Display current date in Viewpager manipulated layout

Question

When I click on a Main Activity button, a Viewpager is created that allows me to move between 7 layouts that I have. The pager is set to present first the layout called "domingo.xml" and everything works normally. I just want this layout to be shown a date, so I use this code:

    Locale local = new Locale("pt", "BR");
    DateFormat sdf = new SimpleDateFormat("EEEE - dd/MM", local);
    Date d = Calendar.getInstance().getTime();
    String mostrarData = sdf.format(d).toUpperCase(local);
    final TextView textoData = (TextView) findViewById(R.id.textView1);
    textoData.setText(mostrarData);

I created a new layout just to test and the date code works and displays the date normally, but in the Domingo.xml layout (which is handled by Viewpager) I can’t at all.

This is the code of the button that calls the Viewpager:

public void btTela1(View v) {
startActivity(new Intent(getBaseContext(), Pager.class));
}

And this is the Viewpager code:

public class Pager extends Activity {

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.pager);

    AdapterPages adapter = new AdapterPages();
    ViewPager myPager = (ViewPager) findViewById(R.id.pager);
    myPager.setAdapter(adapter);
    myPager.setCurrentItem(0);
}}

There is also the Pageradapter code used to configure Viewpager. Where should I write the date code? I have tried in several places, but it is always a mistake. I do not know if there is some conceptual error that I do not understand. I’m new to programming and this is the first time I’ve put on a forum. If you need more information tell me what I add. Thanks.

Code of the Pageradapter:

public class AdapterPages extends PagerAdapter {

@Override
public int getCount() {
    return 7;
}

@Override
public Object instantiateItem(View collection, int position) {

    LayoutInflater inflater = (LayoutInflater) collection.getContext()
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    int resId = 0;
    switch (position) {
    case 0:
        resId = R.layout.domingo;
        break;
    case 1:
        resId = R.layout.segunda;
        break;
    case 2:
        resId = R.layout.terca;
        break;
    case 3:
        resId = R.layout.quarta;
        break;
    case 4:
        resId = R.layout.quinta;
        break;
    case 5:
        resId = R.layout.sexta;
        break;
    case 6:
        resId = R.layout.sabado;
        break;
    }

    View view = inflater.inflate(resId, null);

    ((ViewPager) collection).addView(view, 0);

    return view;
}

@Override
public void destroyItem(View arg0, int arg1, Object arg2) {
    ((ViewPager) arg0).removeView((View) arg2);
}

@Override
public boolean isViewFromObject(View arg0, Object arg1) {

    return arg0 == ((View) arg1);
}

@Override
public Parcelable saveState() {
    return null;
}}

Code of Sunday.xml:

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

    <TextView
        android:id="@+id/data_domingo"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:background="#BEBEBE"
        android:gravity="center"
        android:textStyle="bold" />
    ...

From what @Wakim taught me I modified a small part of the Pageradapter code and stayed like this:

View view = inflater.inflate(resId, null);
((ViewPager) collection).addView(view, 0);
Locale local = new Locale("pt", "BR");
DateFormat sdf = new SimpleDateFormat("EEEE - dd/MM", local);
Date d = Calendar.getInstance().getTime();
String mostrarData = sdf.format(d).toUpperCase(local);
TextView textoData = (TextView) collection
        .findViewById(R.id.data_domingo);
textoData.setText(mostrarData);
return view;

Now the date appeared, however, when I slide to the third layout hangs everything. What is happening ?

Answer 1

The ViewPager works in a similar way that the ListView, displaying a small part of the associated model.

The Model is associated through a Adapter, where it is responsible for returning the visual presentation of the model, to a given position.

In case your template is a list of dates, which can be derived from only one date.

I will assume that the domingo.xml will be the default for all dates, where what varies is the content of TextView whose ID is data_domingo that it displays. If there are more changes in the layout, just say that I help to mount.

Your Activity Pager remains the same.

What changes is yours AdapterPages which remains:

public class AdapterPages extends PagerAdapter {

    // Data base do ViewPager (posição 0), onde cada posição derivará dessa
    Calendar mBaseDate = Calendar.getInstance();
    // DateFormat usado para formatar a data
    DateFormat mDateFormat = new SimpleDateFormat("EEEE - dd/MM", Locale.getDefault());

    // É legal "cachear" o LayoutInflater, para não ficar requisitando um toda hora. 
    LayoutInflater mLayoutInflater;

    public AdapterPages() {
        // Configurar a data base para corresponder ao primeiro dia da semana, domingo.
        mBaseDate.set(Calendar.HOUR_OF_DAY, 0); // ! clear would not reset the hour of day !
        mBaseDate.clear(Calendar.MINUTE);
        mBaseDate.clear(Calendar.SECOND);
        mBaseDate.clear(Calendar.MILLISECOND);

        // get start of this week in milliseconds
        mBaseDate.set(Calendar.DAY_OF_WEEK, mBaseDate.getFirstDayOfWeek());
    }

    @Override
    public int getCount() {
        // Ok, sao 7 dias
        return 7;
    }

    @Override
    public Object instantiateItem(View collection, int position) {

        if(mInflater == null) {
            mInflater = LayoutInflater.from(collection.getContext());
        }

        // Infla o layout padrão do ViewPager. É retornado uma
        // referência para a raiz (LinearLayout).
        // A partir dele, você consegue acessar todos os filhos.
        View view = mInflater.inflate(R.layout.domingo, null);

        TextView tv = view.findViewById(R.id.data_domingo);

        // Calculo qual o dia baseado na posicao e no dia base
        Calendar currentDate = (Calendar) mBaseDate.clone();
        currentDate.add(Calendar.DAY_OF_YEAR, posicao);

        // Fornece a data formatada relativa à posição do modelo
        tv.setText(mDateFormat.format(currentDate.getDate()).toUpperCase());

        // Voce pode fazer mais customizacoes aqui baseada na "view" e seus
        // elementos, e o seu modelo, a data relativa a posicao que vai ser exibida.

        ((ViewPager) collection).addView(view);

        return view;
    }

    @Override
    public void destroyItem(View arg0, int arg1, Object arg2) {
        ((ViewPager) arg0).removeView((View) arg2);
    }

    @Override
    public boolean isViewFromObject(View arg0, Object arg1) {
        return arg0 == ((View) arg1);
    }

    @Override
    public Parcelable saveState() {
        return null;
    }
}

I think it’s nice to also quote that the ViewPager builds the Views on demand, that is, it by default keeps in memory 3 Views (the visible, the previous and the next), as you navigate he destroys and builds the Views. This behavior can be changed by the attribute OffscreenPageLimit (being 1 by default), but his idea is to give fluidity to the movement of Slide.

References:

1. https://stackoverflow.com/questions/2937086/how-to-get-the-first-day-of-the-current-week-and-month
2. http://developer.android.com/reference/android/support/v4/view/ViewPager.html