Application

android.app.Application这个包的onCreate()才是真正的Android入口点，只不过大多数开发者无需重写该类

重写Application

import android.app.Application;
import android.content.ComponentName;
import android.content.Context;
import android.content.pm.ActivityInfo;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.pm.ServiceInfo;
import android.os.Bundle;
import android.util.Log;

public class MyApplication extends Application {
    
    private static final String TAG = MainActivity.TAG;
    
    @Override
    public void onCreate() {
        Log.d(TAG, "MyApplication onCreate()");
        super.onCreate();
        
        try {
            ApplicationInfo appInfo = getPackageManager().getApplicationInfo(getPackageName(),
                    PackageManager.GET_META_DATA);     
            Bundle appBundle = appInfo.metaData;
            String appId = appBundle.getString("APP_ID");
            Log.d(TAG, "appId: " + appId);
            
            ActivityInfo activityInfo = getPackageManager().getActivityInfo(
                    new ComponentName(this, MainActivity.class), PackageManager.GET_META_DATA);
            String dataName = activityInfo.metaData.getString("data_Name");
            Log.d(TAG, "activity dataName: " + dataName);
            
            ServiceInfo serviceInfo = getPackageManager().getServiceInfo(
                    new ComponentName(this, MyService.class), PackageManager.GET_META_DATA);
            String serviceDataName = serviceInfo.metaData.getString("service_data_name");
            Log.d(TAG, "service dataName: " + serviceDataName);
        } catch (NameNotFoundException e) {
            e.printStackTrace();
        }        
    }
    
    @Override
    protected void attachBaseContext(Context base) {
        super.attachBaseContext(base);
    }    
}

 

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

public class MainActivity extends Activity {
    
    public static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        Log.d(TAG, "MainActivity onCreate()");
    }
}

 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.chameleon"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="21" />

    <application
        android:name="MyApplication"
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <meta-data
            android:name="APP_ID"
            android:value="App123" />

        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <meta-data
                android:name="data_Name"
                android:value="this is MainActivity" />

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

        <service android:name=".MyService" >
            <meta-data
                android:name="service_data_name"
                android:value="this is a service" />
        </service>
    </application>

</manifest>

muhe221@muhe:~/code$ adb logcat -s MainActivity
D/MainActivity(11348): MyApplication onCreate()
D/MainActivity(11348): appId: App123
D/MainActivity(11348): activity dataName: this is MainActivity
D/MainActivity(11348): service dataName: this is a service
D/MainActivity(11348): MainActivity onCreate()