如何創建android自定義操作欄

Question

我想在Activity中創建自定義操作欄。運行后，應用程序崩潰並在處獲取空指針異常。原因：java.lang.NullPointerException：嘗試在其上調用虛擬方法'void android.app.ActionBar.setDisplayShowHomeEnabled（boolean）'空對象引用。謝謝。

她是我的CustomActionBar xml文件代碼

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >

    <FrameLayout
        android:layout_width="fill_parent"
        android:layout_height="45dp">

        <RelativeLayout
            android:padding="2dp"
            android:layout_width="match_parent"
            android:layout_height="45dp"
            android:layout_gravity="fill_horizontal"
            android:background="#3A86CF"

            >
            <ImageView
                android:id="@+id/imgOptions"
                android:layout_width="30dp"
                android:layout_height="30dp"
                android:layout_alignParentLeft="true"
                android:scaleType="centerInside"
                android:src="@drawable/white_three_dots"
                android:layout_centerVertical="true"/>

            <TextView
                android:id="@+id/txtTitle"
                android:layout_width="wrap_content"
                android:layout_height="30dp"
                android:layout_marginLeft="150dp"
                android:gravity="center_vertical|center_horizontal"
                android:text="Posts"
                android:textColor="@android:color/white"  android:layout_centerVertical="true"/>


            <ImageView
                android:id="@+id/imgSearchButton"
                android:layout_width="30dp"
                android:layout_height="30dp"
                android:layout_toLeftOf="@+id/imgAdd"
                android:layout_centerVertical="true"
                android:src="@android:drawable/ic_menu_search"
                android:layout_marginRight="2dp"/>

            <ImageView
                android:id="@+id/imgAdd"
                android:layout_width="30dp"
                android:layout_height="30dp"
                android:layout_alignParentRight="true"
                android:src="@android:drawable/ic_menu_add"
                android:layout_centerVertical="true"/>



        </RelativeLayout>

    </FrameLayout>


</RelativeLayout>

這是我的班級代碼

public class CustomActionActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.all_post);

        ActionBar mActionBar = getActionBar();
        mActionBar.setDisplayShowHomeEnabled(false);
        mActionBar.setDisplayShowTitleEnabled(false);
        LayoutInflater mInflater = LayoutInflater.from(this);

        View mCustomView = mInflater.inflate(R.layout.custom_actionbar, null);


        mActionBar.setCustomView(mCustomView);
        mActionBar.setDisplayShowCustomEnabled(true);
    }

}

這是我的原木貓

12-03 16:48:43.318  28201-28201/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.tazeen.classnkk, PID: 28201
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tazeen.classnkk/com.example.tazeen.classnkk.CustomActionActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayShowHomeEnabled(boolean)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2329)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2389)
            at android.app.ActivityThread.access$900(ActivityThread.java:147)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1296)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            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:898)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayShowHomeEnabled(boolean)' on a null object reference
            at com.example.tazeen.classnkk.CustomActionActivity.onCreate(CustomActionActivity.java:20)
            at android.app.Activity.performCreate(Activity.java:5933)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2282)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2389)
            at android.app.ActivityThread.access$900(ActivityThread.java:147)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1296)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            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:898)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
12-03 16:48:43.320      649-665/? W/ActivityManager﹕ Force finishing activity com.example.tazeen.classnkk/.CustomActionActivity
12-03 16:48:43.624      649-665/? I/WindowManager﹕ Screenshot max retries 4 of Token{f908566 ActivityRecord{5a6e9c1 u0 com.example.tazeen.classnkk/.CustomActionActivity t10131 f}} appWin=Window{58f91f2 u0 Starting com.example.tazeen.classnkk} drawState=3
12-03 16:48:43.624      649-665/? E/ActivityManager﹕ Invalid thumbnail dimensions: 384x384

Answer 1

更正了以下代碼：

public class CustomActionActivity extends AppCompactActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.all_post);

    ActionBar mActionBar =  getSupportActionBar();

    LayoutInflater mInflater = LayoutInflater.from(this);

    View mCustomView = mInflater.inflate(R.layout.custom_actionbar, null);

    mActionBar.setDisplayShowHomeEnabled(false);
    mActionBar.setDisplayShowTitleEnabled(false);

    mActionBar.setCustomView(mCustomView);
    mActionBar.setDisplayShowCustomEnabled(true);
}

}

刪除了ActionBar，請使用ToolBar

此處： Android工具欄，而不是操作欄