Android ActionBar 始终为空
Android ActionBar always null
我有一个 activity，带有一个在片段之间轻弹的导航抽屉。没什么特别的。
但是我想要的是操作栏出现在 activity 的顶部。问题是我一直得到 nullpointerexception 的 Actionbar。
我试过以下页面的答案：
getActionBar returns null
getActionBar() returns Null (AppCompat-v7 21)
None 其中有效，所以我想我会用我自己的代码提交我自己的问题。
MainActivity.java
package com.jampez.smalltalk;
import com.jampez.smalltalk.fragments.HomeFragment;
import com.jampez.smalltalk.fragments.MessageFragment;
import com.jampez.smalltalk.fragments.PreferencesFragment;
import com.jampez.smalltalk.fragments.SettingsFragment;
import com.jampez.smalltalk.helper.SessionManager;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarDrawerToggle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends FragmentActivity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
private String[] items;
int selectedPosition;
private SessionManager session;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getActionBar().setTitle("");
// Session manager
session = new SessionManager(getApplicationContext());
if (!session.isLoggedIn()) {
// User is already logged in. Take him to main activity
Intent intent = new Intent(MainActivity.this, LoginActivity.class);
startActivity(intent);
finish();
}
items = getResources().getStringArray(R.array.menus);
// Getting reference to the DrawerLayout
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.drawer_list);
/* Creating an ArrayAdapter to add items to mDrawerList */
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.drawer_list_item, items);
mDrawerList.setAdapter(adapter);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer,
R.string.drawer_open) {
/* Called when drawer is closed */
public void onDrawerClosed(View view) {
//Put your code here
}
/* Called when a drawer is opened */
public void onDrawerOpened(View drawerView) {
//Put your code here
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
// Enabling Home button
getActionBar().setHomeButtonEnabled(true);
getActionBar().setDisplayHomeAsUpEnabled(true);
// Setting item click listener for the listview mDrawerList
mDrawerList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectedPosition = position;
/* Replace fragment content */
displayView(position);
/* Closing the drawer */
mDrawerLayout.closeDrawer(mDrawerList);
}
});
/* Setting default fragment */
selectedPosition = 0;
displayView(0);
}
private void displayView(int position) {
// update the main content by replacing fragments
android.app.Fragment fragment = null;
Log.i("position", position+"");
switch (position) {
case 0:
fragment = new HomeFragment();
break;
case 1:
fragment = new MessageFragment();
break;
case 2:
fragment = new PreferencesFragment();
break;
case 3:
fragment = new SettingsFragment();
break;
case 4:
Intent sendIntent = new Intent();
sendIntent.setAction(Intent.ACTION_SEND);
sendIntent.putExtra(Intent.EXTRA_TEXT, "This is my text to send.");
sendIntent.setType("text/plain");
startActivity(sendIntent);
break;
case 5:
String url = "http://www.example.com";
Intent i = new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse(url));
startActivity(i);
break;
default:
break;
}
if (fragment != null) {
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content_frame, fragment);
fragmentTransaction.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
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
mDrawerToggle.syncState();
}
}
activity_main.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"
android:theme="@android:style/Theme.WithActionBar" >
<!-- The main content view -->
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<!-- The navigation drawer list-->
<ListView
android:id="@+id/drawer_list"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:background="#111"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp" />
</android.support.v4.widget.DrawerLayout>
HomeFragment.java
package com.jampez.smalltalk.fragments;
import com.jampez.smalltalk.R;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class HomeFragment extends Fragment {
public HomeFragment(){}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_home, container, false);
//getActivity().getActionBar().setTitle(R.string.home);
return rootView;
}
}
fragment_home.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#e5e5e5"
android:orientation="vertical" >
<TextView
android:id="@+id/home_text"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:layout_gravity="start|center_vertical"
android:text="@string/home"/>
</LinearLayout>
Android 清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.jampez.smalltalk"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="23" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.USE_CREDENTIALS" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<!-- To auto-complete the email text field in the login form with the user's emails -->
<uses-permission android:name="android.permission.READ_PROFILE" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<application
android:name=".app.AppController"
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<meta-data
android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
<meta-data
android:name="com.facebook.sdk.ApplicationId"
android:value="@string/facebook_app_id" />
<activity
android:name=".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=".LoginActivity"
android:label="@string/app_name"
android:windowSoftInputMode="adjustResize|stateHidden" >
</activity>
<activity
android:name="com.facebook.FacebookActivity"
android:configChanges="keyboard|keyboardHidden|screenLayout|screenSize|orientation"
android:label="@string/app_name"
android:theme="@android:style/Theme.Translucent.NoTitleBar" />
</application>
styles.xml
<resources>
<!--
Base application theme, dependent on API level. This theme is replaced
by AppBaseTheme from res/values-vXX/styles.xml on newer devices.
-->
<style name="AppBaseTheme" parent="android:Theme.Holo.Light.DarkActionBar">
<!--
Theme customizations available in newer API levels can go in
res/values-vXX/styles.xml, while customizations related to
backward-compatibility can go here.
-->
</style>
<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
<!-- All customizations that are NOT specific to a particular API-level can go here. -->
<item name="android:actionBarStyle">@style/MyActionBar</item>
<item name="android:actionOverflowButtonStyle">@style/MyActionButtonOverflow</item>
<item name="drawerArrowStyle">@style/DrawerArrowStyle</item>
</style>
<style name="DrawerArrowStyle" parent="Widget.AppCompat.DrawerArrowToggle">
<item name="spinBars">true</item>
<item name="color">@color/white</item>
</style>
<style name="MyActionButtonOverflow" parent="android:style/Widget.Holo.ActionButton.Overflow">
<item name="android:color">@color/white</item>
</style>
<style name="MyActionBar" parent="@android:style/Widget.Holo.Light.ActionBar">
<item name="android:background">#25a0da</item>
</style>
Logcat输出
11-08 19:17:38.618: E/AndroidRuntime(6347): FATAL EXCEPTION: main
11-08 19:17:38.618: E/AndroidRuntime(6347): Process: com.jampez.smalltalk, PID: 6347
11-08 19:17:38.618: E/AndroidRuntime(6347): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jampez.smalltalk/com.jampez.smalltalk.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2658)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.access0(ActivityThread.java:172)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.os.Handler.dispatchMessage(Handler.java:102)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.os.Looper.loop(Looper.java:145)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.main(ActivityThread.java:5832)
11-08 19:17:38.618: E/AndroidRuntime(6347): at java.lang.reflect.Method.invoke(Native Method)
11-08 19:17:38.618: E/AndroidRuntime(6347): at java.lang.reflect.Method.invoke(Method.java:372)
11-08 19:17:38.618: E/AndroidRuntime(6347): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
11-08 19:17:38.618: E/AndroidRuntime(6347): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
11-08 19:17:38.618: E/AndroidRuntime(6347): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
11-08 19:17:38.618: E/AndroidRuntime(6347): at com.jampez.smalltalk.MainActivity.onCreate(MainActivity.java:37)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.Activity.performCreate(Activity.java:6221)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2611)
11-08 19:17:38.618: E/AndroidRuntime(6347): ... 10 more
如果您根本没有获得 ActionBar，就像 visualy 一样，请尝试重写您的 Activity 以便您能够使用 AppCompatActivity。 thread suggests to use ActionbarActivity instead of FragmentActivity. Since ActionbarActivity is deprecated, AppCompatActivity 。
对于空指针问题：
始终与您使用的内容保持一致。如果您决定使用 AppCompat，请确保您正在扩展 AppCompatActivity。仔细检查所有导入 - 您可能使用的是普通 Fragment 而不是 AppCompat 版本。
检查您的样式并确保使用 AppCompat parents 而不是 holo parents。这也包括你的 Actionbar。而不是 Widget.Holo.Light.ActionBar 使用 parent="@style/Widget.AppCompat.Light.ActionBar"。
始终调用 getSupportActionBar 而不是 getActionBar()。有时甚至可能需要将片段中使用 getActivity() 获得的 Activity 转换为 AppCompatActivity 以确保获得正确的 ((AppCompatActivity)getActivity()).getSupportActionBar().setTitle("");。
*首先在你的 gradle 文件中包含这个依赖项
compile 'com.android.support:appcompat-v7:22.2.0'
*您应该将 activity 扩展到 AppCompactActivity 并开始使用 toolbar 而不是 ActionBar.
*这就是您在 MainActivity
中使用工具栏的方式
public class MainActivity extends AppCompatActivity {
private Toolbar mToolbar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mToolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(mToolbar);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
}
*这是在 activity_main.xml
中添加工具栏的方法
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="?attr/actionBarSize"
android:background="?attr/colorPrimary"
local:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
local:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
*你的主题应该是这样的 styles.xml
<style name="MyMaterialTheme" parent="MyMaterialTheme.Base">
</style>
<style name="MyMaterialTheme.Base" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="windowNoTitle">true</item>
<item name="windowActionBar">false</item>
<item name="colorPrimary">@color/colorPrimary</item>
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="colorAccent">@color/colorAccent</item>
</style>
确保在您的应用程序的清单中添加此样式名称。
*使用v4.app.Fragment比使用Fragment更好
*这是您应该如何从 片段 class
中设置标题
((AppCompatActivity)getActivity()).getSupportActionBar().setTitle(R.string.home);
参考this清晰的教程，它一定会帮助你设置material导航抽屉。
如果您想快速上手而不会有太多痛苦，那么您可以尝试集成 this 第三方库。
好的 none 发布的答案让我取得了很大的成功。然而，我设法显示了操作栏，但功能有限。
我做的第一件事是用 android-support-v7-appcompat 替换 appcompat_v7 库。这样做允许我使用 getActionBar().
调用操作栏
限制来自试图控制操作栏的各个方面。我可以很好地设置标题和图标，但如果我尝试使用 ActionBarDrawerToggle，我会得到一个 NullPointerException。我还注意到，在正常情况下打开抽屉时，点击操作栏不会执行任何操作。
你试过把getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
在你的 onCreate() 方法中？它帮助了我一次。也尝试将主题更改为 Holo
我有一个 activity，带有一个在片段之间轻弹的导航抽屉。没什么特别的。
但是我想要的是操作栏出现在 activity 的顶部。问题是我一直得到 nullpointerexception 的 Actionbar。
我试过以下页面的答案：
getActionBar returns null
getActionBar() returns Null (AppCompat-v7 21)
None 其中有效，所以我想我会用我自己的代码提交我自己的问题。
MainActivity.java
package com.jampez.smalltalk;
import com.jampez.smalltalk.fragments.HomeFragment;
import com.jampez.smalltalk.fragments.MessageFragment;
import com.jampez.smalltalk.fragments.PreferencesFragment;
import com.jampez.smalltalk.fragments.SettingsFragment;
import com.jampez.smalltalk.helper.SessionManager;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarDrawerToggle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends FragmentActivity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
private String[] items;
int selectedPosition;
private SessionManager session;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getActionBar().setTitle("");
// Session manager
session = new SessionManager(getApplicationContext());
if (!session.isLoggedIn()) {
// User is already logged in. Take him to main activity
Intent intent = new Intent(MainActivity.this, LoginActivity.class);
startActivity(intent);
finish();
}
items = getResources().getStringArray(R.array.menus);
// Getting reference to the DrawerLayout
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.drawer_list);
/* Creating an ArrayAdapter to add items to mDrawerList */
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.drawer_list_item, items);
mDrawerList.setAdapter(adapter);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer,
R.string.drawer_open) {
/* Called when drawer is closed */
public void onDrawerClosed(View view) {
//Put your code here
}
/* Called when a drawer is opened */
public void onDrawerOpened(View drawerView) {
//Put your code here
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
// Enabling Home button
getActionBar().setHomeButtonEnabled(true);
getActionBar().setDisplayHomeAsUpEnabled(true);
// Setting item click listener for the listview mDrawerList
mDrawerList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectedPosition = position;
/* Replace fragment content */
displayView(position);
/* Closing the drawer */
mDrawerLayout.closeDrawer(mDrawerList);
}
});
/* Setting default fragment */
selectedPosition = 0;
displayView(0);
}
private void displayView(int position) {
// update the main content by replacing fragments
android.app.Fragment fragment = null;
Log.i("position", position+"");
switch (position) {
case 0:
fragment = new HomeFragment();
break;
case 1:
fragment = new MessageFragment();
break;
case 2:
fragment = new PreferencesFragment();
break;
case 3:
fragment = new SettingsFragment();
break;
case 4:
Intent sendIntent = new Intent();
sendIntent.setAction(Intent.ACTION_SEND);
sendIntent.putExtra(Intent.EXTRA_TEXT, "This is my text to send.");
sendIntent.setType("text/plain");
startActivity(sendIntent);
break;
case 5:
String url = "http://www.example.com";
Intent i = new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse(url));
startActivity(i);
break;
default:
break;
}
if (fragment != null) {
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content_frame, fragment);
fragmentTransaction.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
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
mDrawerToggle.syncState();
}
}
activity_main.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"
android:theme="@android:style/Theme.WithActionBar" >
<!-- The main content view -->
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<!-- The navigation drawer list-->
<ListView
android:id="@+id/drawer_list"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:background="#111"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp" />
</android.support.v4.widget.DrawerLayout>
HomeFragment.java
package com.jampez.smalltalk.fragments;
import com.jampez.smalltalk.R;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class HomeFragment extends Fragment {
public HomeFragment(){}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_home, container, false);
//getActivity().getActionBar().setTitle(R.string.home);
return rootView;
}
}
fragment_home.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#e5e5e5"
android:orientation="vertical" >
<TextView
android:id="@+id/home_text"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:layout_gravity="start|center_vertical"
android:text="@string/home"/>
</LinearLayout>
Android 清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.jampez.smalltalk"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="23" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.USE_CREDENTIALS" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<!-- To auto-complete the email text field in the login form with the user's emails -->
<uses-permission android:name="android.permission.READ_PROFILE" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<application
android:name=".app.AppController"
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<meta-data
android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
<meta-data
android:name="com.facebook.sdk.ApplicationId"
android:value="@string/facebook_app_id" />
<activity
android:name=".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=".LoginActivity"
android:label="@string/app_name"
android:windowSoftInputMode="adjustResize|stateHidden" >
</activity>
<activity
android:name="com.facebook.FacebookActivity"
android:configChanges="keyboard|keyboardHidden|screenLayout|screenSize|orientation"
android:label="@string/app_name"
android:theme="@android:style/Theme.Translucent.NoTitleBar" />
</application>
styles.xml
<resources>
<!--
Base application theme, dependent on API level. This theme is replaced
by AppBaseTheme from res/values-vXX/styles.xml on newer devices.
-->
<style name="AppBaseTheme" parent="android:Theme.Holo.Light.DarkActionBar">
<!--
Theme customizations available in newer API levels can go in
res/values-vXX/styles.xml, while customizations related to
backward-compatibility can go here.
-->
</style>
<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
<!-- All customizations that are NOT specific to a particular API-level can go here. -->
<item name="android:actionBarStyle">@style/MyActionBar</item>
<item name="android:actionOverflowButtonStyle">@style/MyActionButtonOverflow</item>
<item name="drawerArrowStyle">@style/DrawerArrowStyle</item>
</style>
<style name="DrawerArrowStyle" parent="Widget.AppCompat.DrawerArrowToggle">
<item name="spinBars">true</item>
<item name="color">@color/white</item>
</style>
<style name="MyActionButtonOverflow" parent="android:style/Widget.Holo.ActionButton.Overflow">
<item name="android:color">@color/white</item>
</style>
<style name="MyActionBar" parent="@android:style/Widget.Holo.Light.ActionBar">
<item name="android:background">#25a0da</item>
</style>
Logcat输出
11-08 19:17:38.618: E/AndroidRuntime(6347): FATAL EXCEPTION: main
11-08 19:17:38.618: E/AndroidRuntime(6347): Process: com.jampez.smalltalk, PID: 6347
11-08 19:17:38.618: E/AndroidRuntime(6347): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jampez.smalltalk/com.jampez.smalltalk.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2658)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.access0(ActivityThread.java:172)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.os.Handler.dispatchMessage(Handler.java:102)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.os.Looper.loop(Looper.java:145)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.main(ActivityThread.java:5832)
11-08 19:17:38.618: E/AndroidRuntime(6347): at java.lang.reflect.Method.invoke(Native Method)
11-08 19:17:38.618: E/AndroidRuntime(6347): at java.lang.reflect.Method.invoke(Method.java:372)
11-08 19:17:38.618: E/AndroidRuntime(6347): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
11-08 19:17:38.618: E/AndroidRuntime(6347): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
11-08 19:17:38.618: E/AndroidRuntime(6347): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
11-08 19:17:38.618: E/AndroidRuntime(6347): at com.jampez.smalltalk.MainActivity.onCreate(MainActivity.java:37)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.Activity.performCreate(Activity.java:6221)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
11-08 19:17:38.618: E/AndroidRuntime(6347): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2611)
11-08 19:17:38.618: E/AndroidRuntime(6347): ... 10 more
如果您根本没有获得 ActionBar，就像 visualy 一样，请尝试重写您的 Activity 以便您能够使用 AppCompatActivity。
对于空指针问题：
始终与您使用的内容保持一致。如果您决定使用 AppCompat，请确保您正在扩展 AppCompatActivity。仔细检查所有导入 - 您可能使用的是普通 Fragment 而不是 AppCompat 版本。
检查您的样式并确保使用 AppCompat parents 而不是 holo parents。这也包括你的 Actionbar。而不是 Widget.Holo.Light.ActionBar 使用 parent="@style/Widget.AppCompat.Light.ActionBar"。
始终调用 getSupportActionBar 而不是 getActionBar()。有时甚至可能需要将片段中使用 getActivity() 获得的 Activity 转换为 AppCompatActivity 以确保获得正确的 ((AppCompatActivity)getActivity()).getSupportActionBar().setTitle("");。
*首先在你的 gradle 文件中包含这个依赖项
compile 'com.android.support:appcompat-v7:22.2.0'
*您应该将 activity 扩展到 AppCompactActivity 并开始使用 toolbar 而不是 ActionBar.
*这就是您在 MainActivity
中使用工具栏的方式public class MainActivity extends AppCompatActivity {
private Toolbar mToolbar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mToolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(mToolbar);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
}
*这是在 activity_main.xml
中添加工具栏的方法<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="?attr/actionBarSize"
android:background="?attr/colorPrimary"
local:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
local:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
*你的主题应该是这样的 styles.xml
<style name="MyMaterialTheme" parent="MyMaterialTheme.Base">
</style>
<style name="MyMaterialTheme.Base" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="windowNoTitle">true</item>
<item name="windowActionBar">false</item>
<item name="colorPrimary">@color/colorPrimary</item>
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="colorAccent">@color/colorAccent</item>
</style>
确保在您的应用程序的清单中添加此样式名称。
*使用v4.app.Fragment比使用Fragment更好
*这是您应该如何从 片段 class
中设置标题((AppCompatActivity)getActivity()).getSupportActionBar().setTitle(R.string.home);
参考this清晰的教程，它一定会帮助你设置material导航抽屉。
如果您想快速上手而不会有太多痛苦，那么您可以尝试集成 this 第三方库。
好的 none 发布的答案让我取得了很大的成功。然而，我设法显示了操作栏，但功能有限。
我做的第一件事是用 android-support-v7-appcompat 替换 appcompat_v7 库。这样做允许我使用 getActionBar().
限制来自试图控制操作栏的各个方面。我可以很好地设置标题和图标，但如果我尝试使用 ActionBarDrawerToggle，我会得到一个 NullPointerException。我还注意到，在正常情况下打开抽屉时，点击操作栏不会执行任何操作。
你试过把getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
在你的 onCreate() 方法中？它帮助了我一次。也尝试将主题更改为 Holo