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KJAVA在这里人气不算很旺，不过这磨灭不了我们这群热爱着J2ME开发的人们 的激情。

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关于这个截屏程序，是需要附加到你的项目中的，因为j2me的手机没听说双线程的。

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此截屏程序的原理：

把缓冲画笔所在的画布img_buffer转成PNG格式保存到指定路径下，image转png需要一些插值加文件头的操作。

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这段代码网上有，我也是copy过来进行创新的。

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你需要做的是：

1.在你的canvas里定义截屏类的对象，初始值null。

2.在你的canvas里定义一个boolean变量，初始值true。

3.在你的canvas里的初始化或者构造方法里new 一个截屏类的对象。

4.在你的canvas里run方法里如同下面代码一样改造，repaint()方法就是重绘方法，c就是截屏类的实例，c.save()方法是保 存图片的方法。

public void run() {
		while (true) {
			startTime = System.currentTimeMillis();
//			if(b_isPaint)
//			{
				repaint();	//重绘
//			}
//			else
//			{
//				mainForm.paint(gg);
//				c.save(img_buffer);	//c是截屏类实例，save方法是保存图片方法，img_buffer是当前缓冲。
//				b_isPaint = true;
//			}
			timeTaken = System.currentTimeMillis() - startTime;
			if (timeTaken < 1000 / DefaultProperties.FPS) {
				try {
					Thread.sleep(1000 / DefaultProperties.FPS - timeTaken);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}
	}

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5.你想要以何种触发事件触发这个截屏方法，如果想要触摸屏点击触发，参考以下方法。其他触发方法照之改之。

	protected void pointerPressed(int x, int y) {
//		if(x < 30 && x > 0 && y < 30 && y > 0)
//		{
//			b_isPaint = false;
//			color = 0;
//		}
//		if(b_isPaint)
			mainForm.pointerPressed(x, y);//程序主触屏事件
	}

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6.在你的程序里添加截屏类(CGAMG.java)? 第45行写你要保存的路径。

import javax.microedition.lcdui.*;
import java.io.*;
import javax.microedition.io.file.FileConnection;
import javax.microedition.io.Connector;

public class CGame extends Canvas {
	public void paint(Graphics g)
	{
	}
    //Image2Bytes by AnderLu
    //生成的byte[]数组可直接用于外部存储为.png格式的图片文件看图软件可直接打开
    public static int IDATPOS;
    public static int haha = 0;
    public static byte[] HEADChunk = {
                                     (byte) 0x89, (byte) 0x50,
                                     (byte) 0x4E, (byte) 0x47,
                                     (byte) 0x0D, (byte) 0x0A,
                                     (byte) 0x1A, (byte) 0x0A,
    };
    public static byte[] tRNSChunk = {
                                     (byte) 0x00, (byte) 0x00,
                                     (byte) 0x00, (byte) 0x01,
                                     (byte) 0x74, (byte) 0x52,
                                     (byte) 0x4E, (byte) 0x53,
                                     (byte) 0x00,
                                     (byte) 0x40, (byte) 0xE6,
                                     (byte) 0xD8, (byte) 0x66,
    };
    public static byte[] IENDChunk = {
                                     //PNGIEND
                                     (byte) 0x00, (byte) 0x00,
                                     (byte) 0x00, (byte) 0x00,
                                     (byte) 0x49, (byte) 0x45,
                                     (byte) 0x4E, (byte) 0x44,
                                     (byte) 0xAE, (byte) 0x42,
                                     (byte) 0x60, (byte) 0x82
    };
    Image img;
    public void save(Image im)
    {
        byte data[] = Image2Bytes(im);
        this.img = Image.createImage(data, 0, data.length);

        
        saveFile("file:///E:/jieping/" + haha +".png", data);	//路径，haha变量递增 保存名为1.png,2.png
        haha++;
    }


    /**保存文件
     * @path:路径
     * @fileData:文件数据
     * @return: 0:出现异常,1:保存成功
     */
    public int saveFile(String path, byte[] fileData) {
        FileConnection fc = null;
        try {
            fc = (FileConnection) Connector.open(path, Connector.READ_WRITE);
            if (!fc.exists()) {
                fc.create();
            }
            OutputStream os = fc.openOutputStream();
            os.write(fileData);
            os.flush();
            os.close();
            fc.close();
            return 1;

        } catch (IOException ex) {
            ex.printStackTrace();
            return 0;
        }
    }

    public byte[] Image2Bytes(Image img) {
        try {
            int w = img.getWidth();
            int h = img.getHeight();
            int offset = 0;
            byte buffer[] = new byte[(w * 4 + 1) * h + offset];
            getImageBufferForImageARGB8888(img, buffer, w, h, offset);
            System.gc();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            DataOutputStream dout = new DataOutputStream(baos);
            WritePng(dout, w, h, buffer, null, false, offset);
            byte[] data = baos.toByteArray();
            writeCRC(data, 8); //更新IHDR CRC
            writeCRC(data, 33); //更新PLTE CRC
            writeCRC(data, IDATPOS); //更新IDAT CRC
            buffer = null;
            System.gc();
            return data;
        } catch (IOException ex) {
            ex.printStackTrace();
            return null;
        }
    }

    public static void writeCRC(byte[] data, int chunkpos) {
        int chunklen = ((data[chunkpos] & 0xFF) << 24)
                       | ((data[chunkpos + 1] & 0xFF) << 16)
                       | ((data[chunkpos + 2] & 0xFF) << 8)
                       | (data[chunkpos + 3] & 0xFF);

        int sum = CRCChecksum(data, chunkpos + 4, 4 + chunklen) ^ 0xffffffff;
        int val = sum;
        int pos = chunkpos + 8 + chunklen;
        data[pos] = (byte) ((val & 0xFF000000) >> 24);
        data[pos + 1] = (byte) ((val & 0xFF0000) >> 16);
        data[pos + 2] = (byte) ((val & 0xFF00) >> 8);
        data[pos + 3] = (byte) (val & 0xFF);
    }

    public static int[] crc_table; //CRC 表
    public static int CRCChecksum(byte[] buf, int off, int len) {
        int c = 0xffffffff;
        int n;
        if (crc_table == null) {
            int mkc;
            int mkn, mkk;
            crc_table = new int[256];
            for (mkn = 0; mkn < 256; mkn++) {
                mkc = mkn;
                for (mkk = 0; mkk < 8; mkk++) {
                    if ((mkc & 1) == 1) {
                        mkc = 0xedb88320 ^ (mkc >>> 1);
                    } else {
                        mkc = mkc >>> 1;
                    }
                }
                crc_table[mkn] = mkc;
            }
        }
        for (n = off; n < len + off; n++) {
            c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >>> 8);
        }
        return c;
    }

    public static long adler32(long adler, byte[] buf, int index, int len) {
        int BASE = 65521;
        int NMAX = 5552;
        //TODO remove this function at all
        if (buf == null) {
            return 1L;
        }

        long s1 = adler & 0xffff;
        long s2 = (adler >> 16) & 0xffff;
        int k;

        while (len > 0) {
            k = len < NMAX ? len : NMAX;
            len -= k;
            while (k >= 16) {
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                s1 += buf[index++] & 0xff;
                s2 += s1;
                k -= 16;
            }
            if (k != 0) {
                do {
                    s1 += buf[index++] & 0xff;
                    s2 += s1;
                } while (--k != 0);
            }
            s1 %= BASE;
            s2 %= BASE;
        }
        return (s2 << 16) | s1;
    }

    public static void WritePng(DataOutputStream output, int width, int height,
                                byte[] buffer, byte[] colors,
                                boolean Transparent, int offset) throws
            IOException {
        int adler = (int) adler32(1l, buffer, offset, buffer.length - offset);
        byte[] lenNlen = { //压缩块的LEN和NLEN信息
                         (byte) 0,
                         (byte) 0xfa, (byte) 0x7e,
                         (byte) 0x05, (byte) 0x81
        };
        IDATPOS = 0;
        output.write(HEADChunk);
        IDATPOS += HEADChunk.length;
        //写IHDR
        output.writeInt(13); //len
        output.writeInt(1229472850); //IHDR type code
        output.writeInt(width); //写宽度
        output.writeInt(height); //写高度
        output.writeByte(8); //1Bitdepth
        if (colors == null) {
            output.writeByte(6); //2ColorType
        } else {
            output.writeByte(3); //2ColorType
        }
        output.writeByte(0); //3CompressionMethod
        output.writeByte(0); //4Filter method
        output.writeByte(0); //5Interlace method
        output.writeInt(0); //写crc
        IDATPOS += 25;
        //写PLTE
        if (colors != null) {
            output.writeInt(colors.length); //len
            output.writeInt(1347179589); //type code
            output.write(colors); //data
            output.writeInt(0); //crc
            IDATPOS += colors.length + 12;
        }
        //写TRNS
        if (Transparent) {
            output.write(tRNSChunk);
            IDATPOS += tRNSChunk.length;
        }
        //写IDAT
        byte[] dpixels = buffer;
        int bufferlen = dpixels.length - offset;
        int blocklen = 32506;
        int blocknum = 1;
        if ((dpixels.length % blocklen) == 0) {
            blocknum = bufferlen / blocklen;
        } else {
            blocknum = (bufferlen / blocklen) + 1;
        }
        int IDATChunkLen = (bufferlen + 6 + blocknum * 5);
        output.writeInt(IDATChunkLen); //len
        output.writeInt(1229209940); //idat type code
        output.writeShort((short) 0x78da); //78da
        for (int i = 0; i < blocknum; i++) {
            int off = i * blocklen;
            int len = bufferlen - off;
            if (len >= blocklen) {
                len = blocklen;
                lenNlen[0] = (byte) 0;
            } else {
                lenNlen[0] = (byte) 1;
            }
            int msb = (len & 0xff);
            int lsb = (len >>> 8);
            lenNlen[1] = (byte) msb;
            lenNlen[2] = (byte) lsb;
            lenNlen[3] = (byte) (msb ^ 0xff);
            lenNlen[4] = (byte) (lsb ^ 0xff);
            output.write(lenNlen);
            output.write(dpixels, off + offset, len);
        }
        output.writeInt(adler); //IDAT adler
        output.writeInt(0); //IDAT crc
        output.write(IENDChunk);
    }

    public static void getImageBufferForImageARGB8888(Image img, byte[] rawByte,
            int w, int h, int off) {
        int n = off;
        int[] raw = new int[w];
        for (int j = 0; j < h; j++) {
            img.getRGB(raw, 0, w, 0, j, w, 1);
            for (int i = 0; i < raw.length; i++) {
                int ARGB = raw[i];
                int a = (ARGB & 0xff000000) >> 24;
                int r = (ARGB & 0xff0000) >> 16;
                int g = (ARGB & 0xff00) >> 8;
                int b = ARGB & 0xff;
                if (i % w == 0) {
                    n += 1;
                }
                rawByte[n] = (byte) r;
                rawByte[n + 1] = (byte) g;
                rawByte[n + 2] = (byte) b;
                rawByte[n + 3] = (byte) a;
                n += 4;
            }
        }
        raw = null;
        System.gc();
    }
}

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注意：截屏命名是以1、2、3、4数字++命名的，如1.png，2.png等等，该程序设计的触发截屏事件是点击屏幕左上角，这个根据具体需要随 意改了，并且图片保存命名规则也需要完善下。

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曾尝试过截屏的时候弄点提示，但这是万万不可的，在屏幕上出现任何提示都将会被截屏记录下来，所以我在写这个功能的时候，很是认真的考虑了截屏的完 整性及安全性，只要触发了，程序会自动屏蔽所有操作等待截屏操作结束，结束后恢复，也就是说机器慢的，触发截屏了，你在点或者做其他的程序界面的操作，那 都是不可能的，截屏生成保存文件这个过程结束后才可以。

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附件：截屏类（其实就是把image对象转成png并保存到指定路径的方法）