Android 下载 网络图片

xml 新建一个ImageView，叫做“show”

流程：

1.新建一个URL类，它是图片的地址

2.用输入流得到URL的地址

3.解析图片为bmp bitmap = BitmapFactory.decodeStream(is);

4.发送Handler到主线程，改变UI

5.结束 is.close();

Java代码：

package com.example.leon.myapplication;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageView;

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


public class MyActivity extends Activity {

   ImageView show;
    //downloaded from internet
    Bitmap bitmap;
    Handler handler = new Handler()
    {
        @Override
        public void handleMessage(Message   msg)
        {
            if(msg.what==0x123)
            {
                show.setImageBitmap(bitmap);
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        show = (ImageView)findViewById(R.id.show);
        new Thread(new Runnable() {
            @Override
            public void run() {
                try{
                    URL url = new URL("http://www.baidu.com/search/img/logo.gif");
                    InputStream is = url.openStream();
                    bitmap = BitmapFactory.decodeStream(is);
                    handler.sendEmptyMessage(0x123);
                    is.close();
                    //filestream
                    is = url.openStream();
                    //Output stream to SDcard
                    OutputStream os = openFileOutput("baidu.gif",MODE_WORLD_READABLE);
                    byte[] buff = new byte[1024];
                    int hasRead = 0;
                    while( hasRead = is.read(buff)>0)
                    {
                        os.write(buff,0,hasRead);
                    }
                    is.close();
                    os.close();

                }
                catch (Exception e)
                {
                    e.printStackTrace();
                }
            }
        }).start();
    }


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