Android 开发实例简单涂鸦板

程序员文章站 2024-03-06 19:02:32

在android上开发一些小应用既可以积累知识又可以增加乐趣，与任务式开发不同，所以想到在andr...

在android上开发一些小应用既可以积累知识又可以增加乐趣，与任务式开发不同，所以想到在android系统上实现一个简单的涂鸦板，这是我们练手的一种好的方法。

涂鸦板应用的代码实现

新建工程mywall，修改/res/layout/main.xml文件，在里面添加一个surfaceview和两个button，用到了relativelayout布局，完整的main.xml文件如下：

xml/html代码

<?xml version="1.0" encoding="utf-8"?> 
 
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="fill_parent" 
android:layout_height="fill_parent" 
android:orientation="vertical" 
> 
 
<surfaceview 
android:id="@+id/surfaceview"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_above="@+id/line"
android:layout_alignparenttop="true"
/>
 
<linearlayout
android:id="@+id/line"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignparentbottom="true"
>
 
<button
android:id="@+id/flushbutton"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="清屏"
/>
 
<button
android:id="@+id/colorbutton"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1" 
android:text="颜色"
/>
</linearlayout>
</relativelayout>

接着，修改mywallactivity.java文件，最主要是重写了ontouchevent()函数，在这个函数里过滤出触屏拖动事件，然后获取其相应的坐标和画线。完整的内容如下：

java代码

package com.nan.wall;   
   
import android.app.activity;   
import android.app.alertdialog;   
import android.app.dialog;   
import android.content.dialoginterface;   
import android.graphics.canvas;   
import android.graphics.color;   
import android.graphics.paint;   
import android.graphics.rect;   
import android.os.bundle;   
import android.view.motionevent;   
import android.view.surfaceholder;    
import android.view.surfaceview;   
import android.view.view;    
import android.widget.button;    
   
public class mywallactivity extends activity    
{    
private surfaceview msurfaceview = null;    
private surfaceholder msurfaceholder = null;    
private button cleanbutton = null;    
private button colorbutton = null;    
   
private float oldx = 0f;    
private float oldy = 0f;    
   
private boolean candraw = false;   
private paint mpaint = null;   
//用来记录当前是哪一种颜色    
private int whichcolor = 0;    
   
/** called when the activity is first created. */   
  @override    
public void oncreate(bundle savedinstancestate)    
{    
super.oncreate(savedinstancestate);   
setcontentview(r.layout.main);   
      
msurfaceview = (surfaceview)this.findviewbyid(r.id.surfaceview);   
msurfaceholder = msurfaceview.getholder();   
   
mpaint = new paint();    
//画笔的颜色    
mpaint.setcolor(color.red);    
//画笔的粗细    
mpaint.setstrokewidth(2.0f);   
cleanbutton = (button)this.findviewbyid(r.id.flushbutton);    
//按钮监听    
cleanbutton.setonclicklistener(new view.onclicklistener()    
{    
   
@override    
public void onclick(view v)    
{    
// todo auto-generated method stub    
//锁定整个surfaceview    
canvas mcanvas = msurfaceholder.lockcanvas();    
mcanvas.drawcolor(color.black);    
//绘制完成，提交修改   
msurfaceholder.unlockcanvasandpost(mcanvas);    
//重新锁一次    
msurfaceholder.lockcanvas(new rect(0, 0, 0, 0));    
msurfaceholder.unlockcanvasandpost(mcanvas);    
}   
});     
   
colorbutton = (button)this.findviewbyid(r.id.colorbutton);   
//按钮监听    
colorbutton.setonclicklistener(new view.onclicklistener()    
{    
   
@override    
public void onclick(view v)    
{    
 // todo auto-generated method stub   
   
dialog mdialog = new alertdialog.builder(mywallactivity.this)    
.settitle("颜色设置")    
.setsinglechoiceitems(new string[]{"红色","绿色","蓝色"}, whichcolor, new dialoginterface.onclicklistener()    
{    
@override   
public void onclick(dialoginterface dialog, int which)    
{    
 // todo auto-generated method stub    
switch(which)    
{    
case 0:    
{    
//画笔的颜色    
mpaint.setcolor(color.red);    
whichcolor = 0;    
break;    
}    
case 1:    
{    
//画笔的颜色   
mpaint.setcolor(color.green);   
whichcolor = 1;   
break;   
}   
case 2:   
{   
//画笔的颜色106                 
mpaint.setcolor(color.blue);   
whichcolor = 2;                 
break;                 
}   
}   
}   
})   
.setpositivebutton("确定", new dialoginterface.onclicklistener()   
{   
@override   
public void onclick(dialoginterface dialog, int which)    
{   
// todo auto-generated method stub   
dialog.dismiss();   
}   
})   
.create();   
mdialog.show();   
}   
});   
   
   
@override   
public boolean ontouchevent(motionevent event)   
{      
//获取x坐标   
float x = event.getx();   
//获取y坐标（不知道为什么要减去一个偏移值才对得准屏幕）   
float y = event.gety()-50;   
//第一次进来先不管   
if(candraw)   
{      
//获取触屏事件   
switch(event.getaction())   
{   
//如果是拖动事件   
case motionevent.action_move:   
{   
//锁定整个surfaceview   
canvas mcanvas = msurfaceholder.lockcanvas();     
mcanvas.drawline(x, y, oldx, oldy, mpaint);   
msurfaceholder.unlockcanvasandpost(mcanvas);   
//重新锁一次   
msurfaceholder.lockcanvas(new rect(0, 0, 0, 0));   
msurfaceholder.unlockcanvasandpost(mcanvas);   
break;   
}   
}   
}   
//保存目前的x坐标值   
oldx = x;   
//保存目前的y坐标值   
oldy = y;   
   
candraw = true;   
   
return true;   
}   
   
}

应用测试

在模拟器上运行此应用是如下效果：

Android 开发实例简单涂鸦板