Android Relative layout button crashes app

Issue

I'm making an app, now i want to make a button with an image and some text on it. But every time I click the button my app crashes, android studio does compile however.

This is how i my xml code to make the layout of the screen.

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <RelativeLayout
        android:id="@+id/buttonStartTest"
        style="@android:style/Widget.Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:ignore="MissingConstraints">

        <ImageView... />

        <TextView.../>
    </RelativeLayout>

</android.support.constraint.ConstraintLayout>

java code:

package com.example.user.ballbounceapp;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RelativeLayout;

public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    RelativeLayout StartTest = findViewById(R.id.buttonStartTest);
    StartTest.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            TestActivity();
        }
    });
}

public void TestActivity(){
    Intent intent = new Intent(MainActivity.this,TestActivity.class);
    startActivity(intent);
}

};

Solution

You may have forgot to declare your TestActivity inside your manifest.
More about activities in manifest here : https://developer.android.com/guide/topics/manifest/activity-element

So you will need something like this : <activity android:name="TestActivity">

If the crash persists, the problem might be in your TestActivity 's OnCreate method.

Answered By - Piou44