我创建了一个导航抽屉，其最后一个选项会打开一个片段，用于设置设备的壁纸。但是，无论何时我选择该片段，我的应用都会一直崩溃。 这是我的代码
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);
}
}
点击此片段后应用崩溃了 片段S.java
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
}
}
这是我的logcat
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
答案 0 :(得分：0)
在片段中，getView()期间null为onCreateView()。
您必须在rootView上找到您的观点：
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
}
}
答案 1 :(得分：0)
在你的Fragment＆＃34; S＆＃34;中，你使用＆＃34; getView（）＆＃34;创建视图时（onCreateView） - ＆gt;它将返回null。使用rootView查找视图：
Button but = (Button) rootView.findViewById(R.id.setwallpaper);