Change TextView Text in an Android Fragment

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I have TextView within a Fragment (a flip). How do I change the text of this TextView ? Here you are giving NullPointer 

qtAllImagensLabel = (TextView)findViewById(R.id.qtAllImagensLabel);

qtAllImagensLabel.setText("texto");

I have already tried to initialize the TextView within onCreateView() , and already tried to change the text inside a Handler . When I try to change within a Handler , it does not change but not NullPointer

Edit: I start the variables globally and in onCreateView() do they get findViewById() 

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_umclique_tab, container, false);

        qtAllImagensLabel = (TextView)findViewById(R.id.qtAllImagensLabel);
        qtAllVideosLabel = (TextView)findViewById(R.id.qtAllVideosLabel);
        qtAllAudioLabel = (TextView)findViewById(R.id.qtAllAudioLabel);

        return view;
}

So far so good, but I tried to set the text in and out of onCreate() , within Button , but not.

Error: 

java.lang.RuntimeException: Unable to start activity ComponentInfo{br.com.tupinikimtecnologia.whatsappmediahidder/br.com.tupinikimtecnologia.whatsappmediahidder.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2216)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5140)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:611)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at br.com.tupinikimtecnologia.whatsappmediahidder.MainActivity.onCreate(MainActivity.java:103)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2170)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5140)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:611)
            at dalvik.system.NativeStart.main(Native Method)

If I put it inside a handler, it does not make a mistake, but it does not change the text either.

Fragment Layout: 

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

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/relative1"
        android:layout_marginBottom="20dp">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="@string/umclique_tab_descricao_label"
            android:id="@+id/textView" />
    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/relative2"
        android:layout_weight="1"
        android:background="@drawable/umclique_tab_border">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="@string/umclique_tab_titulo_imagem"
            android:id="@+id/imagensTituloLabel"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="@string/umclique_tab_qt_imagem"
            android:id="@+id/visEsconderLabel1"
            android:layout_below="@+id/imagensTituloLabel"
            android:layout_centerHorizontal="true" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="@string/umclique_tab_qt_all_label"
            android:id="@+id/qtAllImagensLabel"
            android:layout_alignTop="@+id/visEsconderLabel1"
            android:layout_toRightOf="@+id/visEsconderLabel1"
            android:layout_marginLeft="5dp" />

        <Button
            android:layout_width="130dp"
            android:layout_height="wrap_content"
            android:text="@string/umclique_tab_botao_revelar"
            android:id="@+id/mostrarButton1"
            android:layout_below="@+id/visEsconderLabel1"
            style="@style/ButtonVerdeMostrar"
            android:layout_toLeftOf="@+id/imagensTituloLabel"
            android:onClick="mostrarImagensUmCliqueTab" />

        <Button
            android:layout_width="130dp"
            android:layout_height="wrap_content"
            android:text="@string/umclique_tab_botao_esconder"
            android:id="@+id/esconderButton1"
            android:layout_below="@+id/visEsconderLabel1"
            android:layout_toRightOf="@+id/imagensTituloLabel"
            style="@style/ButtonVermelhoEsconder"
            android:onClick="esconderImagensUmCliqueTab" />

    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/relativeLayout"
        android:layout_weight="1"
        android:background="@drawable/umclique_tab_border">

        <Button
            android:layout_width="130dp"
            android:layout_height="wrap_content"
            android:text="@string/umclique_tab_botao_revelar"
            android:id="@+id/mostrarButton2"
            android:layout_alignWithParentIfMissing="false"
            android:layout_below="@+id/visEsconderLabel2"
            android:layout_toLeftOf="@+id/textView6"
            style="@style/ButtonVerdeMostrar"
            android:onClick="mostrarVideosUmCliqueTab" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="@string/umclique_tab_titulo_video"
            android:id="@+id/textView6"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="@string/umclique_tab_qt_video"
            android:id="@+id/visEsconderLabel2"
            android:layout_below="@+id/textView6"
            android:layout_centerHorizontal="true" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="@string/umclique_tab_qt_all_label"
            android:id="@+id/qtAllVideosLabel"
            android:layout_alignTop="@+id/visEsconderLabel2"
            android:layout_toRightOf="@+id/visEsconderLabel2"
            android:layout_marginLeft="5dp" />

        <Button
            android:layout_width="130dp"
            android:layout_height="wrap_content"
            android:text="@string/umclique_tab_botao_esconder"
            android:id="@+id/esconderButton2"
            android:layout_alignTop="@+id/mostrarButton2"
            android:layout_toRightOf="@+id/textView6"
            style="@style/ButtonVermelhoEsconder"
            android:onClick="esconderVideosUmCliqueTab" />
    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/relativeLayout2"
        android:layout_weight="1"
        android:background="@color/preto">

        <Button
            android:layout_width="130dp"
            android:layout_height="wrap_content"
            android:text="@string/umclique_tab_botao_revelar"
            android:id="@+id/mostrarButton3"
            android:layout_below="@+id/visEsconderLabel3"
            android:layout_toLeftOf="@+id/textView9"
            style="@style/ButtonVerdeMostrar" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="@string/umclique_tab_titulo_audio"
            android:id="@+id/textView9"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="@string/umclique_tab_qt_audio"
            android:id="@+id/visEsconderLabel3"
            android:layout_below="@+id/textView9"
            android:layout_centerHorizontal="true" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="@string/umclique_tab_qt_all_label"
            android:id="@+id/qtAllAudioLabel"
            android:layout_alignTop="@+id/visEsconderLabel3"
            android:layout_toRightOf="@+id/visEsconderLabel3"
            android:layout_marginLeft="5dp" />

        <Button
            android:layout_width="130dp"
            android:layout_height="wrap_content"
            android:text="@string/umclique_tab_botao_esconder"
            android:id="@+id/esconderButton3"
            android:layout_below="@+id/visEsconderLabel3"
            android:layout_toRightOf="@+id/textView9"
            style="@style/ButtonVermelhoEsconder" />
    </RelativeLayout>

</LinearLayout>
    
asked by anonymous 15.07.2014 / 18:17

1 answer

4

There is a mistake in this code, this is referring to Fragment but this code is running in a Activity correct? I say this because only the Activity class (by taking Views ) has the findViewById method, at documentation of class Fragment does not have this method.

The problem you're encountering is because of a life-cycle issue, the onCreateView method in Activity is called to inflate layout of Activity , which in turn has the tag declaration <fragment> correct, will start Fragment by calling its onCreate and later onCreateView .

The cycle would be something like:

  • Activity.onCreate
  • Activity.onCreateView
  • Fragment.onAttach
  • Fragment.onCreate
  • Fragment.onCreateView

    • More details on Fragment LifeCycle

    And when you make findViewById by elements of Fragment in method onCreateView , it does not yet exist and is not built. So it does not find the elements, and in addition, Root View of Activity was not built completely, just inflated. So you can not use findViewById , you would have to use view.findViewById to find elements of this layout, not the Fragment layout.

    Looking at this layout, to use Fragment would have to have a layout for Activity in this way (I believe you're using it right?): 

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

    <fragment
        android:id="@+id/id_do_fragment"
        android:name="pacote.da.classe.ClasseDoFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:tag="@string/tag_do_fragment" />
</FrameLayout>

    You would use this layout as being of Activity and within the layout of Fragment what you put in the question.

    You will have to change the approach.

    In this case I suggest two simple ( recommend the first ):

  • Migrate these references to Fragment , using the onCreateView method of Fragment to initialize them. The code would look very much like the current one, except the logic changes that are recommended, because it ends up delegating some responsibilities to Fragment . Making the code less coupled (if done right) and more modularizable.

  • Or use the onViewCreated method of Fragment to notify Activity (using Listener or the Activity itself) that View has been built and is safe to access. >

    No Fragment: 

     @Override
 public void onViewCreated (View view, Bundle savedInstanceState) {
     ((SuaActivity) getActivity()).onFragmentViewCreated(view); // Metodo que deve ser implementado na Activity
 }

    In Activity: 

     public void onFragmentViewCreated(View view) {
     // Iniciar os campos buscando no layout do Fragment
     qtAllImagensLabel = (TextView) view.findViewById(R.id.qtAllImagensLabel);
     qtAllVideosLabel = (TextView) view.findViewById(R.id.qtAllVideosLabel);
     qtAllAudioLabel = (TextView) view.findViewById(R.id.qtAllAudioLabel);
 }
    • 15.07.2014 / 19:29
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