ListView中嵌套EditText造成ListView的子Item点击无响应问题简要分析

最新推荐文章于 2022-01-22 17:03:08 发布

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#android #listview #edittext

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解析ListView嵌套EditText时，EditText导致ListView点击回调失效的原因。通过对源码的深入分析，找到问题关键在于EditText使得child.hasExplicitFocusable()返回true，进而阻止了回调的执行。

继上一篇处理ListView嵌套EditText出现的问题，有一个问题EditText使ListView的setOnItemClickListener回调失效，最新看了源码，得出了一些结论，如有错误欢迎指出,不需要看完整代码，看标记的最关键的就行。

1.我们来一步步看这个回调过程

    首先我们看到，这个回调发生在ListView的父类AdapterView的performItemClick中，下面是源码
    /**
     * Call the OnItemClickListener, if it is defined. Performs all normal
     * actions associated with clicking: reporting accessibility event, playing
     * a sound, etc.
     *
     * @param view The view within the AdapterView that was clicked.
     * @param position The position of the view in the adapter.
     * @param id The row id of the item that was clicked.
     * @return True if there was an assigned OnItemClickListener that was
     *         called, false otherwise is returned.
     */
    public boolean performItemClick(View view, int position, long id) {
        final boolean result;
        if (mOnItemClickListener != null) {
            playSoundEffect(SoundEffectConstants.CLICK);
            mOnItemClickListener.onItemClick(this, view, position, id);
            result = true;
        } else {
            result = false;
        }

        if (view != null) {
            view.sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
        }
        return result;
    }

2.我们再来看是哪里调用了performItemClick，可以看到是在AbsListView中

    private class PerformClick extends WindowRunnnable implements Runnable {
        int mClickMotionPosition;

        @Override
        public void run() {
            // The data has changed since we posted this action in the event queue,
            // bail out before bad things happen
            if (mDataChanged) return;

            final ListAdapter adapter = mAdapter;
            final int motionPosition = mClickMotionPosition;
            if (adapter != null && mItemCount > 0 &&
                    motionPosition != INVALID_POSITION &&
                    motionPosition < adapter.getCount() && sameWindow() &&
                    adapter.isEnabled(motionPosition)) {
                final View view = getChildAt(motionPosition - mFirstPosition);
                // If there is no view, something bad happened (the view scrolled off the
                // screen, etc.) and we should cancel the click
                if (view != null) {
                //这里这里这里！！！！！
                    performItemClick(view, motionPosition, adapter.getItemId(motionPosition));
                }
            }
        }
    }

3.当然这里是利用线程，然后再看在哪里启动的，结果还是在这个类里面

   private void onTouchUp(MotionEvent ev) {
        switch (mTouchMode) {
        case TOUCH_MODE_DOWN:
        case TOUCH_MODE_TAP:
        case TOUCH_MODE_DONE_WAITING:
            final int motionPosition = mMotionPosition;
            final View child = getChildAt(motionPosition - mFirstPosition);
            if (child != null) {
                if (mTouchMode != TOUCH_MODE_DOWN) {
                    child.setPressed(false);
                }

                final float x = ev.getX();
                final boolean inList = x > mListPadding.left && x < getWidth() - mListPadding.right;
                //！！！！！！！！！！
                if (inList && !child.hasExplicitFocusable()) {
                    if (mPerformClick == null) {
                        mPerformClick = new PerformClick();
                    }

                    final AbsListView.PerformClick performClick = mPerformClick;
                    performClick.mClickMotionPosition = motionPosition;
                    performClick.rememberWindowAttachCount();

                    mResurrectToPosition = motionPosition;

                    if (mTouchMode == TOUCH_MODE_DOWN || mTouchMode == TOUCH_MODE_TAP) {
                        removeCallbacks(mTouchMode == TOUCH_MODE_DOWN ?
                                mPendingCheckForTap : mPendingCheckForLongPress);
                        mLayoutMode = LAYOUT_NORMAL;
                        if (!mDataChanged && mAdapter.isEnabled(motionPosition)) {
                            mTouchMode = TOUCH_MODE_TAP;
                            setSelectedPositionInt(mMotionPosition);
                            layoutChildren();
                            child.setPressed(true);
                            positionSelector(mMotionPosition, child);
                            setPressed(true);
                            if (mSelector != null) {
                                Drawable d = mSelector.getCurrent();
                                if (d != null && d instanceof TransitionDrawable) {
                                    ((TransitionDrawable) d).resetTransition();
                                }
                                mSelector.setHotspot(x, ev.getY());
                            }
                            if (mTouchModeReset != null) {
                                removeCallbacks(mTouchModeReset);
                            }
                            mTouchModeReset = new Runnable() {
                                @Override
                                public void run() {
                                    mTouchModeReset = null;
                                    mTouchMode = TOUCH_MODE_REST;
                                    child.setPressed(false);
                                    setPressed(false);
                                    if (!mDataChanged && !mIsDetaching && isAttachedToWindow()) {
                                        performClick.run();
                                    }
                                }
                            };
                            postDelayed(mTouchModeReset,
                                    ViewConfiguration.getPressedStateDuration());
                        } else {
                            mTouchMode = TOUCH_MODE_REST;
                            updateSelectorState();
                        }
                        return;
                    } else if (!mDataChanged && mAdapter.isEnabled(motionPosition)) {
                        //线程在这里被启动！！！！！！！！！！！
                        performClick.run();
                    }
                }
            }
            mTouchMode = TOUCH_MODE_REST;
            updateSelectorState();
            break;

上面的代码没有截取完整的，但是这部分就够了，实验发现，问题出在了上面第一次的连续！标记处，即
inList && !child.hasExplicitFocusable()，根据debug发现inList为true，所以问题在右边 !child.hasExplicitFocusable()为false造成下面的代码没执行，performclick没有启动，也就是child.hasExplicitFocusable()为true，这个方法代码如下

只要自己或自己里面的的View有明确的可获得焦点的都会返回true
/**
     * Returns true if this view is focusable or if it contains a reachable View
     * for which {@link #hasExplicitFocusable()} returns {@code true}.
     * A "reachable hasExplicitFocusable()" is a view whose parents do not block descendants focus.
     * Only {@link #VISIBLE} views for which {@link #getFocusable()} would return
     * {@link #FOCUSABLE} are considered focusable.
     *
     * <p>This method preserves the pre-{@link Build.VERSION_CODES#O} behavior of
     * {@link #hasFocusable()} in that only views explicitly set focusable will cause
     * this method to return true. A view set to {@link #FOCUSABLE_AUTO} that resolves
     * to focusable will not.</p>
     *
     * @return {@code true} if the view is focusable or if the view contains a focusable
     *         view, {@code false} otherwise
     *
     * @see #hasFocusable()
     */
    public boolean hasExplicitFocusable() {
        return hasFocusable(false, true);
    }

    boolean hasFocusable(boolean allowAutoFocus, boolean dispatchExplicit) {
        if (!isFocusableInTouchMode()) {
            for (ViewParent p = mParent; p instanceof ViewGroup; p = p.getParent()) {
                final ViewGroup g = (ViewGroup) p;
                if (g.shouldBlockFocusForTouchscreen()) {
                    return false;
                }
            }
        }

        // Invisible and gone views are never focusable.
        if ((mViewFlags & VISIBILITY_MASK) != VISIBLE) {
            return false;
        }

        //debug发现最终代码执行到了这个if语句里面，说明这个if是成立的
        // Only use effective focusable value when allowed.
        if ((allowAutoFocus || getFocusable() != FOCUSABLE_AUTO) && isFocusable()) {
            return true;
        }

        return false;
    }

4.根据文档说明
if the view is focusable or if the view contains a focusable
view, {@code false} otherwise
意思是如果这个View是可获得焦点或者它包含一个可获得焦点的View就返回True，经过验证EditText是默认可获得焦点的，这就使方法返回true，所以child.hasExplicitFocusable()为true，所以造成回调无法被执行。

这个回调可以看到是在onTouchUp中被调用，而onTouchUp是在OnTouchEvent中，接收到事件ACTION_UP时候被调用

 @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if (!isEnabled()) {
            // A disabled view that is clickable still consumes the touch
            // events, it just doesn't respond to them.
            return isClickable() || isLongClickable();
        }

        if (mPositionScroller != null) {
            mPositionScroller.stop();
        }

        if (mIsDetaching || !isAttachedToWindow()) {
            // Something isn't right.
            // Since we rely on being attached to get data set change notifications,
            // don't risk doing anything where we might try to resync and find things
            // in a bogus state.
            return false;
        }

        startNestedScroll(SCROLL_AXIS_VERTICAL);

        if (mFastScroll != null && mFastScroll.onTouchEvent(ev)) {
            return true;
        }

        initVelocityTrackerIfNotExists();
        final MotionEvent vtev = MotionEvent.obtain(ev);

        final int actionMasked = ev.getActionMasked();
        if (actionMasked == MotionEvent.ACTION_DOWN) {
            mNestedYOffset = 0;
        }
        vtev.offsetLocation(0, mNestedYOffset);
        switch (actionMasked) {
            case MotionEvent.ACTION_DOWN: {
                onTouchDown(ev);
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                onTouchMove(ev, vtev);
                break;
            }
/**
！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！这里
*/
            case MotionEvent.ACTION_UP: {
                onTouchUp(ev);
                break;
            }