完成初始化操作       完成耗時操作              更新進度條                得到doInBackground的返回值進行處理

接下來新建一個Android專案測試一下，新建Android專案之後，直接新增一個MyAsyncTask類：

public class MyAsyncTask extends AsyncTask<Void, Void, Void> {
	private static final String TAG = "MyAsyncTask";

	@Override
	protected Void doInBackground(Void... arg0) {
		Log.e(TAG, "****doInBackground****");
		publishProgress();
		return null;
	}

	@Override
	protected void onPostExecute(Void result) {
		Log.e(TAG, "****onPostExecute****");
		super.onPostExecute(result);
	}

	@Override
	protected void onPreExecute() {
		Log.e(TAG, "****onPreExecute****");
		super.onPreExecute();
	}

	@Override
	protected void onProgressUpdate(Void... values) {
		Log.e(TAG, "****onProgressUpdate****");
		super.onProgressUpdate(values);
	}

	
}
 

public class MainActivity extends ActionBarActivity {


	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		MyAsyncTask task = new MyAsyncTask();
		task.execute();
	}
	
}

根據列印的Log，我們可以發現四個方法的執行順序。

接下來我們修改一下並繼續編寫專案，簡單的使用一下AsyncTask。

MyAsyncTask類：

public class MyAsyncTask extends AsyncTask<String, Void, Bitmap> {
	private static final String TAG = "MyAsyncTask";
	private ImageView imageView;
	
	public MyAsyncTask(ImageView imageView){
		this.imageView = imageView;
	}
	
	@Override
	protected Bitmap doInBackground(String... arg0) {
		Log.e(TAG, "****doInBackground****");
		publishProgress();
		//獲取傳遞進來的引數
		String url = arg0[0];
		Bitmap bitmap = null;
		URLConnection connection;
		InputStream is;
		
		try {
			connection = new URL(url).openConnection();
			is = connection.getInputStream();
			BufferedInputStream bis = new BufferedInputStream(is);
			//通過decodeStream解析輸入流
			bitmap = BitmapFactory.decodeStream(bis);
			is.close();
			bis.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		//將Bitmap作為返回值
		return bitmap;
	}

	@Override
	protected void onPostExecute(Bitmap bitmap) {
		Log.e(TAG, "****onPostExecute****");
		imageView.setImageBitmap(bitmap);
		super.onPostExecute(bitmap);
	}

	@Override
	protected void onPreExecute() {
		Log.e(TAG, "****onPreExecute****");
		super.onPreExecute();
	}

	@Override
	protected void onProgressUpdate(Void... values) {
		Log.e(TAG, "****onProgressUpdate****");
		super.onProgressUpdate(values);
	}

	
}

MainActivity類：

public class MainActivity extends ActionBarActivity {
	private final String URL = "https://www.baidu.com/img/bd_logo1.png";
	private ImageView imageView1;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		imageView1 = (ImageView) findViewById(R.id.imageView1);
		MyAsyncTask task = new MyAsyncTask(imageView1);
		task.execute(URL);
	}
	
}

activity_main.xml佈局檔案：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.itman.asynctaskdemo.MainActivity" >


    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:src="@drawable/ic_launcher" />

</RelativeLayout>