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Android手掌抑制功能的实现
近期须要实现一个功能，在Activity中有一个手写区域，为了更好的用户体验，须要满足即使整个手掌放在屏幕上时（android平板，屏幕比較大）也仅仅响应手写区域内的操作，即在支持多点触控的情况下，仅仅响应指定的区域，我将这个功能称作“手掌抑制”，即在手写时。手掌放在屏幕上面不做不论什么响应。
初看这个功能非常easy，依照之前处理listview、gridview里面的子view不能响应的方式，仅仅要在activity层不拦截向手写view传递的消息就可以实现想要的效果，但经过实际測试和对android消息机制的具体研究发现。要实现这个功能会有点小复杂。
一、android的消息传递机制：
1、基础知识：
(1) 全部Touch事件都被封装成了MotionEvent对象。包含Touch的位置、时间、历史记录以及第几个手指(多指触摸)等。
(2) 事件类型分为ACTION_DOWN, ACTION_UP, ACTION_MOVE, ACTION_POINTER_DOWN, ACTION_POINTER_UP, ACTION_CANCEL，每一个事件都是以ACTION_DOWN開始ACTION_UP结束。
(3) 对事件的处理包含三类：
传递——dispatchTouchEvent()
拦截——onInterceptTouchEvent()
消费——onTouchEvent()和OnTouchListener
2、传递流程
(1) 事件从Activity.dispatchTouchEvent()開始传递，仅仅要没有被停止或拦截，从最上层的View(ViewGroup)開始一直往下(子View)传递。子View能够通过onTouchEvent()对事件进行处理。
(2) 事件由父View(ViewGroup)传递给子View，ViewGroup能够通过onInterceptTouchEvent()对事件做拦截，停止其往下传递。
(3) 假设事件从上往下传递过程中一直没有被停止，且最底层子View没有消费事件。事件会反向往上传递，这时父View(ViewGroup)能够进行消费，假设还是没有被消费的话，最后会到Activity的onTouchEvent()函数。
(4) 假设View没有对ACTION_DOWN进行消费，之后的其它事件不会传递过来。
(5) OnTouchListener优先于onTouchEvent()对事件进行消费。
上面的消费即表示对应函数返回值为true。
3、实际情况：
可以响应事件处理方法的控件包含：ViewGroup、View、Activity，各类控件对三个事件响应处理方法的支持情况例如以下：
这三个控件。Activity是处于最外层的，消息的传递首先是系统回调消息给Activity。Activity将消息传递给每个ViewGroup，然后ViewGroup会将消息传递给对应地子View。
本文所描写叙述的手写控件是一个view，在有系统消息回调时仅仅有上层控件将消息分发下来，它才可以消费和处理这些消息。
二、问题现象：
接着我们进入正题，依照我在开篇介绍的那种处理方式，写一个手写view，在Activity和ViewGroup（自己定义一个Layout就可以）层将消息分发给该view，眼下的代码看上去是这样子的：
public class DrawView extends View {
public DrawView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initPaintView( );
}
public DrawView(Context context, AttributeSet attrs) {
super(context, attrs);
initPaintView( );
}
public DrawView(Context context) {
super(context);
initPaintView( );
}
public void clear() {
if (null != mPath) {
mPath.reset();
invalidate();
}
}
private void initPaintView() {
mPaint.setAntiAlias(true);
mPaint.setColor(Color.WHITE);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeWidth(5f);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mViewWidth = MeasureSpec.getSize(widthMeasureSpec); //获取ViewGroup宽度
mViewHeight = MeasureSpec.getSize(heightMeasureSpec); //获取ViewGroup高度
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(mPath, mPaint);
}
public boolean inArea( float x, float y ){
return ( x >= 0 && x <= mViewWidth && y >= 0 && y <= mViewHeight)?true:false;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = event.getX( );
float eventY = event.getY( );
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: {
mPath.moveTo(eventX, eventY);
mLastTouchX = eventX;
mLastTouchY = eventY;
invalidate( );
}
return true;
case MotionEvent.ACTION_MOVE:{
drawView( event, eventX, eventY );
}
break;
case MotionEvent.ACTION_UP:{
drawView( event, eventX, eventY );
}
break;
default:
return false;
}
return true;
}
private void drawView( MotionEvent event, float eventX, float eventY ){
resetDirtyRect(eventX, eventY);
int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
float historicalX = event.getHistoricalX(i);
float historicalY = event.getHistoricalY(i);
getDirtyRect(historicalX, historicalY);
mPath.lineTo(historicalX, historicalY);
}
mPath.lineTo(eventX, eventY);
invalidate((int) (mDirtyRect.left - HALF_STROKE_WIDTH),
(int) (mDirtyRect.top - HALF_STROKE_WIDTH),
(int) (mDirtyRect.right + HALF_STROKE_WIDTH),
(int) (mDirtyRect.bottom + HALF_STROKE_WIDTH));
mLastTouchX = eventX;
mLastTouchY = eventY;
}
private void getDirtyRect(float historicalX, float historicalY) {
if (historicalX < mDirtyRect.left) {
mDirtyRect.left = historicalX;
} else if (historicalX > mDirtyRect.right) {
mDirtyRect.right = historicalX;
}
if (historicalY < mDirtyRect.top) {
mDirtyRect.top = historicalY;
} else if (historicalY > mDirtyRect.bottom) {
mDirtyRect.bottom = historicalY;
}
}
private void resetDirtyRect(float eventX, float eventY) {
mDirtyRect.left = Math.min(mLastTouchX, eventX);
mDirtyRect.right = Math.max(mLastTouchX, eventX);
mDirtyRect.top = Math.min(mLastTouchY, eventY);
mDirtyRect.bottom = Math.max(mLastTouchY, eventY);
}
private static final float STROKE_WIDTH = 5f;
private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;
private float mLastTouchX = 0;
private float mLastTouchY = 0;
private int mViewWidth = 0;
private int mViewHeight = 0;
private final RectF mDirtyRect = new RectF();
private Paint mPaint = new Paint();
private Path mPath = new Path();
} 你会发现，当你将activity的dispatchTouchEvent和viewgroup的dispatchTouchEvent、onInterceptTouchEvent方法的返回值都设置为false时，整个屏幕都不会响应不论什么消息了，当我们去掉activity和viewgroup的dispatchTouchEvent方法，仅仅有viewgroup的onInterceptTouchEvent返回值被置为false时，手写区域可以响应。但当手掌靠在手写区域外，在手写区域内手写就失效了，事实上和去掉viewgroupd的onInterceptTouchEvent方法效果是一样的，也就是说明这样的处理方式是不可行的。
三、解决方式：
加了同意分发消息的方法。不拦截向下分发消息反而还不行，这个问题详细原因我没有找到。个人觉得是系统针对activity的消息事件处理做了特殊处理，它的优先级是最高的，尽管能够复写它的消息分发dispatchTouchEvent方法，可是无论是返回true还是false结果都是屏幕不能响应不论什么操作。这一点有知道的大拿欢迎指点指点。
要实现本文想要的功能显然不能使用开篇讲到的方法，在研究这个问题的过程中，发现尽管activity的dispatchTouchEvent无法控制，但其onTouchEvent方法是有效的，仅仅要在屏幕的不论什么一个地方操作，onTouchEvent里面都会有打印消息，细致回想上面提到的android消息分发机制会发现，仅仅要我们在屏幕上操作时，模拟系统在activity的onTouchEvent方法里面向手写view派发消息就可以实现想要的功能。详细方法例如以下：
1、向下派发消息的实现以及view和activity之间的坐标转换：
如上面所讲，当在屏幕上操作时监听activity的onTouchEvent方法，将在手写控件内的操作派发给手写view就可以实现想要的功能。
（1）坐标转换：
本文的手写view基于activity居中的，它的坐标原点和activity的坐标原点不同样，为了推断在acitivity上操作的地方是否在手写view内。须要通过坐标转换之后才干推断：
如上图所看到的，在activity中推断一个点(x,y)是否在手写view里面时，转换成的坐标应该是(x-view.getLeft(),y-view.getTop())。
（2）眼下的view和activity看起来是这样子的：
DrawView：
public class DrawView extends View {
public DrawView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initPaintView( );
}
public DrawView(Context context, AttributeSet attrs) {
super(context, attrs);
initPaintView( );
}
public DrawView(Context context) {
super(context);
initPaintView( );
}
public void clear() {
if (null != mPath) {
mPath.reset();
invalidate();
}
}
private void initPaintView() {
mPaint.setAntiAlias(true);
mPaint.setColor(Color.WHITE);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeWidth(5f);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mViewWidth = MeasureSpec.getSize(widthMeasureSpec); //获取ViewGroup宽度
mViewHeight = MeasureSpec.getSize(heightMeasureSpec); //获取ViewGroup高度
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(mPath, mPaint);
}
public boolean inArea( float x, float y ){
return ( x >= 0 && x <= mViewWidth && y >= 0 && y <= mViewHeight)?true:false;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = -1;
float eventY = -1;
int pointId = 0;
int pointCnt = event.getPointerCount( );
for( int index = 0; index < pointCnt; index++ ){
if( inArea( event.getX( index ) - getLeft( ), event.getY( index ) - getTop( ) ) ){
pointId = index;
eventX = event.getX( index ) - getLeft( );
eventY = event.getY( index ) - getTop( );
break;
}
}
if( ( eventX == -1 || eventY == -1 ) || ( eventX == 0 || eventY == 0 ) ){
return false;
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: {
mPath.moveTo(eventX, eventY);
mLastTouchX = eventX;
mLastTouchY = eventY;
invalidate( );
}
return true;
case MotionEvent.ACTION_MOVE:{
drawView( event, eventX, eventY, pointId );
}
break;
case MotionEvent.ACTION_UP:{
drawView( event, eventX, eventY, pointId );
}
break;
default:
return false;
}
return true;
}
private void drawView( MotionEvent event, float eventX, float eventY, int pointId ){
resetDirtyRect(eventX, eventY);
int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
float historicalX = event.getHistoricalX(pointId,i) - getLeft( );
float historicalY = event.getHistoricalY(pointId,i) - getTop( );
getDirtyRect(historicalX, historicalY);
mPath.lineTo(historicalX, historicalY);
}
mPath.lineTo(eventX, eventY);
invalidate((int) (mDirtyRect.left - HALF_STROKE_WIDTH),
(int) (mDirtyRect.top - HALF_STROKE_WIDTH),
(int) (mDirtyRect.right + HALF_STROKE_WIDTH),
(int) (mDirtyRect.bottom + HALF_STROKE_WIDTH));
mLastTouchX = eventX;
mLastTouchY = eventY;
}
private void getDirtyRect(float historicalX, float historicalY) {
if (historicalX < mDirtyRect.left) {
mDirtyRect.left = historicalX;
} else if (historicalX > mDirtyRect.right) {
mDirtyRect.right = historicalX;
}
if (historicalY < mDirtyRect.top) {
mDirtyRect.top = historicalY;
} else if (historicalY > mDirtyRect.bottom) {
mDirtyRect.bottom = historicalY;
}
}
private void resetDirtyRect(float eventX, float eventY) {
mDirtyRect.left = Math.min(mLastTouchX, eventX);
mDirtyRect.right = Math.max(mLastTouchX, eventX);
mDirtyRect.top = Math.min(mLastTouchY, eventY);
mDirtyRect.bottom = Math.max(mLastTouchY, eventY);
}
private static final float STROKE_WIDTH = 5f;
private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;
private float mLastTouchX = 0;
private float mLastTouchY = 0;
private int mViewWidth = 0;
private int mViewHeight = 0;
private final RectF mDirtyRect = new RectF();
private Paint mPaint = new Paint();
private Path mPath = new Path();
}Activity：
@Override
public boolean onTouchEvent(MotionEvent event) {
int pointCnt = event.getPointerCount( );
for( int index = 0; index < pointCnt; index++ ){
if( mDrawView.inArea( event.getX( index ) - mDrawView.getLeft( ), event.getY( index ) - mDrawView.getTop( ) ) ){
mDrawView.onTouchEvent( event );
System.out.println( "action === pointIndex " + index );
return false;
}
}
//mDrawView.setInView( false );
return super.onTouchEvent(event);
} DrawView的inArea方法为核心方法。经过上面的处理后，可以实现当手掌放在手写区域外时在手写区域手写的功能。效果例如以下图所看到的。但你会发现当在手写区域手写的手指抬起再放下继续手写时，会直接画一条直线。通过接下来对android事件机制中ACTION_DOWN和ACTION_UP消息的分析，该问题将会得到解决。
2、android消息事件中ACTION_DOWN和ACTION_UP的触发时机即改善方案：
通过实际測试发现，android消息事件中ACTION_DOWN和ACTION_UP的触发时机分别为：
ACTION_DOWN：仅仅要有手指接触屏幕即会触发；
ACTION_UP：当屏幕上没有不论什么触控操作时触发；
对于多点触控。当某个手指抬起或者松开时会分别触发：ACTION_POINTER_DOWN和ACTION_POINTER_UP，所以对于上面遇到的问题，是因为在多点触控的情况下，仅仅点下或者松开某一根手指时，这两个消息不会触发导致，将ACTION_POINTER_DOWN和ACTION_POINTER_UP这两类消息在DrawView的onTouchEvent方法中一并处理就可以解决，改善后的view代码是这样子的：
public class DrawView extends View {
public DrawView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initPaintView( );
}
public DrawView(Context context, AttributeSet attrs) {
super(context, attrs);
initPaintView( );
}
public DrawView(Context context) {
super(context);
initPaintView( );
}
public void clear() {
if (null != mPath) {
mPath.reset();
invalidate();
}
}
private void initPaintView() {
mPaint.setAntiAlias(true);
mPaint.setColor(Color.WHITE);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeWidth(5f);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mViewWidth = MeasureSpec.getSize(widthMeasureSpec); //获取ViewGroup宽度
mViewHeight = MeasureSpec.getSize(heightMeasureSpec); //获取ViewGroup高度
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(mPath, mPaint);
}
public boolean inArea( float x, float y ){
return ( x >= 0 && x <= mViewWidth && y >= 0 && y <= mViewHeight)?true:false;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = -1;
float eventY = -1;
int pointId = 0;
int pointCnt = event.getPointerCount( );
for( int index = 0; index < pointCnt; index++ ){
if( inArea( event.getX( index ) - getLeft( ), event.getY( index ) - getTop( ) ) ){
pointId = index;
eventX = event.getX( index ) - getLeft( );
eventY = event.getY( index ) - getTop( );
break;
}
}
if( ( eventX == -1 || eventY == -1 ) || ( eventX == 0 || eventY == 0 ) ){
return false;
}
switch (event.getAction()) {
case MotionEvent.ACTION_POINTER_1_DOWN:
case MotionEvent.ACTION_POINTER_2_DOWN:
case MotionEvent.ACTION_POINTER_3_DOWN:
case MotionEvent.ACTION_DOWN: {
mPath.moveTo(eventX, eventY);
mLastTouchX = eventX;
mLastTouchY = eventY;
invalidate( );
}
return true;
case MotionEvent.ACTION_MOVE:{
drawView( event, eventX, eventY, pointId );
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_1_UP:
case MotionEvent.ACTION_POINTER_2_UP:
case MotionEvent.ACTION_POINTER_3_UP:{
drawView( event, eventX, eventY, pointId );
}
break;
default:
return false;
}
return true;
}
private void drawView( MotionEvent event, float eventX, float eventY, int pointId ){
resetDirtyRect(eventX, eventY);
int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
float historicalX = event.getHistoricalX(pointId,i) - getLeft( );
float historicalY = event.getHistoricalY(pointId,i) - getTop( );
getDirtyRect(historicalX, historicalY);
mPath.lineTo(historicalX, historicalY);
}
mPath.lineTo(eventX, eventY);
invalidate((int) (mDirtyRect.left - HALF_STROKE_WIDTH),
(int) (mDirtyRect.top - HALF_STROKE_WIDTH),
(int) (mDirtyRect.right + HALF_STROKE_WIDTH),
(int) (mDirtyRect.bottom + HALF_STROKE_WIDTH));
mLastTouchX = eventX;
mLastTouchY = eventY;
}
private void getDirtyRect(float historicalX, float historicalY) {
if (historicalX < mDirtyRect.left) {
mDirtyRect.left = historicalX;
} else if (historicalX > mDirtyRect.right) {
mDirtyRect.right = historicalX;
}
if (historicalY < mDirtyRect.top) {
mDirtyRect.top = historicalY;
} else if (historicalY > mDirtyRect.bottom) {
mDirtyRect.bottom = historicalY;
}
}
private void resetDirtyRect(float eventX, float eventY) {
mDirtyRect.left = Math.min(mLastTouchX, eventX);
mDirtyRect.right = Math.max(mLastTouchX, eventX);
mDirtyRect.top = Math.min(mLastTouchY, eventY);
mDirtyRect.bottom = Math.max(mLastTouchY, eventY);
}
private static final float STROKE_WIDTH = 5f;
private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;
private float mLastTouchX = 0;
private float mLastTouchY = 0;
private int mViewWidth = 0;
private int mViewHeight = 0;
private final RectF mDirtyRect = new RectF();
private Paint mPaint = new Paint();
private Path mPath = new Path();
}
效果也算比較理想了：
3、边界问题处理：
经过上面两步操作，基本上可以实现手掌抑制功能了，但经过细致測试会发现，当多点触控屏幕时。某根手指从手写控件外移动到手写控件内时，会在手写区域边界直接绘制成直线的现象，例如以下图：
这是由于在android中一个完整的消息流程离不开ACTION_DOWN和ACTION_UP，当手指从手写区域外移动到手写区域内时，手写区域根本没有接收到ACTION_DOWN消息，针对这样的情况，我们须要在activity中对view做特殊处理。即当检測到有手指在手写区域但没有触发ACTION_DOWN消息时，在ACTION_MOVE消息中处理ACTION_DOWN消息应该处理的事情。
改善后的代码是这个样子的：
DrawView：
public class DrawView extends View {
public DrawView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initPaintView( );
}
public DrawView(Context context, AttributeSet attrs) {
super(context, attrs);
initPaintView( );
}
public DrawView(Context context) {
super(context);
initPaintView( );
}
public void clear() {
if (null != mPath) {
mPath.reset();
invalidate();
}
}
private void initPaintView() {
mPaint.setAntiAlias(true);
mPaint.setColor(Color.WHITE);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeWidth(5f);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mViewWidth = MeasureSpec.getSize(widthMeasureSpec); //获取ViewGroup宽度
mViewHeight = MeasureSpec.getSize(heightMeasureSpec); //获取ViewGroup高度
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(mPath, mPaint);
}
public boolean inArea( float x, float y ){
return ( x >= 0 && x <= mViewWidth && y >= 0 && y <= mViewHeight)?true:false;
}
@SuppressWarnings("deprecation")
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = -1;
float eventY = -1;
int pointId = 0;
int pointCnt = event.getPointerCount( );
for( int index = 0; index < pointCnt; index++ ){
if( inArea( event.getX( index ) - getLeft( ), event.getY( index ) - getTop( ) ) ){
pointId = index;
eventX = event.getX( index ) - getLeft( );
eventY = event.getY( index ) - getTop( );
break;
}
}
if( ( eventX == -1 || eventY == -1 ) || ( eventX == 0 || eventY == 0 ) ){
return false;
}
switch (event.getAction()) {
case MotionEvent.ACTION_POINTER_1_DOWN:
case MotionEvent.ACTION_POINTER_2_DOWN:
case MotionEvent.ACTION_POINTER_3_DOWN:
case MotionEvent.ACTION_DOWN: {
mPath.moveTo(eventX, eventY);
mLastTouchX = eventX;
mLastTouchY = eventY;
mInView = true;
invalidate( );
}
return true;
case MotionEvent.ACTION_MOVE:{
if( !mInView ){
mInView = true;
mLastTouchX = eventX;
mLastTouchY = eventY;
mPath.moveTo(eventX, eventY);
}
drawView( event, eventX, eventY, pointId );
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_1_UP:
case MotionEvent.ACTION_POINTER_2_UP:
case MotionEvent.ACTION_POINTER_3_UP:{
drawView( event, eventX, eventY, pointId );
}
break;
default:
return false;
}
return true;
}
public void setInView( boolean inView ){
mInView = inView;
}
private void drawView( MotionEvent event, float eventX, float eventY, int pointId ){
resetDirtyRect(eventX, eventY);
int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
float historicalX = event.getHistoricalX(pointId,i) - getLeft( );
float historicalY = event.getHistoricalY(pointId,i) - getTop( );
getDirtyRect(historicalX, historicalY);
mPath.lineTo(historicalX, historicalY);
}
mPath.lineTo(eventX, eventY);
invalidate((int) (mDirtyRect.left - HALF_STROKE_WIDTH),
(int) (mDirtyRect.top - HALF_STROKE_WIDTH),
(int) (mDirtyRect.right + HALF_STROKE_WIDTH),
(int) (mDirtyRect.bottom + HALF_STROKE_WIDTH));
mLastTouchX = eventX;
mLastTouchY = eventY;
}
private void getDirtyRect(float historicalX, float historicalY) {
if (historicalX < mDirtyRect.left) {
mDirtyRect.left = historicalX;
} else if (historicalX > mDirtyRect.right) {
mDirtyRect.right = historicalX;
}
if (historicalY < mDirtyRect.top) {
mDirtyRect.top = historicalY;
} else if (historicalY > mDirtyRect.bottom) {
mDirtyRect.bottom = historicalY;
}
}
private void resetDirtyRect(float eventX, float eventY) {
mDirtyRect.left = Math.min(mLastTouchX, eventX);
mDirtyRect.right = Math.max(mLastTouchX, eventX);
mDirtyRect.top = Math.min(mLastTouchY, eventY);
mDirtyRect.bottom = Math.max(mLastTouchY, eventY);
}
private static final float STROKE_WIDTH = 5f;
private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;
private float mLastTouchX = 0;
private float mLastTouchY = 0;
private boolean mInView = false;
private int mViewWidth = 0;
private int mViewHeight = 0;
private final RectF mDirtyRect = new RectF();
private Paint mPaint = new Paint();
private Path mPath = new Path();
}
activity也须要添加一句话：
@Override
public boolean onTouchEvent(MotionEvent event) {
int pointCnt = event.getPointerCount( );
for( int index = 0; index < pointCnt; index++ ){
if( mDrawView.inArea( event.getX( index ) - mDrawView.getLeft( ), event.getY( index ) - mDrawView.getTop( ) ) ){
mDrawView.onTouchEvent( event );
System.out.println( "action === pointIndex " + index );
return false;
}
}
mDrawView.setInView( false );
return super.onTouchEvent(event);
}最后最终实现了我们想要的效果：
四、參考文档：
Android Touch事件传递机制
Android 编程下 Touch 事件的分发和消费机制
五、代码：
最后附上本文的代码：Android手掌抑制demo
Android手掌抑制功能的实现