Android Activity的生命周期、意图(Intent)

package cn.lwx.activitycreate;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

    @Override //当页面创建的时候执行
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_example);

        Log.i("MainActivity","调用onCreate()方法");
    }


    @Override //当页面可见执行
    protected void onStart() {
        super.onStart();
        Log.i("MainActivity","调用onStart()方法");
    }

    @Override //当Activity获取焦点开始与用户交互时
    protected void onResume() {
        super.onResume();
        Log.i("MainActivity","调用onResume()方法");
    }

    @Override //当Activity被覆盖（失去焦点,用户不可进行交互）
    protected void onPause() {
        super.onPause();
        Log.i("MainActivity","调用onPause()方法");
    }

    @Override //当页面不可见的时候执行
    protected void onStop() {
        super.onStop();
        Log.i("MainActivity","调用onStop()方法");
    }

    @Override //当页面销毁时执行
    protected void onDestroy() {
        super.onDestroy();
        Log.i("MainActivity","调用onDestroy()方法");
    }

    @Override //当页面重新启动时执行
    protected void onRestart() {
        super.onRestart();
        Log.i("MainActivity","调用onRestart()方法");
    }
}

package cn.lwx.activitycreate;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

    @Override //当页面创建的时候执行
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_example);

        Log.i("MainActivity","调用onCreate()方法");

        // 1、通过显示意图开启Activity
        Intent intent = new Intent(this, ActivityExample.class);
        startActivity(intent);


        // 2、通过隐式意图开启Activity 清单文件
        Intent intent2 = new Intent();
        intent.setAction("com.lwx.main2");
        intent.addCategory("android.intent.category.DEFAULT");
        startActivity(intent);
    }