activity代码如下，其中线的颜色，宽度等属性都可以修改。
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package com.example.administrator.main;
import android.content.intent;
import android.graphics.bitmap;
import android.graphics.canvas;
import android.graphics.color;
import android.graphics.paint;
import android.net.uri;
import android.os.environment;
import android.support.v7.app.appcompatactivity;
import android.os.bundle;
import android.view.motionevent;
import android.view.view;
import android.widget.button;
import android.widget.imageview;
import android.widget.toast;
import java.io.file;
import java.io.fileoutputstream;
public class drawactivity extends appcompatactivity {
private imageview iv;
private bitmap basebitmap;
private button btn_resume;
private button btn_save;
private canvas canvas;
private paint paint;
float radio;
@override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_draw);
radio = 10;
iv = (imageview) findviewbyid(r.id.iv);
// 初始化一个画笔，笔触宽度为5，颜色为红色
paint = new paint();
paint.setstrokewidth(radio);
paint.setcolor(color.black);
iv = (imageview) findviewbyid(r.id.iv);
btn_resume = (button) findviewbyid(r.id.btn_resume);
btn_save = (button) findviewbyid(r.id.btn_save);
btn_resume.setonclicklistener(click);
btn_save.setonclicklistener(click);
iv.setontouchlistener(touch);
}
private view.ontouchlistener touch = new view.ontouchlistener() {
// 定义手指开始触摸的坐标
float startx;
float starty;
@override
public boolean ontouch(view v, motionevent event) {
switch (event.getaction()) {
// 用户按下动作
case motionevent.action_down:
// 第一次绘图初始化内存图片，指定背景为白色
if (basebitmap == null) {
basebitmap = bitmap.createbitmap(iv.getwidth(),
iv.getheight(), bitmap.config.argb_8888);
canvas = new canvas(basebitmap);
canvas.drawcolor(color.white);
}
// 记录开始触摸的点的坐标
startx = event.getx();
starty = event.gety();
break;
// 用户手指在屏幕上移动的动作
case motionevent.action_move:
// 记录移动位置的点的坐标
float stopx = event.getx();
float stopy = event.gety();
thread t = new thread(new runnable() {
@override
public void run() {
radio += 0.1;
try {
thread.sleep(1000);
} catch (interruptedexception e) {
e.printstacktrace();
}
}
});
t.start();
paint.setstrokewidth(radio);
//根据两点坐标，绘制连线
canvas.drawline(startx, starty, stopx, stopy, paint);
// 更新开始点的位置
startx = event.getx();
starty = event.gety();
// 把图片展示到imageview中
iv.setimagebitmap(basebitmap);
break;
case motionevent.action_up:
radio = 5;
break;
default:
break;
}
return true;
}
};
private view.onclicklistener click = new view.onclicklistener() {
@override
public void onclick(view v) {
switch (v.getid()) {
case r.id.btn_save:
savebitmap();
break;
case r.id.btn_resume:
resumecanvas();
break;
default:
break;
}
}
};
/**
* 保存图片到sd卡上
*/
protected void savebitmap() {
try {
// 保存图片到sd卡上
string filename = "/sdcard/"+system.currenttimemillis() + ".png";
file file = new file(filename);
fileoutputstream stream = new fileoutputstream(file);
basebitmap.compress(bitmap.compressformat.png, 100, stream);
toast.maketext(drawactivity.this, "保存图片成功", toast.length_short).show();
// android设备gallery应用只会在启动的时候扫描系统文件夹
// 这里模拟一个媒体装载的广播，用于使保存的图片可以在gallery中查看
intent intent = new intent();
intent.setaction(intent.action_media_mounted);
intent.setdata(uri.fromfile(environment
.getexternalstoragedirectory()));
sendbroadcast(intent);
} catch (exception e) {
toast.maketext(drawactivity.this, "保存图片失败", toast.length_short).show();
e.printstacktrace();
}
}
// 手动清除画板的绘图，重新创建一个画板
protected void resumecanvas() {
if (basebitmap != null) {
basebitmap = bitmap.createbitmap(iv.getwidth(),
iv.getheight(), bitmap.config.argb_8888);
canvas = new canvas(basebitmap);
canvas.drawcolor(color.white);
iv.setimagebitmap(basebitmap);
toast.maketext(drawactivity.this, "清除画板成功，可以重新开始绘图", toast.length_short).show();
}
}
}
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