一、Android自定义View步骤 ：

自定义属性；

选择和设置构造方法；

重写onMeasure()方法；

重写onDraw()方法；

重写onLayout()方法；

重写其他事件的方法(滑动监听等)。

二、代码实现

工具类代码：

package com.smt.saveviewtocream.utils;

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.util.AttributeSet;

import android.view.MotionEvent;

import android.view.View;

import androidx.annotation.ColorInt;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStream;

/**

* 描述: Android自定义实现手写签名功能

*/

public class LinePathView extends View {

private Context mContext;

/**

* 笔画X坐标起点

*/

private float mX;

/**

* 笔画Y坐标起点

*/

private float mY;

/**

* 手写画笔

*/

private final Paint mGesturePaint = new Paint();

/**

* 路径

*/

private final Path mPath = new Path();

/**

* 签名画笔

*/

private Canvas cacheCanvas;

/**

* 签名画布

*/

private Bitmap cachebBitmap;

/**

* 是否已经签名

*/

private boolean isTouched = false;

/**

* 画笔宽度 px；

*/

private int mPaintWidth = 10;

/**

* 前景色

*/

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;

//签名开始与结束

private Touch touch;

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);

}

public 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

cachebBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);

cacheCanvas = new Canvas(cachebBitmap);

cacheCanvas.drawColor(mBackColor);

isTouched = false;

}

@Override

public boolean onTouchEvent(MotionEvent event) {

if (touch != null) touch.OnTouch(true);

switch (event.getAction()) {

case MotionEvent.ACTION_DOWN:

touchDown(event);

break;

case MotionEvent.ACTION_MOVE:

isTouched = true;

if (touch != null) touch.OnTouch(false);

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;

}

@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);

}

// 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) {

isTouched = false;

//更新画板信息

mGesturePaint.setColor(mPenColor);

cacheCanvas.drawColor(mBackColor, PorterDuff.Mode.CLEAR);

mGesturePaint.setColor(mPenColor);

invalidate();

}

}

public interface Touch {

void OnTouch(boolean isTouch);

}

public Touch getTouch() {

return touch;

}

public void setTouch(Touch touch) {

this.touch = touch;

}

/**

* 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();

}

}

/**

* 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;

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);

}

/**

* 是否有签名

*

* @return

*/

public boolean getTouched() {

return isTouched;

}

}

三、功能实现

layout_main.xml:

android:layout_width="match_parent"

android:layout_height="match_parent"

android:background="@android:color/white"

android:fitsSystemWindows="true"

android:orientation="vertical">

android:id="@+id/mPathView"

android:layout_width="match_parent"

android:layout_height="0dp"

android:layout_weight="1"

android:background="#FFFFFF" />

android:layout_width="match_parent"

android:layout_height="@dimen/qb_px_60"

android:orientation="horizontal">

android:id="@+id/mBtnClear"

android:layout_width="wrap_content"

android:layout_height="match_parent"

android:layout_weight="1"

android:text="清除" />

android:id="@+id/mBtnSave"

android:layout_width="wrap_content"

android:layout_height="match_parent"

android:layout_weight="1"

android:text="保存" />

Maintivity.kt:

import android.graphics.Color

import android.os.Bundle

import android.widget.Toast

import androidx.appcompat.app.AppCompatActivity

import com.smt.saveviewtocream.R

import kotlinx.android.synthetic.main.activity_font_siaze.*

import java.io.IOException

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {

super.onCreate(savedInstanceState)

setContentView(R.layout.activity_font_siaze)

//修改背景、笔宽、颜色

mPathView.setBackColor(Color.WHITE)

mPathView.setPaintWidth(20)

mPathView.setPenColor(Color.BLACK)

mPathView.clear()

//清除

mBtnClear.setOnClickListener {

mPathView.clear()

mPathView.setBackColor(Color.WHITE)

mPathView.setPaintWidth(20)

mPathView.setPenColor(Color.BLACK)

}

//保存

mBtnSave.setOnClickListener {

if (mPathView.touched) {

try {

mPathView.save("/sdcard/qm.png", true, 10)

setResult(100)

Toast.makeText(this@MainActivity, "保存成功~", Toast.LENGTH_SHORT).show()

} catch (e: IOException) {

e.printStackTrace()

}

} else {

Toast.makeText(this@MainActivity, "您没有签名~", Toast.LENGTH_SHORT).show()

}

}

}

}

权限：