ProgressBar空点异常使应用程序崩溃

Question

我是Android应用程序开发的新手，正在从事一个项目。我收到以下错误，但似乎无法找出解决方案，这会使我的应用程序崩溃。

日志猫在这里

2020-05-27 01：08：00.427 25788-25788 / com.example.auth E / AndroidRuntime：FATAL EXCEPTION：main流程：com.example.auth，PID：25788java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.auth / com.example.auth.RegisterActivity}：java.lang.NullPointerException：尝试调用虚拟方法'void android.widget.ProgressBar.setVisibility（int） '在空对象引用上在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2913）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:3048）在android.app.servertransaction.LaunchActivityItem.execute（LaunchActivityItem.java:78）在android.app.servertransaction.TransactionExecutor.executeCallbacks（TransactionExecutor.java:108）在android.app.servertransaction.TransactionExecutor.execute（TransactionExecutor.java:68）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1808）在android.os.Handler.dispatchMessage（Handler.java:106）在android.os.Looper.loop（Looper.java:193）在android.app.ActivityThread.main（ActivityThread.java:6669）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:493）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:858）原因：java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'void android.widget.ProgressBar.setVisibility（int）'在com.example.auth.RegisterActivity.onCreate（RegisterActivity.java:35）在android.app.Activity.performCreate（Activity.java:7136）在android.app.Activity.performCreate（Activity.java:7127）在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1271）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2893）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:3048）在android.app.servertransaction.LaunchActivityItem.execute（LaunchActivityItem.java:78）在android.app.servertransaction.TransactionExecutor.executeCallbacks（TransactionExecutor.java:108）在android.app.servertransaction.TransactionExecutor.execute（TransactionExecutor.java:68）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1808）在android.os.Handler.dispatchMessage（Handler.java:106）在android.os.Looper.loop（Looper.java:193）在android.app.ActivityThread.main（ActivityThread.java:6669）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:493）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:858）2020-05-27 01：08：00.452 25788-25788 / com.example.auth I / Process：正在发送信号。 PID：25788 SIG：9

这里是RegisterActivity.java

package com.example.auth;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Patterns;
import android.view.View;
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;
import com.google.firebase.database.FirebaseDatabase;

public class RegisterActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText editTextName, editTextEmail, editTextPassword, editTextPhone;
    private ProgressBar progressBar;

    private FirebaseAuth mAuth;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editTextName = findViewById(R.id.edit_text_name);
        editTextEmail = findViewById(R.id.edit_text_email);
        editTextPassword = findViewById(R.id.edit_text_password);
        editTextPhone = findViewById(R.id.edit_text_phone);
        progressBar = (ProgressBar) findViewById(R.id.progressbar);
        **progressBar.setVisibility(View.GONE);**

        mAuth = FirebaseAuth.getInstance();

        findViewById(R.id.button_register).setOnClickListener(this);
    }

    @Override
    protected void onStart() {
        super.onStart();

        if (mAuth.getCurrentUser() != null) {
            //handle the already login user
        }
    }

    private void registerUser() {
        final String name = editTextName.getText().toString().trim();
        final String email = editTextEmail.getText().toString().trim();
        String password = editTextPassword.getText().toString().trim();
        final String phone = editTextPhone.getText().toString().trim();

        if (name.isEmpty()) {
            editTextName.setError(getString(R.string.input_error_name));
            editTextName.requestFocus();
            return;
        }

        if (email.isEmpty()) {
            editTextEmail.setError(getString(R.string.input_error_email));
            editTextEmail.requestFocus();
            return;
        }

        if (!Patterns.EMAIL_ADDRESS.matcher(email).matches()) {
            editTextEmail.setError(getString(R.string.input_error_email_invalid));
            editTextEmail.requestFocus();
            return;
        }

        if (password.isEmpty()) {
            editTextPassword.setError(getString(R.string.input_error_password));
            editTextPassword.requestFocus();
            return;
        }

        if (password.length() < 6) {
            editTextPassword.setError(getString(R.string.input_error_password_length));
            editTextPassword.requestFocus();
            return;
        }

        if (phone.isEmpty()) {
            editTextPhone.setError(getString(R.string.input_error_phone));
            editTextPhone.requestFocus();
            return;
        }

        if (phone.length() != 10) {
            editTextPhone.setError(getString(R.string.input_error_phone_invalid));
            editTextPhone.requestFocus();
            return;
        }


        progressBar.setVisibility(View.VISIBLE);
        mAuth.createUserWithEmailAndPassword(email, password)
                .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {

                        if (task.isSuccessful()) {

                            User user = new User(
                                    name,
                                    email,
                                    phone
                            );

                            FirebaseDatabase.getInstance().getReference("Users")
                                    .child(FirebaseAuth.getInstance().getCurrentUser().getUid())
                                    .setValue(user).addOnCompleteListener(new OnCompleteListener<Void>() {
                                @Override
                                public void onComplete(@NonNull Task<Void> task) {
                                    progressBar.setVisibility(View.GONE);
                                    if (task.isSuccessful()) {
                                        Toast.makeText(RegisterActivity.this, getString(R.string.registration_success), Toast.LENGTH_LONG).show();
                                    } else {
                                        //display a failure message
                                    }
                                }
                            });

                        } else {
                            Toast.makeText(RegisterActivity.this, task.getException().getMessage(), Toast.LENGTH_LONG).show();
                        }
                    }
                });

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button_register:
                registerUser();
                break;
        }
    }
}

Answer 1

错误消息：

java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'void android.widget.ProgressBar.setVisibility（int）'

告诉您progressBar为空。您不能在空对象上调用方法。这是空的，因为findViewById找不到具有给定ID的视图。您将不得不检查您的膨胀。布局以找出原因。