安卓开发实例：随机数

点击按钮生成一个1-100之间的随机数

activity_random_number.xml

<?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=".RandomNumber">
  <LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center">
    <TextView
      android:text="-"
      android:textSize="200sp"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content" android:id="@+id/tv_random_number"
      tools:ignore="HardcodedText,MissingConstraints"/>
    <Button
      android:text="随机数"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/btn_generate_random_number"
      tools:ignore="HardcodedText"/>
    <TextView
      android:text="点击按钮生成随机数"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content" android:id="@+id/tv1"
      tools:ignore="HardcodedText"/>
  </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

RandomNumber.java

package com.weijun901.show;

import android.view.View;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;

public class RandomNumber extends AppCompatActivity {

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

    // 设置标题栏的文字
    getSupportActionBar().setTitle("随机数");

    TextView tvRandomNumber = findViewById(R.id.tv_random_number);
    View btnGenerateRandomNumber = findViewById(R.id.btn_generate_random_number);

    btnGenerateRandomNumber.setOnClickListener(view -> {
      int randomNumber = (int) (Math.random() * 100);
      tvRandomNumber.setText(String.valueOf(randomNumber));
    });
  }
}