Activity 生命周期及关联组件

代码清单：

SimpleActivity.java

package foolstudio.demo;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.app.Application;
import android.content.Context;
import android.content.ContentResolver;
import android.content.res.AssetManager;
import android.content.res.Resources;
import android.graphics.drawable.Drawable;
import android.view.LayoutInflater;
import android.view.MenuInflater;
import android.view.Window;
import android.view.WindowManager;
import android.view.ViewGroup.LayoutParams;
import android.view.Display;

public class SimpleActivity extends Activity {
    private static final String TAG = "SIMPLE_ACT";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Log.i(TAG, "Activity creating...");
    }

    @Override
    public void onStart() {
        super.onStart();

        Log.i(TAG, "Activity starting...");

        showInfo();
    }

    @Override
    public void onStop() {
        super.onStop();

        Log.i(TAG, "Activity stopping...");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        Log.i(TAG, "Activity destroying...");
    }

    //显示Activity组件关联组件信息
    private void showInfo() {
        Log.i(TAG, "Title: " + this.getTitle().toString() );
        Log.i(TAG, "Calling activity: " + this.getCallingPackage() );

        //获取应用程序实例
        Application app = this.getApplication();
        Log.i(TAG, "Package:" + app.getPackageName() );
        //获取应用程序上下文实例
        Context appContext = this.getApplicationContext();
        Log.i(TAG, "AppContext: " + appContext.toString() );
        //获取资产管理器
        AssetManager am = this.getAssets();
        Log.i(TAG, "AssetManager: " + am.getLocales()[1]);
        //获取基础上下文
        Context baseContext = this.getBaseContext();
        Log.i(TAG, "BaseContext: " + baseContext.toString() );
        //内容解决者
        ContentResolver resolver = this.getContentResolver();
        Log.i(TAG, "Resolver: " + resolver.toString() );
        //布局填充器
        LayoutInflater inflater = this.getLayoutInflater();
        Log.i(TAG, "LayoutInflater: " + inflater.toString() );
        //菜单填充器
        MenuInflater inflater2 = this.getMenuInflater();
        Log.i(TAG, "MenuInflater: " + inflater2.toString() );
        //资源管理器
        Resources resources = this.getResources();
        Log.i(TAG, "Resources: " + resources.toString() );
        //墙纸
        Drawable wallpaper = this.getWallpaper();
        Log.i(TAG, "Wallpaper: " + wallpaper.toString() );
        //获取窗体实例
        Window window = this.getWindow();
        LayoutParams layoutParams = window.getAttributes();

        Log.i(TAG, "Layout height: " + layoutParams.height +
                    ", width: " + layoutParams.width);
        //获取窗体管理器
        WindowManager wm = this.getWindowManager();
        Display display = wm.getDefaultDisplay();
        Log.i(TAG, "Window height: " + display.getHeight() +
                    ", width: " + display.getWidth() );
    }
};

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=""
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello"/>
</LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android=""
      package="foolstudio.demo"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".SimpleActivity" android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
    <uses-sdk android:minSdkSimpleActivity.javaVersion="3" />
</manifest>

Activity关联组件

从表现形式上，Activity程序用来提供可视界面，但是在后台方面，Activity几乎关联了Android应用程序中的大
部分组件。从SimpleActivity.java中的“showInfo"方法（第41行）可以看出，Activity的关联组件有：应用程序
、应用程序上下文、资产管理器、基础上下文、内容解决者、布局填充器、菜单填充器、资源管理器、墙纸、窗
体布局和窗体管理器。