App not running after intent added: how to fix?

Question

I've been trying to create an app which opens the data settings, via a intent. After watching tons of tutorials online, I made this code, which now will not run. Can anyone help?

I'm using the latest verison of android studio, on a java project. In mainactivity.java, "setComponent" is flagged as 'non-resolvable' by the program.

Java Code:

package com.example.datamaster;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;

public abstract class MainActivity extends AppCompatActivity {
    Intent intent = new Intent();
    intent.setComponent(newComponentName("com.android.settings","com.android.settings.Settings$DataUsageSummaryActivity"));
    startActivity(intent);


}

Xml Code:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"/>

When attempting to run, the error message is "Compilation failed; see the compiler error output for details." As new and young coder, I really am confused on this. Thank you in advance for the answers.

Answer 1

as you mentioned you'r new and a younger coder. Let me clear your confusion. First you need to remove abstract keyword

package com.example.datamaster;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {


}

and then you need to override onCreate() activity lifecycle methode after that your code will look like

    package com.example.datamaster;

    import androidx.appcompat.app.AppCompatActivity;

    import android.content.Intent;
    import android.os.Bundle;
    import android.view.View;

    public class MainActivity extends AppCompatActivity {

    @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
           //your XML layout name
            setContentView(R.layout.activity_main);
            Toolbar toolbar = findViewById(R.id.toolbar);
            setSupportActionBar(toolbar);

//Button click to luanch settings data uses activity
            FloatingActionButton fab = findViewById(R.id.fab);
            fab.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Intent intent = new Intent();
                    intent.setComponent(new ComponentName("com.android.settings","com.android.settings.Settings$DataUsageSummaryActivity"));
                    startActivity(intent);
                }
            });
        }
    }

you can add this in your xml

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

    <com.google.android.material.appbar.AppBarLayout
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:theme="@style/AppTheme.AppBarOverlay">

        <androidx.appcompat.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" />

    </com.google.android.material.appbar.AppBarLayout>



    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        app:srcCompat="@android:drawable/ic_dialog_email" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

add these lines in your values/styles folder

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>
    <style name="AppTheme.NoActionBar">
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>
    </style>
    <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
    <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />

replace

@color/colorPrimary
       @color/colorPrimaryDark
       @color/colorAccent

these with your color name or color code like #cccccc