Changing number of columns with GridLayoutManager and RecyclerView

问题

Inside my fragment I'm setting my GridLayout in the following way: mRecycler.setLayoutManager(new GridLayoutManager(rootView.getContext(), 2));

So, I just want to change that 2 for a 4 when the user rotates the phone/tablet. I've read about onConfigurationChanged and I tried to make it work for my case, but it isn't going in the right way. When I rotate my phone, the app crashes...

Could you tell me how to solve this issue?

Here is my approach to find the solution, which is not working correctly:

  @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);

        int orientation = newConfig.orientation;

        if (orientation == Configuration.ORIENTATION_PORTRAIT) {
            mRecycler.setLayoutManager(new GridLayoutManager(mContext, 2));
        } else if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
            mRecycler.setLayoutManager(new GridLayoutManager(mContext, 4));
        }
    }

Thanks in advance!

回答1:

Try handling this inside your onCreateView method instead since it will be called each time there's an orientation change:

if(getActivity().getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT){
     mRecycler.setLayoutManager(new GridLayoutManager(mContext, 2));
}
else{
     mRecycler.setLayoutManager(new GridLayoutManager(mContext, 4));
}

回答2:

If you have more than one condition or use the value in multiple places this can go out of hand pretty fast. I suggest to create the following structure:

res
  - values
    - dimens.xml
  - values-land
    - dimens.xml

with res/values/dimens.xml being:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <integer name="gallery_columns">2</integer>
</resources>

and res/values-land/dimens.xml being:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <integer name="gallery_columns">4</integer>
</resources>

And the code then becomes (and forever stays) like this:

final int columns = getResources().getInteger(R.integer.gallery_columns);
mRecycler.setLayoutManager(new GridLayoutManager(mContext, columns));

You can easily see how easy it is to add new ways of determining the column count, for example using -w500dp/-w600dp/-w700dp resource folders instead of -land.

It's also quite easy to group these folders into separate resource folder in case you don't want to clutter your other (more relevant) resources:

android {
    sourceSets.main.res.srcDir 'src/main/res-overrides' // add alongside src/main/res
}

回答3:

The Recycle View supports AutofitRecycleView.

You need to add android:numColumns="auto_fit" in your xml file.

You can refer to this AutofitRecycleViewLink

回答4:

A more robust way to determine the no. of columns would be to calculate it based on the screen width and at runtime. I normally use the following function for that.

public static int calculateNoOfColumns(Context context) {
    DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
    float dpWidth = displayMetrics.widthPixels / displayMetrics.density;
    int scalingFactor = 200; // You can vary the value held by the scalingFactor
    // variable. The smaller it is the more no. of columns you can display, and the
    // larger the value the less no. of columns will be calculated. It is the scaling
    // factor to tweak to your needs.
    int columnCount = (int) (dpWidth / scalingFactor);
    return (columnCount>=2?columnCount:2); // if column no. is less than 2, we still display 2 columns
}

It is a more dynamic method to accurately calculate the no. of columns. This will be more adaptive for users of varying screen sizes without being resticted to only two possible values.

NB: You can vary the value held by the scalingFactor variable. The smaller it is the more no. of columns you can display, and the larger the value the less no. of columns will be calculated. It is the scaling factor to tweak to your needs.

回答5:

In the onCreate () event you can use StaggeredGridLayoutManager

mRecyclerView = (RecyclerView) v.findViewById(R.id.recyclerView);      

mStaggeredGridLayoutManager = new StaggeredGridLayoutManager(
       1, //number of grid columns
       GridLayoutManager.VERTICAL);      

mRecyclerView.setLayoutManager(mStaggeredGridLayoutManager);

Then when the user rotates the screen capture the event, and change the number of columns automatically

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    if (getActivity().getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) {           
            mStaggeredGridLayoutManager.setSpanCount(1);

    } else {           
            //show in two columns
            mStaggeredGridLayoutManager.setSpanCount(2);           
    }
}

回答6:

I ended up handling this in the onCreate method.

private RecyclerView recyclerView = null;

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

    recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    recyclerView.setHasFixedSize(true);
    Configuration orientation = new Configuration();
    if(this.recyclerView.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) {
        recyclerView.setLayoutManager(new GridLayoutManager(this, 2));
    } else if (this.recyclerView.getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE) {
        recyclerView.setLayoutManager(new GridLayoutManager(this, 4));
    }
            connectGetApiData();
}

It worked out perfectly for my app.

回答7:

You can implement the method in your recyclerView onMeasure. First, create the java class AutofitRecyclerView

public class AutofitRecyclerView extends RecyclerView {
//private GridLayoutManager manager;
private StaggeredGridLayoutManager manager;
private int columnWidth = -1;

public AutofitRecyclerView(Context context) {
    super(context);
    init(context, null);
}

public AutofitRecyclerView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context, attrs);
}

public AutofitRecyclerView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init(context, attrs);
}

private void init(Context context, AttributeSet attrs) {
    if (attrs != null) {
        int[] attrsArray = {
                android.R.attr.columnWidth
        };
        TypedArray array = context.obtainStyledAttributes(attrs, attrsArray);
        columnWidth = array.getDimensionPixelSize(0, -1);
        array.recycle();
    }

    manager = new StaggeredGridLayoutManager(1, GridLayoutManager.VERTICAL);
    setLayoutManager(manager);

}

@Override
protected void onMeasure(int widthSpec, int heightSpec) {
    super.onMeasure(widthSpec, heightSpec);
    if (columnWidth > 0) {
        int spanCount = Math.max(1, getMeasuredWidth() / columnWidth);
        manager.setSpanCount(spanCount);
    }
}}

In your xlm layout file activity_main.xml

<yourpackagename.AutofitRecyclerView
            android:id="@+id/recycler_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:columnWidth="@dimen/column_width"
            android:clipToPadding="false"/>

Then set the variable to the width of each item in the file size of the values folder values/dimens.xml

<resources>
  <dimen name="column_width">250dp</dimen>
</resources>

It can be for different screen resolutions values-xxhdpi/dimens.xml

<resources>
 <dimen name="column_width">280dp</dimen>
</resources>

In your activity in the onCreate event place the following code

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    recyclerView.addItemDecoration(new MarginDecoration(this));
    recyclerView.setHasFixedSize(true);
    recyclerView.setAdapter(new NumberedAdapter(50));
}

来源：https://stackoverflow.com/questions/29579811/changing-number-of-columns-with-gridlayoutmanager-and-recyclerview