应用程序因空指针异常而崩溃
App crashing due to nullpointer exception
我一直在开发一个应用程序，需要一次性屏幕以便输入一些一次性变量。我让用户输入卷号，如果它大于 101400000，我只需要在第一个屏幕上制作另一个 EditText。
然后它移动到具有导航滑块的主 Activity。
OneTime Activity 显示屏幕。
package com.example.thereaper.thaparexpress;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
public class OneTime extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ot);
int counter=0;
if(counter==0) {
int roll = 0;
final Global global = (Global) getApplicationContext();
EditText rollNo = (EditText) findViewById(R.id.rollNo);
try {
roll = Integer.parseInt(rollNo.getText().toString());
} catch (NumberFormatException e) {
Toast.makeText(this, "Invalid roll number", Toast.LENGTH_SHORT);
}
if (roll >= 10140000) {
rollNo.setVisibility(View.VISIBLE);
}
EditText group = (EditText) findViewById(R.id.groupNo);
global.setGroup(group.getText().toString());
global.setRoll_No(roll);
counter++;
}
Intent i = new Intent(this,Main.class);
startActivity(i);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_one_time, menu);
return true;
}
}
一次性xml文件
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="text|number"
android:hint="Roll Number"
android:ems="10"
android:id="@+id/rollNo"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="128dp" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="text|number"
android:hint="Group"
android:ems="10"
android:id="@+id/groupNo"
android:layout_marginTop="115dp"
android:layout_below="@+id/rollNo"
android:layout_centerHorizontal="true"
android:visibility="gone"/>
主要Activity
package com.example.thereaper.thaparexpress;
import java.util.ArrayList;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.support.v7.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.widget.AdapterView;
import android.widget.ListView;
import com.example.thereaper.thaparexpress.com.example.thereaper.thaparexpress.slider.adapter.NavDrawerListAdapter;
import com.example.thereaper.thaparexpress.fragments.Contribute;
import com.example.thereaper.thaparexpress.fragments.Event;
import com.example.thereaper.thaparexpress.fragments.Societies;
import com.example.thereaper.thaparexpress.fragments.Home;
import com.example.thereaper.thaparexpress.fragments.ThaparLogs;
import com.example.thereaper.thaparexpress.fragments.TimeTable;
import com.example.thereaper.thaparexpress.slider.model.NavDrawerItem;
public class Main extends Activity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
// nav drawer title
private CharSequence mDrawerTitle;
// used to store app title
private CharSequence mTitle;
// slide menu items
private String[] navMenuTitles;
private TypedArray navMenuIcons;
private ArrayList<NavDrawerItem> navDrawerItems;
private NavDrawerListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle = mDrawerTitle = getTitle();
// load slide menu items
navMenuTitles = getResources().getStringArray(R.array.navDrawer);
// nav drawer icons from resources
navMenuIcons = getResources()
.obtainTypedArray(R.array.navDrawerIcons);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.list_sliderMenu);
navDrawerItems = new ArrayList<NavDrawerItem>();
// adding nav drawer items to array
// Home
navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
// Find People
navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
// Photos
navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
// Communities, Will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "22"));
// Pages
navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
// What's hot, We will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "50+"));
// Recycle the typed array
navMenuIcons.recycle();
mDrawerList.setOnItemClickListener(new SlideMenuClickListener());
// setting the nav drawer list adapter
adapter = new NavDrawerListAdapter(getApplicationContext(),
navDrawerItems);
mDrawerList.setAdapter(adapter);
// enabling action bar app icon and behaving it as toggle button
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.string.app_name, // nav drawer open - description for accessibility
R.string.app_name // nav drawer close - description for accessibility
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
// calling onPrepareOptionsMenu() to show action bar icons
invalidateOptionsMenu();
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
// calling onPrepareOptionsMenu() to hide action bar icons
invalidateOptionsMenu();
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
// on first time display view for first nav item
displayView(0);
}
}
/**
* Slide menu item click listener
* */
private class SlideMenuClickListener implements
ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// display view for selected nav drawer item
displayView(position);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// toggle nav drawer on selecting action bar app icon/title
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action bar actions click
switch (item.getItemId()) {
case R.id.action_settings:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/***
* Called when invalidateOptionsMenu() is triggered
*/
@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);
}
/**
* Diplaying fragment view for selected nav drawer list item
* */
private void displayView(int position) {
// update the main content by replacing fragments
Fragment fragment = null;
switch (position) {
case 0:
fragment = new Home();
break;
case 1:
fragment = new Societies();
break;
case 2:
fragment = new Event();
break;
case 3:
fragment = new ThaparLogs();
break;
case 4:
fragment = new TimeTable();
break;
case 5:
fragment = new Contribute();
break;
default:
break;
}
if (fragment != null) {
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.frame_Container, fragment).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(navMenuTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
} else {
// error in creating fragment
Log.e("MainActivity", "Error in creating fragment");
}
}
@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);
}
}
主要活动xml
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="@+id/frame_Container"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
<ListView
android:id="@+id/list_sliderMenu"
android:layout_width="280dp"
android:listSelector="@drawable/abc_list_selector_holo_dark"
android:choiceMode="singleChoice"
android:dividerHeight="1dp"
android:background="@drawable/abc_list_selector_background_transition_holo_dark"
android:layout_height="fill_parent">
</ListView>
错误
Process: com.example.thereaper.thaparexpress, PID: 25672
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.thereaper.thaparexpress/com.example.thereaper.thaparexpress.Main}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at com.example.thereaper.thaparexpress.Main.onCreate(Main.java:92)
at android.app.Activity.performCreate(Activity.java:5953)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
01-17 19:20:13.131 27231-27231/com.example.thereaper.thaparexpress I/art﹕ Late-enabling -Xcheck:jni
01-17 19:20:13.290 27231-27252/com.example.thereaper.thaparexpress D/OpenGLRenderer﹕ Render dirty regions requested: true
01-17 19:20:13.306 27231-27231/com.example.thereaper.thaparexpress D/Atlas﹕ Validating map...
01-17 19:20:13.377 27231-27252/com.example.thereaper.thaparexpress I/Adreno-EGL﹕ <qeglDrvAPI_eglInitialize:410>: EGL 1.4 QUALCOMM build: AU_LINUX_ANDROID_LA.BF.1.1.04.04.02.162.107_msm8226_LA.BF.1.1__release_AU ()
OpenGL ES Shader Compiler Version: E031.25.01.03
Build Date: 10/28/14 Tue
Local Branch:
Remote Branch: quic/l_LNX.LA.3.6
Local Patches: NONE
Reconstruct Branch: AU_LINUX_ANDROID_LA.BF.1.1.04.04.02.162.107 + cb93e16 + f50fe49 + d7c18e6 + 5b9a565 + 0f3a25d + 607156e + 75511aa + e4d16c0 + 686f3eb + 211a271 + dd281ee + NOTHING
01-17 19:20:13.390 27231-27252/com.example.thereaper.thaparexpress I/OpenGLRenderer﹕ Initialized EGL, version 1.4
01-17 19:20:13.502 27231-27252/com.example.thereaper.thaparexpress D/OpenGLRenderer﹕ Enabling debug mode 0
01-17 19:20:16.737 27231-27231/com.example.thereaper.thaparexpress D/AndroidRuntime﹕ Shutting down VM
01-17 19:20:16.745 27231-27231/com.example.thereaper.thaparexpress E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.thereaper.thaparexpress, PID: 27231
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.thereaper.thaparexpress/com.example.thereaper.thaparexpress.Main}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at com.example.thereaper.thaparexpress.Main.onCreate(Main.java:92)
at android.app.Activity.performCreate(Activity.java:5953)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
我不明白我哪里出错了。请帮忙
编辑：更改后的新样式 xml 文件
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar">
<!-- Customize your theme here. -->
</style>
现在有一个新的错误
01-17 20:12:03.071 27036-27036/com.example.thereaper.thaparexpress E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.thereaper.thaparexpress, PID: 27036
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.thereaper.thaparexpress/com.example.thereaper.thaparexpress.Main}: java.lang.IllegalArgumentException: View android.widget.ListView{2c9eb14c VFED.VC. ......I. 0,0-0,0 #7f090041 app:id/list_sliderMenu} is not a sliding drawer
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.IllegalArgumentException: View android.widget.ListView{2c9eb14c VFED.VC. ......I. 0,0-0,0 #7f090041 app:id/list_sliderMenu} is not a sliding drawer
at android.support.v4.widget.DrawerLayout.closeDrawer(DrawerLayout.java:1306)
at com.example.thereaper.thaparexpress.Main.displayView(Main.java:203)
at com.example.thereaper.thaparexpress.Main.onCreate(Main.java:115)
at android.app.Activity.performCreate(Activity.java:5953)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
您正在使用 2 个活动：Activity 和 ActionBarActivity。后者来自支持包，需要 AppCompat 主题。
这意味着 Activity 正在使用 AppCompat 主题，getActionBar() 将 return 为空。
您的选择：
让 Main 扩展 ActionBarActivity 并将 getActionBar 替换为 getSupportActionBar。
两个活动都扩展 Activity 并将您的主题更改为更新的主题，例如：Holo:
<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar">
</style>
您可以更改 style.xml 文件。
例如：
<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar">
<!-- Customize your theme here. -->
</style>
并在 .java 文件后扩展 Activity class。
例如：
public class MainActivity extends Activity {.....}
解决方案 - 在 styles.xml 中将父级从 'android:Theme.Light' 更改为 'android:Theme.Holo.Light.DarkActionBar' 解决了空指针异常。
<resources>
<!-- style name="AppTheme" parent="android:Theme.Light" -->
<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar">
<item name="android:displayOptions">useLogo</item>
</style>
</resources>
我从
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
</style>
至
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
</style>
这解决了我的错误....
我一直在开发一个应用程序，需要一次性屏幕以便输入一些一次性变量。我让用户输入卷号，如果它大于 101400000，我只需要在第一个屏幕上制作另一个 EditText。
然后它移动到具有导航滑块的主 Activity。
OneTime Activity 显示屏幕。
package com.example.thereaper.thaparexpress;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
public class OneTime extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ot);
int counter=0;
if(counter==0) {
int roll = 0;
final Global global = (Global) getApplicationContext();
EditText rollNo = (EditText) findViewById(R.id.rollNo);
try {
roll = Integer.parseInt(rollNo.getText().toString());
} catch (NumberFormatException e) {
Toast.makeText(this, "Invalid roll number", Toast.LENGTH_SHORT);
}
if (roll >= 10140000) {
rollNo.setVisibility(View.VISIBLE);
}
EditText group = (EditText) findViewById(R.id.groupNo);
global.setGroup(group.getText().toString());
global.setRoll_No(roll);
counter++;
}
Intent i = new Intent(this,Main.class);
startActivity(i);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_one_time, menu);
return true;
}
}
一次性xml文件
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="text|number"
android:hint="Roll Number"
android:ems="10"
android:id="@+id/rollNo"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="128dp" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="text|number"
android:hint="Group"
android:ems="10"
android:id="@+id/groupNo"
android:layout_marginTop="115dp"
android:layout_below="@+id/rollNo"
android:layout_centerHorizontal="true"
android:visibility="gone"/>
主要Activity
package com.example.thereaper.thaparexpress;
import java.util.ArrayList;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.support.v7.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.widget.AdapterView;
import android.widget.ListView;
import com.example.thereaper.thaparexpress.com.example.thereaper.thaparexpress.slider.adapter.NavDrawerListAdapter;
import com.example.thereaper.thaparexpress.fragments.Contribute;
import com.example.thereaper.thaparexpress.fragments.Event;
import com.example.thereaper.thaparexpress.fragments.Societies;
import com.example.thereaper.thaparexpress.fragments.Home;
import com.example.thereaper.thaparexpress.fragments.ThaparLogs;
import com.example.thereaper.thaparexpress.fragments.TimeTable;
import com.example.thereaper.thaparexpress.slider.model.NavDrawerItem;
public class Main extends Activity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
// nav drawer title
private CharSequence mDrawerTitle;
// used to store app title
private CharSequence mTitle;
// slide menu items
private String[] navMenuTitles;
private TypedArray navMenuIcons;
private ArrayList<NavDrawerItem> navDrawerItems;
private NavDrawerListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle = mDrawerTitle = getTitle();
// load slide menu items
navMenuTitles = getResources().getStringArray(R.array.navDrawer);
// nav drawer icons from resources
navMenuIcons = getResources()
.obtainTypedArray(R.array.navDrawerIcons);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.list_sliderMenu);
navDrawerItems = new ArrayList<NavDrawerItem>();
// adding nav drawer items to array
// Home
navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
// Find People
navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
// Photos
navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
// Communities, Will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "22"));
// Pages
navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
// What's hot, We will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "50+"));
// Recycle the typed array
navMenuIcons.recycle();
mDrawerList.setOnItemClickListener(new SlideMenuClickListener());
// setting the nav drawer list adapter
adapter = new NavDrawerListAdapter(getApplicationContext(),
navDrawerItems);
mDrawerList.setAdapter(adapter);
// enabling action bar app icon and behaving it as toggle button
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.string.app_name, // nav drawer open - description for accessibility
R.string.app_name // nav drawer close - description for accessibility
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
// calling onPrepareOptionsMenu() to show action bar icons
invalidateOptionsMenu();
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
// calling onPrepareOptionsMenu() to hide action bar icons
invalidateOptionsMenu();
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
// on first time display view for first nav item
displayView(0);
}
}
/**
* Slide menu item click listener
* */
private class SlideMenuClickListener implements
ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// display view for selected nav drawer item
displayView(position);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// toggle nav drawer on selecting action bar app icon/title
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action bar actions click
switch (item.getItemId()) {
case R.id.action_settings:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/***
* Called when invalidateOptionsMenu() is triggered
*/
@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);
}
/**
* Diplaying fragment view for selected nav drawer list item
* */
private void displayView(int position) {
// update the main content by replacing fragments
Fragment fragment = null;
switch (position) {
case 0:
fragment = new Home();
break;
case 1:
fragment = new Societies();
break;
case 2:
fragment = new Event();
break;
case 3:
fragment = new ThaparLogs();
break;
case 4:
fragment = new TimeTable();
break;
case 5:
fragment = new Contribute();
break;
default:
break;
}
if (fragment != null) {
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.frame_Container, fragment).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(navMenuTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
} else {
// error in creating fragment
Log.e("MainActivity", "Error in creating fragment");
}
}
@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);
}
}
主要活动xml
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="@+id/frame_Container"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
<ListView
android:id="@+id/list_sliderMenu"
android:layout_width="280dp"
android:listSelector="@drawable/abc_list_selector_holo_dark"
android:choiceMode="singleChoice"
android:dividerHeight="1dp"
android:background="@drawable/abc_list_selector_background_transition_holo_dark"
android:layout_height="fill_parent">
</ListView>
错误
Process: com.example.thereaper.thaparexpress, PID: 25672
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.thereaper.thaparexpress/com.example.thereaper.thaparexpress.Main}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at com.example.thereaper.thaparexpress.Main.onCreate(Main.java:92)
at android.app.Activity.performCreate(Activity.java:5953)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
01-17 19:20:13.131 27231-27231/com.example.thereaper.thaparexpress I/art﹕ Late-enabling -Xcheck:jni
01-17 19:20:13.290 27231-27252/com.example.thereaper.thaparexpress D/OpenGLRenderer﹕ Render dirty regions requested: true
01-17 19:20:13.306 27231-27231/com.example.thereaper.thaparexpress D/Atlas﹕ Validating map...
01-17 19:20:13.377 27231-27252/com.example.thereaper.thaparexpress I/Adreno-EGL﹕ <qeglDrvAPI_eglInitialize:410>: EGL 1.4 QUALCOMM build: AU_LINUX_ANDROID_LA.BF.1.1.04.04.02.162.107_msm8226_LA.BF.1.1__release_AU ()
OpenGL ES Shader Compiler Version: E031.25.01.03
Build Date: 10/28/14 Tue
Local Branch:
Remote Branch: quic/l_LNX.LA.3.6
Local Patches: NONE
Reconstruct Branch: AU_LINUX_ANDROID_LA.BF.1.1.04.04.02.162.107 + cb93e16 + f50fe49 + d7c18e6 + 5b9a565 + 0f3a25d + 607156e + 75511aa + e4d16c0 + 686f3eb + 211a271 + dd281ee + NOTHING
01-17 19:20:13.390 27231-27252/com.example.thereaper.thaparexpress I/OpenGLRenderer﹕ Initialized EGL, version 1.4
01-17 19:20:13.502 27231-27252/com.example.thereaper.thaparexpress D/OpenGLRenderer﹕ Enabling debug mode 0
01-17 19:20:16.737 27231-27231/com.example.thereaper.thaparexpress D/AndroidRuntime﹕ Shutting down VM
01-17 19:20:16.745 27231-27231/com.example.thereaper.thaparexpress E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.thereaper.thaparexpress, PID: 27231
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.thereaper.thaparexpress/com.example.thereaper.thaparexpress.Main}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at com.example.thereaper.thaparexpress.Main.onCreate(Main.java:92)
at android.app.Activity.performCreate(Activity.java:5953)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
我不明白我哪里出错了。请帮忙
编辑：更改后的新样式 xml 文件
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar">
<!-- Customize your theme here. -->
</style>
现在有一个新的错误
01-17 20:12:03.071 27036-27036/com.example.thereaper.thaparexpress E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.thereaper.thaparexpress, PID: 27036
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.thereaper.thaparexpress/com.example.thereaper.thaparexpress.Main}: java.lang.IllegalArgumentException: View android.widget.ListView{2c9eb14c VFED.VC. ......I. 0,0-0,0 #7f090041 app:id/list_sliderMenu} is not a sliding drawer
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.IllegalArgumentException: View android.widget.ListView{2c9eb14c VFED.VC. ......I. 0,0-0,0 #7f090041 app:id/list_sliderMenu} is not a sliding drawer
at android.support.v4.widget.DrawerLayout.closeDrawer(DrawerLayout.java:1306)
at com.example.thereaper.thaparexpress.Main.displayView(Main.java:203)
at com.example.thereaper.thaparexpress.Main.onCreate(Main.java:115)
at android.app.Activity.performCreate(Activity.java:5953)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access0(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
您正在使用 2 个活动：Activity 和 ActionBarActivity。后者来自支持包，需要 AppCompat 主题。
这意味着 Activity 正在使用 AppCompat 主题，getActionBar() 将 return 为空。
您的选择：
让 Main 扩展
ActionBarActivity并将getActionBar替换为getSupportActionBar。两个活动都扩展
Activity并将您的主题更改为更新的主题，例如：Holo:<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar"> </style>
您可以更改 style.xml 文件。 例如：
<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar"> <!-- Customize your theme here. --> </style>并在 .java 文件后扩展 Activity class。 例如：
public class MainActivity extends Activity {.....}
解决方案 - 在 styles.xml 中将父级从 'android:Theme.Light' 更改为 'android:Theme.Holo.Light.DarkActionBar' 解决了空指针异常。
<resources>
<!-- style name="AppTheme" parent="android:Theme.Light" -->
<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar">
<item name="android:displayOptions">useLogo</item>
</style>
</resources>
我从
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
</style>
至
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
</style>
这解决了我的错误....