网络图片查看器

public class MainActivity extends Activity implements OnClickListener {

    private static final String TAG = "MainActivity";
    protected static final int ERROR = 1;
    private EditText etUrl;
    private ImageView ivIcon;
    private final int SUCCESS = 0;
    
    private Handler handler = new Handler() {

        /**
         * 接收消息
         */
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            
            Log.i(TAG, "what = " + msg.what);
            if(msg.what == SUCCESS) {    // 当前是访问网络, 去显示图片
                ivIcon.setImageBitmap((Bitmap) msg.obj);        // 设置imageView显示的图片
            } else if(msg.what == ERROR) {
                Toast.makeText(MainActivity.this, "抓取失败", 0).show();
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        ivIcon = (ImageView) findViewById(R.id.iv_icon);
        etUrl = (EditText) findViewById(R.id.et_url);
        
        findViewById(R.id.btn_submit).setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        final String url = etUrl.getText().toString();
        
        new Thread(new Runnable() {

            @Override
            public void run() {
                Bitmap bitmap = getImageFromNet(url);

//                ivIcon.setImageBitmap(bitmap);        // 设置imageView显示的图片
                if(bitmap != null) {
                    Message msg = new Message();
                    msg.what = SUCCESS;
                    msg.obj = bitmap;
                    handler.sendMessage(msg);
                } else {
                    Message msg = new Message();
                    msg.what = ERROR;
                    handler.sendMessage(msg);
                }
            }}).start();
        
    }

    /**
     * 根据url连接取网络抓去图片返回
     * @param url
     * @return url对应的图片
     */
    private Bitmap getImageFromNet(String url) {
        HttpURLConnection conn = null;
        try {
            URL mURL = new URL(url);    // 创建一个url对象
            
            // 得到http的连接对象
            conn = (HttpURLConnection) mURL.openConnection();
            
            conn.setRequestMethod("GET");        // 设置请求方法为Get
            conn.setConnectTimeout(10000);        // 设置连接服务器的超时时间, 如果超过10秒钟, 没有连接成功, 会抛异常
            conn.setReadTimeout(5000);        // 设置读取数据时超时时间, 如果超过5秒, 抛异常
            
            conn.connect();        // 开始链接
            
            int responseCode = conn.getResponseCode(); // 得到服务器的响应码
            if(responseCode == 200) {
                // 访问成功
                InputStream is = conn.getInputStream();    // 获得服务器返回的流数据
                
                Bitmap bitmap = BitmapFactory.decodeStream(is); // 根据 流数据 创建一个bitmap位图对象
                
                return bitmap;
            } else {
                Log.i(TAG, "访问失败: responseCode = " + responseCode);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if(conn != null) {
                conn.disconnect();        // 断开连接
            }
        }
        return null;
    }
}