本文实例为大家分享了Android实现手写板功能的具体代码，供大家参考，具体内容如下
自定义个一个手写板的重点:
笔画为一次down-move-up的集合
撤销笔画并非一次path的动作撤销 应该也是一次down-move -up的撤销
为了更好的笔画需要使用贝塞尔曲线来完成
效果如下:
截图中清楚 的意思是清除 !
具体代码如下:
package com.kyli.base.view;
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.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import androidx.annotation.Nullable;
import java.util.ArrayList;
import java.util.List;
/**
* 绘制画板
*/
public class SignBoradView extends View {
/*4个像素点*/
private int beierThreshold = 4;
private float x = 0;
private float y = 0;
/*画笔*/
private Paint mPaint;
/*宽度*/
private int strokeWidth = 10;
/*yanbse*/
private int color = Color.BLACK;
/*当前笔画*/
private Path path;
private int state = State.CLEAR;
private interface State {
/*画板可以使用了*/
int START = 0;
/*停止使用画板*/
int STOP = 1;
/*清空画板*/
int CLEAR = 2;
}
private List<EveryPenPath> everyPenPaths = new ArrayList<>();
/*每一个笔画*/
private static class EveryPenPath {
public Path path;
}
public SignBoradView(Context context) {
super(context);
}
public SignBoradView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
public SignBoradView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
private void initPaint() {
if (mPaint == null) {
mPaint = new Paint();
mPaint.setStrokeWidth(strokeWidth);
mPaint.setColor(color);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setAntiAlias(true);
mPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
}
}
public void start() {
state = State.START;
initPaint();
}
/*停止使用*/
public void stop() {
state = State.STOP;
}
/*清空画板*/
public void clear() {
state = State.CLEAR;
for (int i = everyPenPaths.size() - 1; i >= 0; i--) {
EveryPenPath everyPenPath = everyPenPaths.get(i);
everyPenPath.path.reset();
everyPenPath.path.close();
everyPenPath.path = null;
}
everyPenPaths.clear();
invalidate();
}
public void back() {
int count = everyPenPaths.size();
if (count < 1)
return;
EveryPenPath everyPenPath = everyPenPaths.get(count - 1);
everyPenPath.path.reset();
everyPenPath.path.close();
everyPenPath.path = null;
everyPenPaths.remove(count - 1);
invalidate();
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (state == State.START) {
/*先绘制完整笔画*/
for (EveryPenPath e : everyPenPaths) {
canvas.drawPath(e.path, mPaint);
}
//当前进行中的 path!=null
if (path != null) {
canvas.drawPath(path, mPaint);
}
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (state == State.START) {
if (event.getAction() == MotionEvent.ACTION_UP) {
actionUp(event);
invalidate();
return true;
}
if (event.getAction() == MotionEvent.ACTION_MOVE) {
actionMove(event);
invalidate();
return true;
}
if (event.getAction() == MotionEvent.ACTION_DOWN) {
actionDown(event);
invalidate();
return true;
}
}
return super.onTouchEvent(event);
}
private void actionUp(MotionEvent event) {
actionMove(event);
/*构成一个笔画*/
EveryPenPath everyPenPath = new EveryPenPath();
everyPenPath.path = path;
everyPenPaths.add(everyPenPath);
//将当前画笔置位null;
path = null;
}
/**/
private void actionMove(MotionEvent event) {
/*每次移动去绘制贝塞尔曲线*/
float cX = event.getX();
float cY = event.getY();
float dX = Math.abs(cX - x);//变化量
float dY = Math.abs(cY - y);
if (dX >= beierThreshold || dY >= beierThreshold) {
float rX = x + (cX - x) / 2;
float rY = y + (cY - y) / 2;
path.quadTo(rX, rY, cX, cY);
//下次的x 域y 将重新计算
x = cX;
y = cY;
}
}
/*开始时*/
private void actionDown(MotionEvent event) {
path = new Path();
x = event.getX();
y = event.getY();
path.moveTo(x, y);
}
public void setBeierThreshold(int beierThreshold) {
this.beierThreshold = beierThreshold;
}
public void setStrokeWidth(int strokeWidth) {
this.strokeWidth = strokeWidth;
}
public void setColor(int color) {
this.color = color;
}
public Bitmap getResult(int bgColor) {
if (everyPenPaths.size() == 0)
return null;
Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
canvas.drawColor(bgColor);
for (int i = 0; i < everyPenPaths.size(); i++) {
if (mPaint == null) {
initPaint();
}
canvas.drawPath(everyPenPaths.get(i).path, mPaint);
}
return bitmap;
}
public Bitmap getResult() {
return getResult(Color.WHITE);
}
}
