[Android][Resolved] Listview not showing the content

MainActivity.java

package net.macdidi.listviewadapter;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    ListView listView;

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

        listView = (ListView) findViewById(R.id.item_list);
        ArrayList<String> data = new ArrayList<>();
        data.add("a");
        data.add("b");
        data.add("c");

        int layoutId = android.R.layout.simple_list_item_1;
        ListView item_list = (ListView)findViewById(R.id.item_list);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, layoutId, data);
        item_list.setAdapter(adapter);

    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="net.macdidi.listviewadapter.MainActivity">

    <ListView        android:id="@+id/item_list"        android:layout_width="match_parent"        android:layout_height="0dp"        android:layout_weight="1"        android:dividerHeight="1sp"        android:divider="@color/divider_color" />

    <TextView        android:id="@+id/show_app_name"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:gravity="center"        android:text="Hello World" />

</RelativeLayout>

Correction:

Check are you using RelativeLayout, the most easy way is change that to LinearLayout and also add the line android:orientation="vertical" to LinearLayout.

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="net.macdidi.listviewadapter.MainActivity">

    <ListView        android:id="@+id/item_list"        android:layout_width="match_parent"        android:layout_height="0dp"        android:layout_weight="1"        android:dividerHeight="1sp"        android:divider="@color/divider_color" />

    <TextView        android:id="@+id/show_app_name"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:gravity="center"        android:text="Hello World" />

</LinearLayout>

Reference:

http://stackoverflow.com/questions/4530940/why-is-my-listview-not-showing-anything