导读

1.简介
2.自定义Application类
3.Application的回调函数
4.Application对象的作用
5.事件框架总线Otto
6.Application VS 静态单例

简介

自定义Application类

Application的回调函数

package com.hala.myapp;

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

/**
 * Created by air on 2018/4/23.
 */

public class MyApp extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
    }

    @Override
    public void onLowMemory() {
        super.onLowMemory();
    }
}

Application对象的作用

配置文件 AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.hala.myapp">

    <application
        android:name=".MyApp"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".Main2Activity"></activity>
    </application>

</manifest>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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="com.hala.myapp.MainActivity">

    <Button
        android:id="@+id/go"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="goto"
        android:onClick="onClick"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/get" />

    <Button
        android:id="@+id/set"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:onClick="onClick"
        android:text="set userName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/get"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:onClick="onClick"
        android:text="get userName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/set" />

</android.support.constraint.ConstraintLayout>

activity_main2.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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="com.hala.myapp.Main2Activity">

    <Button
        android:id="@+id/get"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:onClick="onClick"
        android:text="get userName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/set" />

</android.support.constraint.ConstraintLayout>

MainActivity.java

package com.hala.myapp;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private static  final String TAG="MainActivity-app";

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

    }

    public void onClick(View v){
        switch (v.getId()){
            case R.id.set:
                MyApp app=(MyApp)getApplication();
                app.setUserName("Emilia Clark");
                Toast.makeText(MainActivity.this, "set userName:"+app.getUserName(), Toast.LENGTH_SHORT).show();
                break;
            case R.id.get:
                MyApp app1=(MyApp)getApplication();
                Toast.makeText(this, "get userName:"+app1.getUserName(), Toast.LENGTH_SHORT).show();
                break;
            case R.id.go:
                startActivity(new Intent(this,Main2Activity.class));
                break;
        }
    }
}

Main2Activity.java

package com.hala.myapp;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class Main2Activity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
    }

    public void onClick(View view){
        switch(view.getId()){
            case R.id.get:
                MyApp app1=(MyApp)getApplication();
                Toast.makeText(this, "get userName:"+app1.getUserName(), Toast.LENGTH_SHORT).show();
                break;
        }
    }
}

MyApp.java

package com.hala.myapp;

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

/**
 * Created by air on 2018/4/23.
 */

public class MyApp extends Application {

    public  String userName;

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
    }

    @Override
    public void onLowMemory() {
        super.onLowMemory();
    }
}

显示结果

事件框架总线Otto

Application VS 静态单例

添加依赖

Application

MyApp类

package com.hala.myapp;

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

import com.squareup.otto.Bus;

/**
 * Created by air on 2018/4/23.
 */

public class MyApp extends Application {

    private Bus bus;

    public Bus getBus() {
        return bus;
    }

    public void setBus(Bus bus) {
        this.bus = bus;
    }


    @Override
    public void onCreate() {
        super.onCreate();
        bus=new Bus();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
    }

    @Override
    public void onLowMemory() {
        super.onLowMemory();
    }
}

MainActivity.java

package com.hala.myapp;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;

import com.squareup.otto.Bus;

public class MainActivity extends AppCompatActivity {
    private static  final String TAG="MainActivity-app";

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

    }


    @Override
    protected void onResume() {
        super.onResume();
        MyApp myApp=(MyApp)getApplication();
        Bus bus= myApp.getBus();
        Log.d(TAG,"onResume:"+bus);
        bus.register(this);
    }

    @Override
    protected void onPause() {
        super.onPause();
        MyApp myApp=(MyApp)getApplication();
        Bus bus= myApp.getBus();
        Log.d(TAG,"onPause:"+bus);
        bus.unregister(this);
    }
}

静态单例

BusProvider.java

package com.hala.myapp;

import com.squareup.otto.Bus;

/**
 * Created by air on 2018/4/24.
 */

public class BusProvider {
    private BusProvider(){

    }

    public static final Bus BUS=new Bus();

    public static Bus getBus(){
        return BUS;
    }
}

Main2Activity.java

package com.hala.myapp;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;

public class Main2Activity extends AppCompatActivity {

    public static final String TAG="Main2Activity-app";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG,"onResume:"+BusProvider.getBus());
        BusProvider.getBus().register(this);
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d(TAG,"onPause:"+BusProvider.getBus());
        BusProvider.getBus().unregister(this);
    }


}