java.lang.IllegalStateException：尝试单击按钮时无法执行android：onClick的方法

Question

When I click the buttons on my page, I get an "IllegalStateException" in my logcat. I'm new at Java development, so I don't really know if it's something simple that i'm doing wrong. All I'm trying to do is get the button to open the activity. It worked fine until i started playing with the fragments etc for the layout.

log cat

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.as1.app172, PID: 5621
    java.lang.IllegalStateException: Could not execute method for android:onClick
        at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
        at android.view.View.performClick(View.java:5637)
        at android.view.View$PerformClick.run(View.java:22429)
        at android.os.Handler.handleCallback(Handler.java:751)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6119)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
    Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
        at android.view.View.performClick(View.java:5637) 
        at android.view.View$PerformClick.run(View.java:22429) 
        at android.os.Handler.handleCallback(Handler.java:751) 
        at android.os.Handler.dispatchMessage(Handler.java:95) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6119) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
     Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.as1.app172/com.as1.app172.LoginActivity}; have you declared this activity in your AndroidManifest.xml?
        at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1805)
        at android.app.Instrumentation.execStartActivity(Instrumentation.java:1523)
        at android.app.Activity.startActivityForResult(Activity.java:4225)
        at android.support.v4.app.BaseFragmentActivityApi16.startActivityForResult(BaseFragmentActivityApi16.java:54)
        at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:67)
        at android.app.Activity.startActivityForResult(Activity.java:4183)
        at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:720)
        at android.app.Activity.startActivity(Activity.java:4522)
        at android.app.Activity.startActivity(Activity.java:4490)
        at com.as1.app172.Import1.BtnLogin_Click(Import1.java:25)
        at java.lang.reflect.Method.invoke(Native Method) 
        at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
        at android.view.View.performClick(View.java:5637) 
        at android.view.View$PerformClick.run(View.java:22429) 
        at android.os.Handler.handleCallback(Handler.java:751) 
        at android.os.Handler.dispatchMessage(Handler.java:95) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6119) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

java

package com.as1.app172;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class Import1 extends AppCompatActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_import1);
    }

    public void BtnRegister_Click (View v) {
        Intent i = new Intent (Import1.this, RegistrationActivity.class);
        startActivity(i);

    }

    public void BtnLogin_Click(View v) {
        Intent i = new Intent (Import1.this, LoginActivity.class);
        startActivity(i);
    }
}

Answer 1

Check your AndroidManifest.xml and make sure you are already declared the activity LoginActivity. <activity android:name=".view.acitvity.LoginActivity" />