图片上涂鸦

代码

MainActivity.java

package com.example.me.myapplication;

import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;

import android.support.v7.app.AppCompatActivity;
import android.widget.Button;


public class MainActivity extends AppCompatActivity{
    private HandWrite handWrite = null;
    private Button clear = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        handWrite = (HandWrite)findViewById(R.id.handwriteview);
        handWrite.setOnTouchListener(new mTouch());
        clear = (Button)findViewById(R.id.clear);
        clear.setOnClickListener(new mClick());
    }

    private class mClick implements View.OnClickListener {
        public void onClick(View v) {
            handWrite.clear();
        }
    }

    private class mTouch implements View.OnTouchListener {
        public boolean onTouch(View v, MotionEvent event) {
            return handWrite.onTouchEvent(event);
        }
    }
}

HandWrite.java

package com.example.me.myapplication;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import java.io.PrintStream;
//自定义 View 组件 HandWrite
public class HandWrite extends View {
    Paint paint = null;//定义画笔
    Bitmap originalBitmap = null;//存放原始图像
    Bitmap new1_Bitmap = null;//存放从原始图像复制的位图图像
    Bitmap new2_Bitmap = null;//存放处理后的图像
    float startX = 0, startY = 0;//画线的起点坐标
    float clickX = 0, clickY = 0;//画线的终点坐标
    boolean isMove = true;//设置是否画线的标记
    boolean isClear = false;//设置是否清除涂鸦的标记
    int color = Color.GREEN;//设置画笔的颜色
    float strokeWidth = 2.0f;//设置画笔的宽度
    
    public HandWrite(Context context, AttributeSet attrs){
        super(context, attrs);
		//获取原始图像
        originalBitmap = BitmapFactory
                .decodeResource(getResources(), R.drawable.a1)
                .copy(Bitmap.Config.ARGB_8888, true);
                //建立原始图像的位图
        new1_Bitmap = Bitmap.createBitmap(originalBitmap);
    }
    //清除图像
    public void clear(){
        isClear = true;
        new2_Bitmap = Bitmap.createBitmap(originalBitmap);
        invalidate();
    }
    public void setstyle(float strokeWidth){
        this.strokeWidth = strokeWidth;
    }
    //显示绘图
    protected void onDraw(Canvas canvas){
        super.onDraw(canvas);
        canvas.drawBitmap(HandWriting(new1_Bitmap), 0, 0, null);
    }
    //记录绘制图像
    public Bitmap HandWriting(Bitmap o_Bitmap){
        Canvas canvas = null;
        //创建绘制画布
        if (isClear){
            canvas = new Canvas(new2_Bitmap);
        }else{
            canvas = new Canvas(o_Bitmap);
        }
        //定义画笔
        paint = new Paint();
        paint.setStyle(Paint.Style.STROKE);
        paint.setAntiAlias(true);
        paint.setColor(color);
        paint.setStrokeWidth(strokeWidth);
        if(isMove){
            canvas.drawLine(startX, startY, clickX, clickY, paint);
        }
        startX = clickX;
        startY = clickY;
        if(isClear){
            return new2_Bitmap;
        }
        return o_Bitmap;
    }
//定义触屏事件
    public boolean onTouchEvent(MotionEvent event){
        clickX = event.getX();
        clickY = event.getY();
        //按下屏幕时无绘图
        if(event.getAction() == MotionEvent.ACTION_DOWN){
            isMove = false;
            invalidate();
            return true;
         //记录在屏幕上滑动的轨迹
        }else if(event.getAction() == MotionEvent.ACTION_MOVE){
            isMove = true;
            invalidate();
            return true;
        }
        return super.onTouchEvent(event);
    }
}

activity_main.xml

<?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">

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="vertical">
        <com.example.me.myapplication.HandWrite
            android:layout_width="fill_parent"
            android:layout_height="380dp"
            android:id="@+id/handwriteview"/>
        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="horizontal"
            android:gravity="center_horizontal">
            <Button
                android:layout_width="200dp"
                android:layout_height="wrap_content"
                android:id="@+id/clear"
                android:text="清屏"/>
        </LinearLayout>
    </LinearLayout>

</android.support.constraint.ConstraintLayout>

执行结果