安卓学习-界面-事件-AsyncTask

异步任务Asynctask完成一个下载

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"
    tools:context="${relativePackage}.${activityClass}" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="23dp"
        android:layout_marginTop="14dp"
        android:text="开始下载" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button1"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/button1"
        android:layout_marginTop="45dp"
        android:ems="10"
        android:inputType="textMultiLine" >

        <requestFocus />
    </EditText>

</RelativeLayout>

MainActivity.java

public class MainActivity extends Activity {

    EditText editText1;
    Button btn1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editText1=(EditText)findViewById(R.id.editText1);
        btn1=(Button)findViewById(R.id.button1);
        btn1.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                MyDown down=new MyDown(MainActivity.this);
                try {
                    down.execute(new URL("http://w.x.baidu.com/alading/anquan_soft_down_normal/12350"));
                } catch (MalformedURLException e) {
                    // TODO 自动生成的 catch 块
                    e.printStackTrace();
                }

            }
        });
    }

    class MyDown extends AsyncTask<URL, Integer, String>{
        //下载进度
        ProgressDialog p;
        //总下载量
        int totalSize=0;
        //当前下载
        int downloadSzie=0;
        Context context;
        //下载开始时间
        Calendar date_s=Calendar.getInstance();
        //下载结束时间
        Calendar date_e;
        public MyDown(Context context){
            this.context=context;
        }

        @Override
        protected void onPreExecute() {
             p=new ProgressDialog(context);
             p.setMax(0);
             p.setTitle("任务执行中");
             p.setMessage("任务执行完成比，请等待......");
             p.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
             p.setCancelable(false);
             p.setIndeterminate(false);
             p.show();
        }

        @Override
        protected String doInBackground(URL... params) {
            StringBuffer str=new StringBuffer();
            try {
                HttpURLConnection http=(HttpURLConnection)params[0].openConnection();
                //获取总下载量
                totalSize=http.getContentLength();
                InputStream in=http.getInputStream();

                byte[] buffer =new byte[1024];
                int readSize=0;
                while ((readSize=in.read(buffer))!=-1){
                    date_e=Calendar.getInstance();
                    //计算下载的总时间，主要是用于计算  K/S
                    int a=(int)(date_e.getTimeInMillis()-date_s.getTimeInMillis())/1000;

                    //总下载数
                    downloadSzie =downloadSzie +readSize;
                    //刷新UI
                    publishProgress(downloadSzie,totalSize,a);
                }

                return str.toString();

            } catch (Exception e) {
                // TODO 自动生成的 catch 块
                e.printStackTrace();
            }

            return null;
        }

        protected void onPostExecute(String result) {
            editText1.setText("下载完成");
            p.dismiss();
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            p.setProgress(values[0]/1024);
            p.setMax(values[1]/1024);
            int sed=0;
            if(values[2]==0) sed=1;else sed=values[0]/1024/values[2];
            p.setMessage("任务执行完成比，请等待......\n 速度 "+sed+" K/S");
        }

    }
}