Android(安卓)实现手绘功能

布局文件如下。

<?xml version="1.0" encoding="utf-8"?>

Activity代码如下，其中线的颜色，宽度等属性都可以修改。

package com.example.administrator.main;import android.content.Intent;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.net.Uri;import android.os.Environment;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.MotionEvent;import android.view.View;import android.widget.Button;import android.widget.ImageView;import android.widget.Toast;import java.io.File;import java.io.FileOutputStream;public class DrawActivity extends AppCompatActivity {    private ImageView iv;    private Bitmap baseBitmap;    private Button btn_resume;    private Button btn_save;    private Canvas canvas;    private Paint paint;    float radio;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_draw);        radio = 10;        iv = (ImageView) findViewById(R.id.iv);        // 初始化一个画笔，笔触宽度为5，颜色为红色        paint = new Paint();        paint.setStrokeWidth(radio);        paint.setColor(Color.BLACK);        iv = (ImageView) findViewById(R.id.iv);        btn_resume = (Button) findViewById(R.id.btn_resume);        btn_save = (Button) findViewById(R.id.btn_save);        btn_resume.setOnClickListener(click);        btn_save.setOnClickListener(click);        iv.setOnTouchListener(touch);    }    private View.OnTouchListener touch = new View.OnTouchListener() {        // 定义手指开始触摸的坐标        float startX;        float startY;        @Override        public boolean onTouch(View v, MotionEvent event) {            switch (event.getAction()) {                // 用户按下动作                case MotionEvent.ACTION_DOWN:                    // 第一次绘图初始化内存图片，指定背景为白色                    if (baseBitmap == null) {                        baseBitmap = Bitmap.createBitmap(iv.getWidth(),                                iv.getHeight(), Bitmap.Config.ARGB_8888);                        canvas = new Canvas(baseBitmap);                        canvas.drawColor(Color.WHITE);                    }                    // 记录开始触摸的点的坐标                    startX = event.getX();                    startY = event.getY();                    break;                // 用户手指在屏幕上移动的动作                case MotionEvent.ACTION_MOVE:                    // 记录移动位置的点的坐标                    float stopX = event.getX();                    float stopY = event.getY();                    Thread t = new Thread(new Runnable() {                        @Override                        public void run() {                            radio += 0.1;                            try {                                Thread.sleep(1000);                            } catch (InterruptedException e) {                                e.printStackTrace();                            }                        }                    });                    t.start();                    paint.setStrokeWidth(radio);                    //根据两点坐标，绘制连线                    canvas.drawLine(startX, startY, stopX, stopY, paint);                    // 更新开始点的位置                    startX = event.getX();                    startY = event.getY();                    // 把图片展示到ImageView中                    iv.setImageBitmap(baseBitmap);                    break;                case MotionEvent.ACTION_UP:                    radio = 5;                    break;                default:                    break;            }            return true;        }    };    private View.OnClickListener click = new View.OnClickListener() {        @Override        public void onClick(View v) {            switch (v.getId()) {                case R.id.btn_save:                    saveBitmap();                    break;                case R.id.btn_resume:                    resumeCanvas();                    break;                default:                    break;            }        }    };    /**     * 保存图片到SD卡上     */    protected void saveBitmap() {        try {            // 保存图片到SD卡上            String fileName = "/sdcard/"+System.currentTimeMillis() + ".png";            File file = new File(fileName);            FileOutputStream stream = new FileOutputStream(file);            baseBitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);            Toast.makeText(DrawActivity.this, "保存图片成功", Toast.LENGTH_SHORT).show();             // Android设备Gallery应用只会在启动的时候扫描系统文件夹             // 这里模拟一个媒体装载的广播，用于使保存的图片可以在Gallery中查看            Intent intent = new Intent();            intent.setAction(Intent.ACTION_MEDIA_MOUNTED);            intent.setData(Uri.fromFile(Environment                    .getExternalStorageDirectory()));            sendBroadcast(intent);        } catch (Exception e) {            Toast.makeText(DrawActivity.this, "保存图片失败", Toast.LENGTH_SHORT).show();            e.printStackTrace();        }    }    // 手动清除画板的绘图，重新创建一个画板    protected void resumeCanvas() {        if (baseBitmap != null) {            baseBitmap = Bitmap.createBitmap(iv.getWidth(),                    iv.getHeight(), Bitmap.Config.ARGB_8888);            canvas = new Canvas(baseBitmap);            canvas.drawColor(Color.WHITE);            iv.setImageBitmap(baseBitmap);            Toast.makeText(DrawActivity.this, "清除画板成功，可以重新开始绘图", Toast.LENGTH_SHORT).show();        }    }}

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