简单的画图板

最新推荐文章于 2023-09-11 16:58:55 发布

dblackde

最新推荐文章于 2023-09-11 16:58:55 发布

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CC 4.0 BY-SA版权

文章标签： float constructor path class up kill

本文链接：https://blog.youkuaiyun.com/dblackde/article/details/7429592

本文介绍了一个Android应用程序，该程序使用自定义视图实现触摸屏绘画功能。文章详细展示了如何利用Canvas、Paint和Path类来捕捉用户的触摸事件并绘制平滑的线条。通过设置Paint属性，如抗锯齿、颜色和笔触样式等，可以实现高质量的绘画体验。

package com.edu;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Bundle;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;

public class Paint_TestActivity extends Activity {
    /** Called when the activity is first created. */
	  Paint mPaint;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
       // setContentView(R.layout.main);
       // Display display=getWindowManager().getDefaultDisplay();
        
        setContentView(new MyView(this));
        mPaint=new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(0xFFFF0000);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(12);
        
    }
    class MyView extends View{
    	   Bitmap mBitmap;
    	   Canvas mCanvas;
    	   Paint mBitmaPaint;
    	   Path mPath;
    		public MyView(Activity activity) {
    			super(activity);
    			// TODO Auto-generated constructor stub
    			Display display=activity.getWindowManager().getDefaultDisplay();
    			mBitmap=Bitmap.createBitmap(display.getWidth(), display.getHeight(), Bitmap.Config.ARGB_8888);
    			
    			mCanvas=new Canvas(mBitmap);
    			mPath=new Path();
    			mBitmaPaint=new Paint(Paint.DITHER_FLAG);
    		}
    		 protected void onDraw(Canvas canvas) {
    	         canvas.drawColor(0xFFAAAAAA);
    	         System.out.println("onDraw>>>>>>>>>>>>>>>>>>>>>"+mPath.toString());
    	         canvas.drawBitmap(mBitmap, 10, 10, mBitmaPaint);
    	         
    	         canvas.drawPath(mPath, mPaint);
    	     }
    		 private float mX, mY;
    	        private static final float TOUCH_TOLERANCE = 4;
    	        
    	        private void touch_start(float x, float y) {
    	            mPath.reset();
    	            mPath.moveTo(x, y);
    	            mX = x;
    	            mY = y;
    	        }
    	        private void touch_move(float x, float y) {
    	        	System.out.println("move 移动中>>>>>>>>>>>>>>>>>>");
    	            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);
    	            	mPath.quadTo(mX, mY, x, y);
    	                mX = x;
    	                mY = y;
    	            }
    	        }
    	        private void touch_up() {
    	            mPath.lineTo(mX, mY);
    	            // commit the path to our offscreen
    	            
    	            mCanvas.drawPath(mPath, mPaint);
    	            System.out.println("接触over。。。》》》》》》》 ");
    	            // kill this so we don't double draw
    	            mPath.reset();
    	        }
    	        
    		 @Override
    	        public boolean onTouchEvent(MotionEvent event) {
//    			 它不停地调用   跟时间 有关系  cpu 是个分时系统  
//    			 画同样长度的线用不同的时间在屏幕   
//    			 在logCat输出的调试信息              时间长的 System.out.println( 越多
    			 
    	            float x = event.getX();
    	            float y = event.getY();
    	            
    	            switch (event.getAction()) {
    	                case MotionEvent.ACTION_DOWN:
    	                    touch_start(x, y);
    	                    invalidate();//回调onDraw 重绘在屏幕上面
    	                    break;
    	                case MotionEvent.ACTION_MOVE:
    	                    touch_move(x, y);
    	                    invalidate();
    	                    break;
    	                case MotionEvent.ACTION_UP:
    	                    touch_up();
    	                    invalidate();
    	                    break;
    	            }
    	            return true;
    	        }
    		
    	}
  
}