在安卓中实现拖放自动滚动的解决方法可以通过使用RecyclerView和ItemTouchHelper结合使用来实现。下面是一个示例代码:
DragScrollController
类,用于监听拖动事件和自动滚动:public class DragScrollController extends ItemTouchHelper.Callback {
private RecyclerView recyclerView;
private LinearLayoutManager layoutManager;
private int scrollSpeed = 8; // 滚动速度
public DragScrollController(RecyclerView recyclerView) {
this.recyclerView = recyclerView;
this.layoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
}
@Override
public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
return makeMovementFlags(0, ItemTouchHelper.UP | ItemTouchHelper.DOWN);
}
@Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
return false;
}
@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
}
@Override
public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
super.onSelectedChanged(viewHolder, actionState);
if (actionState == ItemTouchHelper.ACTION_STATE_DRAG) {
// 开始拖动时开始自动滚动
startAutoScroll();
}
}
@Override
public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
super.clearView(recyclerView, viewHolder);
// 停止自动滚动
stopAutoScroll();
}
private void startAutoScroll() {
recyclerView.removeCallbacks(scrollRunnable);
recyclerView.post(scrollRunnable);
}
private void stopAutoScroll() {
recyclerView.removeCallbacks(scrollRunnable);
}
private Runnable scrollRunnable = new Runnable() {
@Override
public void run() {
int firstVisibleItemPosition = layoutManager.findFirstVisibleItemPosition();
int lastVisibleItemPosition = layoutManager.findLastVisibleItemPosition();
int itemCount = recyclerView.getAdapter().getItemCount();
if (firstVisibleItemPosition == RecyclerView.NO_POSITION ||
lastVisibleItemPosition == RecyclerView.NO_POSITION) {
return;
}
if (firstVisibleItemPosition == 0 && lastVisibleItemPosition == itemCount - 1) {
// 所有项都可见,停止滚动
stopAutoScroll();
return;
}
if (firstVisibleItemPosition > 0 && lastVisibleItemPosition < itemCount - 1) {
// 所有项都可见,停止滚动
stopAutoScroll();
return;
}
if (firstVisibleItemPosition == 0) {
recyclerView.smoothScrollBy(0, -scrollSpeed);
} else if (lastVisibleItemPosition == itemCount - 1) {
recyclerView.smoothScrollBy(0, scrollSpeed);
}
recyclerView.postDelayed(scrollRunnable, 10);
}
};
}
DragScrollController
来设置拖放自动滚动:RecyclerView recyclerView = findViewById(R.id.recyclerView);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
DragScrollController dragScrollController = new DragScrollController(recyclerView);
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(dragScrollController);
itemTouchHelper.attachToRecyclerView(recyclerView);
这样,当你拖动RecyclerView中的项时,如果到达边界,它将开始自动滚动。你可以根据需要调整滚动速度和触发自动滚动的边界条件。
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