最近了解到了BottomSheetBehavior，感觉是个很有意思的布局，刚好项目中有实际场景可以应用，就拿它来实现了，下面是我们要实现的最终效果：

gif.gif

布局界面代码

布局界面就是一个关闭按钮的图片，两个TextView和一个自定义的密码输入控件，下面贴上代码

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".activity.PasswordcheckActivity">


    <RelativeLayout
        android:background="@color/back"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ImageView
            android:id="@+id/img_close"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_marginTop="20dp"
            android:layout_marginLeft="20dp"
            android:src="@drawable/ic_close" />

        <TextView
            android:id="@+id/textView4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="@dimen/dp_120"
            android:textColor="@color/title_black"
            android:textSize="25sp"
            android:text="添加银行卡" />

        <TextView
            android:id="@+id/textView5"
            android:textColor="@color/title_black"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@+id/textView4"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="@dimen/dp_20"
            android:text="请输入支付密码，以验证身份" />

        <com.xxx.xxx.PassEditView
            android:id="@+id/pass_edit"
            android:layout_width="256dp"
            android:layout_height="48dp"
            android:layout_below="@+id/textView5"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="60dp"
            android:padding="1dp" />
    </RelativeLayout>
    
    
    <LinearLayout
        android:background="@color/white"
        android:id="@+id/line_pass_bottom"
        app:layout_behavior="android.support.design.widget.BottomSheetBehavior"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="@dimen/dp_300">
        <LinearLayout
            android:id="@+id/Line_bom"
            android:gravity="center"
            android:layout_width="match_parent"
            android:layout_height="@dimen/dp_20">
        <ImageView
            android:layout_width="@dimen/dp_30"
            android:layout_height="@dimen/dp_20"
            android:src="@drawable/bottom"
            />
        </LinearLayout>

       <GridLayout
           android:columnCount="3"
           android:rowCount="4"
           android:layout_width="match_parent"
           android:layout_height="match_parent">


            <TextView
                android:id="@+id/text_num_1"
                android:layout_height="70dp"
                android:layout_columnWeight="1"
                android:gravity="center"
                android:text="1"
                android:textSize="25sp"
                android:textColor="@color/black"
                />
           <TextView
               android:id="@+id/text_num_2"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="2"
               android:textSize="25sp"
               android:textColor="@color/black"
               />
           <TextView
               android:id="@+id/text_num_3"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="3"
               android:textSize="25sp"
               android:textColor="@color/black"
               />

           <TextView
               android:id="@+id/text_num_4"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="4"
               android:textSize="25sp"
               android:textColor="@color/black"
               />
           <TextView
               android:id="@+id/text_num_5"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="5"
               android:textSize="25sp"
               android:textColor="@color/black"
               />
           <TextView
               android:id="@+id/text_num_6"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="6"
               android:textSize="25sp"
               android:textColor="@color/black"
               />

           <TextView
               android:id="@+id/text_num_7"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="7"
               android:textSize="25sp"
               android:textColor="@color/black"
               />
           <TextView
               android:id="@+id/text_num_8"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="8"
               android:textSize="25sp"
               android:textColor="@color/black"
               />
           <TextView
               android:id="@+id/text_num_9"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="9"
               android:textSize="25sp"
               android:textColor="@color/black"
               />

           <TextView
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text=""
               android:textSize="25sp"
               android:textColor="@color/black"
               />
           <TextView
               android:id="@+id/text_num_0"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               android:gravity="center"
               android:text="0"
               android:textSize="25sp"
               android:textColor="@color/black"
               />
           <RelativeLayout
               android:id="@+id/text_num_d"
               android:layout_height="70dp"
               android:layout_columnWeight="1"
               >
                <ImageView
                    android:layout_centerInParent="true"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:src="@drawable/ic_close"
                    />
           </RelativeLayout>
       </GridLayout>
    </LinearLayout>
</android.support.design.widget.CoordinatorLayout>

除了几个颜色资源和图片外，没有用到其他的资源文件，注意的是com.xxx.xxx.PassEditView这个自定义控件需要将代码复制到你项目下使用，替换成你的包名，而且BottomSheetBehavior布局的界面要加入以下一句：

 app:layout_behavior="android.support.design.widget.BottomSheetBehavior"

而且BottomSheetBehavior是可以设置初始高度等属性的，感兴趣的同学可以搜索百度BottomSheetBehavior
下面是PassEditView这个密码输入框的代码：

public class PassEditView extends View {


    private Paint mPaint;
    private InputFinishListener inputFinishListener;//输入完成监听

    private int inputNum=0;//当前输入的密码个数
    private int passwordNum=6;//密码个数

    private int boundWidth=2;//外层框线条粗细
    private int boundColor= R.color.view_blue;//外层框线条颜色
    private int boundRadius=0;//外框圆角半径

    private int deliverWidth=1;//分割线粗细
    private int deliverColor=Color.GRAY;//分割线条颜色
    private int deliverPadding=5;//分割线距离框的大小

    private int circleRadius =15;//密码圆点半径大小
    private int circleColor= Color.BLACK;//密码圆点颜色

    private StringBuilder currentPassword;//用户输入的密码

    public PassEditView(Context context) {
        super(context);
        init();
    }

    public PassEditView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }


    @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

    }

    private void init() {
        currentPassword=new StringBuilder();
        mPaint=new Paint(Paint.ANTI_ALIAS_FLAG);
    }

    private int dip2px(float dpValue) {
        final float scale = getContext().getResources().getDisplayMetrics().density;
        return (int) (dpValue * scale + 0.5f);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int widthMode=MeasureSpec.getMode(widthMeasureSpec);
        int widthSize=MeasureSpec.getSize(widthMeasureSpec);
        int heightMode=MeasureSpec.getMode(heightMeasureSpec);
        int heightSize=MeasureSpec.getSize(heightMeasureSpec);
        int width,height;
        if (widthMode==MeasureSpec.AT_MOST){
            width=dip2px(36)*passwordNum;
        }else {
            width=widthSize;
        }
        if (heightMode==MeasureSpec.AT_MOST){
            height=dip2px(36);
        }else{
            height=heightSize;
        }
        setMeasuredDimension(width,height);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int width = getWidth();
        int height = getHeight();
        float deliverSize=(width-getPaddingLeft()-getPaddingRight())/passwordNum;
        //1.画外框
        drawBound(canvas, width, height);
        //2.画分割线
        drawDeliver(canvas, height, deliverSize);
        //3.输入密码之后显示的图案
        drawCircle(canvas, height, deliverSize);
    }

    private void drawCircle(Canvas canvas, int height, float deliverSize) {
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setColor(circleColor);
        for (int i = 0; i < inputNum; i++) {
            canvas.drawCircle(deliverSize*i+getPaddingLeft()+deliverSize/2,(height-getPaddingTop()-getPaddingBottom())/2+getPaddingTop(), circleRadius,mPaint);
        }
    }

    private void drawDeliver(Canvas canvas, int height, float deliverSize) {

        mPaint.setStrokeWidth(deliverWidth);
        mPaint.setColor(deliverColor);
        Path path = new Path();
        for (int i = 1; i < passwordNum; i++) {
            path.reset();
            path.moveTo(deliverSize*i+getPaddingLeft(),0+deliverPadding+getPaddingTop());
            path.lineTo(deliverSize*i+getPaddingLeft(),height-deliverPadding-getPaddingBottom());
            canvas.drawPath(path,mPaint);
        }
    }

    private void drawBound(Canvas canvas, int width, int height) {
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(boundWidth);
        mPaint.setColor(getResources().getColor(boundColor));
        RectF rectF = new RectF(getPaddingLeft(),getPaddingTop(),width-getPaddingRight(),height-getPaddingBottom());
        canvas.drawRoundRect(rectF,boundRadius,boundRadius,mPaint);
    }


    public void inputPassword(Object pwd){
        if (inputNum<passwordNum) {
            currentPassword.append(pwd);
            inputNum++;
        }
        invalidate();
        if (inputNum==passwordNum){
            if (inputFinishListener!=null){
                inputFinishListener.onFinish(getPassword());
            }
        }
    }
    //删除一个密码
    public void deletePassword(){
        if (currentPassword.length()>0) {
            currentPassword.deleteCharAt(currentPassword.length() - 1);
            inputNum--;
        }
        invalidate();
    }
    //清空输入的所有密码
    public void cleanInput(){
        inputNum=0;
        currentPassword.delete(0,currentPassword.length());
        invalidate();
    }
    //获取输入的所有密码
    public String getPassword(){
        return currentPassword.toString();
    }

    public void setInputFinishListener(InputFinishListener inputFinishListener) {
        this.inputFinishListener = inputFinishListener;
    }

    public interface InputFinishListener{
        void onFinish(String pwd);
    }
}

PassEditView这个自定义View并不是作者本人写的哦，网上有很多一样的轮子，就拿来用了，感谢作者的开源，其中包含有四个主要方法，输入密码-inputPassword，传入一个数字、删除一个密码-deletePassword()、清空所有密码-cleanInput()、以及获取所有密码-getPassword()，值得注意的是，这个控件有输入完成的回调，实现这个回调就能直接获取到输入的密码。

Java代码部分

在java代码中我们要实现点击键盘数字，输入密码，点击输入框掉起数字键盘，点击返回键，收起键盘等等，总体来说功能并不难；这里代码中设置BottomSheetBehavior的初始状态：

public class PasswordcheckActivity extends AppCompatActivity {

    BottomSheetBehavior bottomSheetBehavior;
    @BindView(R.id.pass_edit)
    PassEditView passEdit;
    @BindView(R.id.Line_bom)
    LinearLayout LineBom;
    @BindView(R.id.text_num_1)
    TextView textNum1;
    @BindView(R.id.text_num_2)
    TextView textNum2;
    @BindView(R.id.text_num_3)
    TextView textNum3;
    @BindView(R.id.text_num_4)
    TextView textNum4;
    @BindView(R.id.text_num_5)
    TextView textNum5;
    @BindView(R.id.text_num_6)
    TextView textNum6;
    @BindView(R.id.text_num_7)
    TextView textNum7;
    @BindView(R.id.text_num_8)
    TextView textNum8;
    @BindView(R.id.text_num_9)
    TextView textNum9;
    @BindView(R.id.text_num_0)
    TextView textNum0;
    @BindView(R.id.text_num_d)
    RelativeLayout textNumD;
    @BindView(R.id.img_close)
    ImageView imgClose;
    @BindView(R.id.line_pass_bottom)
    LinearLayout linePassBottom;
    boolean isshowPass = true;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_passwordcheck);
        ButterKnife.bind(this);
        init();
    }

    private void init() {
        bottomSheetBehavior = BottomSheetBehavior.from(findViewById(R.id.line_pass_bottom));
        bottomSheetBehavior.setSkipCollapsed(true);
        bottomSheetBehavior.setHideable(true);
        bottomSheetBehavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
        passEdit.setInputFinishListener(new PassEditView.InputFinishListener() {
            @Override
            public void onFinish(String pwd) {
                Toast.makeText(PasswordcheckActivity.this, pwd, Toast.LENGTH_SHORT).show();
            }
        });
    }

    @OnClick({R.id.img_close,R.id.pass_edit, R.id.Line_bom, R.id.text_num_1, R.id.text_num_2, R.id.text_num_3, R.id.text_num_4, R.id.text_num_5, R.id.text_num_6, R.id.text_num_7, R.id.text_num_8, R.id.text_num_9, R.id.text_num_0, R.id.text_num_d})
    public void onViewClicked(View view) {
        switch (view.getId()) {
            case R.id.pass_edit:
                isshowPass = true;
                bottomSheetBehavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
                break;
            case R.id.Line_bom:
                isshowPass = false;
                bottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN);
                break;
            case R.id.text_num_1:
                passEdit.inputPassword(1);
                break;
            case R.id.text_num_2:
                passEdit.inputPassword(2);
                break;
            case R.id.text_num_3:
                passEdit.inputPassword(3);
                break;
            case R.id.text_num_4:
                passEdit.inputPassword(4);
                break;
            case R.id.text_num_5:
                passEdit.inputPassword(5);
                break;
            case R.id.text_num_6:
                passEdit.inputPassword(6);
                break;
            case R.id.text_num_7:
                passEdit.inputPassword(7);
                break;
            case R.id.text_num_8:
                passEdit.inputPassword(8);
                break;
            case R.id.text_num_9:
                passEdit.inputPassword(9);
                break;
            case R.id.text_num_0:
                passEdit.inputPassword(0);
                break;
            case R.id.text_num_d:
                passEdit.deletePassword();
                break;
            case R.id.img_close:
                finish();
                break;
        }
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            if(isshowPass){
                isshowPass = false;
                bottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN);
            }else {
                finish();
            }
            return false;
        }
        return super.onKeyDown(keyCode, event);
    }
}

以上呢，就完成了我们需要的效果，大致上与微信的输入密码页面差不多，关于BottomSheetBehavior的更多用法，大家有兴趣可以去搜索一下，在没了解之前做底部抽屉都是用弹窗的形式，BottomSheetBehavior很好的帮我们免去了写一个新页面的麻烦哦。