android涂鸦的撤销功能的性能问题？！

Posted 2023-05-06

撤销功能的思想是每画一笔就记住它的path和paint，把它们存在堆栈里，撤销的时候就remove最后一笔，清空画布，把剩下的重新画在画布上，撤销可以完成。。但是当你存足够多的笔画时，撤销动作会滞后，会有严重的性能问题，请各位大神给几个优化方案！不胜感激，也可以留下QQ 一起研究一下！

恩 楼上的用sqlite是一种解决方法 其实有关内存不足 把数据保存到本地的一个临时文件里也是一种方法 现在有不少软件也是使用临时工作空间 即是从本地申请一个存储区域来进行缓存操作 不过读写需要时间 就要你来权衡了 参考技术A 可以存到sqlite3微型数据库中啊！内存中只保留五次，然后，每次堆栈中满5笔然后存入一次数据库。用的时候再读出来。这样应该能解决你说的滞留问题！

Android 实现涂鸦笔效果

1、主要可以通过手指绘制各种图案、还可以清除回撤等效果，实现比较简单。

 

2、主要实现代码，功能实现比较简单。

package com.example.mytestproject;


import android.content.Context;
import android.graphics.BlurMaskFilter;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import androidx.annotation.Nullable;
import java.util.ArrayList;
import java.util.List;

public class DrawView extends View 
    public float mCurrentX = 40;
    public float mCurrentY = 50;
    private float mDownX;
    private float mDownY;
    private Paint mPaint;
    private Line mCurrentLine = new Line();
    private ArrayList<Line> lines = new ArrayList<>();
    private float mLastMoveX = 0;
    private float mLastMoveY = 0;
    private int mSpace;
    private Matrix mMatrix;
    private Drawable[] mDrawables = new Drawable[3];
    private List<Line> mCheLines = new ArrayList<>();
    private int mResetPosition = 0;

    public DrawView(Context context) 
        this(context, null);
    

    public DrawView(Context context, @Nullable AttributeSet attrs) 
        this(context, attrs, 0);
    

    public DrawView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) 
        super(context, attrs, defStyleAttr);

        // mPaint.setShader(new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.MIRROR));
//        BlurMaskFilter maskFilter = new BlurMaskFilter(10, BlurMaskFilter.Blur.NORMAL);
//        mPaint.setMaskFilter(maskFilter);
        //Shader shader0 = new BitmapShader(mBitmap, Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
//        Shader shader = new LinearGradient(0, 0, 30, 0, new int[]Color.WHITE, Color.RED, Color.RED, new float[]0f, 0.5f, 1f, Shader.TileMode.REPEAT);
//        Shader shader1 = new RadialGradient(10, 10, 10, new int[]Color.GREEN, Color.WHITE, Color.GREEN, new float[]0, 0.5f, 1, Shader.TileMode.MIRROR);
//        Shader shader2 = new SweepGradient(15, 15, Color.RED, Color.BLUE);
//        Shader shader3 = new ComposeShader(shader, shader1, PorterDuff.Mode.MULTIPLY);
//        mMatrix = new Matrix();
//        mLinearGradient.setLocalMatrix(mMatrix);
        //  mPaint.setShader(shader);

        BlurMaskFilter PaintBGBlur = new BlurMaskFilter(10, BlurMaskFilter.Blur.SOLID);
        mPaint = new Paint();
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setMaskFilter(PaintBGBlur);
        //mPaint.setAntiAlias(true);
        mPaint.setColor(Color.RED);
        mDrawables[0] = getResources().getDrawable(R.mipmap.star_big_off);
        mDrawables[1] = getResources().getDrawable(R.mipmap.star_big_on);
        mDrawables[2] = getResources().getDrawable(R.mipmap.rate_star_med_on_holo_light);

        mSpace = mDrawables[0].getIntrinsicWidth();
        mPaint.setStrokeWidth(mDrawables[0].getIntrinsicWidth());
    


    @Override
    protected void onDraw(Canvas canvas) 
        super.onDraw(canvas);
        for (int i = 0; i < lines.size(); i++) 
            drawLine(canvas, lines.get(i));
        
        drawLine(canvas, mCurrentLine);
    

    private void drawLine(Canvas canvas, Line line) 
        for (int i = 0; i < line.points.size() - 1; i++) 
            float x = line.points.get(i).x;
            float y = line.points.get(i).y;
            int size = mDrawables.length;
            int surplus = i%size;
            for (int j=0;j<size;j++)
                if (surplus==j)
                    mDrawables[j].setBounds((int) x, (int) y, (int) x + mDrawables[j].getIntrinsicWidth(), (int) y + mDrawables[j].getIntrinsicHeight());
                    mDrawables[j].draw(canvas);
                    break;
                
            
        
    

    @Override
    public boolean onTouchEvent(MotionEvent event) 

        switch (event.getAction()) 

            case MotionEvent.ACTION_DOWN:
                mDownX = event.getX();
                mDownY = event.getY();
                mLastMoveX = mDownX;
                mLastMoveY = mDownY;
                break;

            case MotionEvent.ACTION_MOVE:
                mCurrentX = event.getX();
                mCurrentY = event.getY();
                if (Math.abs(mCurrentX - mLastMoveX) > mSpace || Math.abs(mCurrentY - mLastMoveY) > mSpace) 
                    ViewPoint point = new ViewPoint();
                    point.x = mCurrentX;
                    point.y = mCurrentY;
                    mCurrentLine.points.add(point);
                    mLastMoveX = mCurrentX;
                    mLastMoveY = mCurrentY;
                

                break;

            case MotionEvent.ACTION_UP:
                lines.add(mCurrentLine);
                mCheLines.add(mCurrentLine);
                mCurrentLine = new Line();
                mResetPosition = mCheLines.size();
                break;

        
        invalidate();
        return true;
    

    public void last() 
        mResetPosition--;
        if (mResetPosition <= 0) 
            mResetPosition = 0;
        
        lines.clear();
        for (int i = 0; i < mResetPosition; i++) 
            lines.add(mCheLines.get(i));
        
        invalidate();
    

    public void next() 
        mResetPosition++;
        if (mResetPosition >= mCheLines.size()) 
            mResetPosition = mCheLines.size();
        
        lines.clear();

        for (int i = 0; i < mResetPosition; i++) 
            lines.add(mCheLines.get(i));
        
        invalidate();
    


    public void clear() 
        mCheLines.clear();
        lines.clear();
        mCurrentLine.points.clear();
        invalidate();