android-API之FingerPaint手指绘图详解

不多废话，马上弄源码。

 

 

 

主Activity类DemoViewPath.java

 package com.geolo.android.demoViewPath;
 import android.app.Activity;
 import android.os.Bundle;
 public class DemoViewPath extends Activity {
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         DemoPath dp = new DemoPath(this);
         setContentView(dp);
         super.onCreate(savedInstanceState);
     }
 }

 

 

绘图类：DemoPath.java

 package com.geolo.android.demoViewPath;
 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.Canvas;
 import android.graphics.Paint;
 import android.graphics.Path;
 import android.view.MotionEvent;
 import android.view.View;
 public class DemoPath extends View {
     private float mX , mY;
     private Path mPath;
     private Paint mPaint;
     private static final float TOUCH_TOLERANCE = 4;
     private Bitmap  mBitmap;
     private Canvas  mCanvas;
     private Paint   mBitmapPaint;

     public DemoPath(Context c) {
         super(c);

         mPaint = new Paint();//创建画笔渲染对象
         mPaint.setAntiAlias(true);//设置抗锯齿，让绘画比较平滑
         mPaint.setDither(true);//设置递色
         mPaint.setColor(0xFFFF0000);//设置画笔的颜色
         mPaint.setStyle(Paint.Style.STROKE);//画笔的类型有三种（1.FILL 2.FILL_AND_STROKE 3.STROKE ）
         mPaint.setStrokeJoin(Paint.Join.ROUND);//默认类型是MITER（1.BEVEL 2.MITER 3.ROUND ）
         mPaint.setStrokeCap(Paint.Cap.ROUND);//默认类型是BUTT（1.BUTT 2.ROUND 3.SQUARE ）
         mPaint.setStrokeWidth(12);//设置描边的宽度，如果设置的值为0那么边是一条极细的线

         mBitmap = Bitmap.createBitmap(320, 480, Bitmap.Config.ARGB_8888);//绘制固定大小的bitmap对象
         mCanvas = new Canvas(mBitmap);//将固定的bitmap对象嵌入到canvas对象中
         mPath = new Path();//创建画笔路径
         mBitmapPaint = new Paint(Paint.DITHER_FLAG);
     }
     @Override
     protected void onDraw(Canvas canvas) {
         canvas.drawColor(0xFFAAAAAA);
         canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
         canvas.drawPath(mPath, mPaint);
         super.onDraw(canvas);
     }
     private void onTouchDown(float x , float y){
         mPath.reset();//将上次的路径保存起来，并重置新的路径。
         mPath.moveTo(x, y);//设置新的路径“轮廓”的开始
         mX = x;
         mY = y;
     }
     private void onTouchMove(float x , float y){
         float dx = Math.abs(x - mX);
         float dy = Math.abs(y - mY);
         if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
             mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
             mX = x;
             mY = y;
         }
     }
     private void onTouchUp(float x , float y){
         mPath.lineTo(mX, mY);//从最后一个指定的xy点绘制一条线，如果没有用moveTo方法，那么起始点表示（0，0）点。
         // commit the path to our offscreen
         mCanvas.drawPath(mPath, mPaint);//手指离开屏幕后，绘制创建的“所有”路径。
         // kill this so we don't double draw
         mPath.reset();
     }
     @Override
     public boolean onTouchEvent(MotionEvent event) {
         float x = event.getX();
         float y = event.getY();
         switch (event.getAction()) {
         case MotionEvent.ACTION_DOWN://手指开始按压屏幕，这个动作包含了初始化位置
             onTouchDown(x , y);
             invalidate();//刷新画布，重新运行onDraw（）方法
             break;
         case MotionEvent.ACTION_MOVE://手指按压屏幕时，位置的改变触发，这个方法在ACTION_DOWN和ACTION_UP之间。
             onTouchMove(x , y);
             invalidate();
             break;
         case MotionEvent.ACTION_UP://手指离开屏幕，不再按压屏幕
             onTouchUp(x , y);
             invalidate();
             break;
         default:
             break;
         }
         return true;
     }
 }