Android手势ImageView三部曲 第二部
废话不多说了,还记得上一节android手势imageview三部曲(一)最后我们提及的那个框架么?这一节我们重点了掌握一下gesturedetector这个类相关的属性方法。
一、那么gesturedetector是干嘛的呢?
顾名思义,字面意思就是“手势检测器“的意思,还记得我们上一节中实现的gestureimageview么?我们在ontouchevent中检测到了各种个样的手势(手指按下、抬起、什么时候属于拖拽、什么时候属于缩放)都是通过我们的计算得到的,但是有了gesturedetector这个类后,我们不需要自己做判断现在是什么手势了,gesturedetector会帮我们做好判断,完了后通过回调函数告诉你,就像官网所说的(this class should only be used with motionevents reported via touch (don't use for trackball events).)这个类仅仅是通过触碰检查事件的,而不是用于跟踪事件的,我检测到了事件,然后告诉你,至于你需要怎么处理这个事件,那就是你自己的事了。
gesturedetector的一些具体的api大家可以去查看谷歌官方文档或启舰大神的博客:
https://developer.android.google.cn/reference/android/view/gesturedetector.html
android手势识别器gesturedetector使用详解
说了这么多估计你都有点累了,下面让我们看看具体怎么使用:
偷一下懒,我就直接用 android手势imageview三部曲(一)
中的matriximageview类改改代码了:
public class matriximageview extends imageview { private static final int mode_none = 190; private static final int mode_drag = 468; private static final int mode_zoom = 685; private int mode; private float startx, starty; private float midx, midy; private matrix currmatrix, savedmatrix; private float prerotate, rotate; private float prespacing; private gesturedetector detector; public matriximageview(context context, attributeset attrs) { super(context, attrs); initview(); detector=new gesturedetector(context,ongesturelistener); } private void initview() { mode = mode_none; currmatrix = new matrix(); savedmatrix = new matrix(); displaymetrics dm = getresources().getdisplaymetrics(); bitmap bitmap = bitmapfactory.decoderesource(getresources(), r.mipmap.test); bitmap = bitmap.createscaledbitmap(bitmap, dm.widthpixels, dm.heightpixels, true); setimagebitmap(bitmap); } @override public boolean ontouchevent(motionevent event) { return detector.ontouchevent(event); } private gesturedetector.simpleongesturelistener ongesturelistener=new gesturedetector.simpleongesturelistener(){ @override public boolean onsingletapup(motionevent e) { log.e("tag", "====onsingletapup====="); return super.onsingletapup(e); } @override public void onlongpress(motionevent e) { log.e("tag", "====onlongpress====="); super.onlongpress(e); } @override public boolean onscroll(motionevent e1, motionevent e2, float distancex, float distancey) { log.e("tag", "====onscroll====="); log.e("tag", "distancex===>"+distancex); log.e("tag", "distancey===>"+distancey); return super.onscroll(e1, e2, distancex, distancey); } @override public void onshowpress(motionevent e) { log.e("tag", "====onshowpress====="); super.onshowpress(e); } @override public boolean ondown(motionevent e) { log.e("tag", "====ondown====="); return true; } @override public boolean ondoubletap(motionevent e) { log.e("tag", "====ondoubletap====="); return super.ondoubletap(e); } @override public boolean ondoubletapevent(motionevent e) { log.e("tag", "====ondoubletapevent====="); return super.ondoubletapevent(e); } @override public boolean onsingletapconfirmed(motionevent e) { log.e("tag", "====onsingletapconfirmed====="); return super.onsingletapconfirmed(e); } @override public boolean oncontextclick(motionevent e) { log.e("tag", "====oncontextclick====="); return super.oncontextclick(e); } @override public boolean onfling(motionevent e1, motionevent e2, float velocityx, float velocityy) { log.e("tag", "====onfling====="); log.e("tag", "velocityx===>"+velocityx); log.e("tag", "velocityy===>"+velocityy); return super.onfling(e1, e2, velocityx, velocityy); } }; }
首先我们在构造方法中创建一个手势监测器的对象gesturedetector:
public matriximageview(context context, attributeset attrs) { super(context, attrs); initview(); detector=new gesturedetector(context,ongesturelistener); }
gesturedetector既然是监听我们的手势的工具类,那我们是不是得把我们得手势交给它呢? 是的!! 于是我们在ontouchevent中把事件交给gesturedetector:
@override public boolean ontouchevent(motionevent event) { return detector.ontouchevent(event); }
那我们把事件交给了gesturedetector,gesturedetector处理完毕后我们怎么知道呢? 还记得我们创建gesturedetector对象的时候传递的参数吗?
detector=new gesturedetector(context,ongesturelistener);
我们传递给了gesturedetector一个ongesturelistener对象,gesturedetector检查完毕手势后,会调用ongesturelistener中的方法进行回调,我们只需要在ongesturelistener对象的相应方法中作出处理就可以了:
private gesturedetector.simpleongesturelistener ongesturelistener=new gesturedetector.simpleongesturelistener(){ @override public boolean onsingletapup(motionevent e) { log.e(“tag”, “====onsingletapup=====”); return super.onsingletapup(e); } @override public void onlongpress(motionevent e) { log.e("tag", "====onlongpress====="); super.onlongpress(e); } @override public boolean onscroll(motionevent e1, motionevent e2, float distancex, float distancey) { log.e("tag", "====onscroll====="); log.e("tag", "distancex===>"+distancex); log.e("tag", "distancey===>"+distancey); return super.onscroll(e1, e2, distancex, distancey); } @override public void onshowpress(motionevent e) { log.e("tag", "====onshowpress====="); super.onshowpress(e); } @override public boolean ondown(motionevent e) { log.e("tag", "====ondown====="); return super.ondown(e); } @override public boolean ondoubletap(motionevent e) { log.e("tag", "====ondoubletap====="); return super.ondoubletap(e); } @override public boolean ondoubletapevent(motionevent e) { log.e("tag", "====ondoubletapevent====="); return super.ondoubletapevent(e); } @override public boolean onsingletapconfirmed(motionevent e) { log.e("tag", "====onsingletapconfirmed====="); return super.onsingletapconfirmed(e); } @override public boolean oncontextclick(motionevent e) { log.e("tag", "====oncontextclick====="); return super.oncontextclick(e); } @override public boolean onfling(motionevent e1, motionevent e2, float velocityx, float velocityy) { log.e("tag", "====onfling====="); log.e("tag", "velocityx===>"+velocityx); log.e("tag", "velocityy===>"+velocityy); return super.onfling(e1, e2, velocityx, velocityy); } };
我们先不管其中方法啥时候调用,我们先重写它的所有方法,然后打上log,看看我们手指操作后相应的回调,于是我们运行代码:
是的,没错!就只是一张图片,因为我们也只是显示了一张图片:
我们轻轻的点击一下屏幕:
03-02 20:47:41.367 1798-1798/com.leo.gestureimageview e/tag: ====ondown=====
03-02 20:47:41.466 1798-1798/com.leo.gestureimageview e/tag: ====onshowpress=====
03-02 20:47:41.967 1798-1798/com.leo.gestureimageview e/tag: ====onlongpress=====
轻轻的点击一下屏幕:
我们可以看到log执行顺序:ondown->onshowpress->onlongpress
我们点击屏幕按下,然后过一会再放开:
03-02 21:51:27.121 17138-17138/com.leo.gestureimageview e/tag: ====ondown=====
03-02 21:51:27.222 17138-17138/com.leo.gestureimageview e/tag: ====onshowpress=====
03-02 21:51:27.722 17138-17138/com.leo.gestureimageview e/tag: ====onlongpress=====
我们滑动一下手指:
03-02 21:51:27.121 17138-17138/com.leo.gestureimageview e/tag: ====ondown=====
03-02 21:51:27.222 17138-17138/com.leo.gestureimageview e/tag: ====onshowpress=====
03-02 21:51:27.722 17138-17138/com.leo.gestureimageview e/tag: ====onlongpress=====
不管我们怎么样操作,打印的log总是这三个方法? 这是咋回事呢? 如果看到这里你有疑问的话,那我告诉你,你android事件传递机制掌握的还不是很好,为什么这么说呢?? 下面我们带着疑问看看源码:
猜都可以猜到gesturedetector处理手势的代码肯定在ontouchevent方法中,那么我们看一下ontouchevent方法:
public boolean ontouchevent(motionevent ev) { if (mdoubletaplistener != null) { boolean hadtapmessage = mhandler.hasmessages(tap); if (hadtapmessage) mhandler.removemessages(tap); if ((mcurrentdownevent != null) && (mpreviousupevent != null) && hadtapmessage && isconsidereddoubletap(mcurrentdownevent, mpreviousupevent, ev)) { // this is a second tap misdoubletapping = true; // give a callback with the first tap of the double-tap handled |= mdoubletaplistener.ondoubletap(mcurrentdownevent); // give a callback with down event of the double-tap handled |= mdoubletaplistener.ondoubletapevent(ev); } else { // this is a first tap mhandler.sendemptymessagedelayed(tap, double_tap_timeout); } } mdownfocusx = mlastfocusx = focusx; mdownfocusy = mlastfocusy = focusy; if (mcurrentdownevent != null) { mcurrentdownevent.recycle(); } mcurrentdownevent = motionevent.obtain(ev); malwaysintapregion = true; malwaysinbiggertapregion = true; mstilldown = true; minlongpress = false; mdeferconfirmsingletap = false; if (mislongpressenabled) { mhandler.removemessages(long_press); mhandler.sendemptymessageattime(long_press, mcurrentdownevent.getdowntime() + tap_timeout + longpress_timeout); } mhandler.sendemptymessageattime(show_press, mcurrentdownevent.getdowntime() + tap_timeout); handled |= mlistener.ondown(ev); break; }
代码太多了,那为什么我们只收到了ondown、onshowpress、onlongpress这三个方法的回调呢?
我们知道,当我们手指刚按下屏幕的时候,action_down会执行,然后我们看到这么一行代码:
handled |= mlistener.ondown(ev);
mlistener是我们传递的simpleongesturelistener,于是就看到了控制台的第一个log:
03-02 21:51:29.706 17138-17138/com.leo.gestureimageview e/tag: ====ondown=====
我们的ondown是打印了,然后handled |= mlistener.ondown(ev);看一下我们返回的是什么值:
@override public boolean ondown(motionevent e) { log.e("tag", "====ondown====="); return super.ondown(e); }
我们直接返回了super.ondown(e),接着我们看一下父类返回的是什么:
public boolean ondown(motionevent e) { return false; }
可以看到,父类直接返回了false,所以handled此时为false,然后当action_down执行完毕后,就回到了我们的自定义view中的ontouchevent方法中了:
@override public boolean ontouchevent(motionevent event) { return detector.ontouchevent(event); }
此时我们的view中的ontouchevent 方法返回的是false,到了这里懂事件传递机制的小伙伴都懂,当我们的ontouchevent返回了false的话,后面的事件都将接收不到了,也就是说只能执行action_down,那么有些小伙伴可能又要说了,那我把view的clickable或者longclickable设置成true,事件不就可以传递了么?
好的~! 我们试一试:
<com.leo.gestureimageview.matriximageview android:clickable="true" android:layout_width="match_parent" android:layout_height="match_parent" android:scaletype="matrix" />
运行代码,还是只打印了那三个方法,那这又是怎么回事呢? 还记得我们view的ontouchevent方法么?我们是这么写的:
@override public boolean ontouchevent(motionevent event) { return detector.ontouchevent(event); }
如果改成这样再试试:
@override public boolean ontouchevent(motionevent event) { detector.ontouchevent(event); return super.ontouchevent(event); }
拖动手指返回结果:
好啦~!! 终于看到我们久违的结果了,如果我们还是想用以前的写法,把ontouchevent的返回结果交给gesturedetector处理该怎么做呢?
@override public boolean ontouchevent(motionevent event) { return detector.ontouchevent(event); }
我们只需要在回调方法的ondown中返回true即可:
@override public boolean ondown(motionevent e) { log.e("tag", "====ondown====="); return true; }
我们再次运行代码并拖动手指:
好啦~! 说了那么多不知道小伙伴们理解了没?还是不理解的小伙伴可以去看看我前几篇事件传递的博客,嘻嘻~我们还是快点往下走吧….
我们长按一下屏幕然后提起手指:
03-02 22:29:37.361 22104-22104/com.leo.gestureimageview e/tag: ====ondown=====
03-02 22:29:37.367 22104-22104/com.leo.gestureimageview e/tag: ====onsingletapup=====
03-02 22:29:37.663 22104-22104/com.leo.gestureimageview e/tag: ====onsingletapconfirmed=====
执行了ondown=>onsingletapup=>onsingletapconfirmed.
我们快速点击一下屏幕:
03-02 22:31:48.603 22104-22104/com.leo.gestureimageview e/tag: ====ondown=====
03-02 22:31:48.610 22104-22104/com.leo.gestureimageview e/tag: ====onsingletapup=====
03-02 22:31:48.903 22104-22104/com.leo.gestureimageview e/tag: ====onsingletapconfirmed=====
执行了ondown=>onsingletapup=>onsingletapconfirmed.
然后我们再次滑动手指:
03-02 22:34:41.820 22104-22104/com.leo.gestureimageview e/tag: ====ondown=====
03-02 22:34:41.920 22104-22104/com.leo.gestureimageview e/tag: ====onshowpress=====
03-02 22:34:42.018 22104-22104/com.leo.gestureimageview e/tag: ====onscroll=====
03-02 22:34:42.018 22104-22104/com.leo.gestureimageview e/tag: distancex===>-117.13138
03-02 22:34:42.018 22104-22104/com.leo.gestureimageview e/tag: distancey===>75.100464
03-02 22:34:42.036 22104-22104/com.leo.gestureimageview e/tag: ====onscroll=====
03-02 22:34:42.036 22104-22104/com.leo.gestureimageview e/tag: distancex===>-75.859314
执行顺序:ondown=》onshowpress=》onscroll(很多次)
最后我们手指拖动距离长一点再快一点:
03-02 22:47:42.453 5103-5103/com.leo.gestureimageview e/tag: distancex===>-274.69336
03-02 22:47:42.453 5103-5103/com.leo.gestureimageview e/tag: distancey===>-0.34838867
03-02 22:47:42.460 5103-5103/com.leo.gestureimageview e/tag: ====onfling=====
03-02 22:47:42.460 5103-5103/com.leo.gestureimageview e/tag: velocityx===>27284.943
03-02 22:47:42.460 5103-5103/com.leo.gestureimageview e/tag: velocityy===>-95.6131
前 面还有一段log没给出了,调用方法顺序为:ondown=》onshowpress=》onscroll(很多次)=》最后松开手指的时候onfling();
好了~! 到这里,我们的回调方法中还有几个没有被调用,就是监听双击事件的时候,于是我们双击屏幕:
03-02 22:50:34.786 5103-5103/com.leo.gestureimageview e/tag: ====ondown=====
03-02 22:50:34.793 5103-5103/com.leo.gestureimageview e/tag: ====onsingletapup=====
03-02 22:50:34.924 5103-5103/com.leo.gestureimageview e/tag: ====ondoubletap=====
03-02 22:50:34.924 5103-5103/com.leo.gestureimageview e/tag: ====ondoubletapevent=====
03-02 22:50:34.924 5103-5103/com.leo.gestureimageview e/tag: ====ondown=====
03-02 22:50:34.932 5103-5103/com.leo.gestureimageview e/tag: ====ondoubletapevent=====
我们双击屏幕执行的方法为:
ondown=>onsingletapup=>ondoubletap=>ondoubletapevent=>ondoubletapevent
可见,执行了一次ondoubletap,两次ondoubletapevent
好啦~! 看完了simpleongesturelistener中所有方法的回调,我们反过来再看一遍这些回调方法:
好啦~!说了那么api内容,下面写个小例子用一下gesturedetector:
package com.leo.gestureimageview; import android.content.context; import android.graphics.bitmap; import android.graphics.bitmapfactory; import android.graphics.matrix; import android.util.attributeset; import android.util.displaymetrics; import android.util.log; import android.view.gesturedetector; import android.view.motionevent; import android.widget.imageview; public class matriximageview extends imageview { private matrix currmatrix; private gesturedetector detector; public matriximageview(context context, attributeset attrs) { super(context, attrs); initview(); detector=new gesturedetector(context,ongesturelistener); } private void initview() { currmatrix = new matrix(); displaymetrics dm = getresources().getdisplaymetrics(); bitmap bitmap = bitmapfactory.decoderesource(getresources(), r.mipmap.test); bitmap = bitmap.createscaledbitmap(bitmap, dm.widthpixels, dm.heightpixels, true); setimagebitmap(bitmap); } @override public boolean ontouchevent(motionevent event) { return detector.ontouchevent(event); } private float currx; private float curry; private gesturedetector.simpleongesturelistener ongesturelistener=new gesturedetector.simpleongesturelistener(){ @override public boolean onscroll(motionevent e1, motionevent e2, float distancex, float distancey) { log.e("tag", "====onscroll====="); log.e("tag", "distancex===>"+distancex); log.e("tag", "distancey===>"+distancey); currx-=distancex; curry-=distancey; currmatrix.reset(); currmatrix.posttranslate(currx,curry); setimagematrix(currmatrix); return super.onscroll(e1, e2, distancex, distancey); } }; }
代码很短,想必大家都看得懂,就是一个随着手指移动而移动的图片:
好啦~~ 这篇有点长,为什么花这么久去研究gesturedetector,这也是为了给下一节的movegesturedetector、rotategesturedetector、shovegesturedetector以及photoview这些大牛写的框架做铺垫。
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持。