android 制作简单的画板

package com.weipeng.xuexi20160119;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

/**
* Created by Administrator on 2016/1/19.
*/
public class DrawView3 extends View {
private int view_width =0;//屏幕宽度
private int view_height=0;//屏幕高度
private float preX;//起始点的X坐标
private float preY;//起始点的Y坐标
private Path path;//路径
public Paint paint =null;//画笔
Bitmap cacheBitmap = null;//定义一个内存中的图片,该图片作为缓冲区
Canvas cacheCanvas =null;//定义cacheBitmap上的Cancas对象
public DrawView3(Context context, AttributeSet attrs) {
super(context, attrs);
view_width = context.getResources().getDisplayMetrics().widthPixels;//获取屏幕宽度
view_height = context.getResources().getDisplayMetrics().heightPixels;//获取屏幕高度
//创建一个与该View相同大小的缓冲区
cacheBitmap = Bitmap.createBitmap(view_width,view_height, Bitmap.Config.ARGB_8888);
cacheCanvas = new Canvas();//创建一个新的画布
path = new Path();
cacheCanvas.setBitmap(cacheBitmap);//在cacheCanvas上绘制cacheBitmap
paint = new Paint(Paint.DITHER_FLAG);
paint.setColor(Color.RED);
//设置画笔风格
paint.setStyle(Paint.Style.STROKE);//设置填充方式为描边
paint.setStrokeJoin(Paint.Join.ROUND);//设置笔刷图形样式
paint.setStrokeCap(Paint.Cap.ROUND);//设置画笔转弯处的连接风格
paint.setAntiAlias(true);//设置抗锯齿功能
paint.setStrokeWidth(1);//设置画笔默认笔触宽度为1像素
paint.setDither(true);//设置抖动效果

}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(0xFFFFFFFF);//设置背景颜色
Paint bmpPaint = new Paint();//采用默认设置创建一个画笔
canvas.drawBitmap(cacheBitmap, 0, 0, bmpPaint);//绘制cacheBitmap
canvas.drawPath(path, paint);//绘制路径
canvas.save(Canvas.ALL_SAVE_FLAG);//保存canvas状态
canvas.restore();
//回复canvas之前保存的状态,防止保存后对canvas执行的操作对后续绘制有影响

}

@Override
public boolean onTouchEvent(MotionEvent event) {
//获取触摸事件的位置
float x = event.getX();
float y = event.getY();
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
path.moveTo(x,y);//将绘制起点到xy坐标点位置
preX = x;
preY = y;
break;
case MotionEvent.ACTION_MOVE:
float dx = Math.abs(x - preX);
float dy = Math.abs(y - preY);
if(dx >= 5 || dy >= 5){//判断是否在允许的范围内
path.quadTo(preX,preY,(x+preX)/2,(y+preY)/2);
preX = x;
preY = y;

}
break;
case MotionEvent.ACTION_UP:
cacheCanvas.drawPath(path,paint);//绘制路径
path.reset();
break;
}
invalidate();
return true;//返回ture表示该方法已经处理该事件
}
public void clear(){
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));//设置图形重叠时的处理方法
paint.setStrokeWidth(50);//设置画笔的宽度
}
public void save(){
try {
saveBitmap("1111");
} catch (IOException e) {
e.printStackTrace();
}
}

private void saveBitmap(String filename) throws IOException {
File file = new File("/sdcard/pictures/"+filename+".png");
file.createNewFile();
FileOutputStream fileOS = new FileOutputStream(file);
cacheBitmap.compress(Bitmap.CompressFormat.PNG,100,fileOS);
fileOS.flush();
fileOS.close();
}

}

在mainActivity中重写方法:
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater menuInflater = new MenuInflater(this);
menuInflater.inflate(R.menu.toolsmenu,menu);
return super.onCreateOptionsMenu(menu);

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
DrawView3 dv = (DrawView3) findViewById(R.id.draw3);
dv.paint.setXfermode(null);//取消擦出效果
dv.paint.setStrokeWidth(1);//初始化画笔宽度
switch (item.getItemId()){
case R.id.red:
dv.paint.setColor(Color.RED);
break;
case R.id.green:
dv.paint.setColor(Color.GREEN);
break;
case R.id.blue:
dv.paint.setColor(Color.BLUE);
break;
case R.id.width_1:
dv.paint.setStrokeWidth(1);
break;
case R.id.width_2:
dv.paint.setStrokeWidth(2);
break;
case R.id.width_3:
dv.paint.setStrokeWidth(3);
break;
case R.id.clear:
dv.clear();
break;
case R.id.save:
dv.save();
break;
}
return super.onOptionsItemSelected(item);
}

自定义menu菜单:
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

<item android:title="颜色">
<menu>
<group android:checkableBehavior="single">
<item android:id="@+id/red" android:title="红色"></item>
<item android:id="@+id/green" android:title="绿色"></item>
<item android:id="@+id/blue" android:title="蓝色"></item>
</group>
</menu>
</item>
<item android:title="width">
<menu>
<group>
<item android:id="@+id/width_1" android:title="width_1"></item>
<item android:id="@+id/width_2" android:title="width_2"></item>
<item android:id="@+id/width_3" android:title="width_3"></item>
</group>
</menu>
</item>
<item android:id="@+id/clear" android:title="清除"></item>
<item android:id="@+id/save" android:title="保存"></item>
</menu>