当我启动一项新活动时，我会收到此强制关闭错误：
03-01 22:44:32.752 2992-2992/com.example.mike.beerportfoliomaterial E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.mike.beerportfoliomaterial, PID: 2992
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mike.beerportfoliomaterial/com.example.mike.beerportfoliomaterial.MainDrawer2}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2404)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2464)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5653)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.mike.beerportfoliomaterial.MainDrawer2.onCreate(MainDrawer2.java:72)
at android.app.Activity.performCreate(Activity.java:5539)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2368)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2464)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5653)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
03-01 22:45:56.047 2992-2992/com.example.mike.beerportfoliomaterial I/Process﹕ Sending signal. PID: 2992 SIG: 9
我的Android清单看起来像这样：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.mike.beerportfoliomaterial" >
<uses-feature
android:glEsVersion="0x00020000"
android:required="true"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<!-- Permission to write to external storage -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.CALL_PHONE" />
<application
android:allowBackup="true"
android:icon="@drawable/logo"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity android:label="@string/app_name" android:name="com.example.mike.beerportfoliomaterial.MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<receiver android:name="com.example.mike.beerportfoliomaterial.HelloWidget" android:label="Beer of the Day">
<intent-filter> <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
<action android:name="android.appwidget.action.APPWIDGET_ENABLED" />
</intent-filter>
<meta-data android:name="android.appwidget.provider" android:resource="@xml/hello_widget_provider" />
</receiver>
<receiver android:name="com.example.mike.beerportfoliomaterial.SearchWidget" android:label="Search ">
<intent-filter>
<action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
<action android:name="android.appwidget.action.APPWIDGET_ENABLED" />
</intent-filter>
<meta-data android:name="android.appwidget.provider" android:resource="@xml/search_widget" />
</receiver>
<activity android:label="@string/app_name" android:name="com.example.mike.beerportfoliomaterial.LogIn">
<intent-filter>
<category android:name="android.intent.category"/>
</intent-filter>
</activity>
<activity android:label="@string/app_name" android:name="com.example.mike.beerportfoliomaterial.Register" android:screenOrientation="portrait">
<intent-filter>
<category android:name="android.intent.category"/>
</intent-filter>
</activity>
<activity android:label="@string/app_name" android:name="com.example.mike.beerportfoliomaterial.MainDraw" android:screenOrientation="portrait">
<intent-filter>
<category android:name="android.intent.category"/>
</intent-filter>
</activity>
<activity android:label="@string/app_name" android:name="com.example.mike.beerportfoliomaterial.MainDrawer2" android:screenOrientation="portrait">
<intent-filter>
<category android:name="android.intent.category"/>
</intent-filter>
</activity>
<meta-data android:name="com.crashlytics.ApiKey" android:value="ffdabd920d55d93f21d643ae41d5f93fb21ed5c1"/>
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="AIzaSyCCDcbrkc0SlZNCKCrGaYHXliLgB0BFB90"/>
</application>
</manifest>
我的MainDrawer2看起来像这样：
/////////////////////////////////////////////// //
package com.example.mike.beerportfoliomaterial;
import android.IntentIntegrator;
import android.IntentResult;
import android.annotation.TargetApi;
import android.content.Context;
import android.content.Intent;
import android.content.res.Configuration;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.Toast;
/**
* Created by Mike and Simon on 2/22/14.
*/
public class MainDrawer2 extends FragmentActivity
{
private static final String EXTRA_NAV_ITEM = "extraNavItem";
private static final String STATE_CURRENT_NAV = "stateCurrentNav";
private ActionBarDrawerToggle mDrawerToggle;
private DrawerLayout mDrawerLayout;
private NavDrawerListAdapter mDrawerAdapter;
private ListView mDrawerList;
private CharSequence mTitle;
private CharSequence mDrawerTitle;
private MainNavItem mCurrentNavItem;
public static Intent createLaunchFragmentIntent(Context context, MainNavItem navItem)
{
return new Intent(context, MainDrawer2.class)
.putExtra(EXTRA_NAV_ITEM, navItem.ordinal());
}
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_main);
//Crashlytics.start(this);
mTitle = mDrawerTitle = getTitle();
mDrawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
mDrawerList = (ListView)findViewById(R.id.drawer);
getActionBar().setDisplayHomeAsUpEnabled(true);
enableHomeButtonIfRequired();
mDrawerAdapter = new NavDrawerListAdapter(getApplicationContext());
mDrawerList.setAdapter(mDrawerAdapter);
mDrawerList.setOnItemClickListener(new ListView.OnItemClickListener()
{
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
displayNavFragment((MainNavItem)parent.getItemAtPosition(position));
}
});
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(getIntent().hasExtra(EXTRA_NAV_ITEM)){
MainNavItem navItem = MainNavItem.values()
[getIntent().getIntExtra(EXTRA_NAV_ITEM,
MainNavItem.STATISTICS.ordinal())];
displayNavFragment(navItem);
}
else if(savedInstanceState != null){
mCurrentNavItem = MainNavItem.values()
[savedInstanceState.getInt(STATE_CURRENT_NAV)];
setCurrentNavItem(mCurrentNavItem);
}
else{
displayNavFragment(MainNavItem.STATISTICS);
}
}
@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
private void enableHomeButtonIfRequired()
{
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH){
getActionBar().setHomeButtonEnabled(true);
}
}
public void setActionBarTitle(String title) {
getActionBar().setTitle(title);
}
@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
protected void onSaveInstanceState(Bundle outState)
{
super.onSaveInstanceState(outState);
if (mCurrentNavItem == null){
}
else{
outState.putInt(STATE_CURRENT_NAV, mCurrentNavItem.ordinal());
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
/*
@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);
}
*/
private void displayNavFragment(MainNavItem navItem)
{
//if(navItem == mCurrentNavItem){
// return;
//}
Fragment fragment = Fragment.instantiate(this,
navItem.getFragClass().getName());
if(fragment != null){
getSupportFragmentManager().beginTransaction()
.replace(R.id.main, fragment)
.commit();
setCurrentNavItem(navItem);
}
}
private void setCurrentNavItem(MainNavItem navItem)
{
int position = navItem.ordinal();
// If navItem is in DrawerAdapter
if(position >= 0 && position < mDrawerAdapter.getCount()){
//mDrawerList.setItemChecked(position, true);
}
else{
// navItem not in DrawerAdapter, de-select current item
if(mCurrentNavItem != null){
//mDrawerList.setItemChecked(mCurrentNavItem.ordinal(), false);
}
}
//test to keep item not selected
int toClear=mDrawerList.getCheckedItemPosition();
if (toClear >= 0) {
mDrawerList.setItemChecked(toClear, false);
}
mDrawerLayout.closeDrawer(mDrawerList);
setTitle(navItem.getTitleResId());
mCurrentNavItem = navItem;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
if(mDrawerLayout.isDrawerOpen(mDrawerList)) {
mDrawerLayout.closeDrawer(mDrawerList);
}
else {
mDrawerLayout.openDrawer(mDrawerList);
}
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void goToSearch(MenuItem item){
//go to search page
Fragment Fragment_one;
FragmentManager man= getSupportFragmentManager();
FragmentTransaction tran = man.beginTransaction();
Fragment_one = new Search();
tran.replace(R.id.main, Fragment_one);//tran.
tran.addToBackStack(null);
tran.commit();
}
public void scanBarcode(MenuItem item){
//open scanner
IntentIntegrator scanIntegrator = new IntentIntegrator(this);
scanIntegrator.initiateScan();
}
public void onActivityResult(int requestCode, int resultCode, Intent intent) {
//retrieve scan result
IntentResult scanningResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, intent);
if (scanningResult != null) {
//we have a result
String scanContent = scanningResult.getContents();
//todo: set scan content into setting, load new fragment which calls async task below. New
//todo: fragment will have same ui as search. :-)
Fragment Fragment_one;
FragmentManager man= this.getSupportFragmentManager();
FragmentTransaction tran = man.beginTransaction();
BarcodeFrag fragmentNew = new BarcodeFrag();
Bundle bundle = new Bundle();
bundle.putString("scanContent", scanContent);
fragmentNew.setArguments(bundle);
tran.replace(R.id.main, fragmentNew);//tran.
tran.addToBackStack(null);
//tran.commit();
tran.commitAllowingStateLoss();
}
else{
Toast toast = Toast.makeText(getApplicationContext(),
"No scan data received!", Toast.LENGTH_SHORT);
toast.show();
}
}
}
答案 0 :(得分：1)
public class MainDrawer2 extends ActionBarActivity
尝试扩展ActionBarActivity.it扩展到片段活动本身。所以你不需要担心片段活动。 希望它会有所帮助。
答案 1 :(得分：0)
我可以看到你没有将抽屉项目列表传递给NavDrawerListAdapter。 那你在哪里设置抽屉物品？