Android-View的绘制

Posted 2021-05-28 爱吃香蕉的猴子0000

View的绘制

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hi, 大家好，我是爱吃香蕉的猴子，今天写写，绘制view;
先绘制一个画笔
效果：

代码：

public class DrawL extends View{
    private int mov_x;//声明起点坐标
    private int mov_y;
    private Paint paint;//声明画笔
    private Canvas canvas;//画布
    private Bitmap bitmap;//位图
    private int blcolor;

    public DrawL(Context context) {
        super(context);
        paint=new Paint(Paint.DITHER_FLAG);//创建一个画笔
        bitmap = Bitmap.createBitmap(480, 854, Bitmap.Config.ARGB_8888); //设置位图的宽高
        canvas=new Canvas();
        canvas.setBitmap(bitmap);
        paint.setStyle(Style.STROKE);//设置非填充
        paint.setStrokeWidth(5);//笔宽5像素
        paint.setColor(Color.RED);//设置为红笔
        paint.setAntiAlias(true);//锯齿不显示

    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawBitmap(bitmap,0,0,null);
    }
    //触摸事件
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction()==MotionEvent.ACTION_MOVE) {//如果拖动
            canvas.drawLine(mov_x, mov_y, event.getX(), event.getY(), paint);//画线
            invalidate();
        }
        if (event.getAction()==MotionEvent.ACTION_DOWN) {//如果点击
            mov_x=(int) event.getX();
            mov_y=(int) event.getY();
            canvas.drawPoint(mov_x, mov_y, paint);//画点
            invalidate();

        }
        mov_x=(int) event.getX();
        mov_y=(int) event.getY();
        return true;
    }
}

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指尖球：
效果：

代码：

public class BallView extends View {

    private float x ;
    private float y ;
    Paint paint = new Paint();

    public BallView(Context context) {
        super(context);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        x = getWidth()/2;//获取x y坐标
        y = getHeight()/2;
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //设置颜色为红色
        paint.setColor(Color.RED);
        canvas.drawCircle(x,y,100,paint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        x = event.getX();
        y = event.getY();

        invalidate();
        return true;
    }

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绘制两个垂直线，然后得到交点坐标
效果：

原理：两个方程： y = b ; x = a; 交点坐标(a ,b )

代码：

package com.example.testdrawline;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.Log;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;

public class Drawline2 extends View {
    public static final String TAG = "Drawline2";

    private Canvas canvas_x;  //按照x轴移动
    private Canvas canvas_y;  //按照y轴移动
    private Paint paint;//声明画笔
    private int start_x = 50;
    private int stop_x = 50;
    private int start_y = 50;
    private int stop_y = 50;

    private int value_X = 0;
    private int value_Y = 0;

    int down_x = 0;
    int down_y = 0;

    private boolean isX = true;
    private boolean isY = true;
    private Context mContext = null;

    public Drawline2(Context context) {
        super(context);
        mContext = context;
        canvas_x = new Canvas();
        canvas_y = new Canvas();

        paint = new Paint(Paint.DITHER_FLAG);//创建一个画笔
        paint.setStyle(Paint.Style.STROKE);//设置非填充
        paint.setStrokeWidth(10);//笔宽5像素
        paint.setColor(Color.RED);//设置为红笔
        paint.setAntiAlias(true);//锯齿不显示
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas_x = canvas;
        canvas_y = canvas;
        canvas_x.drawLine(start_x, 0, stop_x, 1200, paint);
        canvas_y.drawLine(0, start_y, 1200, stop_y, paint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                down_x = (int) event.getX();
                down_y = (int) event.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i(TAG, "onTouchEvent: ==xxx= " + Math.abs(down_x - event.getX()));
                Log.i(TAG, "onTouchEvent: ==yyy=" + Math.abs(down_y - event.getY()));

                //8是经验值，表示移动了
                //100是一个实验(该判读可以去掉)
                if ((Math.abs(down_x - event.getX()) > 8) && (Math.abs(down_y - event.getY()) < 100) && isX) {
                    start_x = (int) event.getX();
                    stop_x = (int) event.getX();
                    isY = false;
                    value_X = start_x;
                }
                if ((Math.abs(down_y - event.getY()) > 8) && (Math.abs(down_x - event.getX()) < 100) && isY) {
                    start_y = (int) event.getY();
                    stop_y = (int) event.getY();
                    isX = false;
                    value_Y = start_y;
                }
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                //是否还需要判读，手指抬起和滑动结束的值对比？？？

                down_x = (int) event.getX();
                down_y = (int) event.getY();
                isY = true;
                isX = true;
                //这里是坐标
                Log.i(TAG, "onTouchEvent: =(x,y)===" + value_X + "----" + value_Y);
                Toast.makeText(mContext, "x=" + value_X, Toast.LENGTH_SHORT).show();
                Toast.makeText(mContext, "y=" + value_Y, Toast.LENGTH_SHORT).show();
                break;
            default:
                break;
        }
        return true;
    }
}

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