Question

I have 5 activities in a Tabhost. (i.e MainActivity.java Home.java, NowReading.java, Favorites.java, and Profile.java). In the main activity I’m loading the tabhost, as show below.

public class MainActivity extends TabActivity {
    TabHost tabHost;
    Context context = MainActivity.this;
    TextView txt_Login;
    View homeTabLayout;
    View reviewLayout;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        txt_Login = (TextView) findViewById(R.id.txt_Login);
        final Spinner spnrLanguage = (Spinner) findViewById(R.id.spnrLanguage);
        final Spinner spnrBrowseBy = (Spinner) findViewById(R.id.spnrBrowseBy);

        tabHost = getTabHost();

        // Android tab
        Intent intentHome = new Intent().setClass(this, Home.class);
        TabSpec tabSpecHome = tabHost
                .newTabSpec("Home")
                .setIndicator("Home",
                        getResources().getDrawable(R.drawable.home))
                .setContent(intentHome);

        tabHost.addTab(tabSpecHome);

        Intent intentNowReading = new Intent().setClass(this, NowReading.class);
        TabSpec tabSpecNowReading = tabHost
                .newTabSpec("Now Reading")

                .setIndicator("Now Reading",
                        getResources().getDrawable(R.drawable.now_reading))
                .setContent(intentNowReading);
        tabHost.addTab(tabSpecNowReading);

        Intent intentFavourite = new Intent().setClass(this, Favorites.class);
        TabSpec tabSpecFavourite = tabHost
                .newTabSpec("Favourite")
                .setIndicator("Favorites",
                        getResources().getDrawable(R.drawable.favorites))
                .setContent(intentFavourite);
        tabHost.addTab(tabSpecFavourite);

        Intent intentProfile = new Intent().setClass(this, Profile.class);
        TabSpec tabSpecProfile = tabHost
                .newTabSpec("Profile")
                .setIndicator("Profile",
                        getResources().getDrawable(R.drawable.profile))
                .setContent(intentProfile);
        tabHost.addTab(tabSpecProfile);
tabHost.setCurrentTabByTag("Home");

in the Mainactivity.java im setting The Home.java as current Tab. as

tabHost.setCurrentTabByTag("Home");

which loads the layout home_activity.xml in the setContentView.

here is the XML code

    <?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/frameLayout01"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <RelativeLayout
        android:id="@+id/rel_HomeLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <GridView
            android:id="@+id/gridview"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center"
            android:numColumns="auto_fit"
            android:stretchMode="columnWidth" >
        </GridView>
    </RelativeLayout>

    <ScrollView
        android:id="@+id/scroll_ReviewLayout"
        android:layout_width="fill_parent"
        android:layout_height="match_parent" >

        <RelativeLayout
            android:id="@+id/rel_ReviewLayout01"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" >

            <ImageView
                android:id="@+id/img_OverVuBookCoverPhoto"
                android:layout_width="130dp"
                android:layout_height="165dp"
                android:layout_margin="5dp"
                android:adjustViewBounds="true"
                android:background="@drawable/rounded_image_borders"
                android:paddingLeft="5dp"
                android:paddingRight="5dp"
                android:src="@drawable/book1" />

            <TextView
                android:id="@+id/txt_revwBookTitle"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignTop="@+id/img_OverVuBookCoverPhoto"
                android:layout_marginTop="10dp"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:text="The Basic Doctrine Of Islam"
                android:textColor="@color/White"
                android:textSize="12sp" />

            <TextView
                android:id="@+id/txt_revwAutherName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txt_revwBookTitle"
                android:layout_marginTop="2dp"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:text="By: Andrew J Newman"
                android:textColor="@color/SkyBlue"
                android:textSize="11sp" />

            <TextView
                android:id="@+id/txt_PublishDate"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txt_revwAutherName"
                android:layout_marginTop="2dp"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:text="Published: July, 30 2007"
                android:textColor="@color/DarkGray"
                android:textSize="11sp" />

            <RatingBar
                android:id="@+id/ratingbar"
                style="?android:attr/ratingBarStyleSmall"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txt_PublishDate"
                android:layout_marginBottom="6dp"
                android:layout_marginTop="6dp"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:isIndicator="false"
                android:numStars="5"
                android:rating="5"
                android:stepSize="1" />

            <Button
                android:id="@+id/btnOpenBook"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignBaseline="@+id/img_OverVuBookCoverPhoto"
                android:layout_below="@+id/ratingbar"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:text="Open Book"
                android:textColor="@color/Black"
                android:textSize="13sp" />

            <ImageButton
                android:id="@+id/btnBack"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignBottom="@+id/btnOpenBook"
                android:layout_alignTop="@+id/btnOpenBook"
                android:layout_marginLeft="5dp"
                android:layout_toRightOf="@+id/btnOpenBook"
                android:src="@drawable/pic_btn_back"
                android:textColor="@color/Black"
                android:textSize="14sp" />

            <TextView
                android:id="@+id/txt_BookOverview"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignLeft="@+id/img_OverVuBookCoverPhoto"
                android:layout_below="@+id/img_OverVuBookCoverPhoto"
                android:layout_marginBottom="10dp"
                android:layout_marginTop="20dp"
                android:text="Book Overview"
                android:textColor="@color/White"
                android:textSize="13sp" />

            <TextView
                android:id="@+id/txt_BookOverviewDetails"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_alignLeft="@+id/img_OverVuBookCoverPhoto"
                android:layout_below="@+id/txt_BookOverview"
                android:lineSpacingExtra="4dp"
                android:lines="10"
                android:text="Lorem ipsum dolor sit amet, there was nothing that I can do she was dead, for this reasean I m gonna loose every thing consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat." >
            </TextView>
        </RelativeLayout>
    </ScrollView>

</FrameLayout>

in the onCreate method of Home.java i have made a Framelayout invisible/Gone (which Contains the Overview of book Cliked) as

  public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.home_activity);

        homeTabLayout = findViewById(R.id.rel_HomeLayout);
        reviewLayout = findViewById(R.id.scroll_ReviewLayout);
        reviewLayout.setVisibility(View.GONE);

now when I click any book it make visible the view which i have made invisible/gone previously on the onCreat method as discussed above using the code

gridView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int pos,
                    long arg3) {
                // TODO Auto-generated method stub

                Toast.makeText(context, BookTitle.get(pos), Toast.LENGTH_SHORT)
                        .show();
                reviewLayout.setVisibility(View.VISIBLE);

Note: that its not the new actvity rather I have just make Visible a view (i.e reviewLayout.setVisibility(View.VISIBLE);) on the click event.

• I want to make this view Invisible/Gone on the onBackPressed() method.
• Where should I call this method, either in the MainActivity.java or in the Home.java file?
• If I’m calling this method in the MainActivity.java its raising a nullPointerException.

Answer 1

You can Override BackPress method…
with help of this you can Hide your Layouts or View…

@Override
public void onBackPressed() {
     super.onBackPressed();
               // Invisible or Gone Your Views here....
    }