Question

我正在尝试在我的项目中使用this <?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:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true" tools:context="info.androidhive.firebase.LoginActivity"> <LinearLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@color/colorPrimary" android:gravity="center" android:orientation="vertical" android:padding="@dimen/activity_horizontal_margin"> <ImageView android:layout_width="@dimen/logo_w_h" android:layout_height="@dimen/logo_w_h" android:layout_gravity="center_horizontal" android:layout_marginBottom="30dp" android:src="@mipmap/ic_launcher" /> <android.support.design.widget.TextInputLayout android:layout_width="match_parent" android:layout_height="wrap_content"> <EditText android:id="@+id/email" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginBottom="10dp" android:hint="@string/hint_email" android:inputType="textEmailAddress" android:textColor="@android:color/white" android:textColorHint="@android:color/white" /> </android.support.design.widget.TextInputLayout> <android.support.design.widget.TextInputLayout android:layout_width="match_parent" android:layout_height="wrap_content"> <EditText android:id="@+id/password" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginBottom="10dp" android:hint="@string/hint_password" android:inputType="textPassword" android:textColor="@android:color/white" android:textColorHint="@android:color/white" /> </android.support.design.widget.TextInputLayout>  <Button android:id="@+id/btn_login" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="20dip" android:background="@color/colorAccent" android:text="@string/btn_login" android:textColor="@android:color/black" /> <Button android:id="@+id/btn_reset_password" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="20dip" android:background="@null" android:text="@string/btn_forgot_password" android:textAllCaps="false" android:textColor="@color/colorAccent" />  <Button android:id="@+id/btn_signup" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="20dip" android:background="@null" android:text="@string/btn_link_to_register" android:textAllCaps="false" android:textColor="@color/white" android:textSize="15dp" /> </LinearLayout> <ProgressBar android:id="@+id/progressBar" android:layout_width="30dp" android:layout_height="30dp" android:layout_gravity="center|bottom" android:layout_marginBottom="20dp" android:visibility="gone" />身份验证，但我无法弄清楚如何解决该错误及其原因：

我的布局xml：

package com.esmad.pdm.friendlymanager;

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;

public class LoginActivity extends AppCompatActivity {


    private EditText inputEmail, inputPassword;
    private FirebaseAuth auth;
    private ProgressBar progressBar;
    private Button btnSignup, btnLogin, btnReset;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        auth = FirebaseAuth.getInstance();

        if (auth.getCurrentUser() != null) {
            startActivity(new Intent(LoginActivity.this, MainActivity.class));
            finish();
        }

        setContentView(R.layout.activity_login);


        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        inputEmail = (EditText) findViewById(R.id.email);
        inputPassword = (EditText) findViewById(R.id.password);
        progressBar = (ProgressBar) findViewById(R.id.progressBar);
        btnSignup = (Button) findViewById(R.id.btn_signup);
        btnLogin = (Button) findViewById(R.id.btn_login);
        btnReset = (Button) findViewById(R.id.btn_reset_password);

        //Get Firebase auth instance
        auth = FirebaseAuth.getInstance();

        btnSignup.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(LoginActivity.this, SignupActivity.class));
            }
        });

        btnReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(LoginActivity.this, ResetPasswordActivity.class));
            }
        });

        btnLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String email = inputEmail.getText().toString();
                final String password = inputPassword.getText().toString();

                if (TextUtils.isEmpty(email)) {
                    Toast.makeText(getApplicationContext(), "Enter email address!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (TextUtils.isEmpty(password)) {
                    Toast.makeText(getApplicationContext(), "Enter password!", Toast.LENGTH_SHORT).show();
                    return;
                }

                progressBar.setVisibility(View.VISIBLE);

                //authenticate user
                auth.signInWithEmailAndPassword(email, password)
                        .addOnCompleteListener(LoginActivity.this, new OnCompleteListener<AuthResult>() {
                            @Override
                            public void onComplete(@NonNull Task<AuthResult> task) {
                                // If sign in fails, display a message to the user. If sign in succeeds
                                // the auth state listener will be notified and logic to handle the
                                // signed in user can be handled in the listener.
                                progressBar.setVisibility(View.GONE);
                                if (!task.isSuccessful()) {
                                    // there was an error
                                    if (password.length() < 6) {
                                        inputPassword.setError(getString(R.string.minimum_password));
                                    } else {
                                        Toast.makeText(LoginActivity.this, getString(R.string.auth_failed), Toast.LENGTH_LONG).show();
                                    }
                                } else {
                                    Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                                    startActivity(intent);
                                    finish();
                                }
                            }
                        });
            }
        });
    }
}

我的代码

ConstraintLayouts

为什么我一直收到此错误，我正在使用pInstance来构建此应用程序，我缺少什么？

Answer 1

您的CoordinatorLayout具有ID“工具栏”

<android.support.design.widget.CoordinatorLayout 
  ..
  android:id="@+id/toolbar"
  ..>

但在Java中，您将其转换为工具栏对象

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

这会引发异常，因为与id R.id.toolbar 关联的View不是工具栏。

要解决此问题，从Java代码中删除以上两行，因为您的布局中实际上没有工具栏。
您可能还应该将CoordinatorLayout的ID更改为更具描述性的内容，例如“@ + id / coordinator”

编辑：如果我查看您正在重新创建的示例，那里没有工具栏。老实说，对于一个登录页面，它不会最有意义。但是，如果要添加它，可以将其添加到布局中。将其作为顶部LinearLayout的第一个子项：

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:popupTheme="@style/AppTheme.PopupOverlay" />

但是如果你对处理布局等没有信心，我会高度建议阅读更多的文档并尝试更简单的例子来获得平台的支持。
一个好的起点是：https://developer.android.com/guide/topics/ui/declaring-layout.html

Answer 2

仔细检查您的导入模块，您应该导入此模块

android.support.v7.widget.Toolbar

而不是这个

android.widget.Toolbar

CoordinatorLayout无法强制转换为android.support.v7.widget.Toolbar

2 个答案: