Android之异步加载网络图片

<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="com.example.android_imagetest.MainActivity" >

<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginLeft="60dp"
android:layout_marginTop="40dp"
/>

</RelativeLayout>

<uses-permission android:name="android.permission.INTERNET"/>

package com.example.android_imagetest;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.support.v7.app.ActionBarActivity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageView;

public class MainActivity extends ActionBarActivity {

private ImageView imageView;
private ProgressDialog dialog;
private final String IMAGE_PATH="https://ss0.bdstatic.com/5aV1bjqh_Q23odCf/static/superman/img/logo/bd_logo1_31bdc765.png";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView=(ImageView) this.findViewById(R.id.imageView1);
dialog=new ProgressDialog(MainActivity.this);
dialog.setTitle("提示");
dialog.setMessage("Loading...");
new MyTask().execute(IMAGE_PATH);

}

public class MyTask extends AsyncTask<String, Void, Bitmap>{

@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
dialog.show();
}

@Override
protected Bitmap doInBackground(String... params) {
// TODO Auto-generated method stub
Bitmap bitmap=null;
try {
URL url=new URL(params[0]);
HttpURLConnection connection=(HttpURLConnection) url.openConnection();
connection.setDoInput(true);
connection.connect();

InputStream inputStream=connection.getInputStream();
bitmap=BitmapFactory.decodeStream(inputStream);
inputStream.close();
}catch(Exception e){
// TODO: handle exception
e.printStackTrace();
}

return bitmap;
}

@Override
protected void onPostExecute(Bitmap result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
imageView.setImageBitmap(result);
dialog.dismiss();
}

}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}