android 制作简单的画板

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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:
@Overridepublic boolean onCreateOptionsMenu(Menu menu) {    MenuInflater menuInflater = new MenuInflater(this);    menuInflater.inflate(R.menu.toolsmenu,menu);    return super.onCreateOptionsMenu(menu);}@Overridepublic 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>
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