/**
 * Created by YyyyQ on 2020/3/5.
 * 电子签名
 */
public class SignatureView extends View {
 private Context context;
 //X轴起点
 private float x;
 //Y轴起点
 private float y;
 //画笔
 private final Paint paint = new Paint();
 //路径
 private final Path path = new Path();
 //画布
 private Canvas canvas;
 //生成的图片
 private Bitmap bitmap;
 //画笔的宽度
 private int paintWidth = 10;
 //签名颜色
 private int paintColor = Color.BLACK;
 //背景颜色
 private int backgroundColor = Color.WHITE;
 //是否已经签名
 private boolean isTouched = false;
 //签名开始与结束
 public interface Touch {
  void OnTouch(boolean isTouch);
 }
 private Touch touch;
 public SignatureView(Context context) {
  super(context);
  init(context);
 }
 public SignatureView(Context context, @Nullable AttributeSet attrs) {
  super(context, attrs);
  init(context);
 }
 public SignatureView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  init(context);
 }
 private void init(Context context) {
  this.context = context;
  //抗锯齿
  paint.setAntiAlias(true);
  //样式
  paint.setStyle(Paint.Style.STROKE);
  //画笔颜色
  paint.setColor(paintColor);
  //画笔宽度
  paint.setStrokeWidth(paintWidth);
 }
 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);
  //创建于view大小一致的bitmap
  bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
  canvas = new Canvas(bitmap);
  canvas.drawColor(backgroundColor);
  isTouched = false;
 }
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  if (touch != null) touch.OnTouch(true);
  switch (event.getAction()) {
   //手指按下
   case MotionEvent.ACTION_DOWN:
    touchDwon(event);
    break;
   //手指移动
   case MotionEvent.ACTION_MOVE:
    isTouched = true;
    if (touch != null) touch.OnTouch(false);
    touchMove(event);
    break;
   //手指抬起
   case MotionEvent.ACTION_UP:
    canvas.drawPath(path, paint);
    path.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(bitmap, 0, 0, paint);
  // 通过画布绘制多点形成的图形
  canvas.drawPath(path, paint);
 }
 //手指按下的方法
 private void touchDwon(MotionEvent event) {
  //重置绘制路径
  path.reset();
  float downX = event.getX();
  float downY = event.getY();
  x = downX;
  y = downY;
  //绘制起点
  path.moveTo(downX, downY);
 }
 //手指滑动的方法
 private void touchMove(MotionEvent event) {
  //当前的x,y坐标点
  final float moveX = event.getX();
  final float moveY = event.getY();
  //之前的x,y坐标点
  final float previousX = x;
  final float previousY = y;
  //获取绝对值
  final float dx = Math.abs(moveX - previousX);
  final float dy = Math.abs(moveY - previousY);
  if (dx >= 3 || dy >= 3) {
   float cX = (moveX + previousX) / 2;
   float cY = (moveY + previousY) / 2;
   path.quadTo(previousX, previousY, cX, cY);
   x = moveX;
   y = moveY;
  }
 }
 /**
  * 设置画笔颜色
  *
  * @param paintColor
  */
 public void setPaintColor(int paintColor) {
  this.paintColor = paintColor;
  paint.setColor(paintColor);
 }
 /**
  * 设置画笔宽度
  *
  * @param paintWidth
  */
 public void setPaintWidth(int paintWidth) {
  this.paintWidth = paintWidth;
  paint.setStrokeWidth(paintWidth);
 }
 /**
  * 设置画板颜色
  *
  * @param canvasColor
  */
 public void setCanvasColor(int canvasColor) {
  this.backgroundColor = canvasColor;
 }
 /**
  * 清除画板
  */
 public void clear() {
  if (canvas != null) {
   isTouched = false;
   //更新画板
   paint.setColor(paintColor);
   paint.setStrokeWidth(paintWidth);
   canvas.drawColor(backgroundColor, PorterDuff.Mode.CLEAR);
   invalidate();
  }
 }
 /**
  * 获取画板的Bitmap
  *
  * @return
  */
 public Bitmap getBitmap() {
  setDrawingCacheEnabled(true);
  buildDrawingCache();
  Bitmap bitmap = getDrawingCache();
  setDrawingCacheEnabled(false);
  return bitmap;
 }
 /**
  * 是否有签名
  *
  * @return
  */
 public Boolean getSigstatus() {
  return isTouched;
 }
 /**
  * 保存画板
  *
  * @param path 保存到路径
  */
 @SuppressLint("WrongThread")
 public Boolean save(String path) throws IOException {
  Bitmap bitmap = this.bitmap;
  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();
   return true;
  } else {
   return false;
  }
 }
}

<?xml version="1.0" encoding="utf-8"?>

 
 
 
  
  
  
 

/**
 * Created by YyyyQ on 2020/3/9.
 */
public class SignatureActivity extends AppCompatActivity {
  @Override
  protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_signature);
    SignatureView signatureView = findViewById(R.id.signature);
    //设置画笔颜色(可以不设置--默认画笔宽度10,画笔颜色黑,背景颜色白)
    signatureView.setPaintColor(Color.BLACK);
    signatureView.setPaintWidth(20);
    signatureView.setCanvasColor(Color.WHITE);
    //清除
    Button clear = findViewById(R.id.clear);
    clear.setOnClickListener(view -> {
      signatureView.clear();
      //设置画笔颜色(可以不设置--默认画笔宽度10,画笔颜色黑,背景颜色白)
      signatureView.setPaintColor(Color.BLACK);
      signatureView.setPaintWidth(20);
      signatureView.setCanvasColor(Color.WHITE);
    });
    //是否含有签名
    Button isSignature = findViewById(R.id.isSignature);
    isSignature.setOnClickListener(view -> {
      if (signatureView.getSigstatus()) {
        Toast.makeText(SignatureActivity.this, "有签名", Toast.LENGTH_SHORT).show();
      } else {
        Toast.makeText(SignatureActivity.this, "无签名", Toast.LENGTH_SHORT).show();
      }
    });
    //保存
    Button save = findViewById(R.id.save);
    save.setOnClickListener(view -> {
      try {
        if (signatureView.save("/sdcard/YyyyQ.png")) {
          Toast.makeText(SignatureActivity.this, "保存成功", Toast.LENGTH_SHORT).show();
        } else {
          Toast.makeText(SignatureActivity.this, "保存失败", Toast.LENGTH_SHORT).show();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    });
  }
}