Question

我正在尝试添加包含TabLayout视图的片段，但我一直收到错误：

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.support.design.widget.TabLayout$Tab android.support.design.widget.TabLayout.newTab()' on a null object reference
                                                                at ca.rev.revcore.MainActivity.onCreate(MainActivity.java:76)

这是我要添加的布局：

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.TabLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/rev_tablayout"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:theme="@style/RevStyle_PlaceNewBagBttn">

    <android.support.design.widget.TabItem
        android:id="@+id/tabItem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tab1" />

</android.support.design.widget.TabLayout>

这就是我试图添加它的方式：

 TabLayout tabLayout = (TabLayout) findViewById(R.id.rev_tablayout);

 tabLayout.addTab(tabLayout.newTab().setText("Upload"));
 tabLayout.addTab(tabLayout.newTab().setText("Pics"));
 tabLayout.addTab(tabLayout.newTab().setText("Vids"));
 tabLayout.addTab(tabLayout.newTab().setText("Papers"));

 tabLayout.getTabAt(0).setIcon(R.drawable.ic_publish_black_24dp);
 tabLayout.getTabAt(1).setIcon(R.drawable.ic_menu_camera);
 tabLayout.getTabAt(2).setIcon(R.drawable.ic_videocam_black_24dp);
 tabLayout.getTabAt(3).setIcon(R.drawable.ic_airplay_black_24dp);

我能错过什么？

Vielen dank im voraus。

Answer 1

如果您正在使用片段。变化

TabLayout tabLayout = (TabLayout) findViewById(R.id.rev_tablayout);

到

TabLayout tabLayout = (TabLayout) view.findViewById(R.id.rev_tablayout);

view是一个对象，它会使您的布局文件膨胀并以onCreateView()方法返回视图。

Answer 2

如果您正在使用片段。在你的oncreate视图中绑定这样的控件，你在那里夸大你的布局

View rootView = inflater.inflate(R.layout.fragment_, container, false);
TabLayout tabLayout = (TabLayout) rootView.findViewById(R.id.tablayout);

Answer 3

覆盖Fragment中的onCreateView（）方法，并对Fragment进行膨胀布局使用LayoutInflater Class对象并通过传递 ViewGroup参数，即片段所在的活动嵌入式。

<RelativeLayout 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"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:animateLayoutChanges="true"
            android:background="@color/transparent_black"
            tools:context="il.co.cambium.sport5radio.fragments.MediaPlayerFragment">

<!-- Loader container -->
<RelativeLayout
    android:id="@+id/mediaPlayerLoader"
    android:layout_width="124dp"
    android:layout_height="124dp"
    android:layout_centerInParent="true"
    android:visibility="gone">

    <!-- Circular image view -->
    <com.mikhaellopez.circularimageview.CircularImageView
        android:layout_width="122dp"
        android:layout_height="122dp"
        android:layout_centerInParent="true"
        android:src="@drawable/icon"
        app:civ_border="true"/>

    <!-- Loader-->
    <fr.castorflex.android.circularprogressbar.CircularProgressBar
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:indeterminate="true"
        app:cpb_color="@color/colorPrimary"
        app:cpb_max_sweep_angle="300"
        app:cpb_min_sweep_angle="10"
        app:cpb_stroke_width="5dp"/>

</RelativeLayout>

<!-- Video display -->
<SurfaceView
    android:id="@+id/mediaPlayerSurfaceView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    android:visibility="invisible"/>

<!-- Controls -->
<RelativeLayout
    android:id="@+id/controlsRootView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:visibility="invisible">

    <!-- Top Bar -->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:layout_alignParentTop="true"
        android:background="@color/transparent_black"
        android:orientation="horizontal">

        <!-- Minimize button + collapsed play button -->
        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:orientation="horizontal">

            <!-- Close icon -->
            <ImageButton
                android:id="@+id/videoBackBtn"
                android:layout_width="30dp"
                android:layout_height="30dp"
                android:layout_gravity="center_vertical"
                android:layout_marginLeft="5dp"
                android:background="@drawable/round_ripple_effect_player"
                android:scaleType="centerInside"
                android:src="@mipmap/player_ic_minimize"
                android:tint="@color/colorPrimaryDark"/>

            <!-- Button play -->
            <ImageButton
                android:id="@+id/collapsedPlayPauseBtn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical"
                android:background="@drawable/round_ripple_effect_player"
                android:padding="5dp"
                android:scaleType="centerInside"
                android:src="@drawable/icon_pause"
                android:visibility="gone"/>

        </LinearLayout>

        <!-- Title -->
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="24dp"
            android:layout_marginLeft="10dp"
            android:layout_marginRight="10dp"
            android:layout_marginTop="9dp"
            android:layout_weight="1"
            android:focusable="true"
            android:focusableInTouchMode="true">

            <TextView
                android:id="@+id/videoPlayerTitle"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:ellipsize="marquee"
                android:fadingEdge="horizontal"
                android:focusable="true"
                android:focusableInTouchMode="true"
                android:marqueeRepeatLimit="marquee_forever"
                android:scrollHorizontally="true"
                android:singleLine="true"
                android:textAppearance="?android:attr/textAppearanceMedium"
                android:textColor="@android:color/black"
                android:textSize="20dp"/>

        </LinearLayout>

        <!-- Live dot -->
        <ImageView
            android:id="@+id/fragmentMediaPlayerBlinkingCircle"
            android:layout_width="20dp"
            android:layout_height="20dp"
            android:layout_marginRight="10dp"
            android:layout_marginTop="10dp"
            android:layout_marginBottom="10dp"
            android:layout_gravity="center_vertical"
            android:scaleType="centerInside"
            android:src="@drawable/ic_circle"
            android:visibility="gone"/>

        <!-- Poster -->
        <ImageView
            android:id="@+id/mediaImage"
            android:layout_width="75dp"
            android:layout_height="48dp"
            android:scaleType="centerCrop"
            android:src="@drawable/icon"/>

    </LinearLayout>

    <!-- Bottom controls -->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:background="@color/transparent_black"
        android:layoutDirection="ltr"
        android:orientation="vertical"
        android:paddingBottom="4dp">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:orientation="horizontal">

            <!--<ImageButton
                android:id="@+id/media_prev"
                style="@android:style/MediaButton.Previous"/>-->

            <!--<ImageButton
                android:id="@+id/media_rew"
                style="@android:style/MediaButton.Rew"/>-->

            <!--<ImageButton
            android:id="@+id/media_play"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:src="@mipmap/notification_ic_play"
            android:background="@drawable/ripple_effect_player"
            android:visibility="gone"/>
            style="@android:style/MediaButton.Play"-->

            <ImageButton
                android:id="@+id/media_play_pause"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:padding="10dp"
                android:background="@drawable/round_ripple_effect_player"
                android:src="@drawable/icon_pause"/>
            <!--style="@android:style/MediaButton.Pause"-->

            <!--<ImageButton
            android:id="@+id/media_ffwd"
            style="@android:style/MediaButton.Ffwd"/>-->

            <!-- <ImageButton
                 android:id="@+id/media_next"
                 style="@android:style/MediaButton.Next"/>-->

        </LinearLayout>

        <LinearLayout
            android:id="@+id/fragmentMediaPlayerProgressContainer"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center_vertical"
            android:orientation="horizontal">

            <TextView
                android:id="@+id/media_position"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:includeFontPadding="false"
                android:paddingLeft="4dp"
                android:paddingRight="4dp"
                android:textColor="@color/black_semi_transparent"
                android:textSize="14sp"
                android:textStyle="bold"/>

            <SeekBar
                android:id="@+id/media_progress"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:padding="4dp"
                android:theme="@style/MyProgressBar"/>

            <TextView
                android:id="@+id/media_duration"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:includeFontPadding="false"
                android:paddingLeft="4dp"
                android:paddingRight="4dp"
                android:textColor="@color/black_semi_transparent"
                android:textSize="14sp"
                android:textStyle="bold"/>

        </LinearLayout>

    </LinearLayout>

</RelativeLayout>

<强>演示

TabLayout tabLayout = (TabLayout) your_View_OBJ.findViewById(R.id.rev_tablayout);

Answer 4

在activity_main xml中是否带有id rev_tablayout的标签布局，还是在片段的布局中？请检查您尝试访问tablayout的位置。

如何在Android中添加片段

4 个答案: