访问网络图片

public class MainActivity extends Activity implements OnClickListener{

protected static final String TAG = "MainActivity";
ImageView image = null;
EditText edit = null;

Handler handler = new Handler(){

//接收一个消息
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);

if(msg.what == 1)
{
Bitmap bitmap = (Bitmap) msg.obj;
image.setImageBitmap(bitmap);
}

}
};

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

image = (ImageView) findViewById(R.id.img);
edit = (EditText) findViewById(R.id.et_net);
Button button = (Button) findViewById(R.id.bt_get);

button.setOnClickListener(this);
}

/**
* 1.访问网络不能直接放在主方法里面（android.os.NetworkOnMainThreadException）,应该放在一个线程里面
* 2. android.view.ViewRootImpl$CalledFromWrongThreadException: 只能在主线程或者UI线程里面修改视图,应该用通信来解决

*
*/
@Override
public void onClick(View v)
{
final String uri = edit.getText().toString();//拿到图片的网络地址

new Thread(new Runnable() {

@Override
public void run() {
Bitmap bitmap = getImageFromNet(uri);
if(null != bitmap)
{
Message msg = new Message();
msg.what = 1; //你是谁
msg.obj = bitmap;

handler.sendMessage(msg); //发送一个消息

//image.setImageBitmap(bitmap);
Log.i(TAG, "========" + bitmap);
}else
{
//Toast.makeText(MainActivity.this, "获取图片失败", 0).show();
}
}
}).start();

}

//返回的不是image了 返回的是bitmap >> 位图
public Bitmap getImageFromNet(String uri)
{
HttpURLConnection conn = null;

try {
//1.首先将地址转换为Uri
//Uri net_uri = Uri.parse(uri); //这种方式是错误的
URL url = new URL(uri);

//2. 获取网络连接
conn = (HttpURLConnection) url.openConnection();//这个地方要转换一次，转换为你获取图片的协议连接

//3. 设置请求的一些常用的参数
conn.setConnectTimeout(30000);//设置超时
conn.setDoInput(true); //设置请求可以放服务器写入数据
conn.setReadTimeout(30000); //设置连接去读取数据的超时时间

//4.真正请求图片,然后把从网络上请求到的二进制流保存到了inputStream里面
conn.connect();

InputStream in = conn.getInputStream();

Bitmap bitmap = BitmapFactory.decodeStream(in);//BitMap的图片工厂，创建出一个图片

return bitmap;

} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally
{
//5. 关闭连接
if(null != conn)
{
conn.disconnect();
}
}

return null;
}
}