android textview settext卡顿深层次原因

最近在公司项目里面发现listview里面的textview在调用settext函数的时候非常耗时，当时都有点不敢相信，这是因为如果你把textview设置成wrap_content，则每次调用settext之后会调用到

<pre name="code" class="java">........
4033
4034
if (mMovement != null) {
4035
mMovement.initialize(this, (Spannable) text);
4036
4037
/*
4038
* Initializing the movement method will have set the
4039
* selection, so reset mSelectionMoved to keep that from
4040
* interfering with the normal on-focus selection-setting.
4041
*/
4042
if (mEditor != null) mEditor.mSelectionMoved = false;
4043
}
4044
}
4045
4046
if (mLayout != null) {
4047
//这个函数非常重要
4047
checkForRelayout();
4048
}
4049
4050
sendOnTextChanged(text, 0, oldlen, textLength);
4051
onTextChanged(text, 0, oldlen, textLength);
4052
4053
notifyViewAccessibilityStateChangedIfNeeded(AccessibilityEvent.CONTENT_CHANGE_TYPE_TEXT);
4054
.........

6807
private void More ...checkForRelayout() {
6808
// If we have a fixed width, we can just swap in a new text layout
6809
// if the text height stays the same or if the view height is fixed.
6810
6811
if ((mLayoutParams.width != LayoutParams.WRAP_CONTENT ||
6812
(mMaxWidthMode == mMinWidthMode && mMaxWidth == mMinWidth)) &&
6813
(mHint == null || mHintLayout != null) &&
6814
(mRight - mLeft - getCompoundPaddingLeft() - getCompoundPaddingRight() > 0)) {
6815
// Static width, so try making a new text layout.
6816
6817
int oldht = mLayout.getHeight();
6818
int want = mLayout.getWidth();
6819
int hintWant = mHintLayout == null ? 0 : mHintLayout.getWidth();
6820
6821
/*
6822
* No need to bring the text into view, since the size is not
6823
* changing (unless we do the requestLayout(), in which case it
6824
* will happen at measure).
6825
*/
6826
makeNewLayout(want, hintWant, UNKNOWN_BORING, UNKNOWN_BORING,
6827
mRight - mLeft - getCompoundPaddingLeft() - getCompoundPaddingRight(),
6828
false);
6829
6830
if (mEllipsize != TextUtils.TruncateAt.MARQUEE) {
6831
// In a fixed-height view, so use our new text layout.
6832
if (mLayoutParams.height != LayoutParams.WRAP_CONTENT &&
6833
mLayoutParams.height != LayoutParams.MATCH_PARENT) {
6834
invalidate();
6835
return;
6836
}
6837
6838
// Dynamic height, but height has stayed the same,
6839
// so use our new text layout.
6840
if (mLayout.getHeight() == oldht &&
6841
(mHintLayout == null || mHintLayout.getHeight() == oldht)) {
6842
invalidate();
6843
return;
6844
}
6845
}
6846
6847
// We lose: the height has changed and we have a dynamic height.
6848
// Request a new view layout using our new text layout.
6849
requestLayout();
6850
invalidate();
6851
} else {
6852
// Dynamic width, so we have no choice but to request a new
6853
// view layout with a new text layout.
6854
nullLayouts();
6855
requestLayout();
6856
invalidate();
6857
}
6858
}

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