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
