Question

崩溃的开始：

01-12 10:37:17.953 6865-6865/c.mycompany.cart E/AndroidRuntime: FATAL EXCEPTION: main
                                                            Process: c.mycompany.cart, PID: 6865
                                                            java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
                                                                at c.mycompany.cart.SignIn$1$1.onDataChange(SignIn.java:63)
                                                                at com.google.android.gms.internal.zzbpx.zza(Unknown Source:13)
                                                                at com.google.android.gms.internal.zzbqx.zzZS(Unknown Source:2)
                                                                at com.google.android.gms.internal.zzbra$1.run(Unknown Source:63)
                                                                at android.os.Handler.handleCallback(Handler.java:789)
                                                                at android.os.Handler.dispatchMessage(Handler.java:98)
                                                                at android.os.Looper.loop(Looper.java:164)
                                                                at android.app.ActivityThread.main(ActivityThread.java:6541)
                                                                at java.lang.reflect.Method.invoke(Native Method)
                                                                at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
                                                                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

这是logcat。

public void onDataChange(DataSnapshot dataSnapshot) {

                    //Check if user dosen't exist in database
                    if (dataSnapshot.child(edtPhone.getText().toString()).exists()) {
                        //Get user information

                        mDialog.dismiss();

                        User user = dataSnapshot.child(edtPhone.getText().toString()).getValue(User.class);
                        if (user.getpassword().equals(edtPassword.getText().toString())) {

                                Intent homeIntent = new Intent(SignIn.this,Home.class);
                                Common.currentUser=user;
                                startActivity(homeIntent);
                                finish();
                            }
                         else {
                            Toast.makeText(SignIn.this, "Incorrect Password !!!", Toast.LENGTH_SHORT).show();
                        }
                    }
                    else
                    {
                        mDialog.dismiss();
                        Toast.makeText(SignIn.this, "User dosen't exist in Database", Toast.LENGTH_SHORT).show();
                    }

                }

这是onDataChange函数的代码。

Answer 1

阅读此问题：What is a NullPointerException, and how do I fix it?

您在尚未初始化的equals()对象上使用String。检查您的代码并确保在调用equals()之前初始化您的对象，以防止这种情况发生。

将代码包裹在if (stringObject != null)左右，以便您的应用不会崩溃：

if (user.getpassword() != null) {
    if(user.getpassword().equals(edtPassword.getText().toString())) {
        Intent homeIntent = new Intent(SignIn.this,Home.class);
        Common.currentUser=user;
        startActivity(homeIntent);
        finish();
        }else {
            Toast.makeText(SignIn.this, "Incorrect Password !!!", Toast.LENGTH_SHORT).show();
        }
}else {
    Toast.makeText(SignIn.this, "getpassword returned null", Toast.LENGTH_SHORT).show();
}

如何调试＆＃34;尝试在空对象引用上调用虚方法＆＃34;？

1 个答案: