Android自定义view,实现电子签名

首先new一个类继承于View

public class SignatureView extends View

自定义view,采用画笔绘制一张图片 定义一个画笔滑动的宽度 还需要对画笔进行跟踪,以便内容区域可以容纳笔划

private static final float STROKE_WIDTH = 5f;
private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;

通过使最小可能区域无效来优化绘制

private Paint paint = new Paint();
private Path path = new Path();

private float lastTouchX;
private float lastTouchY;
private final RectF dirtyRect = new RectF();

构造方法里面初始化画笔

public SignatureView(Context context, AttributeSet attrs) {
super(context, attrs);

paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(STROKE_WIDTH);
}

处理手势,触发画笔路径

@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = event.getX();
float eventY = event.getY();

switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
path.moveTo(eventX, eventY);
lastTouchX = eventX;
lastTouchY = eventY;
// 现在还没有终点,所以不要浪费周期使其失效。
return true;

case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_UP:
//开始跟画笔区域。
resetDirtyRect(eventX, eventY);

// 当硬件跟踪事件的速度快于事件的交付速度时
// 事件将包含这些跳过点的历史记录。
int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
float historicalX = event.getHistoricalX(i);
float historicalY = event.getHistoricalY(i);
expandDirtyRect(historicalX, historicalY);
path.lineTo(historicalX, historicalY);
}

// 回放历史记录后,将线路连接到触点。
path.lineTo(eventX, eventY);
break;

default:

return false;
}

// 包括一半笔划宽度以避免剪裁
invalidate(
(int) (dirtyRect.left - HALF_STROKE_WIDTH),
(int) (dirtyRect.top - HALF_STROKE_WIDTH),
(int) (dirtyRect.right + HALF_STROKE_WIDTH),
(int) (dirtyRect.bottom + HALF_STROKE_WIDTH));

lastTouchX = eventX;
lastTouchY = eventY;

return true;
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(path, paint);
}

抬起时调用,以确包含所有路径

private void expandDirtyRect(float historicalX, float historicalY) {
if (historicalX < dirtyRect.left) {
dirtyRect.left = historicalX;
} else if (historicalX > dirtyRect.right) {
dirtyRect.right = historicalX;
}
if (historicalY < dirtyRect.top) {
dirtyRect.top = historicalY;
} else if (historicalY > dirtyRect.bottom) {
dirtyRect.bottom = historicalY;
}
}

到这里,手写功能就已经能使用了,接下来是做一些处理

在运动事件发生时重置
lastTouchX和lastTouchY是在动作结束时设置的

private void resetDirtyRect(float eventX, float eventY) {
dirtyRect.left = Math.min(lastTouchX, eventX);
dirtyRect.right = Math.max(lastTouchX, eventX);
dirtyRect.top = Math.min(lastTouchY, eventY);
dirtyRect.bottom = Math.max(lastTouchY, eventY);
}

清除签名

那写错了怎么办,肯定要有清除签名啦

public void clear() {
path.reset();
// 重新绘制整个视图
invalidate();
}

获取图片缓存

public Bitmap getBitmapFromView(){
this.setDrawingCacheEnabled(true); //开启图片缓存
buildDrawingCache(); //构建图片缓存
Bitmap bitmap = Bitmap.createBitmap(getDrawingCache());
setDrawingCacheEnabled(false); //关闭图片缓存
return bitmap;
}

效果图

微信图片_20211115231808.jpg


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