我尝试了导航抽屉。但是，发生了异常。
为什么会出现错误信息？
你介意你能解决这个问题吗？
MainActivity.java
public class MainActivity extends Activity implements OnPageChangeListener, OnClickListener {
private ListView listView;
private ViewPager mPager;
private String[] navItems = {"Brown", "Cadet Blue", "Dark Olive Green", "Dark Orange", "Golden Rod"};
private ListView lvLeftSlideMenu;
private FrameLayout flMainContent;
private DrawerLayout dlDrawer;
private ActionBarDrawerToggle dtToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
listView = (ListView) findViewById(R.id.list);
mAdapter = new MainListAdapter(this);
listView.setAdapter(mAdapter);
listView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
...
}
});
mPager = (ViewPager)findViewById(R.id.pager);
mPager.setAdapter(new MyPagerAdapter(getApplicationContext()));
flMainContent = (FrameLayout) findViewById(R.id.fl_main_content);
lvLeftSlideMenu = (ListView) findViewById(R.id.lv_left_slide_menu);
lvLeftSlideMenu.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, navItems));
lvLeftSlideMenu.setOnItemClickListener(new DrawerItemClickListener());
dlDrawer = (DrawerLayout)findViewById(R.id.dl_activity_main_drawer);
dtToggle = new ActionBarDrawerToggle(this, dlDrawer, R.drawable.ic_drawer, R.string.open_drawer, R.string.close_drawer) {
@Override
public void onDrawerClosed(View drawerView) {
super.onDrawerClosed(drawerView);
}
@Override
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
}
};
dlDrawer.setDrawerListener(dtToggle);
getActionBar().setDisplayHomeAsUpEnabled(true);
}
protected void onPostCreate(Bundle savedInstanceState){
super.onPostCreate(savedInstanceState);
dtToggle.syncState(); // exception occurred...
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// TODO Auto-generated method stub
if(dtToggle.onOptionsItemSelected(item)){
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
// TODO Auto-generated method stub
super.onConfigurationChanged(newConfig);
dtToggle.onConfigurationChanged(newConfig);
}
private class DrawerItemClickListener implements ListView.OnItemClickListener{
@Override
public void onItemClick(AdapterView<?> adapter, View view, int position, long id) {
switch(position){
case 0:
flMainContent.setBackgroundColor(Color.parseColor("#A52A2A"));
break;
case 1:
flMainContent.setBackgroundColor(Color.parseColor("#5F9EA0"));
break;
case 2:
flMainContent.setBackgroundColor(Color.parseColor("#556B2F"));
break;
case 3:
flMainContent.setBackgroundColor(Color.parseColor("#FF8C00"));
break;
case 4:
flMainContent.setBackgroundColor(Color.parseColor("#DAA520"));
break;
}
dlDrawer.closeDrawer(lvLeftSlideMenu);
}
}
private class MyPagerAdapter extends PagerAdapter {
private LayoutInflater mInflater;
public MyPagerAdapter(Context context) {
super();
mInflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
return 2;
}
@Override
public Object instantiateItem(View pager, int position) {
View v = null;
if(position==0) {
v = mInflater.inflate(R.layout.main_menu_01, null);
...
} else if(position==1) {
v = mInflater.inflate(R.layout.main_menu_02, null);
...
}
((ViewPager)pager).addView(v, 0);
return v;
}
@Override
public void destroyItem(View pager, int position, Object view) {
((ViewPager)pager).removeView((View)view);
}
@Override
public boolean isViewFromObject(View view, Object obj) {
return view == obj;
}
@Override public void finishUpdate(View arg0) { }
@Override public void restoreState(Parcelable arg0, ClassLoader arg1) {}
@Override public Parcelable saveState() { return null; }
@Override public void startUpdate(View arg0) {}
@Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
}
@Override
public void onPageScrollStateChanged(int arg0) {}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {}
@Override
public void onPageSelected(int position) {}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
finish();
}
return false;
}
}
activity_main.xml中
<!-- Main Layout -->
<FrameLayout
android:id="@+id/fl_main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/all_blank" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<RelativeLayout
android:id="@+id/titlebar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/main_tit" >
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentRight="true" >
<TextView
android:id="@+id/userInfo"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_marginRight="10px"
android:gravity="left"
android:textColor="@color/grayblack"
android:textSize="12dp" />
</LinearLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_below="@id/userInfo" >
</LinearLayout>
<TextView
android:id="@+id/userJisa"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/linearLayout1"
android:layout_marginRight="10px"
android:gravity="left"
android:textColor="@color/grayblack"
android:textSize="12dp" />
</RelativeLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/sub_tit_01"
android:orientation="vertical" >
<ImageView
android:id="@+id/btnRefresh"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right"
android:layout_marginTop="1.0dip"
android:paddingRight="6.0dip"
android:src="@drawable/icon_refresh" />
</LinearLayout>
<LinearLayout
android:id="@+id/topBg"
android:layout_width="match_parent"
android:layout_height="164dp"
android:background="@drawable/top_bg"
android:gravity="center"
android:orientation="vertical" >
<ListView
android:id="@+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:drawSelectorOnTop="false" />
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/sub_tit_02"
android:orientation="vertical" >
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/bottom_bg"
android:orientation="vertical" >
<android.support.v4.view.ViewPager
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="200dip" />
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/location_area"
android:gravity="center"
android:orientation="horizontal" >
<LinearLayout
android:id="@+id/page_mark"
android:layout_width="fill_parent"
android:layout_height="30dp"
android:layout_centerInParent="true"
android:gravity="center"
android:orientation="horizontal" />
<TextView
android:id="@+id/versionInfo"
android:layout_width="wrap_content"
android:layout_height="30dp"
android:layout_alignParentRight="true"
android:gravity="bottom"
android:textColor="@color/grayblack"
android:textSize="12sp" />
</RelativeLayout>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/notice_bg"
android:gravity="center"
android:orientation="horizontal" >
<ViewFlipper
android:id="@+id/ViewFlipper01"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center" >
</ViewFlipper>
</LinearLayout>
</LinearLayout>
</FrameLayout>
<!-- Main Layout -->
<!-- Left Slide Menu -->
<ListView
android:layout_width="240dp"
android:layout_height="match_parent"
android:id="@+id/lv_left_slide_menu"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp"
android:background="#EDEDED"/>
<!-- Left Slide Menu -->
错误消息
FATAL EXCEPTION: main
Process: com.ex.himan.safetyPatrol, PID: 19664
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ex.himan.safetyPatrol/com.ex.himan.safetyPatrol.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.ActionBarDrawerToggle.syncState()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2712)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2779)
at android.app.ActivityThread.access$900(ActivityThread.java:179)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1462)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5974)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1388)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1183)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.ActionBarDrawerToggle.syncState()' on a null object reference
at com.ex.himan.safetyPatrol.MainActivity.onPostCreate(MainActivity.java:260)
at android.app.Instrumentation.callActivityOnPostCreate(Instrumentation.java:1200)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2694)
... 10 more
答案 0 :(得分：0)
getActionBar（）方法返回null，因此您将获得NullPointerException.Use ActionBarActivity而不是Activity，如下所示
MainActivity extends ActionBarActivity
而不是getActionBar（）而是使用getSupportActionBar（）。希望它会有所帮助。