Java Android:导航抽屉NullPointerException
我正在使用开发者网站()中的代码安装导航抽屉,但是,我在这个方法中得到了一个NullPointerException:Java Android:导航抽屉NullPointerException,java,android,eclipse,android-layout,Java,Android,Eclipse,Android Layout,我正在使用开发者网站()中的代码安装导航抽屉,但是,我在这个方法中得到了一个NullPointerException: /* Called whenever we call invalidateOptionsMenu() */ @Override public boolean onPrepareOptionsMenu(Menu menu) { // If the nav drawer is open, hide action items related to the content vi
/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_search).setVisible(!drawerOpen);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
这里是错误
04-14 20:51:39.720: D/dalvikvm(826): GC_FOR_ALLOC freed 93K, 6% free 3119K/3284K, paused 95ms, total 96ms
04-14 20:51:39.970: I/Choreographer(826): Skipped 69 frames! The application may be doing too much work on its main thread.
04-14 20:51:40.360: I/Choreographer(826): Skipped 256 frames! The application may be doing too much work on its main thread.
04-14 20:51:40.440: D/gralloc_goldfish(826): Emulator without GPU emulation detected.
04-14 20:51:40.730: D/AndroidRuntime(826): Shutting down VM
04-14 20:51:40.730: W/dalvikvm(826): threadid=1: thread exiting with uncaught exception (group=0xb2ac7ba8)
04-14 20:51:40.740: E/AndroidRuntime(826): FATAL EXCEPTION: main
04-14 20:51:40.740: E/AndroidRuntime(826): Process: com.example.myfirstapp, PID: 826
04-14 20:51:40.740: E/AndroidRuntime(826): java.lang.NullPointerException
04-14 20:51:40.740: E/AndroidRuntime(826): at com.example.myfirstapp.MainActivity.onPrepareOptionsMenu(MainActivity.java:139)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.app.Activity.onPreparePanel(Activity.java:2556)
04-14 20:51:40.740: E/AndroidRuntime(826): at com.android.internal.policy.impl.PhoneWindow.preparePanel(PhoneWindow.java:464)
04-14 20:51:40.740: E/AndroidRuntime(826): at com.android.internal.policy.impl.PhoneWindow.doInvalidatePanelMenu(PhoneWindow.java:800)
04-14 20:51:40.740: E/AndroidRuntime(826): at com.android.internal.policy.impl.PhoneWindow$1.run(PhoneWindow.java:221)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.view.Choreographer.doCallbacks(Choreographer.java:574)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.view.Choreographer.doFrame(Choreographer.java:543)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.os.Handler.handleCallback(Handler.java:733)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.os.Handler.dispatchMessage(Handler.java:95)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.os.Looper.loop(Looper.java:136)
04-14 20:51:40.740: E/AndroidRuntime(826): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-14 20:51:40.740: E/AndroidRuntime(826): at java.lang.reflect.Method.invokeNative(Native Method)
04-14 20:51:40.740: E/AndroidRuntime(826): at java.lang.reflect.Method.invoke(Method.java:515)
04-14 20:51:40.740: E/AndroidRuntime(826): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-14 20:51:40.740: E/AndroidRuntime(826): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-14 20:51:40.740: E/AndroidRuntime(826): at dalvik.system.NativeStart.main(Native Method)
以下是主要活动的其余部分
package com.example.myfirstapp;
import java.util.Locale;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.SearchManager;
import android.content.Intent;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.Toast;
public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
private String[] mPlanetTitles;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle = mDrawerTitle = getTitle();
mPlanetTitles = getResources().getStringArray(R.array.navigation_drawer_options);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
// set a custom shadow that overlays the main content when the drawer opens
mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
// set up the drawer's list view with items and click listener
mDrawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, mPlanetTitles));
mDrawerList.setOnItemClickListener(new DrawerItemClickListener());
// enable ActionBar app icon to behave as action to toggle nav drawer
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions
// between the sliding drawer and the action bar app icon
mDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_drawer, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close /* "close drawer" description for accessibility */
) {
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) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_search).setVisible(!drawerOpen);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
@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;
}
// Handle action buttons
// switch(item.getItemId()) {
// case R.id.action_websearch:
// // create intent to perform web search for this planet
// Intent intent = new Intent(Intent.ACTION_WEB_SEARCH);
// intent.putExtra(SearchManager.QUERY, getActionBar().getTitle());
// // catch event that there's no activity to handle intent
// if (intent.resolveActivity(getPackageManager()) != null) {
// startActivity(intent);
// } else {
// Toast.makeText(this, R.string.app_not_available, Toast.LENGTH_LONG).show();
// }
// return true;
// default:
return super.onOptionsItemSelected(item);
// }
}
/* The click listner for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int position) {
}
@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);
}
}
package com.example.myfirstapp;
导入java.util.Locale;
导入android.app.Activity;
导入android.app.Fragment;
导入android.app.FragmentManager;
导入android.app.SearchManager;
导入android.content.Intent;
导入android.content.res.Configuration;
导入android.os.Bundle;
导入android.support.v4.app.ActionBarDrawerToggle;
导入android.support.v4.view.GravityCompat;
导入android.support.v4.widget.DrawerLayout;
导入android.view.LayoutInflater;
导入android.view.Menu;
导入android.view.MenuInflater;
导入android.view.MenuItem;
导入android.view.view;
导入android.view.ViewGroup;
导入android.widget.AdapterView;
导入android.widget.ArrayAdapter;
导入android.widget.ImageView;
导入android.widget.ListView;
导入android.widget.Toast;
公共类MainActivity扩展了活动{
公共最终静态字符串EXTRA_MESSAGE=“com.example.myfirstapp.MESSAGE”;
私人抽屉布局mDrawerLayout;
私有列表视图mDrawerList;
私有操作bardrawertoggle mDrawerToggle;
私有字符序列mDrawerTitle;
私有字符序列mTitle;
私有字符串[]mplanettiles;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle=mDrawerTitle=getTitle();
mPlanetTitles=getResources().getStringArray(R.array.navigation\u drawer\u选项);
mDrawerLayout=(抽屉布局)findViewById(R.id.抽屉布局);
mDrawerList=(ListView)findViewById(R.id.left\u抽屉);
//设置抽屉打开时覆盖主要内容的自定义阴影
mDrawerLayout.setDrawerShadow(R.drawable.drawer\u shadow,GravityCompat.START);
//使用项目设置抽屉的列表视图,然后单击listener
mDrawerList.setAdapter(新阵列适配器,
R.布局图.抽屉(列表项,MPLANETITLES);
setOnItemClickListener(新的DrawerItemClickListener());
//启用ActionBar应用程序图标作为切换导航抽屉的操作
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
//ActionBarDrawerToggle将适当的交互连接在一起
//在滑动抽屉和操作栏应用程序图标之间
mDrawerToggle=新操作bardrawertoggle(
此,/*主机活动*/
mDrawerLayout,/*抽屉布局对象*/
R.drawable.ic_抽屉,/*导航抽屉图像替换“Up”插入符号*/
R.string.drawer\u open,/*“open drawer”描述,用于辅助功能*/
R.string.drawer\u close/*“close drawer”可访问性说明*/
) {
公共无效onDrawerClosed(视图){
getActionBar().setTitle(mTitle);
InvalidateOptions SMenu();//创建对OnPrepareOptions SMenu()的调用
}
打开图纸上的公共空白(视图抽屉视图){
getActionBar().setTitle(mDrawerTitle);
InvalidateOptions SMenu();//创建对OnPrepareOptions SMenu()的调用
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
如果(savedInstanceState==null){
选择项目(0);
}
}
@凌驾
公共布尔onCreateOptions菜单(菜单){
MenuInflater充气机=getMenuInflater();
充气机。充气(右菜单。主菜单,菜单);
返回super.onCreateOptions菜单(菜单);
}
/*调用InvalidateOptions菜单()时调用*/
@凌驾
公共布尔值OnPrepareOptions菜单(菜单){
//如果导航抽屉打开,则隐藏与内容视图相关的操作项
boolean-DrawerLayout=mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action\u search).setVisible(!drawerropen);
menu.findItem(R.id.action\u设置).setVisible(!drawerropen);
返回super.onPrepareOptions菜单(菜单);
}
@凌驾
公共布尔值onOptionsItemSelected(菜单项项){
//操作栏home/up操作应打开或关闭抽屉。
//ActionBarDrawerToggle会处理好的。
如果(MDRAWERTOGLE.onOptionsItemSelected(项目)){
返回true;
}
//手柄动作按钮
//开关(item.getItemId()){
//案例R.id.action_网站搜索:
////创建对该星球执行web搜索的意图
//意向意向=新意向(意向.行动\网络\搜索);
//intent.putExtra(SearchManager.QUERY,getActionBar().getTitle());
////捕获没有要处理的活动的事件
//if(intent.resolveActivity(getPackageManager())!=null){
//星触觉(意向);
//}其他{
//Toast.makeText(this,R.string.app_不可用,Toast.LENGTH_LONG.show();
// }
//返回true;
//默认值:
返回super.onOptionsItemSelected(项目);
// }
}
/*在导航抽屉中单击ListView的listner*/
私有类DrawerItemClickListener实现ListView.OnItemClickListener{
@凌驾
public void onItemClick(AdapterView父对象、视图、整型位置、长id){
选择项目(位置);
}
}
私有void selectItem(内部位置){
}
@凌驾
公共无效设置标题(字符序列标题){
mTitle=标题;
getActionBar().setTitle(mTitle);
}
/**
*使用ActionBarDrawerToggle时,必须在
*onPostCreate()和onConfigurationChanged()。。。
*/
@凌驾
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context="com.example.myfirstapp.MainActivity" >
<item
android:id="@+id/action_settings"
android:orderInCategory="100"
android:title="@string/action_settings"
app:showAsAction="never"/>
</menu>
<item
android:id="@+id/action_search"
android:icon="@drawable/ic_action_search"
android:title="@string/action_search"
app:actionViewClass="android.support.v7.widget.SearchView"
app:showAsAction="ifRoom|collapseActionView" />