自定义控件之canvas变换和裁剪

1.平移

 //构造两个画笔，一个红色，一个绿色

        Paint paint_green = generatePaint(Color.GREEN, Paint.Style.STROKE, 3);

        Paint paint_red   = generatePaint(Color.RED, Paint.Style.STROKE, 3);

        //构造一个矩形

        Rect rect1 = new Rect(0,0,400,220);

        //在平移画布前用绿色画下边框

        canvas.drawRect(rect1, paint_green);

        //平移画布后,再用红色边框重新画下这个矩形

        canvas.translate(100, 100);

        canvas.drawRect(rect1, paint_red);

2.旋转

 Paint paint_green = generatePaint(Color.GREEN, Paint.Style.FILL, 5);

        Paint paint_red   = generatePaint(Color.RED, Paint.Style.STROKE, 5);

        Rect rect1 = new Rect(300,10,500,100);

        canvas.drawRect(rect1, paint_red); //画出原轮廓

        canvas.rotate(30);//顺时针旋转画布

        canvas.drawRect(rect1, paint_green);//画出旋转后的矩形

3.缩放

　　　　　Paint paint_green = generatePaint(Color.GREEN, Paint.Style.STROKE, 5);

        Paint paint_red   = generatePaint(Color.RED, Paint.Style.STROKE, 5);

        Paint paint_yellow   = generatePaint(Color.YELLOW, Paint.Style.STROKE, 5);

        Rect rect1 = new Rect(10,10,200,100);

        canvas.drawRect(rect1, paint_green);

        canvas.scale(0.5f, 1);

        canvas.drawRect(rect1, paint_red);

4.扭曲

 Paint paint_green = generatePaint(Color.GREEN, Paint.Style.STROKE, 5);

        Paint paint_red   = generatePaint(Color.RED, Paint.Style.STROKE, 5);

        Rect rect1 = new Rect(10,10,200,100);

        canvas.drawRect(rect1, paint_green);

        canvas.skew(1.732f,0);//X轴倾斜60度，Y轴不变

        canvas.drawRect(rect1, paint_red);

5.裁剪

 canvas.drawColor(Color.RED);

        //保存的画布大小为全屏幕大小

        int c1 = canvas.save();

        canvas.clipRect(new Rect(100, 100, 800, 800));

        canvas.drawColor(Color.GREEN);

        //保存画布大小为Rect(100, 100, 800, 800)

        int c2 = canvas.save();

        canvas.clipRect(new Rect(200, 200, 700, 700));

        canvas.drawColor(Color.BLUE);

        //保存画布大小为Rect(200, 200, 700, 700)

        int c3 = canvas.save();

        canvas.clipRect(new Rect(300, 300, 600, 600));

        canvas.drawColor(Color.BLACK);

        //保存画布大小为Rect(300, 300, 600, 600)

        int c4 = canvas.save();

        canvas.clipRect(new Rect(400, 400, 500, 500));

        canvas.drawColor(Color.WHITE);

        //连续出栈三次，将最后一次出栈的Canvas状态作为当前画布，并画成黄色背景

        canvas.restoreToCount(c2);

        canvas.drawColor(Color.YELLOW);

获取画笔方法

  private Paint generatePaint(int color,Paint.Style style,int width){

        Paint paint = new Paint();

        paint.setColor(color);

        paint.setStyle(style);

        paint.setStrokeWidth(width);

        return paint;

    }

画布的保存和恢复

canvas.save()

canvas.restore();

save()每次调用save函数,都会先保存画布的状态,然后将其放入特定的栈中

restore()都会把栈中顶层的画布状态取出来,并按照这个状态恢复当前的画布,然后在这个画布上作画

restoreToCount函数

restoreToCount(int saveCount)

        int c2 = canvas.save();//返回栈的索引

        canvas.restoreToCount(c2);//根据索引返回当前画布

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示例代码-圆形代码

public class BasisView extends View {

    private Bitmap mBmp;

    private Paint mPaint;

    private Path mPath;

    public BasisView(Context context) {

        super(context);

        init();

    }

    public BasisView(Context context, @Nullable AttributeSet attrs) {

        super(context, attrs);

        init();

    }

    public BasisView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {

        super(context, attrs, defStyleAttr);

        init();

    }

    private void init(){

        setLayerType(LAYER_TYPE_SOFTWARE,null);

        mBmp = BitmapFactory.decodeResource(getResources(), R.drawable.avator);

        mPaint = new Paint();

        mPath = new Path();

        int width = mBmp.getWidth();

        int height = mBmp.getHeight();

        mPath.addCircle(width/2,height/2,width/2, Path.Direction.CCW);

    }

    @Override

    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);

        canvas.save();

        canvas.clipPath(mPath);

        canvas.drawBitmap(mBmp,0,0,mPaint);

        canvas.restore();

    }

}

裁剪动画

package com.loaderman.customviewdemo.paint;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Paint;

import android.graphics.Path;

import android.graphics.RectF;

import android.graphics.Region;

import android.support.annotation.Nullable;

import android.util.AttributeSet;

import android.view.View;

import com.loaderman.customviewdemo.R;

public class BasisView extends View {

    private Path mPath;

    private Bitmap mBitmap;

    private int clipWidth = 0;

    private int width;

    private int heigth;

    private static final int CLIP_HEIGHT = 30;

    private Region mRgn;

    public BasisView(Context context) {

        super(context);

        init();

    }

    public BasisView(Context context, @Nullable AttributeSet attrs) {

        super(context, attrs);

        init();

    }

    public BasisView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {

        super(context, attrs, defStyleAttr);

        init();

    }

    private void init() {

        setLayerType(LAYER_TYPE_SOFTWARE, null);

        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.avator);

        width = mBitmap.getWidth();

        heigth = mBitmap.getHeight();

        mRgn = new Region();

        mPath=new Path();

    }

    @Override

    protected void onDraw(Canvas canvas) {

        mRgn.setEmpty();

        int i = 0;

        while (i * CLIP_HEIGHT <= heigth) {

            if (i % 2 == 0) {

                mPath.addRect(new RectF(0, i * CLIP_HEIGHT, clipWidth, (i + 1) * CLIP_HEIGHT),Path.Direction.CCW);

            } else {

                mPath.addRect(new RectF(width - clipWidth, i * CLIP_HEIGHT, width, (i + 1) * CLIP_HEIGHT),Path.Direction.CCW);

            }

            i++;

        }

        canvas.clipPath(mPath);

        canvas.drawBitmap(mBitmap, 0, 0, new Paint());

        if (clipWidth > width) {

            return;

        }

        clipWidth += 5;

        invalidate();

    }

}

效果: