使用CardScrollView的Google Glass多个嵌入式布局

Question

What im doing is I'm inserting card using CardScrollView in google glass using an EMBEDDED LAYOUT because the table layout is not yet available in card builder. Let's assume that every table has 1 textView. What's happening is when I insert 1-3 layout, there's is no any error but when i inserted the 4th layout it gives me a java.lang.NullPointerException in this line.

    tv4.setText('Value for table 4');

This is my code:

NOTE: I have atleast 5 TextView in each table. make it simple here.

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    createCards();

    mCardScrollView = new CardScrollView(this);
    mAdapter = new ExampleCardScrollAdapter();
    mCardScrollView.setAdapter(mAdapter);
    mCardScrollView.activate();
    setContentView(mCardScrollView);


    TextView tv1 = (TextView) findViewById(R.id.textView1);
    TextView tv2 = (TextView) findViewById(R.id.textView2);
    TextView tv3 = (TextView) findViewById(R.id.textView3);
    TextView tv4 = (TextView) findViewById(R.id.textView4);



    tv1.setText('Value for table 1');
    tv2.setText('Value for table 2');
    tv3.setText('Value for table 3');
    tv4.setText('Value for table 4');
    }

private void createCards(){
    mCards = new ArrayList<CardBuilder>();

     mCards.add(new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
    .setEmbeddedLayout(R.layout.activity_layout1)
    .setFootnote("TABLE 1"));

     mCards.add(new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
    .setEmbeddedLayout(R.layout.activity_layout2)
    .setFootnote("TABLE 2"));

     mCards.add(new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
    .setEmbeddedLayout(R.layout.activity_layout3)
    .setFootnote("TABLE 3"));

     mCards.add(new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
    .setEmbeddedLayout(R.layout.activity_layout4)
    .setFootnote("TABLE 4")); 
    }

private class ExampleCardScrollAdapter extends CardScrollAdapter {

    @Override
    public int getPosition(Object item) {
        return mCards.indexOf(item);
    }

    @Override
    public int getCount() {
        return mCards.size();
    }

    @Override
    public Object getItem(int position) {
        return mCards.get(position);
    }

    @Override
    public int getViewTypeCount() {
        return CardBuilder.getViewTypeCount();
    }

    @Override
    public int getItemViewType(int position){
        return mCards.get(position).getItemViewType();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        return mCards.get(position).getView(convertView, parent);
    }
}

activity_layout1

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

<TableRow>

    <TextView
        android:padding="3dip"
        android:textSize="20sp"
        android:text="@string/textViewTitle1"
        android:textColor="@color/muted" />
    <TextView
        android:id="@+id/textView1"
        android:gravity="right"
        android:padding="3dip"
        android:textSize="20sp" />

</TableRow>
</TableLayout>

activity_layout2

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

<TableRow>

    <TextView
        android:padding="3dip"
        android:textSize="20sp"
        android:text="@string/textViewTitle2"
        android:textColor="@color/muted" />
    <TextView
        android:id="@+id/textView2"
        android:gravity="right"
        android:padding="3dip"
        android:textSize="20sp" />

</TableRow>
</TableLayout>

activity_layout3

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

<TableRow>

    <TextView
        android:padding="3dip"
        android:textSize="20sp"
        android:text="@string/textViewTitle4"
        android:textColor="@color/muted" />
    <TextView
        android:id="@+id/textView3"
        android:gravity="right"
        android:padding="3dip"
        android:textSize="20sp" />

</TableRow>
</TableLayout>

activity_layout4

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

<TableRow>

    <TextView
        android:padding="3dip"
        android:textSize="20sp"
        android:text="@string/textViewTitle4"
        android:textColor="@color/muted" />
    <TextView
        android:id="@+id/textView4"
        android:gravity="right"
        android:padding="3dip"
        android:textSize="20sp" />

</TableRow>
</TableLayout>

Adapter

    private class ExampleCardScrollAdapter extends CardScrollAdapter {

    @Override
    public int getPosition(Object item) {
        return mCards.indexOf(item);
    } 

    @Override
    public int getCount() {
        return mCards.size();
    }


    @Override
    public Object getItem(int position) {
        return mCards.get(position);
    }

    @Override
    public int getViewTypeCount() {
        return CardBuilder.getViewTypeCount();
    }

    @Override
    public int getItemViewType(int position){
        return mCards.get(position).getItemViewType();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        return mCards.get(position).getView(convertView, parent);
    }
}

Please help because I'm stuck in here for days. Thank you!

Answer 1

There a few things that are wrong with the way you are setting text for your various views.

Why it crashes

The reason it crashes is because the CardScrollView currently retrieves 5 Views at a time, the current one and 2 for either directions. Since the CardScrollView starts at position 0, only Views at position 0, 1, and 2 are loaded: this makes setting text for tv1 , tv2 and tv2 possible as they are in the view hierarchy.

Since tv4 has not been added, trying to retrieve the View will return null .

How to fix this

Since each card in your CardScrollView has the same layout, you don't need to create 4 separate ones and initiliaze them in onCreate . You should instead inflate the Views when needed and set the text or other data appropriately.

card_layout.xml :

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

<TableRow>

    <TextView
        android:padding="3dip"
        android:textSize="20sp"
        android:text="@string/textViewTitle"
        android:textColor="@color/muted" />
    <TextView
        android:id="@+id/textView"
        android:gravity="right"
        android:padding="3dip"
        android:textSize="20sp" />

</TableRow>
</TableLayout>

Adapter :

private class ExampleCardScrollAdapter extends CardScrollAdapter {

    @Override
    public int getPosition(Object item) {
        return mTexts.indexOf(item);
    } 

    @Override
    public int getCount() {
        return mTexts.size();
    }


    @Override
    public Object getItem(int position) {
        return mTexts.get(position);
    }

    @Override
    public int getViewTypeCount() {
        return 1;
    }

    @Override
    public int getItemViewType(int position){
        return CardBuilder.EMBED_INSIDE.ordinal();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = new CardBuilder(this, CardBuilder.Layout.EMBED_INSIDE)
                .setEmbeddedLayout(R.layout.card_layout)
                .setFootnote("TABLE " + position)
                .getView(convertView, parent);
        TextView textView = view.findViewById(R.id.textView);

        textView.setText(mTexts.get(position));
        return view;        
    }
}

Then, in your Activity :

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    createTexts();

    mCardScrollView = new CardScrollView(this);
    mAdapter = new ExampleCardScrollAdapter();
    mCardScrollView.setAdapter(mAdapter);
    mCardScrollView.activate();  // This should be moved in onResume.
    setContentView(mCardScrollView);
}

private void createTexts(){
    mTexts = new ArrayList<String>();

    mTexts.add("Value for table 1");
    mTexts.add("Value for table 2");
    mTexts.add("Value for table 3");
    mTexts.add("Value for table 4");
}