1.Application的生命周期

自定义Application

package com.tiger.chapter06;

import android.app.Application;
import android.content.res.Configuration;
import android.util.Log;

import androidx.annotation.NonNull;

public class MyApplication extends Application {

    //在App启动时调用
    @Override
    public void onCreate() {
        super.onCreate();
        Log.d("ning"," MyApplication onCreate");
    }

    //在App终止时调用
    @Override
    public void onTerminate() {
        super.onTerminate();
        Log.d("ning","onTerminate");

    }

    //在配置改变时调用，例如从竖屏变为横屏
    @Override
    public void onConfigurationChanged(@NonNull Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        Log.d("ning","onConfigurationChanged");
    }
}

一个应用就一个Application

贯穿整个生命周期

比MainActivity要先创建

屏幕旋转 MainActivity会重新创建

 

 

package com.tiger.chapter06;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.EditText;

public class AppWriteActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText et_name;
    private EditText et_age;
    private EditText et_height;
    private EditText et_weight;
    private CheckBox ck_married;
    private MyApplication app;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_app_write);
        et_name = findViewById(R.id.et_name);
        et_age = findViewById(R.id.et_age);
        et_height = findViewById(R.id.et_height);
        et_weight = findViewById(R.id.et_weight);
        ck_married = findViewById(R.id.ck_married);

        findViewById(R.id.btn_save).setOnClickListener(this);

        app = MyApplication.getInstance();
        reload();

    }


    private void reload() {
        String name = app.infoMap.get("name");
        if (name == null) {
            return;
        }
        String age = app.infoMap.get("age");
        String height = app.infoMap.get("height");
        String weight = app.infoMap.get("weight");
        String married = app.infoMap.get("married");
        et_name.setText(name);
        et_age.setText(age);
        et_height.setText(height);
        et_weight.setText(weight);
        if ("是".equals(married)) {
            ck_married.setChecked(true);
        } else {
            ck_married.setChecked(false);
        }
    }

    @Override
    public void onClick(View v) {
        String name = et_name.getText().toString();
        String age = et_age.getText().toString();
        String height = et_height.getText().toString();
        String weight = et_weight.getText().toString();

        app.infoMap.put("name", name);
        app.infoMap.put("age", age);
        app.infoMap.put("height", height);
        app.infoMap.put("weight", weight);
        app.infoMap.put("married", ck_married.isChecked() ? "是" : "否");
    }


}

package com.tiger.chapter06;

import android.app.Application;
import android.content.res.Configuration;
import android.util.Log;

import androidx.annotation.NonNull;

import java.util.HashMap;

public class MyApplication extends Application {
    private static MyApplication mApp;

    public static MyApplication getInstance(){
        return mApp;
    }

    public HashMap<String,String> infoMap = new HashMap<>();

    //在App启动时调用
    @Override
    public void onCreate() {
        super.onCreate();
        mApp=this;
        Log.d("ning"," MyApplication onCreate");
    }

    //在App终止时调用
    @Override
    public void onTerminate() {
        super.onTerminate();
        Log.d("ning","onTerminate");

    }

    //在配置改变时调用，例如从竖屏变为横屏
    @Override
    public void onConfigurationChanged(@NonNull Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        Log.d("ning","onConfigurationChanged");
    }
}