如何实现无界面Android app

前言

在Android开发中，可能会遇到只需要在后台运行服务，不需要界面的情况，接下来说一下如何实现无界面APP。

代码实现

AndroidManifest.xml

将AndroidManifest.xml的主activity配置为不展示模式：

android:theme="@android:style/Theme.NoDisplay"

然后添加需要运行的service：

<service android:name=".MyService"/>

以下为完整示例代码：

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

    <application
        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">
        <!--设置activity为不显示-->
        <activity
            android:name=".MainActivity"
            android:theme="@android:style/Theme.NoDisplay"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

MainActivity.java

在MainActivity中启动需要运行的service，如下为示例代码：

package com.example.serviceapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //启动service
        Intent service = new Intent(MainActivity.this, MyService.class);
        MainActivity.this.startService(service);
    }

    //8.0以上手机需要添加此代码才能正常运行
    public void onResume() {
        super.onResume();
        finish();
    }
}

MyService.java

编写需要运行的service的代码，以下为示例代码，service运行过程中打印日志，便于观察service是否正常运行：

package com.example.serviceapp;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MyService extends Service {
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        Log.v("Jason", "MyService onBind");
        return null;
    }

    @Override
    public void onCreate() {
        Log.v("Jason", "MyService onCreate");
        super.onCreate();
    }

    @Override
    public void onStart(Intent intent, int startId) {
        Log.v("Jason", "MyService onStart");
        super.onStart(intent, startId);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.v("Jason", "MyService onStartCommand");
        ExecutorService threadPool = Executors.newCachedThreadPool();
        threadPool.execute(new Runnable() {
            @Override
            public void run() {
                int time = 0;
                while(true) {
                    Log.d("Jason", "time:" + time);
                    try {
                        Thread.sleep(10000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    time++;
                }
            }
        });

        return super.onStartCommand(intent, flags, startId);
    }
}