滚动RecyclerView以在顶部显示所选项目-Java 学习之路

160

我正在寻找一种滚动 RecyclerView 以在顶部显示所选项目的方法 .

在一个 ListView 中，我能够通过使用 scrollTo(x,y) 并获得需要居中的元素的顶部来做到这一点 .

就像是：

@Override
public void onItemClick(View v, int pos){
    mylistView.scrollTo(0, v.getTop());
}

问题是 RecyclerView 在使用它的 scrollTo 方法时会返回错误

RecyclerView不支持滚动到绝对位置

如何滚动 RecyclerView 将所选项目放在视图顶部？

12 回答

与速度调节器相同

public class SmoothScrollLinearLayoutManager extends LinearLayoutManager {
private static final float MILLISECONDS_PER_INCH = 110f;
private Context mContext;

public SmoothScrollLinearLayoutManager(Context context,int orientation, boolean reverseLayout) {
    super(context,orientation,reverseLayout);
    mContext = context;
}

@Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
                                   int position) {
    RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext()){
        //This controls the direction in which smoothScroll looks for your view
        @Override
        public PointF computeScrollVectorForPosition(int targetPosition) {
            return new PointF(0, 1);
        }

        //This returns the milliseconds it takes to scroll one pixel.
        @Override
        protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
            return MILLISECONDS_PER_INCH / displayMetrics.densityDpi;
        }
    };
    smoothScroller.setTargetPosition(position);
    startSmoothScroll(smoothScroller);
}


private class TopSnappedSmoothScroller extends LinearSmoothScroller {
    public TopSnappedSmoothScroller(Context context) {
        super(context);

    }

    @Override
    public PointF computeScrollVectorForPosition(int targetPosition) {
        return SmoothScrollLinearLayoutManager.this
                .computeScrollVectorForPosition(targetPosition);
    }

    @Override
    protected int getVerticalSnapPreference() {
        return SNAP_TO_START;
    }
}
}

回复于 2024-04-27T20:49:50+08:00

18

你只需要拨打 recyclerview.scrollToPosition(position) . 没关系！

如果要在适配器中调用它，只需让适配器具有recyclelerview实例或包含recyclerview的活动或片段，而不是在其中实现方法 getRecyclerview() .

我希望它可以帮到你 .

回复于 2024-04-27T20:49:50+08:00
11
在特定位置滚动
这对我很有帮助 . 通过单击侦听器，您可以获得适配器中的位置
```
layoutmanager.scrollToPosition(int position);
```
回复于 2024-04-27T20:49:50+08:00

If you want to scroll automatic without show scroll motion then you need to write following code:

**=> mRecyclerView.getLayoutManager().scrollToPosition(position);**

If you want to display scroll motion then you need to add following code.
=>Step 1: You need to declare SmoothScroller.

RecyclerView.SmoothScroller smoothScroller = new
                LinearSmoothScroller(this.getApplicationContext()) {
                    @Override
                    protected int getVerticalSnapPreference() {
                        return LinearSmoothScroller.SNAP_TO_START;
                    }
                };

=>step 2: You need to add this code any event you want to perform scroll to specific position.
=>First you need to set target position to SmoothScroller.

**smoothScroller.setTargetPosition(position);**

=>Then you need to set SmoothScroller to LayoutManager.
                        **mRecyclerView.getLayoutManager().startSmoothScroll(smoothScroller);**

回复于 2024-04-27T20:49:50+08:00

-3
如果您使用的是LinearLayoutManager或StaggeredGridLayoutManager，它们每个都有一个scrollToPositionWithOffset方法，它从RecyclerView的开头获取项目开头的位置和偏移量，这似乎可以完成您的需要（设置偏移量） 0应该与顶部对齐） .

例如：
```
//Scroll item 2 to 20 pixels from the top
linearLayoutManager.scrollToPositionWithOffset(2, 20);
```
回复于 2024-04-27T20:49:50+08:00

在我的情况下，我的 RecyclerView 有这样的填充顶部

<android.support.v7.widget.RecyclerView
     ...
     android:paddingTop="100dp"
     android:clipToPadding="false"
/>

然后，为了将项目滚动到顶部，我需要

recyclerViewLinearLayoutManager.scrollToPositionWithOffset(position, -yourRecyclerView.getPaddingTop());

回复于 2024-04-27T20:49:50+08:00

尝试一下对我有用的东西！

创建一个变量 private static int displayedposition = 0;

现在，您可以在Activity中找到RecyclerView的位置 .

myRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);

                LinearLayoutManager llm = (LinearLayoutManager) myRecyclerView.getLayoutManager();


                displayedposition = llm.findFirstVisibleItemPosition();


            }
        });

将此语句放在您希望它将前一个站点显示在视图中的位置 .

LinearLayoutManager llm = (LinearLayoutManager) mRecyclerView.getLayoutManager();
        llm.scrollToPositionWithOffset(displayedposition , youList.size());

那就是它，它对我来说很好\ o /

回复于 2024-04-27T20:49:50+08:00

309

在点击按钮后刷新RecyclerView后我做了什么来恢复滚动位置：

if (linearLayoutManager != null) {

    index = linearLayoutManager.findFirstVisibleItemPosition();
    View v = linearLayoutManager.getChildAt(0);
    top = (v == null) ? 0 : (v.getTop() - linearLayoutManager.getPaddingTop());
    Log.d("TAG", "visible position " + " " + index);
}

else{
    index = 0;
}

linearLayoutManager = new LinearLayoutManager(getApplicationContext());
linearLayoutManager.scrollToPositionWithOffset(index, top);

在创建linearLayoutManager对象之前从顶部获取第一个可见项的偏移量，并在实例化之后调用LinearLayoutManager对象的scrollToPositionWithOffset .

回复于 2024-04-27T20:49:50+08:00

如果您正在寻找垂直LinearLayout Manager，您可以使用自定义 LinearSmoothScroller 实现平滑滚动：

import android.content.Context;
import android.graphics.PointF;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.LinearSmoothScroller;
import android.support.v7.widget.RecyclerView;

public class SnappingLinearLayoutManager extends LinearLayoutManager {

    public SnappingLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
                                       int position) {
        RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext());
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

    private class TopSnappedSmoothScroller extends LinearSmoothScroller {
        public TopSnappedSmoothScroller(Context context) {
            super(context);

        }

        @Override
        public PointF computeScrollVectorForPosition(int targetPosition) {
            return SnappingLinearLayoutManager.this
                    .computeScrollVectorForPosition(targetPosition);
        }

        @Override
        protected int getVerticalSnapPreference() {
            return SNAP_TO_START;
        }
    }
}

在循环视图中使用layoutmanager的实例，然后调用 recyclerView.smoothScrollToPosition(pos); 将平滑滚动到选定位置到回收器视图的顶部

回复于 2024-04-27T20:49:50+08:00

//滚动项目pos

linearLayoutManager.scrollToPositionWithOffset(pos, 0);

回复于 2024-04-27T20:49:50+08:00

只需简单地调用此方法：

((LinearLayoutManager)RecyclerView.getLayoutManager()).scrollToPositionWithOffset(yourItemPosition,0);

代替：

RecyclerView.scrollToPosition(yourItemPosition);

回复于 2024-04-27T20:49:50+08:00

我使用下面的代码将项目（thisView）平滑滚动到顶部 .
它也适用于GridLayoutManager，具有不同高度的视图：

View firstView = mRecyclerView.getChildAt(0);
int toY = firstView.getTop();
int firstPosition = mRecyclerView.getChildAdapterPosition(firstView);
View thisView = mRecyclerView.getChildAt(thisPosition - firstPosition);
int fromY = thisView.getTop();

mRecyclerView.smoothScrollBy(0, fromY - toY);

似乎工作得很好，可以快速解决问题 .

回复于 2024-04-27T20:49:50+08:00

滚动RecyclerView以在顶部显示所选项目

12 回答

相关问题