Android surfaceView+绘画

布局:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <SurfaceView
        android:id="@+id/surfaceview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />


</android.support.constraint.ConstraintLayout>

主类:

package com.example.day06huihua;

import android.annotation.SuppressLint;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    private SurfaceView surfaceview;

    @SuppressLint("ClickableViewAccessibility")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();

        final SurfaceHolder holder = surfaceview.getHolder();
        holder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder holder) {

            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {

            }
        });
        surfaceview.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                float x = event.getX();
                float y = event.getY();
                int action = event.getAction();
                switch (action) {
                    case MotionEvent.ACTION_DOWN://落笔
                        break;
                    case MotionEvent.ACTION_MOVE://滚动

                        Canvas canvas = holder.lockCanvas();//锁定画布
                        Paint paint = new Paint();//画笔
                        paint.setColor(Color.BLUE);//设置画笔颜色
                        paint.setStrokeWidth(20);//画笔的字体大小
                        canvas.save();//保存上次的画图
                        canvas.drawPoint(x, y, paint);//画点
                        canvas.restore();//与上次合并在一块
                        holder.unlockCanvasAndPost(canvas);//提交画

                        break;
                    case MotionEvent.ACTION_UP://提笔
                        break;
                }
                return true;
            }
        });
    }

    private void initView() {
        surfaceview = (SurfaceView) findViewById(R.id.surfaceview);
    }
}

效果: