我从Null Pointer Exception到NavigationDrawer拨打包含MainActivity.java（login.class）的课程时收到intent。在login中我正在执行登录检查，之后我在提交NavigationDrawer点击时调用包含button的类。
（如果我单独运行导航抽屉类，我的代码工作正常。）
错误： -
03-27 01:05:50.741: E/AndroidRuntime(3823): FATAL EXCEPTION: main
03-27 01:05:50.741: E/AndroidRuntime(3823): Process: com.sunmobileappnow.mobileappnow, PID: 3823
03-27 01:05:50.741: E/AndroidRuntime(3823): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sunmobileappnow.mobileappnow/com.sunmobileappnow.mobileappnow.MainActivity}: java.lang.NullPointerException
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.app.ActivityThread.access$700(ActivityThread.java:135)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.os.Handler.dispatchMessage(Handler.java:102)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.os.Looper.loop(Looper.java:137)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.app.ActivityThread.main(ActivityThread.java:4998)
03-27 01:05:50.741: E/AndroidRuntime(3823): at java.lang.reflect.Method.invokeNative(Native Method)
03-27 01:05:50.741: E/AndroidRuntime(3823): at java.lang.reflect.Method.invoke(Method.java:515)
03-27 01:05:50.741: E/AndroidRuntime(3823): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
03-27 01:05:50.741: E/AndroidRuntime(3823): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
03-27 01:05:50.741: E/AndroidRuntime(3823): at dalvik.system.NativeStart.main(Native Method)
03-27 01:05:50.741: E/AndroidRuntime(3823): Caused by: java.lang.NullPointerException
03-27 01:05:50.741: E/AndroidRuntime(3823): at com.sunmobileappnow.mobileappnow.MainActivity.onCreate(MainActivity.java:93)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.app.Activity.performCreate(Activity.java:5243)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-27 01:05:50.741: E/AndroidRuntime(3823): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
03-27 01:05:50.741: E/AndroidRuntime(3823): ... 11 more
这是我的代码： -
package com.sunmobileappnow.mobileappnow;
import com.sunmobile.navigationdrawer.adapter.NavDrawerListAdapter;
import com.sunmobile.navigationdrawer.model.NavDrawerItem;
import java.util.ArrayList;
import android.os.Bundle;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.ListView;
import com.sunmobile.navigationdrawer.*;
public class MainActivity extends Activity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
private String[] navMenuTitles;
private TypedArray navMenuIcons;
private ArrayList<NavDrawerItem> navDrawerItems;
private NavDrawerListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
setContentView(R.layout.activity_main1);
mTitle = mDrawerTitle = getTitle();
navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);
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>();
navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1)));
navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
// list item in slider at 6 LinkedIn details
navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1)));
navDrawerItems.add(new NavDrawerItem(navMenuTitles[6], navMenuIcons.getResourceId(6, -1)));
navDrawerItems.add(new NavDrawerItem(navMenuTitles[7], navMenuIcons.getResourceId(7, -1)));
navDrawerItems.add(new NavDrawerItem(navMenuTitles[8], navMenuIcons.getResourceId(8, -1)));
navMenuIcons.recycle();
mDrawerList.setOnItemClickListener(new SlideMenuClickListener());
adapter = new NavDrawerListAdapter(getApplicationContext(),
navDrawerItems);
mDrawerList.setAdapter(adapter);
// Enable action bar icon_luncher as toggle Home Button
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, R.string.app_name, R.string.app_name) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
invalidateOptionsMenu();
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
invalidateOptionsMenu();
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
displayView(0);
}
}
private class SlideMenuClickListener implements
ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
displayView(position);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
switch (item.getItemId()) {
case R.id.action_settings:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
//called when invalidateOptionsMenu() invoke
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// if Navigation drawer is opened, hide the action items
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
private void displayView(int position) {
// update the main content with called Fragment
Fragment fragment = null;
switch (position) {
case 0:
fragment = new Fragment1SendJob();
break;
case 1:
fragment = new Fragment2Facebook();
break;
case 2:
fragment = new Fragment3Google();
break;
case 3:
fragment = new Fragment4Apple();
break;
case 4:
fragment = new Fragment5Microsoft();
break;
case 5:
fragment = new Fragment6LinkedIn();
break;
default:
break;
}
if (fragment != null) {
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(navMenuTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
} else {
Log.e("this is mainActivity", "Error in else case");
}
}
@Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
mDrawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
mDrawerToggle.onConfigurationChanged(newConfig);
}
}