//生成二维码的类
public class BPUtil {/*** 用于生成二维码的字符*/private static final char[] CHARS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9','a','b','c','d','e','f','g','h','i','j','k','m','l','n','o','p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','I','J','K','M','L','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};private static BPUtil bpUtil;public static BPUtil getInstance() {if(bpUtil == null)bpUtil = new BPUtil();return bpUtil;}//            width="60" height="30"
//              base_padding_left="5"
//            range_padding_left="10"
//            base_padding_top="15"
//            range_padding_top="10"
//            codeLength="4"
//            line_number="3"
//            font_size="20"//default settingsprivate static final int DEFAULT_CODE_LENGTH = 4;private static final int DEFAULT_FONT_SIZE = 20;private static final int DEFAULT_LINE_NUMBER = 3;private static final int BASE_PADDING_LEFT = 5, RANGE_PADDING_LEFT = 10, BASE_PADDING_TOP = 15, RANGE_PADDING_TOP = 10;private static final int DEFAULT_WIDTH = 60, DEFAULT_HEIGHT = 30;//settings decided by the layout xml//canvas width and heightprivate int width = DEFAULT_WIDTH, height = DEFAULT_HEIGHT; //random word space and pading_topprivate int base_padding_left = BASE_PADDING_LEFT, range_padding_left = RANGE_PADDING_LEFT, base_padding_top = BASE_PADDING_TOP, range_padding_top = RANGE_PADDING_TOP;//number of chars, lines; font sizeprivate int codeLength = DEFAULT_CODE_LENGTH, line_number = DEFAULT_LINE_NUMBER, font_size = DEFAULT_FONT_SIZE;//variablesprivate String code;private int padding_left, padding_top;private Random random = new Random();public Bitmap createBitmap() {padding_left = 0;Bitmap bp = Bitmap.createBitmap(width, height, Config.ARGB_8888); Canvas c = new Canvas(bp);code = createCode();c.drawColor(Color.WHITE);Paint paint = new Paint();paint.setTextSize(font_size);for (int i = 0; i < code.length(); i++) {randomTextStyle(paint);randomPadding();c.drawText(code.charAt(i) + "", padding_left, padding_top, paint);}for (int i = 0; i < line_number; i++) {drawLine(c, paint);}c.save( Canvas.ALL_SAVE_FLAG );//保存  c.restore();//
        return bp;}public String getCode() {return bpUtil.createCode();}private String createCode() {StringBuilder buffer = new StringBuilder();for (int i = 0; i < codeLength; i++) {buffer.append(CHARS[random.nextInt(CHARS.length)]);}return buffer.toString();}private void drawLine(Canvas canvas, Paint paint) {int color = randomColor();int startX = random.nextInt(width);int startY = random.nextInt(height);int stopX = random.nextInt(width);int stopY = random.nextInt(height);paint.setStrokeWidth(1);paint.setColor(color);canvas.drawLine(startX, startY, stopX, stopY, paint);}private int randomColor() {return randomColor(1);}private int randomColor(int rate) {int red = random.nextInt(256) / rate;int green = random.nextInt(256) / rate;int blue = random.nextInt(256) / rate;return Color.rgb(red, green, blue);}private void randomTextStyle(Paint paint) {int color = randomColor();paint.setColor(color);paint.setFakeBoldText(random.nextBoolean());  //true为粗体，false为非粗体float skewX = random.nextInt(11) / 10;skewX = random.nextBoolean() ? skewX : -skewX;paint.setTextSkewX(skewX); //float类型参数，负数表示右斜，整数左斜
//        paint.setUnderlineText(true); //true为下划线，false为非下划
//        paint.setStrikeThruText(true); //true为删除线，false为非删除
    }private void randomPadding() {padding_left += base_padding_left + random.nextInt(range_padding_left);padding_top = base_padding_top + random.nextInt(range_padding_top);}
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context="${relativePackage}.${activityClass}" android:orientation="vertical"><LinearLayout android:layout_width="fill_parent"android:layout_height="fill_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="center_horizontal"android:text="@string/yanzheng" /><LinearLayout android:orientation="horizontal"android:layout_width="fill_parent"android:layout_height="wrap_content" ><TextViewandroid:layout_weight="1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/name" /><EditText android:id="@+id/name"android:layout_width="wrap_content"android:layout_weight="6"android:layout_height="wrap_content"android:hint="@string/name_new"android:singleLine="true"/></LinearLayout><LinearLayout android:orientation="horizontal"android:layout_width="fill_parent"android:layout_height="wrap_content" ><TextViewandroid:layout_weight="1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/password" /><EditText android:id="@+id/pass"android:layout_weight="6"android:layout_width="wrap_content"android:layout_height="wrap_content"android:hint="@string/pass_new"android:singleLine="true"/></LinearLayout><LinearLayout android:id="@+id/layout_yanzhengma"android:visibility="gone"android:orientation="horizontal"android:layout_width="fill_parent"android:layout_height="wrap_content" ><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/yanzhengma" /><TextViewandroid:id="@+id/rander"android:layout_weight="1"android:layout_width="wrap_content"android:layout_height="wrap_content"/><EditTextandroid:id="@+id/rander_input"android:layout_weight="1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:singleLine="true"/></LinearLayout><LinearLayout android:orientation="horizontal"android:layout_width="fill_parent"android:layout_height="wrap_content" ><Buttonandroid:id="@+id/get"android:layout_weight="1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/get" /><Buttonandroid:id="@+id/post"android:layout_weight="1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/post" /></LinearLayout></LinearLayout></RelativeLayout>

public class MainActivity extends Activity {private TextView mytext = null;private EditText myname = null;//用户名private EditText mypass = null;//密码private EditText myrander =  null;//验证码private Button mygetbutton = null;//Get方式发送Http请求private Button mypostbutton = null;//Post方式发送Http请求private LinearLayout myline = null;//控制二维码的显示private static int n = 0;//用户输错密码次数统计static String name = null;//用户输入的用户名static String password = null;//用户输入的密码private String edit;//用户输入用户输入的验证码private String code;//验证码
    @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mytext = (TextView)findViewById(R.id.rander);myname = (EditText)findViewById(R.id.name);mypass = (EditText)findViewById(R.id.pass);myrander = (EditText)findViewById(R.id.rander_input);mygetbutton = (Button)findViewById(R.id.get);mypostbutton = (Button)findViewById(R.id.post);myline = (LinearLayout)findViewById(R.id.layout_yanzhengma);mygetbutton.setOnClickListener(new mygetbutton());mypostbutton.setOnClickListener(new mypostbutton());} class mygetbutton implements OnClickListener{public void onClick(View v) {name = myname.getText().toString();password = mypass.getText().toString();if(n>=3){//连续三次输错密码edit = myrander.getText().toString();boolean boo = captcha (code , edit);if(boo){new Thread(new Runnable() {public void run() {final boolean flag = SendServer.getsave(name, password);runOnUiThread(new Runnable() {public void run() {if(flag){Toast.makeText(MainActivity.this, "登录成功", Toast.LENGTH_SHORT).show();n=0;}else{Toast.makeText(MainActivity.this, "登录失败", Toast.LENGTH_SHORT).show();n++;if(n>=3){myline.setVisibility(View.VISIBLE);}}}});}}).start();}else{code = BPUtil.getInstance().getCode().toLowerCase();//生成新的二维码mytext.setText(code);//展示在用户面前
                }}else{new Thread(new Runnable() {public void run() {final boolean flag = SendServer.getsave(name, password);runOnUiThread(new Runnable() {public void run() {if(flag){Toast.makeText(MainActivity.this, "登录成功", Toast.LENGTH_SHORT).show();n=0;}else{Toast.makeText(MainActivity.this, "登录失败", Toast.LENGTH_SHORT).show();n++;if(n>=3){myline.setVisibility(1);code = BPUtil.getInstance().getCode().toLowerCase();mytext.setText(code);}}}});}}).start();}}}class mypostbutton implements OnClickListener{public void onClick(View v) {name = myname.getText().toString();password = mypass.getText().toString();new Thread(new Runnable() {public void run() {final boolean flag = SendServer.postsave(name, password);runOnUiThread(new Runnable() {@Overridepublic void run() {if(flag){Toast.makeText(MainActivity.this, "登录成功", Toast.LENGTH_SHORT).show();n=0;}else{Toast.makeText(MainActivity.this, "登录失败", Toast.LENGTH_SHORT).show();n++;if(n>=3){myline.setVisibility(1);}}}});}}).start();}}@SuppressLint("ShowToast")private boolean captcha (String code , String edit) {boolean flag = false; if (code.equals(edit)) {flag = true;}else {flag = false;Toast.makeText(MainActivity.this, " 验证码错误", 0).show();//            imageview.setImageBitmap(bitmap);
            }return flag;}protected void onRestart() {super.onRestart();n=0;}protected void onDestroy() {super.onDestroy();n=0;}}

public class SendServer {//GET方式请求public static boolean getsave(String name, String password) {boolean flag = false;HttpURLConnection conn = null;try {//防止中文乱码String username = URLEncoder.encode(name, "UTF-8");String userpassword = URLEncoder.encode(password, "UTF-8");URL url = new URL("http://10.20.90.3:8080/Register/ManageServlet?"+"name="+username+"&password="+userpassword);conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(5000);conn.setReadTimeout(5000);int responseCode = conn.getResponseCode();if(responseCode == 200){InputStream is = conn.getInputStream();String stu = getStringFromInputStream(is);if(stu.equals("登录成功")){flag = true;}}} catch (MalformedURLException e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();} finally{if(conn != null){conn.disconnect();  //关闭连接
            }}return flag;}//POST请求public static boolean postsave(String name, String password) {boolean flag = false;HttpURLConnection conn = null;try {URL url = new URL("http://10.20.90.3:8080/Register/ManageServlet?");conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("POST");conn.setConnectTimeout(5000);conn.setReadTimeout(5000);//post请求参数String data = "name="+name+"&password="+password;OutputStream out = conn.getOutputStream();out.write(data.getBytes());out.flush();out.close();//            conn.setRequestProperty("Content-Length", 500);//  内容长度设置为500；请求头消息格式设置int respon = conn.getResponseCode();if(respon == 200){InputStream is = conn.getInputStream();String stu = getStringFromInputStream(is);if(stu.equals("登录成功")){flag = true;}}} catch (Exception e) {e.printStackTrace();}finally{if(conn != null){conn.disconnect();}}return flag;}//解析服务返回的请求private static String getStringFromInputStream(InputStream is) throws Exception{ByteArrayOutputStream baos = new ByteArrayOutputStream();byte[] buffer = new byte[1024*8];int len = -1;while((len = is.read(buffer)) != -1){baos.write(buffer, 0, len);}is.close();String html = new String(baos.toByteArray(), "GBK");//接收服务器端的数据时，防止出现中文乱码。//String html = baos.toString();
        baos.close();return html;}}