var startx, starty;
//獲得角度
function getAngle(angx, angy) {
return
Math.atan2(angy, angx) * 180 / Math.PI;
};
//根據起點終點返回方向 1向上 2向下 3向左 4向右 0未滑動
function getDirection(startx, starty, endx, endy) {
var
angx = endx - startx;
var
angy = endy - starty;
var
result = 0;
//如果滑動距離太短
if
(Math.abs(angx) < 2 && Math.abs(angy) < 2) {
return
result;
}
var
angle = getAngle(angx, angy);
if
(angle >= -135 && angle <= -45) {
result = 1;
}
else
if
(angle > 45 && angle < 135) {
result = 2;
}
else
if
((angle >= 135 && angle <= 180) || (angle >= -180 && angle < -135)) {
result = 3;
}
else
if
(angle >= -45 && angle <= 45) {
result = 4;
}
return
result;
}
//手指接觸屏幕
document.addEventListener(
"touchstart"
, function(e) {
startx = e.touches[0].pageX;
starty = e.touches[0].pageY;
},
false
);
//手指離開屏幕
document.addEventListener(
"touchend"
, function(e) {
var
endx, endy;
endx = e.changedTouches[0].pageX;
endy = e.changedTouches[0].pageY;
var
direction = getDirection(startx, starty, endx, endy);
switch
(direction) {
case
0:
alert(
"未滑動！"
);
break
;
case
1:
alert(
"向上！"
)
break
;
case
2:
alert(
"向下！"
)
break
;
case
3:
alert(
"向左！"
)
break
;
case
4:
alert(
"向右！"
)
break
;
default
:
}
},
false
);