Implementing a drawing board

 PackageCom.pingyijinren.helloworld;ImportAndroid.content.Context;ImportAndroid.graphics.Canvas;ImportAndroid.graphics.Color;ImportAndroid.graphics.Paint;ImportAndroid.graphics.Point;ImportAndroid.util.AttributeSet;Importandroid.view.MotionEvent;ImportAndroid.view.View;Importjava.util.ArrayList;ImportJava.util.Iterator;/*** Created by Administrator on 2016/6/2 0002.*/ Public classMypaintviewextendsView {PrivateArraylist<point> allpoints=NewArraylist<point>();  PublicMypaintview (Context context, AttributeSet attrs) {Super(context, attrs);        SetBackgroundColor (Color.White); Setontouchlistener (NewOntouchlistener () {@Override Public BooleanOnTouch (View V, motionevent event) { point point=NewPoint (int) Event.getx (), (int) event.gety ()); if(event.getaction () = =Motionevent.action_down) {allpoints=NewArraylist<point>();                Allpoints.add (point); }                Else if(event.getaction () = =motionevent.action_up)                {Allpoints.add (point); }                Else if(event.getaction () = =motionevent.action_move)                    {Allpoints.add (point); Mypaintview. This. Postinvalidate (); }                return true;    }        }); } @Overrideprotected voidOnDraw (canvas canvas) {Super. OnDraw (canvas); Paint Paint=NewPaint ();        Paint.setcolor (color.red); if(Allpoints.size () >1) {Iterator<Point> iterator=Allpoints.iterator (); Point Firstpoint=NULL; Point Lastpoint=NULL;  while(Iterator.hasnext ()) {if(firstpoint==NULL) {Firstpoint=Iterator.next (); }                Else{                    if(lastpoint!=NULL) {Firstpoint=Lastpoint; } lastpoint=Iterator.next ();                Canvas.drawline (Firstpoint.x,firstpoint.y,lastpoint.x,lastpoint.y,paint); }            }        }    }}

<?xml version= "1.0" encoding= "Utf-8"? ><linearlayout xmlns:android= "http://schemas.android.com/apk/res/ Android "    xmlns:tools=" Http://schemas.android.com/tools "    android:layout_width=" Match_ Parent "    android:layout_height=" Match_parent "    android:orientation=" vertical "     tools:context= "Com.pingyijinren.helloworld.MainActivity" >    <  Com.pingyijinren.helloworld.MyPaintView        android:layout_width= "Match_parent"        android: Layout_height= "Match_parent"/></linearlayout>

 Package Com.pingyijinren.helloworld; Import android.support.v7.app.AppCompatActivity; Import Android.os.Bundle;  Public class extends appcompatactivity {    @Override    protectedvoid  onCreate (Bundle Savedinstancestate) {        super. OnCreate (savedinstancestate);        Setcontentview (R.layout.activity_main);    }}

Implementing a drawing board