我的导航抽屉在MainActivity中实现。如果我使用MainAktivity作为发射器，它可以完美运行。但是，当我使用另一个活动作为LAUNCHER并从另一个活动运行MainActivity时，我的应用程序崩溃了。请查看我的Manifest XML。谢谢！
此版本有效：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.examples.pk"
android:versionCode="1"
android:versionName="1.0" >
<uses-permission android:name="android.permission.INTERNET" >
</uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" >
</uses-permission>
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:hardwareAccelerated="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.examples.pk.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.examples.pk.Introduction"
android:label="@string/app_name"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="android.intent.action.INTRODUCTION" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.examples.pk.SetAccess"
android:label="@string/app_name"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="com.examples.pk.SETACCESS" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.example.pk.LogIn"
android:label="@string/app_name"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="com.examples.pk.LOGIN" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<service android:name=".ConnectionService" >
</service>
</application>
</manifest>
这个版本不起作用：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.examples.pk"
android:versionCode="1"
android:versionName="1.0" >
<uses-permission android:name="android.permission.INTERNET" >
</uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" >
</uses-permission>
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:hardwareAccelerated="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.examples.pk.Introduction"
android:label="@string/app_name"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.examples.pk.SetAccess"
android:label="@string/app_name"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="com.examples.pk.SETACCESS" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.example.pk.LogIn"
android:label="@string/app_name"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="com.examples.pk.LOGIN" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.examples.pk.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAINACTIVITY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<service android:name=".ConnectionService" >
</service>
</application>
</manifest>
错误日志：
03-29 22:38:51.755: E/AndroidRuntime(1331): FATAL EXCEPTION: main
03-29 22:38:51.755: E/AndroidRuntime(1331): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.pk/com.example.pk.MainActivity}: java.lang.NullPointerException
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.app.ActivityThread.access$600(ActivityThread.java:141)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.os.Handler.dispatchMessage(Handler.java:99)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.os.Looper.loop(Looper.java:137)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.app.ActivityThread.main(ActivityThread.java:5041)
03-29 22:38:51.755: E/AndroidRuntime(1331): at java.lang.reflect.Method.invokeNative(Native Method)
03-29 22:38:51.755: E/AndroidRuntime(1331): at java.lang.reflect.Method.invoke(Method.java:511)
03-29 22:38:51.755: E/AndroidRuntime(1331): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-29 22:38:51.755: E/AndroidRuntime(1331): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-29 22:38:51.755: E/AndroidRuntime(1331): at dalvik.system.NativeStart.main(Native Method)
03-29 22:38:51.755: E/AndroidRuntime(1331): Caused by: java.lang.NullPointerException
03-29 22:38:51.755: E/AndroidRuntime(1331): at com.example.pk.MainActivity.onCreate(MainActivity.java:75)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.app.Activity.performCreate(Activity.java:5104)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
03-29 22:38:51.755: E/AndroidRuntime(1331): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
03-29 22:38:51.755: E/AndroidRuntime(1331): ... 11 more
已更新 MainActivity：
package com.examples.pk;
import java.util.ArrayList;
import java.util.List;
import android.os.Bundle;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.content.res.Configuration;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
public class MainActivity extends Activity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
CustomDrawerAdapter adapter;
List<DrawerItem> dataList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initializing
dataList = new ArrayList<DrawerItem>();
mTitle = mDrawerTitle = getTitle();
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow,
GravityCompat.START);
// Add Drawer Item to dataList
dataList.add(new DrawerItem("Message", R.drawable.ic_action_email));
dataList.add(new DrawerItem("Likes", R.drawable.ic_action_good));
dataList.add(new DrawerItem("Games", R.drawable.ic_action_gamepad));
dataList.add(new DrawerItem("Lables", R.drawable.ic_action_labels));
dataList.add(new DrawerItem("Search", R.drawable.ic_action_search));
dataList.add(new DrawerItem("Cloud", R.drawable.ic_action_cloud));
dataList.add(new DrawerItem("Camara", R.drawable.ic_action_camera));
dataList.add(new DrawerItem("Video", R.drawable.ic_action_video));
dataList.add(new DrawerItem("Groups", R.drawable.ic_action_group));
dataList.add(new DrawerItem("Import & Export",
R.drawable.ic_action_import_export));
dataList.add(new DrawerItem("About", R.drawable.ic_action_about));
dataList.add(new DrawerItem("Settings", R.drawable.ic_action_settings));
dataList.add(new DrawerItem("Help", R.drawable.ic_action_help));
adapter = new CustomDrawerAdapter(this, R.layout.custom_drawer_item,
dataList);
mDrawerList.setAdapter(adapter);
mDrawerList.setOnItemClickListener(new DrawerItemClickListener());
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, R.string.drawer_open,
R.string.drawer_close) {
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) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
public void SelectItem(int possition) {
Fragment fragment = null;
Bundle args = new Bundle();
switch (possition) {
case 0:
fragment = new FragmentOne();
args.putString(FragmentOne.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentOne.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
case 1:
fragment = new FragmentTwo();
args.putString(FragmentTwo.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentTwo.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
case 2:
fragment = new FragmentThree();
args.putString(FragmentThree.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentThree.IMAGE_RESOURCE_ID, dataList
.get(possition).getImgResID());
break;
case 3:
fragment = new FragmentOne();
args.putString(FragmentOne.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentOne.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
case 4:
fragment = new FragmentTwo();
args.putString(FragmentTwo.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentTwo.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
case 5:
fragment = new FragmentThree();
args.putString(FragmentThree.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentThree.IMAGE_RESOURCE_ID, dataList
.get(possition).getImgResID());
break;
case 6:
fragment = new FragmentOne();
args.putString(FragmentOne.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentOne.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
case 7:
fragment = new FragmentTwo();
args.putString(FragmentTwo.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentTwo.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
case 8:
fragment = new FragmentThree();
args.putString(FragmentThree.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentThree.IMAGE_RESOURCE_ID, dataList
.get(possition).getImgResID());
break;
case 9:
fragment = new FragmentOne();
args.putString(FragmentOne.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentOne.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
case 10:
fragment = new FragmentTwo();
args.putString(FragmentTwo.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentTwo.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
case 11:
fragment = new FragmentThree();
args.putString(FragmentThree.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentThree.IMAGE_RESOURCE_ID, dataList
.get(possition).getImgResID());
break;
case 12:
fragment = new FragmentOne();
args.putString(FragmentOne.ITEM_NAME, dataList.get(possition)
.getItemName());
args.putInt(FragmentOne.IMAGE_RESOURCE_ID, dataList.get(possition)
.getImgResID());
break;
default:
break;
}
fragment.setArguments(args);
FragmentManager frgManager = getFragmentManager();
frgManager.beginTransaction().replace(R.id.content_frame, fragment)
.commit();
mDrawerList.setItemChecked(possition, true);
setTitle(dataList.get(possition).getItemName());
mDrawerLayout.closeDrawer(mDrawerList);
}
@Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
@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 toggles
mDrawerToggle.onConfigurationChanged(newConfig);
}
@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;
}
return false;
}
private class DrawerItemClickListener implements
ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
SelectItem(position);
}
}
}