最終更新:2017-02-11 (土) 09:10:40 (2628d)
android.os.AsyncTask
Top / android.os.AsyncTask
public abstract class android.os.AsyncTask<Params, Progress, Result>
AsyncTask enables proper and easy use of the UI thread.
http://developer.android.com/reference/android/os/AsyncTask.html
使い方
- defined by 3 generic types, called Params, Progress and Result,
- and 4 steps, called onPreExecute?, doInBackground?, onProgressUpdate? and onPostExecute?.
パラメータ
- final AsyncTask<Params, Progress, Result>
Params
Progress
Result
メモ
- AsyncTaskはExecutorによってAsyncTaskを複数実行したときの挙動が決まる
- API11以降ではTHREAD_POOL_EXECUTOR, SERIAL_EXECUTORが選べ、デフォルトはSERIAL_EXECUTOR
用途
- 数秒の処理用
- 特定の画面を見ている間に裏で処理をする
長い処理
親クラス
メソッド
- AsyncTask.onPreExecute?()
- AsyncTask.doInBackground(Params... params) - 処理
- AsyncTask.onProgressUpdate?()
- AsyncTask.onPostExecute() - 結果 (このメソッドはUIスレッド上で実行される)
- AsyncTask.execute?
概要
- You can specify the type of the parameters, the progress values, and the final value of the task, using generics
- The method doInBackground() executes automatically on a worker thread onPreExecute?(), onPostExecute?(), and onProgressUpdate?() are all invoked on the UI thread
- The value returned by doInBackground?() is sent to onPostExecute?()
- You can call publishProgress() at anytime in doInBackground?() to execute onProgressUpdate?() on the UI thread
- You can cancel the task at any time, from any thread
動作
- AsyncTask.onPreExecute? - invoked on the UI thread before the task is executed.
- AsyncTask.doInBackground - invoked on the background thread immediately after onPreExecute?() finishes executing.
- AsyncTask.onProgressUpdate? - invoked on the UI thread after a call to publishProgress(Progress...).
- AsyncTask.onPostExecute - invoked on the UI thread after the background computation finishes.
