Android中在屏幕上涂鸦的例子

 

这个例子，自定义了一个View，可以接受touch动作，然后在屏幕上即时的显示出touch的轨迹，类似于线条的涂鸦。这个例子主要是演示如何将onTouchEvent与draw配合起来使用。在这个基础上，可以做很多有用的程序。

 

（注意invalidate()这个方法。这个比较关键。加入这个方法的调用主要是为了强制View进行重画。）

 

package com.arui;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Path;import android.graphics.Paint.Style;import android.view.MotionEvent;import android.view.View;/** * Example for hand writing. * * @author http://blog.csdn.net/arui319 * @version 2010/09/07 * */public class HandwritingView extends View {private Paint paint = null;private Path path = null;public HandwritingView(Context context) {super(context);path = new Path();paint = new Paint();paint.setColor(Color.YELLOW);paint.setStyle(Style.STROKE);paint.setAntiAlias(true);this.setBackgroundColor(Color.BLACK);}@Overridepublic boolean onTouchEvent(MotionEvent event) {if (event.getAction() == MotionEvent.ACTION_DOWN) {int x = (int) event.getX();int y = (int) event.getY();path.moveTo(x, y);invalidate();return true;} else if (event.getAction() == MotionEvent.ACTION_MOVE) {int x = (int) event.getX();int y = (int) event.getY();path.lineTo(x, y);invalidate();return true;}return super.onTouchEvent(event);}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);if (path != null) {canvas.drawPath(path, paint);}}}