Hướng dẫn lập trình Android cho người mới bắt đầu - Các ví dụ cơ bản

<?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">

    <Button
        android:id="@+id/button1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Go to Example1 Activity"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Go to Example2 Activity"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button1" />

    <Button
        android:id="@+id/button3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Go to Example3 Activity"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button2" />

    <Button
        android:id="@+id/button4"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Go to Example4 Activity"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button3" />

    <Button
        android:id="@+id/button5"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Go to Example5 Activity"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button4" />
</androidx.constraintlayout.widget.ConstraintLayout>

// Lấy ra button theo ID
Button button1 = (Button) this.findViewById(R.id.go_button1);

// Sét đặt sự kiện Click vào Button1.
button1.setOnClickListener(new Button.OnClickListener() {

  @Override
  public void onClick(View v) {

      // Tạo một Intent:
      // (Đối tượng chứa nội dung sẽ được gửi đến Example1Activity).
      Intent myIntent = new Intent(MainActivity.this, Example1Activity.class);

      // Các tham số gắn trên Intent (Không bắt buộc).
      myIntent.putExtra("text1", "This is text1 sent from MainActivity at " + new Date());
      myIntent.putExtra("text2", "This is text2 sent from MainActivity at " + new Date());

      // Yêu cầu chạy Example1Activity.
      MainActivity.this.startActivity(myIntent);
  }
});

package org.o7planning.androidbasic2;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.content.Intent;
import android.view.View;
import android.widget.Button;

import java.util.Date;

public class MainActivity extends AppCompatActivity {

    private Button button1;
    private Button button2;
    private Button button3;
    private Button button4;
    private Button button5;

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

        // Find Button by its ID
        this.button1 = (Button) this.findViewById(R.id.button1);

        // Find button by its ID
        this.button2 = (Button) this.findViewById(R.id.button2);

        // Find button by its ID.
        this.button3 = (Button) this.findViewById(R.id.button3);

        // Find button by its ID.
        this.button4 = (Button) this.findViewById(R.id.button4);

        // Find button by its ID.
        this.button5 = (Button) this.findViewById(R.id.button5);

        // Called when the user clicks the button1.
        button1.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {

                // Create a Intent:
                // (This object contains content that will be sent to Example1Activity).
                Intent myIntent = new Intent(MainActivity.this, Example1Activity.class);

                // Put parameters
                myIntent.putExtra("text1", "This is text1 sent from MainActivity at " + new Date());
                myIntent.putExtra("text2", "This is text2 sent from MainActivity at " + new Date());

                // Start Example1Activity.
                MainActivity.this.startActivity(myIntent);
            }
        });

        // Called when the user clicks the button2.
        button2.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {

                // Create a Intent:
                // (This object contains content that will be sent to Example2Activity).
                Intent myIntent = new Intent(MainActivity.this, Example2Activity.class);

                // Start Example2Activity.
                MainActivity.this.startActivity(myIntent);
            }
        });

        // Called when the user clicks the button3.
        button3.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {

                // Create a Intent:
                // (This object contains content that will be sent to Example3Activity).
                Intent myIntent = new Intent(MainActivity.this, Example3Activity.class);


                MainActivity.this.startActivity(myIntent);
            }
        });

        button4.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {

                // Create a Intent:
                // (This object contains content that will be sent to Example4Activity).
                Intent myIntent = new Intent(MainActivity.this, Example4Activity.class);

                // Start Example4Activity.
                MainActivity.this.startActivity(myIntent);
            }
        });

        button5.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {

                // Create a Intent:
                // (This object contains content that will be sent to Example5Activity).
                Intent myIntent = new Intent(MainActivity.this, Example5Activity.class);

                // Start Example5Activity.
                MainActivity.this.startActivity(myIntent);
            }
        });
    }
}

<?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=".Example1Activity">

    <TextView
        android:id="@+id/textView1"
        android:layout_width="0dp"
        android:layout_height="51dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="54dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:gravity="center"
        android:text="TextView"
        android:textSize="22sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="0dp"
        android:layout_height="36dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="37dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:gravity="center"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView1" />

    <Button
        android:id="@+id/button_clickMe"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="36dp"
        android:text="Click me"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

    <Button
        android:id="@+id/button_back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="22dp"
        android:text="Back"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button_clickMe" />
</androidx.constraintlayout.widget.ConstraintLayout>

package org.o7planning.androidbasic2;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.content.Intent;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;


public class Example1Activity extends AppCompatActivity {

    private Button buttonClickMe;
    private Button buttonBack;
    private TextView textView1;
    private TextView textView2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_example1);

        // Find TextView by its ID
        this.textView1  = (TextView)this.findViewById(R.id.textView1);

        // Find TextView by its ID
        this.textView2 = (TextView)this.findViewById(R.id.textView2);

        this.buttonClickMe = (Button)this.findViewById(R.id.button_clickMe);

        this.buttonBack = (Button)this.findViewById(R.id.button_back);

        // Get the intent sent from MainActivity.
        Intent intent = getIntent();

        // Parameter in Intent, sent from MainActivity
        String value1 = intent.getStringExtra("text1");

        // Parameter in Intent, sent from MainActivity
        String value2 = intent.getStringExtra("text2");

        this.textView1.setText(value1);
        this.textView2.setText(value2);

        // When user click "Click me" button.
        this.buttonClickMe.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {
                textView2.setText("You click button");
            }
        });

        // When user long click "Click me" button.
        this.buttonClickMe.setOnLongClickListener(new Button.OnLongClickListener() {


            // return true if the callback consumed the long click, false otherwise.
            @Override
            public boolean onLongClick(View v) {
                textView2.setText("You long click button");
                return true;
            }
        });

        // When user click "Back" button.
        this.buttonBack.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {
                // Back to previous Activity.
                Example1Activity.this.finish();
            }
        });

    }
}