Android 手绘 - 支持保存为图片

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啊，好难看的机器人。。。。


应 yzuo_08 要求做了此Demo，跟以前那个手写板Demo不同的是可以将画布的内容保存为图片。

附上关键代码：

MainView.java

[java] view
plaincopy

package com.tszy.views;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.Bitmap.CompressFormat;

import android.graphics.Bitmap.Config;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.util.AttributeSet;

import android.view.MotionEvent;

import android.view.View;

public class MainView extends View {

private Paint paint;

private Canvas cacheCanvas;

private Bitmap cachebBitmap;

private Path path;

private int clr_bg, clr_fg;

public MainView(Context context, AttributeSet attrs) {

super(context, attrs);

clr_bg = Color.WHITE;

clr_fg = Color.CYAN;

paint = new Paint();

paint.setAntiAlias(true); // 抗锯齿

paint.setStrokeWidth(3); // 线条宽度

paint.setStyle(Paint.Style.STROKE); // 画轮廓

paint.setColor(clr_fg); // 颜色

path = new Path();

// 创建一张屏幕大小的位图，作为缓冲

cachebBitmap = Bitmap.createBitmap(480, 800, Config.ARGB_8888);

cacheCanvas = new Canvas(cachebBitmap);

cacheCanvas.drawColor(clr_bg);

}

public MainView(Context context) {

super(context);

}

@Override

protected void onDraw(Canvas canvas) {

canvas.drawColor(clr_bg);

// 绘制上一次的，否则不连贯

canvas.drawBitmap(cachebBitmap, 0, 0, null);

canvas.drawPath(path, paint);

}

/**

* 清空画布

*/

public void clear() {

path.reset();

cacheCanvas.drawColor(clr_bg);

invalidate();

}

/**

* 将画布的内容保存到文件

* @param filename

* @throws FileNotFoundException

*/

public void saveToFile(String filename) throws FileNotFoundException {

File f = new File(filename);

if(f.exists())

throw new RuntimeException("文件：" + filename + " 已存在！");

FileOutputStream fos = new FileOutputStream(new File(filename));

//将 bitmap 压缩成其他格式的图片数据

cachebBitmap.compress(CompressFormat.PNG, 50, fos);

try {

fos.close();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

private float cur_x, cur_y;

private boolean isMoving;

@Override

public boolean onTouchEvent(MotionEvent event) {

// TODO Auto-generated method stub

float x = event.getX();

float y = event.getY();

switch (event.getAction()) {

case MotionEvent.ACTION_DOWN : {

cur_x = x;

cur_y = y;

path.moveTo(cur_x, cur_y);

isMoving = true;

break;

}

case MotionEvent.ACTION_MOVE : {

if (!isMoving)

break;

// 二次曲线方式绘制

path.quadTo(cur_x, cur_y, x, y);

// 下面这个方法貌似跟上面一样

// path.lineTo(x, y);

cur_x = x;

cur_y = y;

break;

}

case MotionEvent.ACTION_UP : {

// 鼠标弹起保存最后状态

cacheCanvas.drawPath(path, paint);

path.reset();

isMoving = false;

break;

}

}

// 通知刷新界面

invalidate();

return true;

}

}

Activity 代码：

[java] view
plaincopy

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

switch (v.getId()) {

case R.id.iv_btn_clear :

view.clear();

break;

case R.id.iv_btn_save : {

try {

String sdState = Environment.getExternalStorageState(); // 判断sd卡是否存在

// 检查SD卡是否可用

if (!sdState.equals(android.os.Environment.MEDIA_MOUNTED)) {

Toast.makeText(this, "SD卡未准备好！", Toast.LENGTH_SHORT).show();

break;

}

//获取系统图片存储路径

File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);

// Make sure the Pictures directory exists.

path.mkdirs();

//根据当前时间生成图片名称

Calendar c = Calendar.getInstance();

String name = ""

+ c.get(Calendar.YEAR) + c.get(Calendar.MONTH) + c.get(Calendar.DAY_OF_MONTH)

+ c.get(Calendar.HOUR_OF_DAY) + c.get(Calendar.MINUTE) + c.get(Calendar.SECOND)

+ ".png";

//合成完整路径，注意 / 分隔符

String string = path.getPath() + "/" + name;

view.saveToFile(string);

Toast.makeText(this, "保存成功！\n文件保存在：" + string, Toast.LENGTH_LONG).show();

} catch (FileNotFoundException e) {

Toast.makeText(this, "保存失败！\n" + e, Toast.LENGTH_LONG).show();

}

break;

}

}

}

没什么难度，主要是将Bitmap转PNG图片那里，找了一会发现 Canvas 没有直接或间接保存的方法，刚好这里我使用了双缓冲，另一块画布的内容位图自己创建的，很自然想到将这个画布的位图保存为文件即可。

再查看 Bitmap 有个 compress(CompressFormat format, int quality,OutputStream stream)
方法，很明显将文件输出流传给这个方法就OK

[java] view
plaincopy

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

switch (v.getId()) {

case R.id.iv_btn_clear :

view.clear();

break;

case R.id.iv_btn_save : {

try {

String sdState = Environment.getExternalStorageState(); // 判断sd卡是否存在

// 检查SD卡是否可用

if (!sdState.equals(android.os.Environment.MEDIA_MOUNTED)) {

Toast.makeText(this, "SD卡未准备好！", Toast.LENGTH_SHORT).show();

break;

}

//获取系统图片存储路径

File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);

// Make sure the Pictures directory exists.

path.mkdirs();

//根据当前时间生成图片名称

Calendar c = Calendar.getInstance();

String name = ""

+ c.get(Calendar.YEAR) + c.get(Calendar.MONTH) + c.get(Calendar.DAY_OF_MONTH)

+ c.get(Calendar.HOUR_OF_DAY) + c.get(Calendar.MINUTE) + c.get(Calendar.SECOND)

+ ".png";

//合成完整路径，注意 / 分隔符

String string = path.getPath() + "/" + name;

view.saveToFile(string);

Toast.makeText(this, "保存成功！\n文件保存在：" + string, Toast.LENGTH_LONG).show();

} catch (FileNotFoundException e) {

Toast.makeText(this, "保存失败！\n" + e, Toast.LENGTH_LONG).show();

}

break;

}

}

}

源码：源码下载