activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/coordinator_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#efeeea"
>
<!--
android:selectAllOnFocus
If the text is selectable, select it all when the view takes focus.
Must be a boolean value, either "true" or "false".
This may also be a reference to a resource (in the form "@[package:]type:name") or
theme attribute (in the form "?[package:][type:]name") containing a value of this type.
This corresponds to the global attribute resource symbol selectAllOnFocus.
-->
<EditText
android:id="@+id/et"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="top|center_horizontal"
android:textSize="25sp"
android:padding="5dp"
android:layout_marginTop="50dp"
android:text="Hello Android."
android:selectAllOnFocus="true"
/>
</android.support.design.widget.CoordinatorLayout>

2. Select all text inside EditText on focus programmatically
MainActivity.java
package com.cfsuman.me.androidcodesnippets;
import android.app.Activity;
import android.content.Context;
import android.support.design.widget.CoordinatorLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
private Context mContext;
private Activity mActivity;
private CoordinatorLayout mCLayout;
private EditText mEditText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Get the application context
mContext = getApplicationContext();
mActivity = MainActivity.this;
// Get the widget reference from XML layout
mCLayout = (CoordinatorLayout) findViewById(R.id.coordinator_layout);
mEditText = (EditText) findViewById(R.id.et);
/*
setSelectAllOnFocus
void setSelectAllOnFocus (boolean selectAllOnFocus)
Set the EditText so that when it takes focus, all the text is selected.
*/
// Select all text inside EditText when it gets focus
mEditText.setSelectAllOnFocus(true);
}
}
