Determine the Current Layout in Android

00_read_me.md

Activity that adapts

To develop great UI the designer impliments different layouts for different breakpoints.

Two Layout

• orientation:vertical (1st break point) - master_frag and detail_frag are each in a FragmentActiity
• orientation:horizontal (2nd break point) - master_detail_act.xml incorprating master_frag and detail_frag fragments

1. Detection is done in onCreate is testing for the articleView View in the detail fragment. if it is available we are in master/detail layout.

• This is stored in mIsDualPane

2. Add a listener - only if the button is available (due to layout or due to API version)

3. We can use the onHeadlineSelected to implemet different behavior based on mIsDualPane ** if dual - update the fragment. ** if not - start an intent.

4. set the actionbar ** if dual - use tabs for navigation ** if not - use spinner

5. reuse of fragment in XML within in a layout

6. and again via code in a FragmentActivity

7. using an interface to decouple activity and fragment

8. the fragment then uses the inerface to access the activity.

9. reacting to config change from single page detail to two pane master/detail.

10. using a strategy pattern to further simplify the handling different breakponits/layouts c.f. https://developer.android.com/training/multiscreen/adaptui

01_AdaptiveDualPaneActivity.java

/**
* use a boolean var mIsDualPane - in the controller logic based on a view's visibility
*/
public class AdaptiveDualPaneActivity extends FragmentActivity {
    boolean mIsDualPane;    //the state

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        
        //detect articleView
        View articleView = findViewById(R.id.article);
        mIsDualPane = articleView != null && articleView.getVisibility() == View.VISIBLE;
      
        this.listenIfExists();
    }
}

02_listenIfExists.java

/**
* only hook up the button listner if the button has been found.
*/
public void listenIfExists(){

  Button catButton = (Button) findViewById(R.id.categorybutton);
  OnClickListener listener = /* create your listener here */;
  if (catButton != null) {
      catButton.setOnClickListener(listener);
  }
}

03_onHeadlineSelected.java

/**
* this is a simple way to handle controller logic based on mIsDualPane
*
*/
@Override
public void onHeadlineSelected(int index) {
    mArtIndex = index;
    if (mIsDualPane) {
        /* display article on the right pane */
        mArticleFragment.displayArticle(mCurrentCat.getArticle(index));
    } else {
        /* start a separate activity */
        Intent intent = new Intent(this, ArticleActivity.class);
        intent.putExtra("catIndex", mCatIndex);
        intent.putExtra("artIndex", index);
        startActivity(intent);
    }
}

04_actionBar.java

final String CATEGORIES[] = { "Top Stories", "Politics", "Economy", "Technology" };

public void onCreate(Bundle savedInstanceState) {
    ....
    if (mIsDualPane) {
        /* use tabs for navigation */
        actionBar.setNavigationMode(android.app.ActionBar.NAVIGATION_MODE_TABS);
        int i;
        for (i = 0; i < CATEGORIES.length; i++) {
            actionBar.addTab(actionBar.newTab().setText(
                CATEGORIES[i]).setTabListener(handler));
        }
        actionBar.setSelectedNavigationItem(selTab);
    }
    else {
        /* use list navigation (spinner) */
        actionBar.setNavigationMode(android.app.ActionBar.NAVIGATION_MODE_LIST);
        SpinnerAdapter adap = new ArrayAdapter<String>(this,
                R.layout.headline_item, CATEGORIES);
        actionBar.setListNavigationCallbacks(adap, handler);
    }
}

05_master_detail_act.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal">
    <fragment android:id="@+id/headlines"
              android:layout_height="fill_parent"
              android:name="com.example.android.newsreader.HeadlinesFragment"
              android:layout_width="400dp"
              android:layout_marginRight="10dp"/>
    <fragment android:id="@+id/article"
              android:layout_height="fill_parent"
              android:name="com.example.android.newsreader.ArticleFragment"
              android:layout_width="fill_parent" />
</LinearLayout>

06_reuse_fragment_ ArticleActivity.java

//reusing this without a layout
getSupportFragmentManager().beginTransaction()
        .add(android.R.id.content, new ArticleFragment())
        .commit();

07_Interface.java

public class HeadlinesFragment extends ListFragment {
    ...
    OnHeadlineSelectedListener mHeadlineSelectedListener = null;

    /* Must be implemented by host activity */
    public interface OnHeadlineSelectedListener {
        public void onHeadlineSelected(int index);
    }
    ...

    public void setOnHeadlineSelectedListener(OnHeadlineSelectedListener listener) {
        mHeadlineSelectedListener = listener;
    }
}

08_HeadlinesFragment.java

public class HeadlinesFragment extends ListFragment {
    ...
    public void onItemClick(AdapterView<?> parent,
                            View view, int position, long id) {
        if (null != mHeadlineSelectedListener) {
            mHeadlineSelectedListener.onHeadlineSelected(position);
        }
    }
    ...
}

09_reacting_to_conf_change.java

public class ArticleActivity extends FragmentActivity {
    int mCatIndex, mArtIndex;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mCatIndex = getIntent().getExtras().getInt("catIndex", 0);
        mArtIndex = getIntent().getExtras().getInt("artIndex", 0);

        // If should be in two-pane mode, finish to return to main activity
        if (getResources().getBoolean(R.bool.has_two_panes)) {
            finish();
            return;
        }
        ...
}

10.strategy.java

public interface Strategy { 
 String reportWeather(); 
}