Android开发笔记之:AsyncTask的应用详解

public class AsyncTaskDemoActivity extends Activity {
    private static int ID = 0;
    private static final int TASK_COUNT = 9;
    private static ExecutorService SINGLE_TASK_EXECUTOR;
    private static ExecutorService LIMITED_TASK_EXECUTOR;
    private static ExecutorService FULL_TASK_EXECUTOR;

    static {
        SINGLE_TASK_EXECUTOR = (ExecutorService) Executors.newSingleThreadExecutor();
        LIMITED_TASK_EXECUTOR = (ExecutorService) Executors.newFixedThreadPool(7);
        FULL_TASK_EXECUTOR = (ExecutorService) Executors.newCachedThreadPool();
    };

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.asynctask_demo_activity);
        String title = "AsyncTask of API " + VERSION.SDK_INT;
        setTitle(title);
        final ListView taskList = (ListView) findViewById(R.id.task_list);
        taskList.setAdapter(new AsyncTaskAdapter(getApplication(), TASK_COUNT));
    }

    private class AsyncTaskAdapter extends BaseAdapter {
        private Context mContext;
        private LayoutInflater mFactory;
        private int mTaskCount;
        List<SimpleAsyncTask> mTaskList;

        public AsyncTaskAdapter(Context context, int taskCount) {
            mContext = context;
            mFactory = LayoutInflater.from(mContext);
            mTaskCount = taskCount;
            mTaskList = new ArrayList<SimpleAsyncTask>(taskCount);
        }

        @Override
        public int getCount() {
            return mTaskCount;
        }
        @Override
        public Object getItem(int position) {
            return mTaskList.get(position);
        }
        @Override
        public long getItemId(int position) {
            return position;
        }
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null) {
                convertView = mFactory.inflate(R.layout.asynctask_demo_item, null);
                SimpleAsyncTask task = new SimpleAsyncTask((TaskItem) convertView);
                /*
                 * It only supports five tasks at most. More tasks will be scheduled only after
                 * first five finish. In all, the pool size of AsyncTask is 5, at any time it only
                 * has 5 threads running.
                 */
//                task.execute();
                // use AsyncTask#SERIAL_EXECUTOR is the same to #execute();
//                task.executeOnExecutor(AsyncTask.SERIAL_EXECUTOR);
                // use AsyncTask#THREAD_POOL_EXECUTOR is the same to older version #execute() (less than API 11)
                // but different from newer version of #execute()
//                task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
                // one by one, same to newer version of #execute()
//                task.executeOnExecutor(SINGLE_TASK_EXECUTOR);
                // execute tasks at some limit which can be customized
//                task.executeOnExecutor(LIMITED_TASK_EXECUTOR);
                // no limit to thread pool size, all tasks run simultaneously
                task.executeOnExecutor(FULL_TASK_EXECUTOR);

                mTaskList.add(task);
            }
            return convertView;
        }
    }

    private class SimpleAsyncTask extends AsyncTask<Void, Integer, Void> {
        private TaskItem mTaskItem;
        private String mName;

        public SimpleAsyncTask(TaskItem item) {
            mTaskItem = item;
            mName = "Task #" + String.valueOf(++ID);
        }

        @Override
        protected Void doInBackground(Void... params) {
            int prog = 1;
            while (prog < 101) {
                SystemClock.sleep(100);
                publishProgress(prog);
                prog++;
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
        }

        @Override
        protected void onPreExecute() {
            mTaskItem.setTitle(mName);
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            mTaskItem.setProgress(values[0]);
        }
    }
}
class TaskItem extends LinearLayout {
    private TextView mTitle;
    private ProgressBar mProgress;

    public TaskItem(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    public TaskItem(Context context) {
        super(context);
    }

    public void setTitle(String title) {
        if (mTitle == null) {
            mTitle = (TextView) findViewById(R.id.task_name);
        }
        mTitle.setText(title);
    }

    public void setProgress(int prog) {
        if (mProgress == null) {
            mProgress = (ProgressBar) findViewById(R.id.task_progress);
        }
        mProgress.setProgress(prog);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="10dip"
    android:paddingRight="10dip"
    android:orientation="vertical" >
    <ListView android:id="@+id/task_list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:divider="#cccccc"
        android:dividerHeight="0.6dip"
        android:footerDividersEnabled="true"
        android:headerDividersEnabled="true" />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<com.hilton.effectiveandroid.os.TaskItem xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="50dip"
    android:gravity="center_vertical"
    android:layout_gravity="center_vertical"
    android:orientation="horizontal" >
    <TextView android:id="@+id/task_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#ffff00"
        android:textSize="26sp" />
    <ProgressBar android:id="@+id/task_progress"
        android:layout_width="fill_parent"
        android:layout_height="15dip"
        android:max="100"
        style="@android:style/Widget.ProgressBar.Horizontal" />
</com.hilton.effectiveandroid.os.TaskItem >