Question

我正在关注android导航抽屉指南，一切顺利，直到我尝试创建导航抽屉基础活动，因此我可以扩展该活动并在所有活动中使用菜单。不幸的是我的应用程序一直在崩溃。

任何人都可以告诉我问题是什么，或者有人可以指出我正确的方向吗？

这是我的基本活动：

public class BaseActivity extends Activity {
    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private ActionBarDrawerToggle mDrawerToggle;

    private CharSequence mDrawerTitle;
    private CharSequence mTitle;
    private String[] mPlanetTitles;

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

        mTitle = mDrawerTitle = getTitle();
        mPlanetTitles = getResources().getStringArray(R.array.planets_array);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer);
        mDrawerList = (ListView) findViewById(R.id.left_drawer1);

        mDrawerList.setAdapter(new ArrayAdapter<String>(this,
                R.layout.drawer_list_item, mPlanetTitles));
        mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

        // enable ActionBar app icon to behave as action to toggle nav drawer
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        mDrawerToggle = new ActionBarDrawerToggle(
                this,                  /* host Activity */
                mDrawerLayout,         /* DrawerLayout object */
                R.drawable.ic_drawer,  /* nav drawer image to replace 'Up' caret */
                R.string.drawer_open,  /* "open drawer" description for accessibility */
                R.string.drawer_close  /* "close drawer" description for accessibility */
                ) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }

            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle(mDrawerTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }
        };
        mDrawerLayout.setDrawerListener(mDrawerToggle);

        if (savedInstanceState == null) {
            selectItem(0);
        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.main, menu);
        return super.onCreateOptionsMenu(menu);
    }

    /* Called whenever we call invalidateOptionsMenu() */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        // If the nav drawer is open, hide action items related to the content view
        boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
        menu.findItem(R.id.action_websearch).setVisible(!drawerOpen);
        return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
         // The action bar home/up action should open or close the drawer.
         // ActionBarDrawerToggle will take care of this.
        if (mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        // Handle action buttons
        switch(item.getItemId()) {
        case R.id.action_websearch:
            // create intent to perform web search for this planet
            Intent intent = new Intent(Intent.ACTION_WEB_SEARCH);
            intent.putExtra(SearchManager.QUERY, getActionBar().getTitle());
            // catch event that there's no activity to handle intent
            if (intent.resolveActivity(getPackageManager()) != null) {
                startActivity(intent);
            } else {
                Toast.makeText(this, R.string.app_not_available, Toast.LENGTH_LONG).show();
            }
            return true;
        default:
            return super.onOptionsItemSelected(item);
        }
    }

    /* The click listner for ListView in the navigation drawer */
    private class DrawerItemClickListener implements ListView.OnItemClickListener {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            selectItem(position);
        }
    }

    private void selectItem(int position) {
        // update the main content by replacing fragments
        Fragment fragment = new PlanetFragment();
        Bundle args = new Bundle();
        args.putInt(PlanetFragment.ARG_PLANET_NUMBER, position);
        fragment.setArguments(args);

        FragmentManager fragmentManager = getFragmentManager();
        fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();

        // update selected item and title, then close the drawer
        mDrawerList.setItemChecked(position, true);
        setTitle(mPlanetTitles[position]);
        mDrawerLayout.closeDrawer(mDrawerList);
    }

    @Override
    public void setTitle(CharSequence title) {
        mTitle = title;
        getActionBar().setTitle(mTitle);
    }

    /**
     * When using the ActionBarDrawerToggle, you must call it during
     * onPostCreate() and onConfigurationChanged()...
     */

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        // Sync the toggle state after onRestoreInstanceState has occurred.
        mDrawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        // Pass any configuration change to the drawer toggls
        mDrawerToggle.onConfigurationChanged(newConfig);
    }

    /**
     * Fragment that appears in the "content_frame", shows a planet
     */
    public static class PlanetFragment extends Fragment {
        public static final String ARG_PLANET_NUMBER = "planet_number";

        public PlanetFragment() {
            // Empty constructor required for fragment subclasses
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_planet, container, false);
            int i = getArguments().getInt(ARG_PLANET_NUMBER);
            String planet = getResources().getStringArray(R.array.planets_array)[i];

            int imageId = getResources().getIdentifier(planet.toLowerCase(Locale.getDefault()),
                            "drawable", getActivity().getPackageName());
            ((ImageView) rootView.findViewById(R.id.image)).setImageResource(imageId);
            getActivity().setTitle(planet);
            return rootView;
        }
    }
}

这是应扩展BaseActivity的About.java：

public class About extends BaseActivity {


/** Called when the activity is first created. */
TextView a_text1,a_text2,a_text3;
ImageView a_img1, a_img2,a_img3;
String about1 = "Svojim kapacitetima i sa zaposlenima Sajam je osposobljen da zainteresovanim poslovnim partnerima pruĹľi najraznovrsnije usluge.\nBeogradski sajam ima zatvoreni i otvoreni izloĹľbeni prostor. ÄŚetrnaest hala Beogradskog sajma poseduje 100.000 kvadratnih metara izloĹľbenog prostora. Centralna hala (Hala 1) je monumentalna graÄ‘evina sa kupolom, ukupne povrĹˇine 21.280m2. Svojom veliÄŤinomizdvajaju se joĹˇ Hala 2 (9.239m2), Hala 3 (4.438m2) i Hala 14 (11.665m2) izloĹľbene povrĹˇine.\nUkupna povrĹˇina otvorenog izloĹľbenog prostora je 35.363m2";
String about2 = "Beogradski sajam raspolaĹľe i poslovnim prostorom, magacinima i radionicama. Na Sajmu funkcioniĹˇu prateÄ‡i sadrĹľaji: poĹˇta, banka, turistiÄŤke agencije, Ĺˇpediterske sluĹľbe, carinska sluĹľba i ambulanta. TakoÄ‘e, u okviru Sajma rade i ugostiteljski objekti razliÄŤite namene.\n\nNa Beogradskom sajmu se odrĹľi godiĹˇnje viĹˇe od 30 redovnih meÄ‘unarodnih sajamskih manifestacija. Sajmovi se odlikuju visokim nivoom organizacije te su mnoge priredbe uÄŤlanjene u ugledne meÄ‘unarodne organizacije: MeÄ‘unarodni sajam tehnike i tehniÄŤkih dostignuÄ‡a, MeÄ‘unarodni sajam odevanja - Moda u svetu, MeÄ‘unarodni sajam nameĹˇtaja, opreme i unutraĹˇnje dekoracije i MeÄ‘unarodni sajam graÄ‘evinarstva ÄŤlanovi su MeÄ‘unarodne unije sajmova (UFI, Pariz).\n\nMeÄ‘unarodni salon automobila je jedan od zvaniÄŤnih registrovanih centara za izlaganje proizvoda automobilske industrije od strane Stalnog biroa proizvoÄ‘aÄŤa motornih vozila (OICA, Pariz).";
String about3 = "Pored redovnih manifestacija pod kupolama Beogradskog sajma odrĹľavaju se brojne izloĹľbe, koncerti, nauÄŤni i specijalizovani skupovi. Ukupna ponuda Beogradskog sajma dopunjuje se bazarom robe Ĺˇiroke potroĹˇnje. Na Beogradskom sajmu godiĹˇnje izlaĹľe oko 5000 kompanija, a obiÄ‘e ga preko 1.500.000 posetilaca. \n\nBeogradski sajam je od 2001. godine ÄŤlan i Centralnoevropske asocijacije sajmova (CEFA). \n\nOd septembra 2003. godine Medjunarodni sajam turizma ÄŤlan je Evropske asocijacije turistiÄŤkih poslovnih sajmova (ITTFA).\nOd 2004.godine Beogradski sajam je ÄŤlan Asocijacije sajmova JugoistoÄŤne Evrope (EASE).\nOd 1991. godine, Svetski trgovaÄŤki centar Beograd ÄŤlan je Asocijacije svetskih trgovaÄŤkih centara (WTCA) sa sediĹˇtem u Njujorku. Povezuje najznaÄŤajnije taÄŤke meÄ‘unarodne trgovine u najsavremeniji komunikacijski sistem i omoguÄ‡ava kontakte sa poslovnim ljudima i firmama iz viĹˇe od 330 gradova ÄŤlanica Asocijacije iz preko sto zemalja.\n\nBeogradski sajam je osnivaÄŤ Svetskog trgovaÄŤkog centra Beograd (1991.)";


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

    setContentView(R.layout.nav_drawer);
    FrameLayout placeHolder = (FrameLayout) findViewById(R.id.frame);
    getLayoutInflater().inflate(R.layout.about, placeHolder);

    a_text1=(TextView)findViewById(R.id.a_text1);
    a_text1.setText(about1);

    a_text2=(TextView)findViewById(R.id.a_text2);
    a_text2.setText(about2);

    a_text3=(TextView)findViewById(R.id.a_text3);
    a_text3.setText(about3);

}

}

这是我的nav_drawer.xml

<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- The main content view -->
<FrameLayout
    android:id="@+id/frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
<!-- The navigation drawer -->
<ListView android:id="@+id/left_drawer1"
    android:layout_width="240dp"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:choiceMode="singleChoice"
    android:divider="@android:color/transparent"
    android:dividerHeight="0dp"
    android:background="#111"/>

logcat的

05-07 21:34:58.106: I/ActivityManager(290): START u0 {cmp=com.example.android.navigationdrawerexample/.About} from pid 800
05-07 21:34:58.126: W/WindowManager(290): Failure taking screenshot for (246x410) to layer 21010
05-07 21:34:58.268: D/AndroidRuntime(800): Shutting down VM
05-07 21:34:58.286: W/dalvikvm(800): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
05-07 21:34:58.456: E/AndroidRuntime(800): FATAL EXCEPTION: main
05-07 21:34:58.456: E/AndroidRuntime(800): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.navigationdrawerexample/com.example.android.navigationdrawerexample.About}: java.lang.NullPointerException
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.os.Looper.loop(Looper.java:137)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.app.ActivityThread.main(ActivityThread.java:5041)
05-07 21:34:58.456: E/AndroidRuntime(800):  at java.lang.reflect.Method.invokeNative(Native Method)
05-07 21:34:58.456: E/AndroidRuntime(800):  at java.lang.reflect.Method.invoke(Method.java:511)
05-07 21:34:58.456: E/AndroidRuntime(800):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-07 21:34:58.456: E/AndroidRuntime(800):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-07 21:34:58.456: E/AndroidRuntime(800):  at dalvik.system.NativeStart.main(Native Method)
05-07 21:34:58.456: E/AndroidRuntime(800): Caused by: java.lang.NullPointerException
05-07 21:34:58.456: E/AndroidRuntime(800):  at com.example.android.navigationdrawerexample.BaseActivity.onCreate(BaseActivity.java:48)
05-07 21:34:58.456: E/AndroidRuntime(800):  at com.example.android.navigationdrawerexample.About.onCreate(About.java:23)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.app.Activity.performCreate(Activity.java:5104)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-07 21:34:58.456: E/AndroidRuntime(800):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-07 21:34:58.456: E/AndroidRuntime(800):  ... 11 more
05-07 21:34:58.616: W/ActivityManager(290):   Force finishing activity com.example.android.navigationdrawerexample/.About
05-07 21:34:58.646: W/ActivityManager(290):   Force finishing activity com.example.android.navigationdrawerexample/.MainActivity
05-07 21:34:59.156: W/ActivityManager(290): Activity pause timeout for ActivityRecord{40efad28 u0 com.example.android.navigationdrawerexample/.About}
05-07 21:34:59.486: I/Choreographer(290): Skipped 78 frames!  The application may be doing too much work on its main thread.
05-07 21:34:59.536: E/SurfaceFlinger(36): ro.sf.lcd_density must be defined as a build property
05-07 21:34:59.546: I/Choreographer(412): Skipped 75 frames!  The application may be doing too much work on its main thread.
05-07 21:34:59.978: E/SurfaceFlinger(36): ro.sf.lcd_density must be defined as a build property
05-07 21:35:12.816: W/ActivityManager(290): Activity destroy timeout for ActivityRecord{40f16b00 u0 com.example.android.navigationdrawerexample/.MainActivity}
05-07 21:35:12.836: W/ActivityManager(290): Activity destroy timeout for ActivityRecord{40efad28 u0 com.example.android.navigationdrawerexample/.About}

如果有什么显而易见的事我明白了，请告诉我，因为我对应用开发社区很新。

任何帮助都会得到极大的赞赏。

谢谢！：）

Answer 1

每DrawerLayout只应有一个Application。它的工作方式是你应该根据抽屉列表上的选择来替换Fragments。 DrawerLayout旨在作为一个集中组件，以便轻松访问View中的深层Application层次结构。例如，如果用户通过3个屏幕进入“配置文件”页面，则可以在抽屉中将其添加为项目时提供更好的体验。

Answer 2

我建议采用与尝试创建使用导航抽屉的多个活动不同的路线。 Android有可用的片段，这是android似乎走向的方式。因此，您应该使用多个片段并在需要时切换片段，而不是使用多个活动。

这个链接是启动导航抽屉的好方法。 https://developer.android.com/training/implementing-navigation/nav-drawer.html

之后，您将只处理抽屉选择并用下一个片段替换主活动中的片段。

您将使用

fragmentManager.beginTransaction()
                   .replace(R.id.content_frame, fragment)
                   .commit();

当您想要切换片段时。

将基本活动扩展到其他活动导航抽屉

2 个答案: