如何在图片上画画呢？这里写了一个demo，供大家参考
一、先看一眼工程结构
工程结构：
二、自定义view
这个自定义view实现了保留轨迹的功能，代码如下
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package picturegame.view;
import android.content.context;
import android.graphics.bitmap;
import android.graphics.bitmapfactory;
import android.graphics.canvas;
import android.graphics.color;
import android.graphics.paint;
import android.graphics.paint.style;
import android.util.attributeset;
import android.view.motionevent;
import android.view.view;
import com.winton.picturegame.r;
public class gameview extends view{
private paint paint = null; //
private bitmap originalbitmap = null;//原始图
private bitmap new1bitmap = null;
private bitmap new2bitmap = null;
private float clickx =0;
private float clicky=0;
private float startx=0;
private float starty=0;
private boolean ismove = true;
private boolean isclear = false;
private int color =color.red;//默认画笔颜色为红色
private float strokewidth =2.0f;//默认画笔粗度
public gameview(context context) {
this(context,null);
// todo auto-generated constructor stub
}
public gameview(context context,attributeset atts) {
this(context,atts,0);
// todo auto-generated constructor stub
}
public gameview(context context,attributeset atts,int defstyle) {
super(context,atts,defstyle);
// todo auto-generated constructor stub
originalbitmap = bitmapfactory.decoderesource(getresources(), r.drawable.default_pic).copy(bitmap.config.argb_8888, true);//加载一张背景
new1bitmap=originalbitmap.createbitmap(originalbitmap);
}
//清除函数
public void clear(){
isclear =true;
new2bitmap=originalbitmap.createbitmap(originalbitmap);
invalidate();//重载
}
public void setstrokewidth(float width){
this.strokewidth=width;
initpaint();
}
@override
protected void ondraw(canvas canvas) {
// todo auto-generated method stub
super.ondraw(canvas);
canvas.drawbitmap(writer(new1bitmap),0,0, null);
}
@override
public boolean ontouchevent(motionevent event) {
// todo auto-generated method stub
clickx =event.getx();
clicky=event.gety();
if(event.getaction()==motionevent.action_down){
ismove =false;
invalidate();
return true;
}
else if(event.getaction()==motionevent.action_move){
ismove =true;
invalidate();
return true;
}
return super.ontouchevent(event);
}
/**
* @title: writer
* @description: todo(生成bitmap)
* @param @param pic
* @param @return 设定文件
* @return bitmap 返回类型
* @throws
*/
public bitmap writer(bitmap pic){
initpaint();
canvas canvas =null;
if(isclear){
canvas=new canvas(new2bitmap);
}else{
canvas=new canvas(pic);
}
if(ismove){
canvas.drawline(startx, starty, clickx, clicky, paint);//划线
}
startx = clickx;
starty =clicky;
if(isclear){
return new2bitmap;
}
return pic;
}
private void initpaint(){
paint = new paint();//新建画笔
paint.setstyle(style.stroke);//设置为画线
paint.setantialias(true);//可以让线条圆滑一些
paint.setcolor(color);//设置画笔颜色
paint.setstrokewidth(strokewidth);//设置画笔线条的粗细
}
/**
* @title: setcolor
* @description: todo(设置线条颜色的对外接口)
* @param @param color 设定文件
* @return void 返回类型
* @throws
*/
public void setcolor(int color){
this.color=color;
initpaint();
}
}
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三、主页面布局文件
主页面布局文件
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<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center_horizontal"
android:orientation="vertical" >
<linearlayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:orientation="horizontal" >
<linearlayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
>
<textview
android:id="@+id/tv_30"
android:layout_width="30dp"
android:layout_height="30dp"
android:background="@drawable/bg_notifaction"
/>
</linearlayout>
<linearlayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
>
<textview
android:id="@+id/tv_25"
android:layout_width="25dp"
android:layout_height="25dp"
android:background="@drawable/bg_notifaction"
/>
</linearlayout>
<linearlayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
>
<textview
android:id="@+id/tv_20"
android:layout_width="20dp"
android:layout_height="20dp"
android:background="@drawable/bg_notifaction"
/>
</linearlayout>
<linearlayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
>
<textview
android:id="@+id/tv_15"
android:layout_width="15dp"
android:layout_height="15dp"
android:background="@drawable/bg_notifaction"
/>
</linearlayout>
<linearlayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
>
<textview
android:id="@+id/tv_10"
android:layout_width="10dp"
android:layout_height="10dp"
android:background="@drawable/bg_notifaction"
/>
</linearlayout>
<linearlayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
>
<textview
android:id="@+id/tv_5"
android:layout_width="5dp"
android:layout_height="5dp"
android:background="@drawable/bg_notifaction"
/>
</linearlayout>
<linearlayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
>
<textview
android:id="@+id/tv_2"
android:layout_width="2dp"
android:layout_height="2dp"
android:background="@drawable/bg_notifaction"
/>
</linearlayout>
</linearlayout>
<picturegame.view.gameview
android:layout_width="match_parent"
android:layout_height="300dp"
android:id="@+id/gameview"
/>
<button
android:layout_width="200dp"
android:layout_height="80dp"
android:text="clear"
android:textcolor="@color/black"
android:id="@+id/btn_clear"
/>
</linearlayout>
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四、主activity代码
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package com.winton.picturegame;
import picturegame.view.gameview;
import android.os.bundle;
import android.view.view;
import android.view.view.onclicklistener;
import android.widget.button;
import android.widget.textview;
import com.winton.basemodule.baseactivity;
public class mainactivity extends baseactivity implements onclicklistener {
private gameview gameview = null;
private button clear = null;
private textview tv30,tv25,tv20,tv15,tv10,tv5,tv2;
@override
protected void oncreate(bundle savedinstancestate) {
// todo auto-generated method stub
super.oncreate(savedinstancestate);
}
@override
public void initview() {
// todo auto-generated method stub
setcontentview(r.layout.activity_main);
gameview=(gameview)findviewbyid(r.id.gameview);
clear =(button)findviewbyid(r.id.btn_clear);
tv30=(textview)findviewbyid(r.id.tv_30);
tv25=(textview)findviewbyid(r.id.tv_25);
tv20=(textview)findviewbyid(r.id.tv_20);
tv15=(textview)findviewbyid(r.id.tv_15);
tv10=(textview)findviewbyid(r.id.tv_10);
tv5=(textview)findviewbyid(r.id.tv_5);
tv2=(textview)findviewbyid(r.id.tv_2);
}
@override
public void initlistener() {
// todo auto-generated method stub
clear.setonclicklistener(this);
tv30.setonclicklistener(this);
tv25.setonclicklistener(this);
tv20.setonclicklistener(this);
tv15.setonclicklistener(this);
tv10.setonclicklistener(this);
tv5.setonclicklistener(this);
tv2.setonclicklistener(this);
}
@override
public void initdata() {
// todo auto-generated method stub
}
@override
public void onclick(view v) {
// todo auto-generated method stub
if(v==clear){
gameview.clear();
return;
}
if(v==tv30){
gameview.setstrokewidth(30f);
return;
}
if(v==tv25){
gameview.setstrokewidth(25f);
return;
}
if(v==tv20){
gameview.setstrokewidth(20f);
return;
}
if(v==tv15){
gameview.setstrokewidth(15f);
return;
}
if(v==tv10){
gameview.setstrokewidth(10f);
return;
}
if(v==tv5){
gameview.setstrokewidth(5f);
return;
}
if(v==tv2){
gameview.setstrokewidth(2f);
return;
}
}
}
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五、效果
运行效果图如下
六、疑问
当线条变粗时，线条会出现如上图中不连续的问题。请问高手这个怎么处理呢？我猜测应该要运行算法，但还不知道怎么运行。
文章就为大家介绍到这，其实还有许多知识点小编也不是很清楚，希望大家可以进行补充扩展，共同进步。