View实现涂鸦功能

前段时间和小米童鞋一起研究了下涂鸦功能的实现，其实单独的涂鸦实现起来还是挺简单的，关键的技术难点是撤销与重做功能的实现。但是这里暂时只说明下涂鸦功能的实现，高手勿喷哈，而且该功能在Android SDK提供的APIDemo当中就有的，但是如果能够将该地方的知识点搞懂的话，我认为View画图基本上是难不倒你了，特别是里面为什么要用一个中间的Bitmap。老规矩，还是先看看效果图吧：

代码如下：

package cn.ych.tuya;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Bitmap.CompressFormat;
import android.os.Environment;
import android.view.MotionEvent;
import android.view.View;

public class TuyaView extends View {

private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;// 画布的画笔
private Paint mPaint;// 真实的画笔
private float mX, mY;//临时点坐标
private static final float TOUCH_TOLERANCE = 4;

private int screenWidth, screenHeight;// 屏幕長寬

public TuyaView(Context context, int w, int h) {
super(context);
screenWidth = w;
screenHeight = h;

mBitmap = Bitmap.createBitmap(screenWidth, screenHeight,
Bitmap.Config.ARGB_8888);
// 保存一次一次绘制出来的图形
mCanvas = new Canvas(mBitmap);

mBitmapPaint = new Paint(Paint.DITHER_FLAG);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);// 设置外边缘
mPaint.setStrokeCap(Paint.Cap.SQUARE);// 形状
mPaint.setStrokeWidth(5);// 画笔宽度
}

@Override
public void onDraw(Canvas canvas) {
canvas.drawColor(0xFFAAAAAA);
// 将前面已经画过得显示出来
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
if (mPath != null) {
// 实时的显示
canvas.drawPath(mPath, mPaint);
}
}

private void touch_start(float x, float y) {
mPath.moveTo(x, y);
mX = x;
mY = y;
}

private void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(mY - y);

//触摸间隔大于阈值才绘制路径
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
// 从x1,y1到x2,y2画一条贝塞尔曲线，更平滑(直接用mPath.lineTo也是可以的)
mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
mX = x;
mY = y;
}
}

private void touch_up() {
mPath.lineTo(mX, mY);
mCanvas.drawPath(mPath, mPaint);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();

switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
// 每次down下去重新new一个Path
mPath = new Path();

touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}

}

在下一篇当中我会给大家介绍下撤销与重做的实现方法。

原文：http://www.apkstory.com/development/view-implement-doodle.html