Android Activity代码简记

package com.dinosaur.hello;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    private final static String TAG = "MainActivity";

    private int cj1;

    private Button exit1, next;

    //  Toast toast = Toast.makeText(MainActivity.this, "退出", Toast.LENGTH_SHORT);
    //  toast.setGravity(Gravity.CENTER, 0, 0);
    //  toast.show();

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

        Log.i(TAG, "onCreate()");

        exit1 = findViewById(R.id.exit1);
        exit1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Log.i(TAG, "退出");
                System.exit(0);
            }
        });


        next = findViewById(R.id.next);
        next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                cj1 = 10;
                Log.i(TAG, "跳转");
                // 启动第二个页面
                Intent intent = new Intent();
                // 1.显示意图
                intent.setClass(MainActivity.this, SecondActivity.class);
                // 2.隐式意图
                // intent.setAction("android.intent.action.MAIN");

                // 向第二个界面传值
                intent.putExtra("mark", cj1); //put extra key-value pairs into the intent
                startActivity(intent);
            }
        });
    }

    // 不可见到可见
    @Override
    protected void onStart() {
        super.onStart();
        Log.i(TAG, "onStart()");

    }

    // 获得焦点
    @Override
    protected void onResume() {
        super.onResume();
        Log.i(TAG, "onResume");
    }

    // 失去焦点
    @Override
    protected void onPause() {
        super.onPause();
        Log.i(TAG, "onPause()");
    }


    // 可见到不可见
    @Override
    protected void onStop() {
        super.onStop();
        Log.i(TAG, "onStop()");
    }

    // 销毁
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "onDestroy()");
    }

}

package com.dinosaur.hello;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class SecondActivity extends AppCompatActivity {

    private final static String TAG = "SecondActivity";

    private Button exit2, back;

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

        Log.i(TAG, "onCreate()");

        exit2 = findViewById(R.id.exit2);
        exit2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });

        back = findViewById(R.id.back);
        back.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                finish();
            }
        });
        // 接受MainActivity的值
        Intent intent = getIntent();
        int cj = intent.getIntExtra("mark", 0);
        Toast.makeText(this, "" + cj, Toast.LENGTH_SHORT).show();

    }


    // 不可见到可见
    @Override
    protected void onStart() {
        super.onStart();
        Log.i(TAG, "onStart()");

    }

    // 获得焦点
    @Override
    protected void onResume() {
        super.onResume();
        Log.i(TAG, "onResume");
    }

    // 失去焦点
    @Override
    protected void onPause() {
        super.onPause();
        Log.i(TAG, "onPause()");
    }

    // 可见到不可见
    @Override
    protected void onStop() {
        super.onStop();
        Log.i(TAG, "onStop()");
    }

    // 销毁
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "onDestroy");
    }
}