【实现思路】
（1）创建画笔
代码语言：javascript复制 private void init(Context context) {
this.mContext = context;
//设置抗锯齿
mGesturePaint.setAntiAlias(true);
//设置签名笔画样式
mGesturePaint.setStyle(Paint.Style.STROKE);
//设置笔画宽度
mGesturePaint.setStrokeWidth(mPaintWidth);
//设置签名颜色
mGesturePaint.setColor(mPenColor);
}（2）创建一个画布 一个bitmap用来保存签名
代码语言：javascript复制 @Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//创建跟view一样大的bitmap，用来保存签名(在控件大小发生改变时调用。)
cachebBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
cacheCanvas = new Canvas(cachebBitmap);
cacheCanvas.drawColor(mBackColor);
}（3）重写onTouchEvent方法拿到绘制的点
代码语言：javascript复制 @Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
touchDown(event);
break;
case MotionEvent.ACTION_MOVE:
touchMove(event);
break;
case MotionEvent.ACTION_UP:
//将路径画到bitmap中，即一次笔画完成才去更新bitmap，而手势轨迹是实时显示在画板上的。
cacheCanvas.drawPath(mPath, mGesturePaint);
mPath.reset();
break;
}
// 更新绘制
invalidate();
return true;
}（4）实现 onDraw 方法把绘制的内容形成图形
代码语言：javascript复制 @Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
//画此次笔画之前的签名
canvas.drawBitmap(cachebBitmap, 0, 0, mGesturePaint);
// 通过画布绘制多点形成的图形
canvas.drawPath(mPath, mGesturePaint);
}【完整代码如下】
代码语言：javascript复制/**
* Created by Xia_焱 on 2017/8/9.
*/
public class LinePathView extends View {
private Context mContext;
//起点X
private float mX;
//起点Y
private float mY;
//手写画笔
private final Paint mGesturePaint = new Paint();
//路径
private final Path mPath = new Path();
//画布
private Canvas cacheCanvas;
//生成的图片
private Bitmap cachebBitmap;
//画笔宽度 px；
private int mPaintWidth = 10;
//画笔颜色
private int mPenColor = Color.BLACK;
//背景色（指最终签名结果文件的背景颜色，默认为透明色）
private int mBackColor=Color.TRANSPARENT;
public LinePathView(Context context) {
super(context);
init(context);
}
public LinePathView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public LinePathView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context);
}
private void init(Context context) {
this.mContext = context;
//设置抗锯齿
mGesturePaint.setAntiAlias(true);
//设置签名笔画样式
mGesturePaint.setStyle(Paint.Style.STROKE);
//设置笔画宽度
mGesturePaint.setStrokeWidth(mPaintWidth);
//设置签名颜色
mGesturePaint.setColor(mPenColor);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//创建跟view一样大的bitmap，用来保存签名(在控件大小发生改变时调用。)
cachebBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
cacheCanvas = new Canvas(cachebBitmap);
cacheCanvas.drawColor(mBackColor);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
//画此次笔画之前的签名
canvas.drawBitmap(cachebBitmap, 0, 0, mGesturePaint);
// 通过画布绘制多点形成的图形
canvas.drawPath(mPath, mGesturePaint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
touchDown(event);
break;
case MotionEvent.ACTION_MOVE:
touchMove(event);
break;
case MotionEvent.ACTION_UP:
//将路径画到bitmap中，即一次笔画完成才去更新bitmap，而手势轨迹是实时显示在画板上的。
cacheCanvas.drawPath(mPath, mGesturePaint);
mPath.reset();
break;
}
// 更新绘制
invalidate();
return true;
}
// 手指点下屏幕时调用
private void touchDown(MotionEvent event) {
// 重置绘制路线
mPath.reset();
float x = event.getX();
float y = event.getY();
mX = x;
mY = y;
// mPath绘制的绘制起点
mPath.moveTo(x,y);
}
// 手指在屏幕上滑动时调用
private void touchMove(MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
final float previousX = mX;
final float previousY = mY;
final float dx = Math.abs(x - previousX);
final float dy = Math.abs(y - previousY);
// 两点之间的距离大于等于3时，生成贝塞尔绘制曲线
if (dx >= 3 || dy >= 3) {
// 设置贝塞尔曲线的操作点为起点和终点的一半
float cX = (x previousX) / 2;
float cY = (y previousY) / 2;
// 二次贝塞尔，实现平滑曲线；previousX, previousY为操作点，cX, cY为终点
mPath.quadTo(previousX, previousY, cX, cY);
// 第二次执行时，第一次结束调用的坐标值将作为第二次调用的初始坐标值
mX = x;
mY = y;
}
}
/**
* 清除画板
*/
public void clear() {
if (cacheCanvas != null) {
//更新画板信息
mGesturePaint.setColor(mPenColor);
cacheCanvas.drawColor(mBackColor, PorterDuff.Mode.CLEAR);
mGesturePaint.setColor(mPenColor);
invalidate();
}
}
/**
* 保存画板
* @param path 保存到路径
*/
public void save(String path) throws IOException {
save(path, false, 0);
}
/**
* 保存画板
* @param path 保存到路径
* @param clearBlank 是否清除边缘空白区域
* @param blank 要保留的边缘空白距离
*/
public void save(String path, boolean clearBlank, int blank) throws IOException {
Bitmap bitmap=cachebBitmap;
//BitmapUtil.createScaledBitmapByHeight(srcBitmap, 300);// 压缩图片
if (clearBlank) {
bitmap = clearBlank(bitmap, blank);
}
ByteArrayOutputStream bos = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);
byte[] buffer = bos.toByteArray();
if (buffer != null) {
File file = new File(path);
if (file.exists()) {
file.delete();
}
OutputStream outputStream = new FileOutputStream(file);
outputStream.write(buffer);
outputStream.close();
}
}
/**
* 保存画板
* @param clearBlank 是否清除边缘空白区域
* @param blank 要保留的边缘空白距离
*/
public Bitmap saveToBitmap(boolean clearBlank, int blank){
Bitmap bitmap=cachebBitmap;
//BitmapUtil.createScaledBitmapByHeight(srcBitmap, 300);// 压缩图片
if (clearBlank) {
bitmap = clearBlank(bitmap, blank);
}
// int width = bitmap.getWidth();
// int height = bitmap.getHeight();
// int w;
// int h;
// if(width>2*height){
// w = width -(width - 2*height);
// h = height;
// } else {
// w = width;
// h = height - (height - width/2);
// }
// return ThumbnailUtils.extractThumbnail(bitmap,w,h);
return bitmap;
}
/**
* 获取画板的bitmap
* @return
*/
public Bitmap getBitMap()
{
setDrawingCacheEnabled(true);
buildDrawingCache();
Bitmap bitmap=getDrawingCache();
setDrawingCacheEnabled(false);
return bitmap;
}
/**
* 逐行扫描 清楚边界空白。
*
* @param bp
* @param blank 边距留多少个像素
* @return
*/
private Bitmap clearBlank(Bitmap bp, int blank) {
int HEIGHT = bp.getHeight();
int WIDTH = bp.getWidth();
int top = 0, left = 0, right = 0, bottom = 0;
int[] pixs = new int[WIDTH];
boolean isStop;
//扫描上边距不等于背景颜色的第一个点
for (int y = 0; y < HEIGHT; y ) {
bp.getPixels(pixs, 0, WIDTH, 0, y, WIDTH, 1);
isStop = false;
for (int pix : pixs) {
if (pix != mBackColor) {
top = y;
isStop = true;
break;
}
}
if (isStop) {
break;
}
}
//扫描下边距不等于背景颜色的第一个点
for (int y = HEIGHT - 1; y >= 0; y--) {
bp.getPixels(pixs, 0, WIDTH, 0, y, WIDTH, 1);
isStop = false;
for (int pix : pixs) {
if (pix != mBackColor) {
bottom = y;
isStop = true;
break;
}
}
if (isStop) {
break;
}
}
pixs = new int[HEIGHT];
//扫描左边距不等于背景颜色的第一个点
for (int x = 0; x < WIDTH; x ) {
bp.getPixels(pixs, 0, 1, x, 0, 1, HEIGHT);
isStop = false;
for (int pix : pixs) {
if (pix != mBackColor) {
left = x;
isStop = true;
break;
}
}
if (isStop) {
break;
}
}
//扫描右边距不等于背景颜色的第一个点
for (int x = WIDTH - 1; x > 0; x--) {
bp.getPixels(pixs, 0, 1, x, 0, 1, HEIGHT);
isStop = false;
for (int pix : pixs) {
if (pix != mBackColor) {
right = x;
isStop = true;
break;
}
}
if (isStop) {
break;
}
}
if (blank < 0) {
blank = 0;
}
//计算加上保留空白距离之后的图像大小
left = left - blank > 0 ? left - blank : 0;
top = top - blank > 0 ? top - blank : 0;
right = right blank > WIDTH - 1 ? WIDTH - 1 : right blank;
bottom = bottom blank > HEIGHT - 1 ? HEIGHT - 1 : bottom blank;
//防止创建null的bitmap 引发的崩溃
if (left==0&&top==0&&right==0&&bottom==0){
left=1;
top=1;
right=351;
bottom=251;
}
return Bitmap.createBitmap(bp, left, top, right - left, bottom - top);
}
/**
* 设置画笔宽度 默认宽度为10px
*
* @param mPaintWidth
*/
public void setPaintWidth(int mPaintWidth) {
mPaintWidth = mPaintWidth > 0 ? mPaintWidth : 10;
this.mPaintWidth = mPaintWidth;
mGesturePaint.setStrokeWidth(mPaintWidth);
}
public void setBackColor(@ColorInt int backColor)
{
mBackColor=backColor;
}
/**
* 设置画笔颜色
*
* @param mPenColor
*/
public void setPenColor(int mPenColor) {
this.mPenColor = mPenColor;
mGesturePaint.setColor(mPenColor);
}
}源码地址：https://download.csdn.net/download/macaopark/11005467
