Android percent screen width in RecyclerView item

问题

How would I get a RecyclerView's item height to be, say, 30% of the screen's height?

I can't simply use a ConstraintLayout or a PercentFrameLayout/PercentRelativeLayout, since those position child layouts relative to parent layouts, whose size might not match the screens.

Preferably, I'd like to do this in pure XML (and not have to use any Runnables to get the screen height dynamically).

EDIT

To clarify, since a lot of solutions suggest restraining the height of the RecyclerView, that's not the intent. The RecyclerView should still populate the screen. Here's what I'm talking about, using the screen width (instead of height):

The idea is to get the card's width to be 33% the screen's width, while keeping the RecyclerView's width unaltered as it scrolls past the screen horizontally.

回答1:

You can override one of the LayoutManager methods used by your RecyclerView to force specific size:

recyclerView.setLayoutManager(new LinearLayoutManager(this){
    @Override
    public boolean checkLayoutParams(RecyclerView.LayoutParams lp) {
        // force height of viewHolder here, this will override layout_height from xml
        lp.height = getHeight() / 3;
        return true;
    }
});

This is assumiing your RecyclerView fits the screen.

回答2:

There is no way to do this in XML that I'm aware of. However, you can do it in Java (without any Runnables etc) by setting your ViewHolder's itemView's LayoutParams before returning the ViewHolder in your adapter's onCreateViewHolder() method:

@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    LayoutInflater inflater = LayoutInflater.from(parent.getContext());
    View itemView = inflater.inflate(R.layout.itemview, parent, false);

    ViewGroup.LayoutParams layoutParams = itemView.getLayoutParams();
    layoutParams.height = (int) (parent.getHeight() * 0.3);
    itemView.setLayoutParams(layoutParams);

    return new MyViewHolder(itemView);
}

回答3:

You can not set percent height of item by XML only. Reason being it is an item which will be inflated at run-time, it is not a activity like layout. Which you write in your XML.

So now i tell you two ways to achieve percent / weight

1st Preferred way is to override height in onCreateViewHolder() method inside your Adapter

private int height = 0; // declared height globally in Adapter class to reuse it.

@Override
public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
    if (height == 0)
        height = (int) (parent.getMeasuredHeight() * .3);
    itemView.setMinimumHeight(height);
    return new ItemViewHolder(itemView);
}

2nd Hack is to use SDP library.

Use height of item in XML in sdp say _160sdp. It will not give you exact results of 30%. But it can adjust according to screen.

回答4:

You can use Display metrices

Define display metrices in constructor, or use any other static method initialization.

DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);

Now you can use it in onCreateViewHolder()

View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);

//setting the height programmatically
itemView.getLayoutParams().height = metrics.heightPixels/3;
itemView.requestLayout();

Or You can use in onBindViewHolder() on parent layout of layout.

回答5:

I achieved this by doing the following inside of my custom RecyclerView Item layout:

override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
    val newMeasuredWidth =
        (MeasureSpec.getSize(widthMeasureSpec) * WIDTH_ADJUSTMENT_RATIO).toInt()
    super.onMeasure(
        MeasureSpec.makeMeasureSpec(newMeasuredWidth, MeasureSpec.EXACTLY),
        heightMeasureSpec
    )
}

回答6:

Well I just tried to fix the issue you're having. I played with few things. Steps as follows:

1. MainActivity View Where RecyclerView has height of exactly 30% of screen.
2. Recycler View Items Height and Width must be match_parent.

What's happening there?

1. recyclerHolder has exactly 30% height of screen height there is no doubt.

2. Inside recyclerHolder we've RecyclerView which takes all those 30% height of parent and takes full width.

3. ListItem Layout takes full height and width of parent, where parent is RecyclerView which has exactly 30% height of screen.

I tried this and works perfectly. There you can find 2 empty views just to test if those fits perfectly on top and bottom, the result yes it does. put whatever inside list item it's gonna take 30% of screen height.

来源：https://stackoverflow.com/questions/51201482/android-percent-screen-width-in-recyclerview-item