我有一个扩展RelativeLayout的自定义视图。我在该视图中有一个子ImageView。 如果我将该视图放在LinearLayot或ListView中，在ImageView上设置边距效果很好。 但是，如果我将它放在自定义AdapterView（它就像ListView）设置边距不起作用。 也就是说，RelativeLayout.LayoutParams.leftMargin字段正在改变，但屏幕上没有变化。
该错误肯定在我的自定义AdapterView中，但我无法确切地看到...在更改ImageView的边距时没有布局。
public class MyListView extends AdapterView<Adapter> {
/** Represents an invalid child index */
private static final int INVALID_INDEX = -1;
/** Distance to drag before we intercept touch events */
private static final int TOUCH_SCROLL_THRESHOLD = 10;
/** Children added with this layout mode will be added below the last child */
private static final int LAYOUT_MODE_BELOW = 0;
/** Children added with this layout mode will be added above the first child */
private static final int LAYOUT_MODE_ABOVE = 1;
/** User is not touching the list */
private static final int TOUCH_STATE_RESTING = 0;
/** User is touching the list and right now it's still a "click" */
private static final int TOUCH_STATE_CLICK = 1;
/** User is scrolling the list */
private static final int TOUCH_STATE_SCROLL = 2;
/** The adapter with all the data */
private Adapter mAdapter;
/** Current touch state */
private int mTouchState = TOUCH_STATE_RESTING;
/** X-coordinate of the down event */
private int mTouchStartX;
/** Y-coordinate of the down event */
private int mTouchStartY;
/**
* The top of the first item when the touch down event was received
*/
private int mListTopStart;
/** The current top of the first item */
private int mListTop;
/**
* The offset from the top of the currently first visible item to the top of
* the first item
*/
private int mListTopOffset;
/** The adaptor position of the first visible item */
private int mFirstItemPosition;
/** The adaptor position of the last visible item */
private int mLastItemPosition;
/** A list of cached (re-usable) item views */
private final LinkedList<View> mCachedItemViews = new LinkedList<View>();
/** Used to check for long press actions */
private Runnable mLongPressRunnable;
/** Reusable rect */
private Rect mRect;
/**
* Constructor
*
* @param context The context
* @param attrs Attributes
*/
public MyListView(final Context context, final AttributeSet attrs) {
super(context, attrs);
}
@Override
public void setAdapter(final Adapter adapter) {
mAdapter = adapter;
removeAllViewsInLayout();
requestLayout();
}
@Override
public Adapter getAdapter() {
return mAdapter;
}
@Override
public void setSelection(final int position) {
throw new UnsupportedOperationException("Not supported");
}
@Override
public View getSelectedView() {
throw new UnsupportedOperationException("Not supported");
}
@Override
public boolean onInterceptTouchEvent(final MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
startTouch(event);
return false;
case MotionEvent.ACTION_MOVE:
return startScrollIfNeeded(event);
default:
endTouch();
return false;
}
}
@Override
public boolean onTouchEvent(final MotionEvent event) {
if (getChildCount() == 0) {
return false;
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
startTouch(event);
break;
case MotionEvent.ACTION_MOVE:
if (mTouchState == TOUCH_STATE_CLICK) {
startScrollIfNeeded(event);
}
if (mTouchState == TOUCH_STATE_SCROLL) {
scrollList((int)event.getY() - mTouchStartY);
}
break;
case MotionEvent.ACTION_UP:
if (mTouchState == TOUCH_STATE_CLICK) {
clickChildAt((int)event.getX(), (int)event.getY());
}
endTouch();
break;
default:
endTouch();
break;
}
return true;
}
@Override
protected void onLayout(final boolean changed, final int left, final int top, final int right,
final int bottom) {
super.onLayout(changed, left, top, right, bottom);
// if we don't have an adapter, we don't need to do anything
if (mAdapter == null) {
return;
}
if (getChildCount() == 0) {
mLastItemPosition = -1;
fillListDown(mListTop, 0);
} else {
final int offset = mListTop + mListTopOffset - getChildAt(0).getTop();
removeNonVisibleViews(offset);
fillList(offset);
}
positionItems();
invalidate();
}
/**
* Sets and initializes all things that need to when we start a touch
* gesture.
*
* @param event The down event
*/
private void startTouch(final MotionEvent event) {
// save the start place
mTouchStartX = (int)event.getX();
mTouchStartY = (int)event.getY();
mListTopStart = getChildAt(0).getTop() - mListTopOffset;
// start checking for a long press
startLongPressCheck();
// we don't know if it's a click or a scroll yet, but until we know
// assume it's a click
mTouchState = TOUCH_STATE_CLICK;
}
/**
* Resets and recycles all things that need to when we end a touch gesture
*/
private void endTouch() {
// remove any existing check for longpress
removeCallbacks(mLongPressRunnable);
// reset touch state
mTouchState = TOUCH_STATE_RESTING;
}
/**
* Scrolls the list. Takes care of updating rotation (if enabled) and
* snapping
*
* @param scrolledDistance The distance to scroll
*/
private void scrollList(final int scrolledDistance) {
mListTop = mListTopStart + scrolledDistance;
requestLayout();
}
/**
* Posts (and creates if necessary) a runnable that will when executed call
* the long click listener
*/
private void startLongPressCheck() {
// create the runnable if we haven't already
if (mLongPressRunnable == null) {
mLongPressRunnable = new Runnable() {
public void run() {
if (mTouchState == TOUCH_STATE_CLICK) {
final int index = getContainingChildIndex(mTouchStartX, mTouchStartY);
if (index != INVALID_INDEX) {
longClickChild(index);
}
}
}
};
}
// then post it with a delay
postDelayed(mLongPressRunnable, ViewConfiguration.getLongPressTimeout());
}
/**
* Checks if the user has moved far enough for this to be a scroll and if
* so, sets the list in scroll mode
*
* @param event The (move) event
* @return true if scroll was started, false otherwise
*/
private boolean startScrollIfNeeded(final MotionEvent event) {
final int xPos = (int)event.getX();
final int yPos = (int)event.getY();
if (xPos < mTouchStartX - TOUCH_SCROLL_THRESHOLD
|| xPos > mTouchStartX + TOUCH_SCROLL_THRESHOLD
|| yPos < mTouchStartY - TOUCH_SCROLL_THRESHOLD
|| yPos > mTouchStartY + TOUCH_SCROLL_THRESHOLD) {
// we've moved far enough for this to be a scroll
removeCallbacks(mLongPressRunnable);
mTouchState = TOUCH_STATE_SCROLL;
return true;
}
return false;
}
/**
* Returns the index of the child that contains the coordinates given.
*
* @param x X-coordinate
* @param y Y-coordinate
* @return The index of the child that contains the coordinates. If no child
* is found then it returns INVALID_INDEX
*/
private int getContainingChildIndex(final int x, final int y) {
if (mRect == null) {
mRect = new Rect();
}
for (int index = 0; index < getChildCount(); index++) {
getChildAt(index).getHitRect(mRect);
if (mRect.contains(x, y)) {
return index;
}
}
return INVALID_INDEX;
}
/**
* Calls the item click listener for the child with at the specified
* coordinates
*
* @param x The x-coordinate
* @param y The y-coordinate
*/
private void clickChildAt(final int x, final int y) {
final int index = getContainingChildIndex(x, y);
if (index != INVALID_INDEX) {
final View itemView = getChildAt(index);
final int position = mFirstItemPosition + index;
final long id = mAdapter.getItemId(position);
performItemClick(itemView, position, id);
}
}
/**
* Calls the item long click listener for the child with the specified index
*
* @param index Child index
*/
private void longClickChild(final int index) {
final View itemView = getChildAt(index);
final int position = mFirstItemPosition + index;
final long id = mAdapter.getItemId(position);
final OnItemLongClickListener listener = getOnItemLongClickListener();
if (listener != null) {
listener.onItemLongClick(this, itemView, position, id);
}
}
/**
* Removes view that are outside of the visible part of the list. Will not
* remove all views.
*
* @param offset Offset of the visible area
*/
private void removeNonVisibleViews(final int offset) {
// We need to keep close track of the child count in this function. We
// should never remove all the views, because if we do, we loose track
// of were we are.
int childCount = getChildCount();
// if we are not at the bottom of the list and have more than one child
if (mLastItemPosition != mAdapter.getCount() - 1 && childCount > 1) {
// check if we should remove any views in the top
View firstChild = getChildAt(0);
while (firstChild != null && firstChild.getBottom() + offset < 0) {
// remove the top view
removeViewInLayout(firstChild);
childCount--;
mCachedItemViews.addLast(firstChild);
mFirstItemPosition++;
// update the list offset (since we've removed the top child)
mListTopOffset += firstChild.getMeasuredHeight();
// Continue to check the next child only if we have more than
// one child left
if (childCount > 1) {
firstChild = getChildAt(0);
} else {
firstChild = null;
}
}
}
// if we are not at the top of the list and have more than one child
if (mFirstItemPosition != 0 && childCount > 1) {
// check if we should remove any views in the bottom
View lastChild = getChildAt(childCount - 1);
while (lastChild != null && lastChild.getTop() + offset > getHeight()) {
// remove the bottom view
removeViewInLayout(lastChild);
childCount--;
mCachedItemViews.addLast(lastChild);
mLastItemPosition--;
// Continue to check the next child only if we have more than
// one child left
if (childCount > 1) {
lastChild = getChildAt(childCount - 1);
} else {
lastChild = null;
}
}
}
}
/**
* Fills the list with child-views
*
* @param offset Offset of the visible area
*/
private void fillList(final int offset) {
final int bottomEdge = getChildAt(getChildCount() - 1).getBottom();
fillListDown(bottomEdge, offset);
final int topEdge = getChildAt(0).getTop();
fillListUp(topEdge, offset);
}
/**
* Starts at the bottom and adds children until we've passed the list bottom
*
* @param bottomEdge The bottom edge of the currently last child
* @param offset Offset of the visible area
*/
private void fillListDown(int bottomEdge, final int offset) {
while (bottomEdge + offset < getHeight() && mLastItemPosition < mAdapter.getCount() - 1) {
mLastItemPosition++;
final View newBottomchild = mAdapter.getView(mLastItemPosition, getCachedView(), this);
addAndMeasureChild(newBottomchild, LAYOUT_MODE_BELOW);
bottomEdge += newBottomchild.getMeasuredHeight();
}
}
/**
* Starts at the top and adds children until we've passed the list top
*
* @param topEdge The top edge of the currently first child
* @param offset Offset of the visible area
*/
private void fillListUp(int topEdge, final int offset) {
while (topEdge + offset > 0 && mFirstItemPosition > 0) {
mFirstItemPosition--;
final View newTopCild = mAdapter.getView(mFirstItemPosition, getCachedView(), this);
addAndMeasureChild(newTopCild, LAYOUT_MODE_ABOVE);
final int childHeight = newTopCild.getMeasuredHeight();
topEdge -= childHeight;
// update the list offset (since we added a view at the top)
mListTopOffset -= childHeight;
}
}
/**
* Adds a view as a child view and takes care of measuring it
*
* @param child The view to add
* @param layoutMode Either LAYOUT_MODE_ABOVE or LAYOUT_MODE_BELOW
*/
private void addAndMeasureChild(final View child, final int layoutMode) {
LayoutParams params = child.getLayoutParams();
if (params == null) {
params = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
}
final int index = layoutMode == LAYOUT_MODE_ABOVE ? 0 : -1;
addViewInLayout(child, index, params, true);
final int itemWidth = getWidth();
child.measure(MeasureSpec.EXACTLY | itemWidth, MeasureSpec.UNSPECIFIED);
}
/**
* Positions the children at the "correct" positions
*/
private void positionItems() {
int top = mListTop + mListTopOffset;
for (int index = 0; index < getChildCount(); index++) {
final View child = getChildAt(index);
final int width = child.getMeasuredWidth();
final int height = child.getMeasuredHeight();
final int left = (getWidth() - width) / 2;
child.layout(left, top, left + width, top + height);
top += height;
}
}
/**
* Checks if there is a cached view that can be used
*
* @return A cached view or, if none was found, null
*/
private View getCachedView() {
if (mCachedItemViews.size() != 0) {
return mCachedItemViews.removeFirst();
}
return null;
}
}