應用程序在單擊片段時崩潰

Question

我創建了一個導航抽屜，它的最后一個選項會打開一個片段，用於設置設備的牆紙。但是，無論何時選擇該片段，我的應用程序都會崩潰。 這是我的代碼

MainActivity.java

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

    // nav drawer title
    private CharSequence mDrawerTitle;

    // used to store app title
    private CharSequence mTitle;

    // slide menu items
    private String[] navMenuTitles;
    private TypedArray navMenuIcons;

    private ArrayList<NavDrawerItem> navDrawerItems;
    private NavDrawerListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mTitle = mDrawerTitle = getTitle();

        // load slide menu items
        navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);

        // nav drawer icons from resources
        navMenuIcons = getResources()
                .obtainTypedArray(R.array.nav_drawer_icons);

        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.list_slidermenu);

        navDrawerItems = new ArrayList<NavDrawerItem>();

        // adding nav drawer items to array
        // Home
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
        // Find People
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
        // Photos
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
        // Communities, Will add a counter here
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "22"));
        // Pages
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
        // What's hot, We  will add a counter here
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "50+"));


        // Recycle the typed array
        navMenuIcons.recycle();

        mDrawerList.setOnItemClickListener(new SlideMenuClickListener());

        // setting the nav drawer list adapter
        adapter = new NavDrawerListAdapter(getApplicationContext(),
                navDrawerItems);
        mDrawerList.setAdapter(adapter);

        // enabling action bar app icon and behaving it as toggle button
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
                R.drawable.ic_drawer, //nav menu toggle icon
                R.string.app_name, // nav drawer open - description for accessibility
                R.string.app_name // nav drawer close - description for accessibility
        ) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                // calling onPrepareOptionsMenu() to show action bar icons
                invalidateOptionsMenu();
            }

            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle(mDrawerTitle);
                // calling onPrepareOptionsMenu() to hide action bar icons
                invalidateOptionsMenu();
            }
        };
        mDrawerLayout.setDrawerListener(mDrawerToggle);

        if (savedInstanceState == null) {
            // on first time display view for first nav item
            displayView(0);
        }
    }

    /**
     * Slide menu item click listener
     * */
    private class SlideMenuClickListener implements
            ListView.OnItemClickListener {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position,
                long id) {
            // display view for selected nav drawer item

            displayView(position);
            switch(position) {
            case 0:
                Intent a = new Intent(getApplicationContext(), Test.class);
                startActivity(a);
                break;
            case 1:
                Intent b = new Intent(getApplicationContext(), MainActivity.class);
                startActivity(b);
                break;
            default:
        }

        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // toggle nav drawer on selecting action bar app icon/title
        if (mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        // Handle action bar actions click
        switch (item.getItemId()) {
        case R.id.action_settings:
            return true;
        default:
            return super.onOptionsItemSelected(item);
        }
    }

    /* *
     * Called when invalidateOptionsMenu() is triggered
     */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        // if nav drawer is opened, hide the action items
        boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
        menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
        return super.onPrepareOptionsMenu(menu);
    }

    /**
     * Diplaying fragment view for selected nav drawer list item
     * */
    private void displayView(int position) {
        // update the main content by replacing fragments
        Fragment fragment = null;
        switch (position) {
        case 0:
            fragment = new HomeFragment();

            break;
        case 1:
            fragment = new FindPeopleFragment();
            break;
        case 2:
            fragment = new PhotosFragment();
            break;
        case 3:
            fragment = new CommunityFragment();
            break;
        case 4:
            fragment = new PagesFragment();
            break;
        case 5:
            fragment = new S();
            break;

        default:
            break;
        }

        if (fragment != null) {
            FragmentManager fragmentManager = getFragmentManager();
            fragmentManager.beginTransaction()
                    .replace(R.id.frame_container, fragment).commit();

            // update selected item and title, then close the drawer
            mDrawerList.setItemChecked(position, true);
            mDrawerList.setSelection(position);
            setTitle(navMenuTitles[position]);
            mDrawerLayout.closeDrawer(mDrawerList);
        } else {
            // error in creating fragment
            Log.e("MainActivity", "Error in creating fragment");
        }
    }

    @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);
    }

}

當我單擊此片段Fragment S.java時，應用程序崩潰

public class S extends Fragment implements OnClickListener {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // to our activity to cover the whole screen


        View rootView = inflater.inflate(R.layout.back, container, false);
        ImageView display;
        int tophone;




            Button but = (Button) getView().findViewById(R.id.setwallpaper);
            tophone = R.drawable.image4;
            but.setOnClickListener(this);
            display = (ImageView) getView().findViewById(R.id.ivdisplay);
            ImageView image1 = (ImageView) getView().findViewById(R.id.IVimage1);
            ImageView image2 = (ImageView) getView().findViewById(R.id.IVimage2);
            ImageView image3 = (ImageView) getView().findViewById(R.id.IVimage3);
            ImageView image4 = (ImageView) getView().findViewById(R.id.IVimage4);
            ImageView image5 = (ImageView) getView().findViewById(R.id.IVimage5);

            image1.setOnClickListener(this);
            image2.setOnClickListener(this);
            image3.setOnClickListener(this);
            image4.setOnClickListener(this);
            image5.setOnClickListener(this);



        return rootView;
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub

    }
}

這是我的日志

11-18 21:19:05.112: E/AndroidRuntime(622): FATAL EXCEPTION: main
11-18 21:19:05.112: E/AndroidRuntime(622): java.lang.NullPointerException
11-18 21:19:05.112: E/AndroidRuntime(622):  at info.androidhive.slidingmenu.S.onCreateView(S.java:31)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:829)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1035)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.app.BackStackRecord.run(BackStackRecord.java:635)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1397)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.os.Handler.handleCallback(Handler.java:615)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.os.Handler.dispatchMessage(Handler.java:92)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.os.Looper.loop(Looper.java:137)
11-18 21:19:05.112: E/AndroidRuntime(622):  at android.app.ActivityThread.main(ActivityThread.java:4745)
11-18 21:19:05.112: E/AndroidRuntime(622):  at java.lang.reflect.Method.invokeNative(Native Method)
11-18 21:19:05.112: E/AndroidRuntime(622):  at java.lang.reflect.Method.invoke(Method.java:511)
11-18 21:19:05.112: E/AndroidRuntime(622):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
11-18 21:19:05.112: E/AndroidRuntime(622):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-18 21:19:05.112: E/AndroidRuntime(622):  at dalvik.system.NativeStart.main(Native Method)
11-18 21:22:52.642: I/Process(622): Sending signal. PID: 622 SIG: 9

Answer 1

在片段中，在onCreateView()期間getView()為null 。

您必須在rootView上找到您的視圖：

public class S extends Fragment implements OnClickListener {

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.back, container, false);
    Button but = (Button) rootView.findViewById(R.id.setwallpaper);
    int tophone = R.drawable.image4;
    but.setOnClickListener(this);
    ImageView display = (ImageView) rootView.findViewById(R.id.ivdisplay);
    ImageView image1 = (ImageView) rootView.findViewById(R.id.IVimage1);
    // ... for all images

    image1.setOnClickListener(this);
    // ... for all images
    return rootView;
  }

  @Override
  public void onClick(View v) {
    // TODO Auto-generated method stub
  }
}

Answer 2

在創建視圖（onCreateView）時，在片段“ S”中使用“ getView（）”->它將返回null。 改為使用rootView查找視圖：

          Button but = (Button) rootView.findViewById(R.id.setwallpaper);