Question

我有一个工具栏。现在，我想在我的应用中使用导航标签。为此，我写了以下代码：

super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        toolbar = (Toolbar) findViewById(R.id.app_bar);
        toolbar.setLogo(R.mipmap.ic_launcher);
//        toolbar.setTitle(" Daily Qura'n Verses");
        setSupportActionBar(toolbar);

        ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        actionBar.setDisplayShowTitleEnabled(false);

        ActionBar.Tab tab = actionBar.newTab()
                .setText("Artistic Fragment")
                .setTabListener(new TabListener<ArtistFragment>(
                        this, "artist", ArtistFragment.class));
        actionBar.addTab(tab);

        tab = actionBar.newTab()
                .setText("Album Fragment")
                .setTabListener(new TabListener<AlbumFragment>(
                        this, "album", AlbumFragment.class));
        actionBar.addTab(tab);

我在styles.xml中没有设置任何操作栏：

 <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorAccent">@color/accentColor</item>
        <item name="colorPrimary">@color/primaryColor</item>
        <item name="colorPrimaryDark">@color/primaryColorDark</item>
    </style>

我有两个片段：

albumFragment
artistFragment

我有一个java类，TabListener：

package com.example.shiza.dailyquranverses;
import android.app.Activity;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBar;

public class TabListener<T extends Fragment> implements ActionBar.TabListener {
    private Fragment mFragment;
    private final Activity mActivity;
    private final String mTag;
    private final Class<T> mClass;

    /** Constructor used each time a new tab is created.
     * @param activity  The host Activity, used to instantiate the fragment
     * @param tag  The identifier tag for the fragment
     * @param clz  The fragment's Class, used to instantiate the fragment
     */
    public TabListener(Activity activity, String tag, Class<T> clz) {
        mActivity = activity;
        mTag = tag;
        mClass = clz;
    }

    /* The following are each of the ActionBar.TabListener callbacks */

    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
        // Check if the fragment is already initialized
        if (mFragment == null) {
            // If not, instantiate and add it to the activity
            mFragment = Fragment.instantiate(mActivity, mClass.getName());
            ft.add(android.R.id.content, mFragment, mTag);
        } else {
            // If it exists, simply attach it in order to show it
            ft.attach(mFragment);
        }
    }

    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
        if (mFragment != null) {
            // Detach the fragment, because another one is being attached
            ft.detach(mFragment);
        }
    }

    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
        // User selected the already selected tab. Usually do nothing.
    }
}

我认为罪魁祸首是以下几行：

actionBar.setNavigationMode（ActionBar.NAVIGATION_MODE_TABS）;

因为它给了我警告。

在运行应用程序时，它给了我错误。请帮我解决这个问题。

getSupportActionBar（）返回带有自定义工具栏的null

0 个答案: