学步园

前言:

过渡页面 的重要性,相当于你在KFC 排队买吃的, 在排队的过程中,你可能会想 "今天我要吃什么?" . 

如果去掉这个过渡的环节, 可能会有些不友好. 二来 ,过渡页面我们可以做一些广告的植入 ..

项目结构

// 原始需求  一个页面加载后一段时间后 ,另外一个页面加载

//  所以首先考虑到的是 AsyncTask 异步线程

//  创建BackgroundLoadable 目的是为了将实例化的过程,延迟到它的实现类中去完成.

过渡页面layout/splash.xml

<?xml version="1.0" encoding="utf-8"?>
<TabHost 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/tabhost"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#ffffff"
    android:gravity="center"
    android:orientation="vertical" >

    <FrameLayout
        android:id="@android:id/tabcontent"
        android:layout_width="fill_parent"
        android:layout_height="0.0dip"
        android:layout_weight="1.0"
        android:visibility="gone" />

    <TabWidget
        android:id="@android:id/tabs"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:visibility="gone" />

    <LinearLayout
        android:id="@+id/welcomelayout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:orientation="vertical" >

        <ImageView 
		    android:contentDescription="@string/contentDescription"
		    android:id="@+id/MainActivity_Image"
		    android:layout_width="match_parent"
		    android:layout_height="match_parent"
	    />
        <TextView
            android:visibility="visible"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:text="@string/welcome"
            android:textSize="20sp" />

        <TextView
            android:visibility="visible"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:text="@string/app_name"
            android:textSize="20sp" />
    </LinearLayout>

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|center_horizontal"
        android:layout_marginBottom="10dp"
        android:text="@string/copyright"
        android:textAppearance="?android:attr/textAppearanceSmall" >
    </TextView>

</TabHost>

interface  BackgroundLoadable

public interface BackgroundLoadable{

    public void onPreLoad();

    public View loadInBackground();

    public void onPostLoad(View view);

}

LoadMainInBackgroundTask

public class LoadMainInBackgroundTask extends AsyncTask<Void,Object,View>{

	BackgroundLoadable activity;
	
	int minLoadTime;
	
	public LoadMainInBackgroundTask(BackgroundLoadable activity,int minLoadTime){
		this.activity = activity;
		this.minLoadTime = minLoadTime;
	}

	protected void onPreExecute() 
	{
		activity.onPreLoad();
	}

	@Override
	protected View doInBackground(Void... params) 
	{
		//  获取当前时间 .毫秒级	
		long time1 = System.currentTimeMillis();
		View view = activity.loadInBackground();
		long time2 = System.currentTimeMillis();	
			
		if ((time2 - time1) < minLoadTime) {
			try {
				Thread.sleep(minLoadTime - (time2 - time1));
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		return view;
	}

	@Override
	protected void onPostExecute(View result) 
	{
		activity.onPostLoad(result);
	}
	
}

MainActivity 

public class MainActivity extends Activity implements BackgroundLoadable{

	protected final int SPLASH_TIME = 2000;
	private ImageView imageView;
	private LoadMainInBackgroundTask task;
	
	public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        
        setContentView(R.layout.splash);
		  
        setTransitionPage(); 
        task = new LoadMainInBackgroundTask(this, SPLASH_TIME);
		task.execute();
    }
    
	private void setTransitionPage(){
		imageView = (ImageView) findViewById(R.id.MainActivity_Image);
        imageView.setImageResource(R.drawable.ic_launcher);
	}
	
	@Override
	public void onPreLoad() {
	
	}
	@Override
	public View loadInBackground() {
		// TODO Auto-generated method stub	
		return getLayoutInflater().inflate(R.layout.activity_main, null);
	}
	@Override
	public void onPostLoad(View view) {
		// TODO Auto-generated method stub
		setContentView(view);
	}
}