window = getWindow();

        // Initializing the window decor can change window feature flags.
        // Make sure that we have the correct set before performing the test below.
        window.getDecorView();

        if (isChild() || !window.hasFeature(Window.FEATURE_ACTION_BAR) || mActionBar != null) {
            return;
        }

        mActionBar = new WindowDecorActionBar(this);
        mActionBar.setDefaultDisplayHomeAsUpEnabled(mEnableDefaultActionBarUp);

        mWindow.setDefaultIcon(mActivityInfo.getIconResource());
        mWindow.setDefaultLogo(mActivityInfo.getLogoResource());
    }

有没有人遇到过这样的事情？如何使其与Theme.AppCompat.Light一起使用？

这是我的档案。

的build.gradle

apply plugin: 'com.android.application'
apply plugin: 'com.neenbedankt.android-apt'

android {
    compileSdkVersion 22
    buildToolsVersion "22.0.1"

    defaultConfig {
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        testHandleProfiling true
        testFunctionalTest true
        applicationId "com.test.swipe"
        minSdkVersion 14
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    packagingOptions {
        exclude 'META-INF/ASL2.0'
        exclude 'META-INF/LICENSE'
        exclude 'META-INF/license.txt'
        exclude 'META-INF/NOTICE'
        exclude 'META-INF/notice.txt'
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.2.0'
    ... some other dependencies ...
}

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mammsoft.phanesmobile" >

    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/Theme.AppCompat.Light.DarkActionBar" >
        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

MainActivity.java

package com.test.swipe;

import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class MainActivity extends FragmentActivity implements ActionBar.TabListener {

    AppSectionsPagerAdapter mAppSectionsPagerAdapter;
    ViewPager mViewPager;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());

        final ActionBar actionBar = getActionBar();
        actionBar.setHomeButtonEnabled(false);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mAppSectionsPagerAdapter);
        mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                actionBar.setSelectedNavigationItem(position);
            }
        });

        for (int i = 0; i < mAppSectionsPagerAdapter.getCount(); i++) {
            actionBar.addTab(
                    actionBar.newTab()
                            .setText(mAppSectionsPagerAdapter.getPageTitle(i))
                            .setTabListener(this));
        }
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
        // When the given tab is selected, switch to the corresponding page in the ViewPager.
        mViewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    }

    public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int i) {
            switch (i) {
                case 0:


                    return new LaunchpadSectionFragment();

                default:
                    Fragment fragment = new DummySectionFragment();
                    Bundle args = new Bundle();
                    args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
                    fragment.setArguments(args);
                    return fragment;
            }
        }

        @Override
        public int getCount() {
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return "Section " + (position + 1);
        }
    }

    public static class LaunchpadSectionFragment extends Fragment {

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_section_launchpad, container, false);

            rootView.findViewById(R.id.demo_collection_button)
                    .setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            Intent intent = new Intent(getActivity(), CollectionDemoActivity.class);
                            startActivity(intent);
                        }
                    });

            rootView.findViewById(R.id.demo_external_activity)
                    .setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            Intent externalActivityIntent = new Intent(Intent.ACTION_PICK);
                            externalActivityIntent.setType("image/*");
                            externalActivityIntent.addFlags(
                                    Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
                            startActivity(externalActivityIntent);
                        }
                    });

            return rootView;
        }
    }

    public static class DummySectionFragment extends Fragment {

        public static final String ARG_SECTION_NUMBER = "section_number";

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
            Bundle args = getArguments();
            ((TextView) rootView.findViewById(android.R.id.text1)).setText(
                    getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
            return rootView;
        }
    }
}

Answer 1

更改您的MainActivity以扩展AppCompatActivity，然后使用以下代码获取操作栏：

 final ActionBar actionBar = getSupportActionBar();

重构你的进口，你应该是金色的。

ActionBar仅适用于ThemeOverlay

1 个答案: