Android简单实现画图功能

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

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(); 
  } 
   
   
} 

三、主页面布局文件
主页面布局文件

<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> 

四、主activity代码

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; 
    } 
     
  } 
    
} 

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。