关键计算地方:
1.当前是上滑动还是下滑动(相对于屏幕) ,使用ev.getRawY()获得当前滑动位置在屏幕哪个地方
2. 计算文本客滑动到哪里即可停止, (行高*总文本行数)- (行高 * 最多显示行数) int sum = getLineHeight() * getLineCount() - getLineHeight() * getMaxLines();
代码：
import android.content.Context;
import android.text.method.ScrollingMovementMethod;
import android.util.AttributeSet;
import android.view.MotionEvent;
/**
* @Description: 可滑动的TextView, 并且解决了与 ScrollView等的滑动冲突
*/
public class ScrollTextView extends android.support.v7.widget.AppCompatTextView {
public ScrollTextView(Context context) {
super(context);
setMovementMethod(ScrollingMovementMethod.getInstance());
}
public ScrollTextView(Context context, AttributeSet attrs) {
super(context, attrs);
setMovementMethod(ScrollingMovementMethod.getInstance());
}
public ScrollTextView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
setMovementMethod(ScrollingMovementMethod.getInstance());
}
float lastScrollY = 0;
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (getLineCount() > getMaxLines()) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
lastScrollY = ev.getRawY();
} else if (ev.getAction() == MotionEvent.ACTION_MOVE) {
//滑动到头并且还在继续上滑动,或者滑动到底部就不要再拦截了(有误差)
int sum = getLineHeight() * getLineCount() - getLineHeight() * getMaxLines();
//计算上次与本次差
float diff = lastScrollY - ev.getRawY();
if (diff>0){//下滑动并且到达了底部也不要处理了
//底部这里用abs的原因是,因为计算sum的时候有些误差
if (Math.abs(sum - getScrollY())<5) {
getParent().requestDisallowInterceptTouchEvent(false);
} else {
getParent().requestDisallowInterceptTouchEvent(true);
}
}else if (diff<0){//上滑动
if (getScrollY() == 0) {//上滑动并且已经到达了顶部就不要在处理了
getParent().requestDisallowInterceptTouchEvent(false);
} else {
getParent().requestDisallowInterceptTouchEvent(true);
}
}
lastScrollY = ev.getRawY();
} else {
getParent().requestDisallowInterceptTouchEvent(false);
}
}
return super.onTouchEvent(ev);
}
}
如果上面方法不能解决你的问题，那就参考下面的文章，让textview实现 NestedScroolChild3 接口，并重写相应的方法，从而实现TextView嵌套滑动。
WebView 实现嵌套滑动，丝滑般实现吸顶效果，完美兼容 X5 webview
我使用的代码：
package com.**.view;
import android.annotation.SuppressLint;
import android.text.StaticLayout;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.text.Layout;
import android.text.TextPaint;
import android.text.method.ScrollingMovementMethod;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewParent;
import android.widget.OverScroller;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.core.view.NestedScrollingChild3;
import androidx.core.view.NestedScrollingChildHelper;
import androidx.core.view.ViewCompat;
public class JustifyTextView extends androidx.appcompat.widget.AppCompatTextView implements NestedScrollingChild3 {
private static final String TAG = "JustifyTextView";
private int mLineY;
private int mViewWidth;
private static final int INVALID_POINTER = -1;
private final int[] mScrollOffset = new int[2];
private final int[] mScrollConsumed = new int[2];
private int mLastMotionY;
private NestedScrollingChildHelper mChildHelper;
private boolean mIsBeingDragged = false;
private VelocityTracker mVelocityTracker;
private int mTouchSlop;
private int mActivePointerId = INVALID_POINTER;
private int mNestedYOffset;
private OverScroller mScroller;
private int mMinimumVelocity;
private int mMaximumVelocity;
private int mLastScrollerY;
public JustifyTextView(Context context) {
super(context);
init();
}
public JustifyTextView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public JustifyTextView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init() {
mScroller = new OverScroller(getContext());
setMovementMethod(ScrollingMovementMethod.getInstance());
setOverScrollMode(TextView.OVER_SCROLL_NEVER);
mChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
}
@Override
protected void onDraw(Canvas canvas) {
TextPaint paint = getPaint();
paint.setColor(getCurrentTextColor());
// 返回绘制状态的资源ID数组表示视图的当前状态
paint.drawableState = getDrawableState();
// 对View上的内容进行测量后得到的View内容占据的宽度
// 前提是你必须在父布局的onLayout()方法或者此View的onDraw()方法里调用measure(0,0);
// 否则你得到的结果和getWidth()得到的结果一样。
mViewWidth = getMeasuredWidth();
// 获取文本
String text = getText().toString();
mLineY = 0;
mLineY += getTextSize();
// 获取用于显示当前文本的布局
Layout layout = getLayout();
if (layout == null) {
return;
}
Paint.FontMetrics fm = paint.getFontMetrics();
int textHeight = (int) (Math.ceil(fm.descent - fm.ascent));
textHeight = (int) (textHeight * layout.getSpacingMultiplier() + layout.getSpacingAdd());
for (int i = 0; i < layout.getLineCount(); i++) {
// 返回文本中的指定行开头的偏移
int lineStart = layout.getLineStart(i);
// 返回文本中的指定行最后一个字符的偏移
int lineEnd = layout.getLineEnd(i);
float width = StaticLayout.getDesiredWidth(text, lineStart, lineEnd, getPaint());
String line = text.substring(lineStart, lineEnd);
if (line.equals("")) {
break;
}
if (i < layout.getLineCount() - 1) {
if (needScale(line)) {
drawScaledText(canvas, lineStart, line, width);
} else {
// canvas.drawText(line.replace("%", ""), 0, mLineY, paint);
canvas.drawText(line, 0, mLineY, paint);
}
} else {
canvas.drawText(line, 0, mLineY, paint);
}
// 增加行高
mLineY += textHeight;
}
}
private void drawScaledText(Canvas canvas, int lineStart, String line,
float lineWidth) {
float x = 0;
if (isFirstLineOfParagraph(lineStart, line)) {
String blanks = " ";
canvas.drawText(blanks, x, mLineY, getPaint());
float bw = StaticLayout.getDesiredWidth(blanks, getPaint());
x += bw;
line = line.substring(3);
}
int gapCount = line.length() - 1;
int i = 0;
if (line.length() > 2 && line.charAt(0) == 12288
&& line.charAt(1) == 12288) {
String substring = line.substring(0, 2);
float cw = StaticLayout.getDesiredWidth(substring, getPaint());
canvas.drawText(substring, x, mLineY, getPaint());
x += cw;
i += 2;
}
float d = (mViewWidth - lineWidth) / gapCount;
for (; i < line.length(); i++) {
String c = String.valueOf(line.charAt(i));
float cw = StaticLayout.getDesiredWidth(c, getPaint());
canvas.drawText(c, x, mLineY, getPaint());
x += cw + d;
}
}
private boolean isFirstLineOfParagraph(int lineStart, String line) {
return line.length() > 3 && line.charAt(0) == ' ' && line.charAt(1) == ' ';
}
private boolean needScale(String line) {
if (line.length() == 0) {
return false;
} else {
// return line.charAt(line.length() - 1) != '%';
return line.charAt(line.length() - 1) != '\n';
}
}
@SuppressLint("ClickableViewAccessibility")
@Override
public boolean onTouchEvent(MotionEvent ev) {
initVelocityTrackerIfNotExists();
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:
if ((mIsBeingDragged = !mScroller.isFinished())) {
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
if (!mScroller.isFinished()) {
abortAnimatedScroll();
}
mLastMotionY = (int) ev.getY();
mActivePointerId = ev.getPointerId(0);
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_TOUCH);
break;
case MotionEvent.ACTION_MOVE:
final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
if (activePointerIndex == -1) {
Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent");
break;
}
final int y = (int) ev.getY(activePointerIndex);
int deltaY = mLastMotionY - y;
if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset,
ViewCompat.TYPE_TOUCH)) {
deltaY -= mScrollConsumed[1];
mNestedYOffset += mScrollOffset[1];
}
if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) {
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
mIsBeingDragged = true;
if (deltaY > 0) {
deltaY -= mTouchSlop;
} else {
deltaY += mTouchSlop;
}
}
if (mIsBeingDragged) {
mLastMotionY = y - mScrollOffset[1];
final int oldY = getScrollY();
final int range = getScrollRange();
// Calling overScrollByCompat will call onOverScrolled, which
// calls onScrollChanged if applicable.
if (overScrollByCompat(0, deltaY, 0, oldY, 0, range, 0,
0, true) && !hasNestedScrollingParent(ViewCompat.TYPE_TOUCH)) {
mVelocityTracker.clear();
}
final int scrolledDeltaY = getScrollY() - oldY;
final int unconsumedY = deltaY - scrolledDeltaY;
mScrollConsumed[1] = 0;
dispatchNestedScroll(0, scrolledDeltaY, 0, unconsumedY, mScrollOffset,
ViewCompat.TYPE_TOUCH, mScrollConsumed);
mLastMotionY -= mScrollOffset[1];
mNestedYOffset += mScrollOffset[1];
}
break;
case MotionEvent.ACTION_UP:
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId);
if ((Math.abs(initialVelocity) > mMinimumVelocity)) {
if (!dispatchNestedPreFling(0, -initialVelocity)) {
dispatchNestedFling(0, -initialVelocity, true);
fling(-initialVelocity);
}
} else if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
getScrollRange())) {
ViewCompat.postInvalidateOnAnimation(this);
}
mActivePointerId = INVALID_POINTER;
endDrag();
break;
case MotionEvent.ACTION_CANCEL:
if (mIsBeingDragged) {
if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
getScrollRange())) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
mActivePointerId = INVALID_POINTER;
endDrag();
break;
case MotionEvent.ACTION_POINTER_DOWN:
final int index = ev.getActionIndex();
mLastMotionY = (int) ev.getY(index);
mActivePointerId = ev.getPointerId(index);
break;
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId));
break;
}
if (mVelocityTracker != null) {
mVelocityTracker.addMovement(vtev);
}
vtev.recycle();
return super.onTouchEvent(ev);
}
private void abortAnimatedScroll() {
mScroller.abortAnimation();
stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
}
private void endDrag() {
mIsBeingDragged = false;
recycleVelocityTracker();
stopNestedScroll();
}
private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK)
>> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = ev.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastMotionY = (int) ev.getY(newPointerIndex);
mActivePointerId = ev.getPointerId(newPointerIndex);
if (mVelocityTracker != null) {
mVelocityTracker.clear();
}
}
}
private void fling(int velocityY) {
int height = getHeight();
mScroller.fling(getScrollX(), getScrollY(), // start
0, velocityY, // velocities
0, 0, // x
Integer.MIN_VALUE, Integer.MAX_VALUE, // y
0, height / 2);
runAnimatedScroll(true);
}
private void runAnimatedScroll(boolean participateInNestedScrolling) {
if (participateInNestedScrolling) {
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_NON_TOUCH);
} else {
stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
}
mLastScrollerY = getScrollY();
ViewCompat.postInvalidateOnAnimation(this);
}
private void initOrResetVelocityTracker() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
} else {
mVelocityTracker.clear();
}
}
private void initVelocityTrackerIfNotExists() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
}
private void recycleVelocityTracker() {
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
@Override
protected boolean overScrollBy(int deltaX, int deltaY,
int scrollX, int scrollY,
int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY,
boolean isTouchEvent) {
// this is causing double scroll call (doubled speed), but this WebView isn't overscrollable
// all overscrolls are passed to appbar, so commenting this out during drag
if (!mIsBeingDragged)
overScrollByCompat(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY,
maxOverScrollX, maxOverScrollY, isTouchEvent);
// without this call webview won't scroll to top when url change or when user pick input
// (webview should move a bit making input still in viewport when "adjustResize")
return true;
}
int getScrollRange() {
//Using scroll range of webview instead of childs as NestedScrollView does.
return computeVerticalScrollRange();
}
@Override
public boolean isNestedScrollingEnabled() {
return mChildHelper.isNestedScrollingEnabled();
}
@Override
public void setNestedScrollingEnabled(boolean enabled) {
mChildHelper.setNestedScrollingEnabled(enabled);
}
@Override
public boolean startNestedScroll(int axes, int type) {
return mChildHelper.startNestedScroll(axes, type);
}
@Override
public boolean startNestedScroll(int axes) {
return startNestedScroll(axes, ViewCompat.TYPE_TOUCH);
}
@Override
public void stopNestedScroll(int type) {
mChildHelper.stopNestedScroll(type);
}
@Override
public void stopNestedScroll() {
stopNestedScroll(ViewCompat.TYPE_TOUCH);
}
@Override
public boolean hasNestedScrollingParent(int type) {
return mChildHelper.hasNestedScrollingParent(type);
}
@Override
public boolean hasNestedScrollingParent() {
return hasNestedScrollingParent(ViewCompat.TYPE_TOUCH);
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed,
int[] offsetInWindow) {
return dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, ViewCompat.TYPE_TOUCH);
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed,
int[] offsetInWindow, int type) {
return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, type);
}
@Override
public void dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed,
@Nullable int[] offsetInWindow, int type, @NonNull int[] consumed) {
mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, type, consumed);
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
return dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, ViewCompat.TYPE_TOUCH);
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow, int type) {
return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type);
}
@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return mChildHelper.dispatchNestedFling(velocityX, velocityY, false);
}
@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
}
@Override
public void computeScroll() {
if (mScroller.isFinished()) {
return;
}
mScroller.computeScrollOffset();
final int y = mScroller.getCurrY();
int unconsumed = y - mLastScrollerY;
mLastScrollerY = y;
// Nested Scrolling Pre Pass
mScrollConsumed[1] = 0;
dispatchNestedPreScroll(0, unconsumed, mScrollConsumed, null,
ViewCompat.TYPE_NON_TOUCH);
unconsumed -= mScrollConsumed[1];
if (unconsumed != 0) {
// Internal Scroll
final int oldScrollY = getScrollY();
overScrollByCompat(0, unconsumed, getScrollX(), oldScrollY, 0, getScrollRange(),
0, 0, false);
final int scrolledByMe = getScrollY() - oldScrollY;
unconsumed -= scrolledByMe;
// Nested Scrolling Post Pass
mScrollConsumed[1] = 0;
dispatchNestedScroll(0, 0, 0, unconsumed, mScrollOffset,
ViewCompat.TYPE_NON_TOUCH, mScrollConsumed);
unconsumed -= mScrollConsumed[1];
}
if (unconsumed != 0) {
abortAnimatedScroll();
}
if (!mScroller.isFinished()) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
// copied from NestedScrollView exacly as it looks, leaving overscroll related code, maybe future use
private boolean overScrollByCompat(int deltaX, int deltaY,
int scrollX, int scrollY,
int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY,
boolean isTouchEvent) {
final int overScrollMode = getOverScrollMode();
final boolean canScrollHorizontal =
computeHorizontalScrollRange() > computeHorizontalScrollExtent();
final boolean canScrollVertical =
computeVerticalScrollRange() > computeVerticalScrollExtent();
final boolean overScrollHorizontal = overScrollMode == View.OVER_SCROLL_ALWAYS
|| (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && canScrollHorizontal);
final boolean overScrollVertical = overScrollMode == View.OVER_SCROLL_ALWAYS
|| (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && canScrollVertical);
int newScrollX = scrollX + deltaX;
if (!overScrollHorizontal) {
maxOverScrollX = 0;
}
int newScrollY = scrollY + deltaY;
if (!overScrollVertical) {
maxOverScrollY = 0;
}
// Clamp values if at the limits and record
final int left = -maxOverScrollX;
final int right = maxOverScrollX + scrollRangeX;
final int top = -maxOverScrollY;
final int bottom = maxOverScrollY + scrollRangeY;
boolean clampedX = false;
if (newScrollX > right) {
newScrollX = right;
clampedX = true;
} else if (newScrollX < left) {
newScrollX = left;
clampedX = true;
}
boolean clampedY = false;
if (newScrollY > bottom) {
newScrollY = bottom;
clampedY = true;
} else if (newScrollY < top) {
newScrollY = top;
clampedY = true;
}
if (clampedY && !hasNestedScrollingParent(ViewCompat.TYPE_NON_TOUCH)) {
mScroller.springBack(newScrollX, newScrollY, 0, 0, 0, getScrollRange());
}
onOverScrolled(newScrollX, newScrollY, clampedX, clampedY);
return clampedX || clampedY;
}
}分享：
定时垂直滚动的textview：GitHub - paradoxie/AutoVerticalTextview: 垂直滚动的textview，继承自TextSwitcher，抽出一个依赖库供以后备用
左右对齐的TextView
GitHub - Giftedcat/JustifyTextView: 左右对齐的TextView，适配各种分辨率，完美实现UI需求