android实现手写签名功能

package com.xx;
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.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.ImageView;
import com.xx.R;
/**
* Description: 签名类
* Copyright:  Copyright (c)2018
* Company:   
* author:   Corwin
* version:   1.0
* date:    2018/9/5 18:32
* Modification History:
* Date     Author   Version   Description
* ------------------------------------------------------------------
* 2018/9/5  Corwin   1.0     1.0 Version
*/
public class SignatureActivity extends AppCompatActivity {
private ImageView imageSign;
private SignatureView mView;
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_signature);
imageSign = findViewById(R.id.iv_sign);
FrameLayout frameLayout = findViewById(R.id.fl_view);
mView = new SignatureView(this);
frameLayout.addView(mView);
mView.requestFocus();
Button btnClear = findViewById(R.id.btn_clear);
btnClear.setOnClickListener((v) -  {
mView.clear();
});
Button btnOk = findViewById(R.id.btn_ok);
btnOk.setOnClickListener((v) -  {
Bitmap imageBitmap = mView.getCachebBitmap();
imageSign.setImageBitmap(imageBitmap);
});
}
/**
* 自定义签名控件
*/
class SignatureView extends View {
//画笔
private Paint paint;
//画布
private Canvas cacheCanvas;
//位图
private Bitmap cachebBitmap;
//图片保存路径
private Path path;
//位图缓存
public Bitmap getCachebBitmap() {
return cachebBitmap;
}
public SignatureView(Context context) {
super(context);
init();
}
/**
* 初始化
*/
private void init() {
//设置画笔
paint = new Paint();
paint.setAntiAlias(true);
paint.setStrokeWidth(3);
paint.setStyle(Paint.Style.STROKE);
paint.setColor(Color.BLACK);
path = new Path();
//创建位图
cachebBitmap = Bitmap.createBitmap(10, 10, Bitmap.Config.ARGB_8888);
//用自定义位图构建画布
cacheCanvas = new Canvas(cachebBitmap);
//设置画布为白色
cacheCanvas.drawColor(Color.WHITE);
}
/**
* 清除画板，重置画笔
*/
public void clear() {
if (cacheCanvas != null) {
paint.setColor(Color.WHITE);
cacheCanvas.drawPaint(paint);
paint.setColor(Color.BLACK);
cacheCanvas.drawColor(Color.WHITE);
invalidate();
}
}
@Override protected void onDraw(Canvas canvas) {
canvas.drawBitmap(cachebBitmap, 0, 0, null);
canvas.drawPath(path, paint);
}
@Override protected void onSizeChanged(int w, int h, int oldw, int oldh) {
int curW = cachebBitmap != null ? cachebBitmap.getWidth() : 0;
int curH = cachebBitmap != null ? cachebBitmap.getHeight() : 0;
if (curW  = w && curH  = h) {
return;
}
if (curW < w) curW = w;
if (curH < h) curH = h;
Bitmap newBitmap = Bitmap.createBitmap(curW, curH, Bitmap.Config.ARGB_8888);
Canvas newCanvas = new Canvas();
newCanvas.setBitmap(newBitmap);
if (cachebBitmap != null) {
newCanvas.drawBitmap(cachebBitmap, 0, 0, null);
}
cachebBitmap = newBitmap;
cacheCanvas = newCanvas;
}
private float cur_x, cur_y;
@Override public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: {
cur_x = x;
cur_y = y;
path.moveTo(cur_x, cur_y);
break;
}
case MotionEvent.ACTION_MOVE: {
path.quadTo(cur_x, cur_y, x, y);
cur_x = x;
cur_y = y;
break;
}
case MotionEvent.ACTION_UP: {
cacheCanvas.drawPath(path, paint);
path.reset();
break;
}
}
invalidate();
return true;
}
}
}

<?xml version="1.0"? 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
<ImageView
android:id="@+id/iv_sign"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_marginBottom="3dp"
android:layout_weight="1"
android:background="@color/white"
/ 
<FrameLayout
android:id="@+id/fl_view"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:background="@color/white"
/ 
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:drawable/bottom_bar"
android:paddingTop="3dp"
<Button
android:id="@+id/btn_ok"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="确定"
/ 
<Button
android:id="@+id/btn_clear"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="清除"
/ 
</LinearLayout 
</LinearLayout