Android 오류 [null 개체 참조에서 가상 메서드 'void android.app.ActionBar'호출 시도]

Android 오류 [null 개체 참조에서 가상 메서드 'void android.app.ActionBar'호출 시도]

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탐색 서랍이있는 viewpager를 구현하는 코드 모듈이 있지만 코드를 실행하면 다음 오류가 발생합니다.

01-26 09:20:02.958: D/AndroidRuntime(18779): Shutting down VM
01-26 09:20:02.959: E/AndroidRuntime(18779): FATAL EXCEPTION: main
01-26 09:20:02.959: E/AndroidRuntime(18779): Process: com.example.tabwithslidingdrawer, PID: 18779
01-26 09:20:02.959: E/AndroidRuntime(18779): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tabwithslidingdrawer/com.example.tabwithslidingdrawer.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.app.ActivityThread.access$800(ActivityThread.java:148)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.os.Handler.dispatchMessage(Handler.java:102)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.os.Looper.loop(Looper.java:135)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.app.ActivityThread.main(ActivityThread.java:5312)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at java.lang.reflect.Method.invoke(Native Method)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at java.lang.reflect.Method.invoke(Method.java:372)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
01-26 09:20:02.959: E/AndroidRuntime(18779): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
01-26 09:20:02.959: E/AndroidRuntime(18779):    at com.example.tabwithslidingdrawer.MainActivity.onCreate(MainActivity.java:95)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.app.Activity.performCreate(Activity.java:5953)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
01-26 09:20:02.959: E/AndroidRuntime(18779):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
01-26 09:20:02.959: E/AndroidRuntime(18779):    ... 10 more

09:20:02.959: E/AndroidRuntime(18779): Caused by:
java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null
object reference 01-26 09:20:02.959: E/AndroidRuntime(18779):     at
com.example.tabwithslidingdrawer.MainActivity.onCreate(MainActivity.java:95)

이 선을 가리킨다

// enabling action bar app icon and behaving it as a toggle button
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

전체 코드 http://pastebin.com/u1K72fr7

내 매니페스트

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.tabwithslidingdrawer"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/Theme.Tabwithpager" >
        <activity
            android:name="com.example.tabwithslidingdrawer.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>
    </application>

</manifest>

android : theme = "@ style / Theme.Tabwithpager"

코드 http://pastebin.com/EFQLzRej

================================================ ================ 편집 / 업데이트 :

이것에서 배운 것

이러한 오류가 발생할 때마다

1. 어떤 종류의 Activity가 사용되고 있는지, 간단한 android.app Activity인지 AppCompatActivity 또는 ActionBarActivity 등인지 확인합니다.

2. 연장 된 활동 유형이 compat 카테고리에 속하는지 확인하십시오.

예제 android.app 기반 Activity / Fragment는 appCompat 유형이 아닌 반면 android.support.v4.app.Fragment 또는 android.support.v4.app.ActivityCompat는 appCompat 기반입니다.

appCompat에 속하면 getSupportActionBar ()를 사용하고 android.app 유형에는 getActionBar ()를 사용할 수 있습니다.

3. 매니페스트 파일에서 해당 활동에 적용된 테마를 확인합니다.

예 : 매니페스트 파일에서 테마가 적용된 경우 android : theme = "@ android : style / Theme.Holo.Dialog"getActionBar ()가 작동합니다.

그러나 매니페스트의 활동에 적용된 테마가 android : theme = "@ style / Theme.AppCompat.Light"와 같으면 getSupportActionBar ()를 사용해야합니다.

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귀하의 코드는 다음과 com.example.tabwithslidingdrawer.MainActivity.onCreate(MainActivity.java:95)같습니다.

        // enabling action bar app icon and behaving it as toggle button
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

문제는 매우 간단합니다 . Activity새로운 android.support.v7.app.ActionBarActivity. getSupportActionBar()대신에 호출을 사용해야합니다 getActionBar().

코드의 65 행 주위를 살펴보면 이미 수행하고 있음을 알 수 있습니다.

        actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);
        // TODO: Remove the redundant calls to getSupportActionBar()
        //       and use variable actionBar instead
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);

그리고 87 번 줄을 아래로 내려 가면 같은 것을 알아 낸 것처럼 보입니다.

        getSupportActionBar().setTitle(
                        Html.fromHtml("<font color=\"black\">" + mTitle + " - "
                                        + menutitles[0] + "</font>"));
        // getActionBar().setTitle(mTitle +menutitles[0]);

어떻게 주석 처리했는지 확인하십시오 getActionBar().

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누군가 android.app.ActionBar 및 android.app.Activity 를 사용하려면 styles.xml 에서 앱 테마를 변경해야 합니다. 예를 들면 다음과 같습니다.

<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar">

문제는 AppCompat 테마를 사용하고있을 수 있다는 것 입니다.

On the other hand, if you want to use android.support.v7.app.ActionBar and you extend your activity with AppCompatActivity then you must use an AppCompat theme to avoid this issue, for example:

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

Hope this helps.

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when you extend appcompatActivity then use

this.getSupportActionBar().setDisplayHomeAsUpEnabled(true);

and when you extend ActionBar then use

this.getActionBar().setDisplayHomeAsUpEnabled(true);

dont forget to call this function in oncreate after initializing the toolbar/actionbar

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I think what you want to do is cast getActivity(). For example:

((AppCompatActivity)getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);

This is what you need to do with the new support libraries. AppCompatActivity has replaced ActionBarActivity.

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Try to check here

res >> values >> styles.xml

make sure that there no code like this

<item name="windowActionBar">false</item>

if there are code like that, you can disable for a while, or erase it

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When use AppCompatActivity must call

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

Before getSupportActionBar()

public class PageActivity extends AppCompatActivity {
     @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_item);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        this.getSupportActionBar().setDisplayHomeAsUpEnabled(false);

    }
}

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The Up Button is usually activated for Low-level Activities. In your manifest I only see the MainActivity. I don't think it makes sense to activate the up button for the main activity. Create an activity, then in the manifest add the parentActivityName attribute. Then activate the up button on the activity's onCreate method.
This should help.
https://developer.android.com/training/appbar/up-action.html

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In my case I had the same error but my mistake was that I didn't declare my Toolbar.

So, before I use getSupportActionBar I had to find my toolbar and set the actionBar

    appbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(appbar);

    getSupportActionBar().setHomeAsUpIndicator(R.drawable.ic_nav_menu);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

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For anyone else who has a BaseActivity, and a child that extends from it, make sure the super.onCreate() is called first before you do anything. The old Activity would work if you called super.onCreate() afterwards.

Child extends Activity - could call super after you did stuff

@Override
protected void onCreate(Bundle savedInstanceState)
{
    getActionBar().setDisplayHomeAsUpEnabled(true);
    super.onCreate(savedInstanceState);

Child extends AppCompatActivity - ya gotta call super first

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState); //do this first
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

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If you are using android.app.ActionBar and android.app.Activity you should change the app theme in application tag:

< application

android:theme="@android:style/Theme.Holo.Light" >

---

in this line in your activity:

super.onCreate(savedInstanceState);
setContentView(R.layout.Activity_Main);

use this:

super.onCreate(savedInstanceState);
setContentView(R.layout.*);

* is your activity

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In my case is because of styles.xml set the wrong parent theme, i.e. NoActionBar theme of course getSupportActionbar() is null:

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">

Changed it to something else fixed it:

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

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For those still having this issue, my issue was resolved in the AndroidManifest.xml file. Where it says <activity android:name=".MainActivity" android:theme="@style/AppTheme.NoActionBar">, you need to remove NoActionBar, making it <activity android:name=".MainActivity" android:theme="@style/AppTheme">, because with NoActionBar set the app doesnt know whether or not it wants an action bar when you call one up inside of MainActivity.java

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I got the same error once, I created a template for a default toolbar( toolbar.xml) and then in another view I created a collapsable toolbar.

I required to add the collapsable toolbar to a view that show some information of the user(like whatsapp), but the method findViewById was referencing the default toolbar(id toolbar), not the collapsable one( id toolbar as well) yes, I wrote the same id to both toolbar, so when I tried to access the activity the app crashed showing me the error.

I fixed the error by changing the id of the collapsable toolbar to id:col_toolbar and the error gone away and my app worked perfectly

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I know that this question is something old. But this can help many who present this problem.

To solve this problem, check if there is a point of nullity. Then apply the corresponding configuration:

if(getSupportActionBar() != null){
 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
 getSupportActionBar().setHomeButtonEnabled(true);
}

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You should try this one. I think it will work.

    Toolbar toolbar = findViewById(R.id.toolbar1);
    setSupportActionBar(toolbar);

    mDrawerLayout = findViewById(R.id.drawer_layout);
    mDrawerLayout = findViewById(R.id.drawer_layout);
    mDrawerLayout.setDrawerShadow(R.drawable.rectagle_with_black_outer,
            GravityCompat.START);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setHomeButtonEnabled(true);

    mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
            toolbar, R.string.navigation_drawer_close,
            R.string.navigation_drawer_close) {
        public void onDrawerClosed(View view) {
            invalidateOptionsMenu();
        }

        public void onDrawerOpened(View drawerView) {
            invalidateOptionsMenu();
        }
    };

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The best solution do this in your Oncreate method

 ActionBar actionBar = getSupportActionBar();

        if(actionBar != null){
            actionBar.setDisplayHomeAsUpEnabled(true);
        }

followed by a new class

@Override
    public boolean onOptionsItemSelected(MenuItem item) {

        int id = item.getItemId();

        if(id == android.R.id.home){
            onBackPressed();
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

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Try doing this:

                getSupportActionBar().setDisplayHomeAsUpEnabled(true);
                getSupportActionBar().setHomeButtonEnabled(true);
                actionBar = getSupportActionBar();
                actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);

Instead of this:

actionBar = getSupportActionBar();
                actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);

                getSupportActionBar().setDisplayHomeAsUpEnabled(true);
                getSupportActionBar().setHomeButtonEnabled(true);

참고URL : https://stackoverflow.com/questions/28144657/android-error-attempt-to-invoke-virtual-method-void-android-app-actionbar-on