关于AsyncTask异步执行任务Demo
public class MainActivity extends Activity { private String url = "https://cache..com/upload/information/20200311/46/200000.jpg"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); testTask(); } public void testTask(){ DownloadPicTask task = new DownloadPicTask(); task.imgPath = url; task.img = (ImageView) findViewById(R.id.p_w_picpathView1); task.execute(url); } }
//任务类
package com.example.task; import org.apache.http.HttpResponse; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.util.EntityUtils; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.AsyncTask; import android.util.Log; import android.widget.ImageView; public class DownloadPicTask extends AsyncTask<String, Integer, String>{ public String imgPath; private byte[] data; public ImageView img; protected void onPrepareExecute(){ Log.v("task", "onPrepareExecute"); super.onPreExecute(); } // doInBackground方法内部执行后台任务,不可在此方法内修改UI @Override protected String doInBackground(String... arg0) { // TODO Auto-generated method stub Log.v("task", "doInBackground " + arg0); HttpClient httpClient = new DefaultHttpClient(); HttpGet httpGet = new HttpGet(imgPath); HttpResponse httpResponse = null; try { httpResponse = httpClient.execute(httpGet); if (httpResponse.getStatusLine().getStatusCode() == 200) { data = EntityUtils.toByteArray(httpResponse .getEntity()); } } catch (Exception e) { e.printStackTrace(); } return null; } // onProgressUpdate方法用于更新进度信息 @Override protected void onProgressUpdate(Integer... progresses) { Log.v("task", "onProgressUpdate"); super.onProgressUpdate(progresses); } // onPostExecute方法用于在执行完后台任务后更新UI,显示结果 @Override protected void onPostExecute(String result) { // progressDialog.dismiss(); Log.v("task", "onPostExecute"); Bitmap bmp=BitmapFactory.decodeByteArray(data, 0, data.length); img.setImageBitmap(bmp); } // onCancelled方法用于在取消执行中的任务时更改UI @Override protected void onCancelled() { Log.v("task", "onCancelled"); } }
//。xml中只有一个ImageView控件