Paint paint = new Paint();

paint.setARGB(255, 255, 0, 0); // 设置 ARGB 颜色 int
paint.setAlpha(0); // 设置透明度 int
paint.setColor(getResources().getColor(android.R.color.black)); // 设置颜色
paint.setAntiAlias(true); // 开启抗锯齿
paint.setDither(true); // 开启抖动处理，使得绘制的图形更清晰
paint.setFilterBitmap(true); // 滤掉对Bitmap图像的优化操作,加快显示速度
paint.setMaskFilter(maskFilter); // 添加滤镜
paint.setColorFilter(colorFilter); // 设置颜色过滤器
paint.setPathEffect(pathEffect); // 设置路径效果(如虚线等)
paint.setShader(shader); // 设置渐变效果
paint.setShadowLayer(2, 2, 2, Color.GRAY); // 半径2,x,y 距离为2，颜色灰色的阴影
paint.setStyle(Paint.Style.FILL_AND_STROKE); // 画笔样式(内部、边框还是both，画封闭图形的时候比较重要)
paint.setStrokeCap(Paint.Cap.SQUARE); // 方形笔刷
paint.setStrokeJoin(Paint.Join.MITER); // 各图形的结合方式
paint.setStrokeWidth(2); // 画笔粗细
paint.setXfermode(xfermode); // 图形重叠时的处理方式
paint.setFakeBoldText(true); // 模拟粗体
paint.setSubpixelText(true); // 提升文字在 LCD 的显示效果
paint.setTextAlign(Paint.Align.CENTER); // 文字对齐方向
paint.setTextScaleX(0.5); // 文字 X 轴缩放
paint.setTextSize(40); // 文字大小
paint.setTextSkewX(30); // 文字倾斜度
paint.setTypeface(Typeface.SANS_SERIF); // 字体风格
paint.setUnderlineText(true); // 下划线
paint.setStrikeThruText(true); // 删除线
paint.setStrokeJoin(Paint.Join.ROUND); // 结合处风格
paint.setStrokeMiter(30); // 画笔倾斜度
paint.setStrokeCap(Paint.Cap.ROUND); // 拐角处风格
paint.ascent(); // baseline之上至字符最高处的距离
paint.descent(); // baseline之下至字符最低处的距离
paint.clearShadowLayer(); // 清除阴影
// 等等

Canvas canvas = new Canvas();
Canvas canvasByBitmap = new Canvas(bitmap);

canvas.drawRect(new RectF(0, 0, 100, 100), mPaint); // 绘制一个方形
canvas.drawRect(0, 0, 100, 100, mPaint); // 绘制一个方形
canvas.drawPath(path, paint); // 绘制一个路径
canvas.drawBitmap(bitmap, src, dst, mPaint); // 第二和第三个参数是 Rect
canvas.drawLine(0, 0, 100, 100, mPaint); // 画线
canvas.drawPoint(100, 20, mPaint); // 画点
canvas.drawText("这是一段文字", 0, 0, mPaint); // 画文字
canvas.drawOval(new RectF(0, 0, 100, 200), mPaint); // 画方形的内切椭圆
canvas.drawCircle(300, 300, 100, mPaint); // 画圆
canvas.drawArc(new RectF(0, 0, 100, 100), 0, 30, true, mPaint); // 一个矩形内的扇形

path.addArc(new RectF(0, 0, 100, 100), 0, 30); // 添加一段圆弧
path.addCircle(300, 300, 100, Path.Direction.CW); // 顺时针圆
path.addOval(rectF, Path.Direction.CCW); // 逆时针椭圆
path.addRect(rectF, Path.Direction.CW); // 添加矩形
path.addRoundRect(rectF, {5, 5, 5, 5}, path.Direction.CW); // 添加圆角矩形
path.isEmpty(); // 是否无路径
path.transform(matrix); // 矩阵变换
path.moveTo(100, 100); // 移动画笔而不绘制
path.lineTo(300, 300); // 默认从(0，0)开始绘制,可以用 moveTo 移动起始点,调用 canvas.drawPath(path, paint) 绘制
path.quadTo(x1, y1, x2, y2); // 绘制贝塞尔曲线,三点(起始点默认(0, 0))确认
path.rCubicTo(x1, y1, x2, y2, x3, y3); // 多一个控制点的贝塞尔曲线
path.arcTo(rectF, 0, 50); // 圆弧

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    // 在构造函数中初始化画笔并设置为黑色
    canvas.drawRect(0, 0, 100, 200, mPaint);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawLine(0, 0, 100, 200, mPaint);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawCircle(100, 100, 100, mPaint);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawColor(getResources().getColor(android.R.color.darker_gray));
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    // 防止数字0出界
    canvas.translate(0, 50);

    for (int i = 0; i <= 100; i++) {
        if (i % 10 == 0) {
            // 带有数字的长刻度
            canvas.drawLine(0, 0, 70, 0, mPaint);
            // 画文字
            canvas.drawText(String.format(Locale.CHINESE, "%d", i / 10), 100, 10, mPaint);
        } else if (i % 5 == 0) {
            // 每隔5的中等长度的刻度
            canvas.drawLine(0, 0, 40, 0, mPaint);
        } else {
            // 其它小刻度
            canvas.drawLine(0, 0, 30, 0, mPaint);
        }
        // 每个刻度画完之后位移
        canvas.translate(0, 15);
    }
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    // 绘制外圈圆
    canvas.drawCircle(400, 400, 400, mPaint);

    // 绘制分针和时针
    canvas.drawLine(400, 400, 400, 200, mPaint);
    canvas.drawLine(400, 400, 550, 400, mPaint);

    // 绘制刻度和文字
    for (int i = 0; i < 12; i++) {
        canvas.drawLine(400, 0, 400, 10, mPaint);
        canvas.drawText(String.format(Locale.CHINESE, "%d", i == 0 ? 12 : i),
                400, 100, mTextPaint);
        // 旋转画布
        canvas.rotate(30, 400, 400);
    }
}

/**
 * 帖子实体类
 * <p/>
 * Created by Loshine on 15/9/8.
 */
public class PostEntity {

    /**
     * 帖子标题
     */
    private String name;
    /**
     * 帖子类别
     */
    private String category;
    /**
     * 帖子链接
     */
    private String link;
    /**
     * 评论数
     */
    private String comments;
    /**
     * 发布者
     */
    private String announcer;
    /**
     * 最新回复时间
     */
    private String replyTime;

    /*
     * 省略 getter setter...
     */

/**
 * 帖子实体类
 * <p/>
 * Created by Loshine on 15/9/8.
 */
public class PostEntity implements Parcelable {

    /**
     * 帖子标题
     */
    private String name;
    /**
     * 帖子类别
     */
    private String category;
    /**
     * 帖子链接
     */
    private String link;
    /**
     * 评论数
     */
    private String comments;
    /**
     * 发布者
     */
    private String announcer;
    /**
     * 最新回复时间
     */
    private String replyTime;

    /*
     * 省略 getter setter...
     */

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(this.name);
        dest.writeString(this.category);
        dest.writeString(this.link);
        dest.writeString(this.comments);
        dest.writeString(this.announcer);
        dest.writeString(this.replyTime);
    }

    public PostEntity() {
    }

    protected PostEntity(Parcel in) {
        this.name = in.readString();
        this.category = in.readString();
        this.link = in.readString();
        this.comments = in.readString();
        this.announcer = in.readString();
        this.replyTime = in.readString();
    }

    public static final Parcelable.Creator<PostEntity> CREATOR = new Parcelable.Creator<PostEntity>() {
        public PostEntity createFromParcel(Parcel source) {
            return new PostEntity(source);
        }

        public PostEntity[] newArray(int size) {
            return new PostEntity[size];
        }
    };

protected PostEntity(Parcel in) {
        this.name = in.readString();
        this.category = in.readString();
        this.link = in.readString();
        this.comments = in.readString();
        this.announcer = in.readString();
        this.replyTime = in.readString();
    }

    public static final Parcelable.Creator<PostEntity> CREATOR = new Parcelable.Creator<PostEntity>() {
        public PostEntity createFromParcel(Parcel source) {
            return new PostEntity(source);
        }

        public PostEntity[] newArray(int size) {
            return new PostEntity[size];
        }
    };

public class StringRequestActivity extends AppCompatActivity {

    /**
     * Volley 请求队列对象
     */
    private RequestQueue mRequestQueue;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_string_request);
        
        // 构造请求队列
        mRequestQueue = Volley.newRequestQueue(context);
        
        StringRequest request = new StringRequest("http://www.baidu.com",
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    JSONObject jsonObject = JSON.parseObject(response, JSONObject.class);
                }
            },
             new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    Log.i("net error", error.getLocalizedMessage());
                }
            });
        mRequestQueue.add(request);
    }
    
    @Override
    protected void onStop() {
        super.onStop();
        // 退出时取消所有网络请求
        mRequestQueue.cancelAll(this);
    }
}

public class XMLRequest extends Request<XmlPullParser> {  

    private final Listener<XmlPullParser> mListener;

    public XMLRequest(int method, String url, Listener<XmlPullParser> listener,
            ErrorListener errorListener) {  
        super(method, url, errorListener);  
        mListener = listener;  
    }  
  
    public XMLRequest(String url, Listener<XmlPullParser> listener, ErrorListener errorListener) {  
        this(Method.GET, url, listener, errorListener);  
    }  
  
    @Override  
    protected Response<XmlPullParser> parseNetworkResponse(NetworkResponse response) {  
        try {  
            String xmlString = new String(response.data,  
                    HttpHeaderParser.parseCharset(response.headers));  
            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            XmlPullParser xmlPullParser = factory.newPullParser();
            xmlPullParser.setInput(new StringReader(xmlString));
            return Response.success(xmlPullParser, HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException e) {
            return Response.error(new ParseError(e));  
        } catch (XmlPullParserException e) {
            return Response.error(new ParseError(e));  
        }
    }
  
    @Override
    protected void deliverResponse(XmlPullParser response) {  
        mListener.onResponse(response);
    }
  
}  

public abstract class AbstractTemplate {
    
    /**
     * 模板方法
     */
    public void templateMethod(){
        // 调用基本方法
        abstractMethod();
        doHookMethod();
        concreteMethod();
    }
    
    /**
     * 抽象方法，子类必须实现的方法
     */
    protected abstract void abstractMethod();
    
    /**
     * 钩子方法，子类可选择是否实现。注意钩子方法一般以 do 开头
     */
    protected void doHookMethod(){}
    
    /**
     * 具体方法，由父类实现，子类无法 override
     */
    private final void concreteMethod(){
        // 业务相关的代码
    }
}

public class ConcreteTemplate extends AbstractTemplate {
    
    // 基本方法的实现
    @Override
    public void abstractMethod() {
        // 业务相关的代码
    }
    
    // 重写父类的方法
    @Override
    public void hookMethod() {
        // 业务相关的代码
    }
}

protected void service(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
 
    String method = req.getMethod();
 
    if (method.equals(METHOD_GET)) {
        long lastModified = getLastModified(req);
        if (lastModified == -1) {
            // servlet doesn't support if-modified-since, no reason
            // to go through further expensive logic
            doGet(req, resp);
        } else {
            long ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
            if (ifModifiedSince < (lastModified / 1000 * 1000)) {
                // If the servlet mod time is later, call doGet()
                // Round down to the nearest second for a proper compare
                // A ifModifiedSince of -1 will always be less
                maybeSetLastModified(resp, lastModified);
                doGet(req, resp);
            } else {
                resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
            }
        }
 
    } else if (method.equals(METHOD_HEAD)) {
        long lastModified = getLastModified(req);
        maybeSetLastModified(resp, lastModified);
        doHead(req, resp);
 
    } else if (method.equals(METHOD_POST)) {
        doPost(req, resp);
 
    } else if (method.equals(METHOD_PUT)) {
        doPut(req, resp);       
 
    } else if (method.equals(METHOD_DELETE)) {
        doDelete(req, resp);
 
    } else if (method.equals(METHOD_OPTIONS)) {
        doOptions(req,resp);
 
    } else if (method.equals(METHOD_TRACE)) {
        doTrace(req,resp);
 
    } else {
        //
        // Note that this means NO servlet supports whatever
        // method was requested, anywhere on this server.
        //
 
        String errMsg = lStrings.getString("http.method_not_implemented");
        Object[] errArgs = new Object[1];
        errArgs[0] = method;
        errMsg = MessageFormat.format(errMsg, errArgs);
 
        resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
    }
}

public class TestServlet extends HttpServlet {
 
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
 
        System.out.println("using the GET method");
 
    }
 
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
 
        System.out.println("using the POST method");
    }
 
}

Snackbar.make(view, "Snackbar comes out", Snackbar.LENGTH_LONG)
                        .setAction("Action", new View.OnClickListener() {
                            @Override
                            public void onClick(View v) {
                                Toast.makeText(
                                        MainActivity.this,
                                        "Toast comes out",
                                        Toast.LENGTH_SHORT).show();
                            }
                        }).show();

TextInputLayout textInputLayout = (TextInputLayout) findViewById(R.id.til_pwd);
EditText editText = textInputLayout.getEditText();
textInputLayout.setHint("Password");

editText.addTextChangedListener(new TextWatcher() {
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        if (s.length() > 4) {
            textInputLayout.setError("Password error");
            textInputLayout.setErrorEnabled(true);
        } else {
            textInputLayout.setErrorEnabled(false);
        }
    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
    }

    @Override
    public void afterTextChanged(Editable s) {
    }
});

TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.addTab(tabLayout.newTab().setText("tab1"));
tabLayout.addTab(tabLayout.newTab().setText("tab2"));
tabLayout.addTab(tabLayout.newTab().setText("tab3"));

mViewPager = (ViewPager) findViewById(R.id.viewpager);
// 设置 ViewPager 的数据等
setupViewPager();
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);

private void setupDrawerContent(NavigationView navigationView) {
    navigationView.setNavigationItemSelectedListener(
        new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {
                menuItem.setChecked(true);
                mDrawerLayout.closeDrawers();
                return true;
            }
        }
    });
}