Java 为什么；can'；找不到android.support.design.widget.TextInputLayout“；？

我的Android Studio版本是3.4，而我的编译器DKVersion 29&buildToolsVersion“29.0.1”。我想使用TextInputLayout，但出现以下错误： 缺少的类： 找不到以下类： -android.support.design.widget.TextInputLayout（修复构建路径、编辑XML、创建类） 提示：尝试构建项目

我搜索了好几天。我添加了这个

implementation 'com.android.support:appcompat-v7:29.0.1'
implementation 'com.android.support:design:29.0.1'

到我的gradle档案。但这个错误仍然存在

以下是我的xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.example.studentv3.tools.RoundImageView
        android:id="@+id/admin_layout_pic"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="100dp"
        android:src="@drawable/admin_photo" />

    <android.support.design.widget.TextInputLayout
        android:id="@+id/tt2"
        android:layout_below="@+id/admin_layout_pic"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <EditText
            android:id="@+id/admin_login_activity_name_input"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_below="@+id/admin_layout_pic"
            android:layout_centerHorizontal="true"
            android:layout_marginLeft="50dp"
            android:layout_marginRight="50dp"
            android:layout_marginTop="20dp"
            android:background="@drawable/input_box"
            android:gravity="center"
            android:hint="请输入账户"
            android:maxLines="1"
            android:paddingLeft="@dimen/input_box_left_padding"
            android:textColor="@color/grey_text" />

    </android.support.design.widget.TextInputLayout>



    <android.support.design.widget.TextInputLayout
        android:id="@+id/tt3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tt2">
        <EditText
            android:id="@+id/admin_login_activity_password_input"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_below="@+id/tt2"
            android:layout_centerHorizontal="true"
            android:layout_marginLeft="50dp"
            android:layout_marginRight="50dp"
            android:layout_marginTop="20dp"
            android:background="@drawable/input_box"
            android:gravity="center"
            android:hint="请输入密码"
            android:inputType="numberPassword"
            android:maxLines="1"
            android:paddingLeft="@dimen/input_box_left_padding"
            android:textColor="@color/grey_text" />

    </android.support.design.widget.TextInputLayout>

该xml的java类中没有错误，但我把它放在这里：

package com.example.studentv3.activities;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.example.studentv3.tools.myDatabaseHelper;
import com.example.studentv3.R;



public class admin_login_activity extends Activity {
    private EditText name;
    private EditText password;
    private Button login;
    private TextView register;
    private TextView forgetNum;
    private myDatabaseHelper dbHelper;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.admin_login_layout);

        dbHelper = myDatabaseHelper.getInstance(this);


        name = (EditText) findViewById(R.id.admin_login_activity_name_input);
        password = (EditText) findViewById(R.id.admin_login_activity_password_input);
        login = (Button) findViewById(R.id.admin_login_activity_login);
        register = (TextView) findViewById(R.id.admin_login_activity_register);
        forgetNum = (TextView) findViewById(R.id.admin_login_activity_forgetNum);


        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String nameInfo = name.getText().toString();
                String passwordInfo = password.getText().toString();

                SQLiteDatabase db = dbHelper.getWritableDatabase();
                Cursor cursor = db.rawQuery("select password from admin where name=?", new String[]{nameInfo});
                String pi = null;
                if (cursor.moveToNext()) {
                    pi = cursor.getString(cursor.getColumnIndex("password"));
                }

                if (passwordInfo.equals(pi)) {
                    Intent intent = new Intent(admin_login_activity.this, admin_activity.class);
                    startActivity(intent);
                    cursor.close();
                } else {
                    Toast.makeText(admin_login_activity.this, "用户名或密码错误", Toast.LENGTH_SHORT).show();
                }


            }
        });


        register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                AlertDialog.Builder builder = new AlertDialog.Builder(admin_login_activity.this);
                LayoutInflater factory = LayoutInflater.from(admin_login_activity.this);
                final View textEntryView = factory.inflate(R.layout.register, null);
                builder.setTitle("用户注册");
                builder.setView(textEntryView);

                final EditText code = (EditText) textEntryView.findViewById(R.id.admin_register_info);
                final EditText name = (EditText) textEntryView.findViewById(R.id.admin_register_name);
                final EditText firstPassword = (EditText) textEntryView.findViewById(R.id.admin_register_first_password);
                final EditText secondPassword = (EditText) textEntryView.findViewById(R.id.admin_register_second_password);


                builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                    }
                });

                builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String codeInfo = code.getText().toString();

                        if (codeInfo.equals("10086")) {
                            String nameInfo = name.getText().toString();
                            String firstPasswordInfo = firstPassword.getText().toString();
                            String secondPasswordInfo = secondPassword.getText().toString();
                            SQLiteDatabase db = dbHelper.getWritableDatabase();

                            if (firstPasswordInfo.matches("[0-9]{6}")) {

                                if (firstPasswordInfo.equals(secondPasswordInfo)) {
                                    Cursor cursor = db.rawQuery("select name from admin where name=? ", new String[]{nameInfo});

                                    if (cursor.moveToNext()) {
                                        Toast.makeText(admin_login_activity.this, "该用户已存在", Toast.LENGTH_SHORT).show();
                                    } else {
                                        db.execSQL("insert into admin(name,password)values(?,?)", new String[]{nameInfo, firstPasswordInfo});
                                    }
                                } else {
                                    Toast.makeText(admin_login_activity.this, "两次密码不相同", Toast.LENGTH_SHORT).show();
                                }
                            } else {
                                Toast.makeText(admin_login_activity.this, "密码为6位纯数字", Toast.LENGTH_SHORT).show();
                            }


                        } else {
                            Toast.makeText(admin_login_activity.this, "注册码错误", Toast.LENGTH_SHORT).show();
                        }
                    }
                });


                builder.create().show();

            }
        });

        forgetNum.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(admin_login_activity.this, "此功能暂不支持", Toast.LENGTH_SHORT).show();
            }
        });

    }
}

---

这个项目可以运行并且可以在我的手机上使用（android 9），但是当我进入上面xml控制的页面时，应用程序突然关闭。我想原因是xml有这样一个错误：找不到android.support.design.widget.TextInputLayout。因为我试图删除所有提到TextInputLayout的代码，所以它不会关闭，但这不是我期望的结果。

您可以使用材质设计来实现TextInputText和TextInputLayout

使用最新版本的材质设计：

api 'com.google.android.material:material:1.1.0-alpha06'

然后实现如下

<com.google.android.material.textfield.TextInputLayout
    android:id="@+id/layout_username"
    style="@style/Widget.ChatMe.TextInputLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginStart="32dp"
    android:layout_marginTop="100dp"
    android:layout_marginEnd="32dp"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent">

    <com.google.android.material.textfield.TextInputEditText
        android:id="@+id/et_username"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:hint="Username" />
</com.google.android.material.textfield.TextInputLayout>

共享崩溃日志！请添加一些关于代码的解释

<com.google.android.material.textfield.TextInputLayout
    android:id="@+id/layout_username"
    style="@style/Widget.ChatMe.TextInputLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginStart="32dp"
    android:layout_marginTop="100dp"
    android:layout_marginEnd="32dp"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent">

    <com.google.android.material.textfield.TextInputEditText
        android:id="@+id/et_username"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:hint="Username" />
</com.google.android.material.textfield.TextInputLayout>

<com.google.android.material.textfield.TextInputLayout
            android:id="@+id/in1"
            android:layout_width="match_parent"
            android:layout_marginTop="20dp"
            android:layout_gravity="center"
            android:gravity="center"
            android:textColorHint="#353536"
            android:layout_marginLeft="15dp"
            android:layout_marginRight="15dp"
            android:layout_height="wrap_content"
            app:passwordToggleEnabled="true">

            <EditText
                android:id="@+id/loginPass"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_centerHorizontal="true"
                android:ems="10"
                android:inputType="textPassword"
                android:hint="@string/loginPassword"
                android:paddingLeft="10dp" />
</com.google.android.material.textfield.TextInputLayout>