안드로이드 앱 만들기 #2 (EditText & Button) - 쉽게 앱 만드는 방법 (현직 개발자 설명) , android studio easy tutorial

Short tutorial (part 2) — Build a simple Android UI

A brief beginner-friendly walkthrough (explained by a current developer) showing how to create a simple Android UI with an EditText and a Button in Android Studio.

Key concepts covered

Project setup

• Create a New Project in Android Studio.
• Choose an Activity type and programming language (Java is used in the video).
• Use the split view to see activity_main.xml (UI) and the Activity Java file (logic).

XML vs Java

• XML defines the static layout (screen structure).
• Java (Activity) handles dynamic behavior: events, listeners, and lifecycle methods.

Layouts

• Change the root layout to LinearLayout.
• Use android:orientation="vertical" or "horizontal" to control element alignment.

UI elements

• EditText
  • Width/height: e.g., 300dp and wrap_content.
  • android:hint shows placeholder text (e.g., “Please enter your ID”) that disappears when focused.
• Button
  • Use android:text for the label.
  • Assign an id (e.g., @+id/btn_test) to reference in code.

Connecting UI to code

• In onCreate() call setContentView(R.layout.activity_main) to link the XML layout.
• Declare variables and bind views:
  • EditText et = findViewById(R.id.your_edittext_id);
  • Button btn = findViewById(R.id.btn_test);
• Fix missing imports using IDE suggestions (Alt+Enter).

Event handling

• Set an OnClickListener on the Button to respond to taps.
• Example action: when the button is clicked, set text of the EditText programmatically to demonstrate dynamic UI changes.

Example Java listener:

btn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        et.setText("Some text");
    }
});

Running / testing

• Run the app on an Android Virtual Device (AVD) or a real Android phone.
• Verify interactivity (keyboard appears, hint disappears on focus, button updates EditText, etc.).

Step-by-step tutorial checklist (as demonstrated)

1. Create New Project; select Activity and language (Java used in the video).
2. Open activity_main.xml; change root to LinearLayout and remove the default TextView.
3. Add EditText: set width (e.g., 300dp), height (wrap_content), and android:hint.
4. Add Button: set android:text and android:id (e.g., @+id/btn_test).
5. Set LinearLayout orientation to vertical (or horizontal as desired).
6. In MainActivity.onCreate():
   • Call setContentView(R.layout.activity_main).
   • Declare and bind EditText and Button with findViewById(...).
   • Add btn.setOnClickListener(...) to update the EditText text.
7. Fix imports/compile errors via Alt+Enter, then run on an AVD or device.

Troubleshooting and tips

• Double-check id names and capitalization — they are case-sensitive.
• Remember to end Java statements with semicolons.
• Use IDE auto-import (Alt+Enter) when a class is unresolved.
• Use wrap_content for flexible sizing; use dp (density-independent pixels) for fixed sizes.
• The hint attribute provides placeholder text that disappears when the EditText gains focus.
• If the video pace is too fast, slow down playback in YouTube to follow the steps.

Main speaker / source: Hongdro (현직 개발자, the instructor in the video).