Android AsyncTask 异步任务操作

1：activity_main.xml

<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"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context=".MainActivity" >    <TextView        android:id="@+id/tvInfo"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/hello_world" />        <ProgressBar            android:layout_below="@id/tvInfo"         android:id="@+id/asyncPb"             style="?android:attr/progressBarStyleHorizontal"          android:layout_width="fill_parent"            android:layout_height="wrap_content"           android:visibility="gone"           />  </RelativeLayout>

2:MainActivity.java

package com.example.async;import android.os.AsyncTask;import android.os.Bundle;import android.view.View;import android.widget.ProgressBar;import android.widget.TextView;import android.app.Activity;public class MainActivity extends Activity {    private ProgressBar asyncPb = null;    private TextView tvInfo = null;        @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                tvInfo = (TextView)findViewById(R.id.tvInfo);                String params = "Welcome to here";        new MyAsyncTask().execute(params);    }        private class MyAsyncTask extends AsyncTask<String, Integer, String>{        @Override          protected void onPreExecute() {              //做一些预处理            asyncPb = (ProgressBar)findViewById(R.id.asyncPb);            asyncPb.setVisibility(View.VISIBLE);        }                @Override        protected String doInBackground(String... params) {            //执行耗时操作，网络任务、文件操作、数据库操作、复杂计算操作            int myProgress = 0;            int length = params[0].length();                        for(int i=1; i<=length; i++){                myProgress = i;                //模拟耗时操作                try {                    Thread.sleep(300);                } catch (InterruptedException e) {                    e.printStackTrace();                }                publishProgress((int)((myProgress/(float)length)*100));            }                        //它将传递给onPostExecute            return params[0];        }                @Override        protected void onProgressUpdate(Integer... values) {            //更新进度条            asyncPb.setProgress(values[0]);            tvInfo.setText("已加载："+(values[0])+"%");        }        @Override        protected void onPostExecute(String result) {            //更新UI            tvInfo.setText("加载完成："+result);        }    }}

更多相关文章

随机推荐