最近学习安卓，今天看下安卓异步加载图片的坑。。。

屏幕快照 2017-03-01 下午5.08.29.png

//按钮的点击事件中，创建新线程，调用 getImage()方法获得图片回调，若不为空利用Handler发送消息更新UI
@Override
    public void onClick(View v) {
        final String url = editText.getText().toString();
        new Thread(new Runnable() {
            @Override
            public void run() {
                bitmap = getImage(url);
                if (bitmap != null) {
                    Message msg = new Message();
                    msg.obj = bitmap;
                    msg.what = 1;
                    handler.sendMessage(msg);
                }
            }

        }).start();
    }

坑1

handler.sendMessage();

此方法一直爆红，查看API，发现有 android.os.Handler java.util.logging.Handler 两个包，导错了包。

坑2

private Bitmap getImage(String url) {
        HttpURLConnection connection = null;
        try {
            URL myurl = new URL(url);
            connection = (HttpURLConnection) myurl.openConnection();
            connection.setConnectTimeout(10000);
            connection.setReadTimeout(5000);
            connection.setRequestMethod("GET");
            connection.connect();
            int responseCode = connection.getResponseCode();
            if (responseCode == 200) {
                InputStream inputStream = connection.getInputStream();
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);//根据读数据创建位图对象
               // Toast.makeText(this, "success" + responseCode, Toast.LENGTH_LONG).show();
                return bitmap;
            } else {
                //Toast.makeText(this, "NONONO" + responseCode, Toast.LENGTH_LONG).show();
            }
        } catch (Exception e) {
            e.printStackTrace();
          //  Toast.makeText(this, "NONONO" + e, Toast.LENGTH_LONG).show();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
        return null;
    }

点击获取图片就崩溃，原因，

       Toast.makeText(this, "success" + responseCode, Toast.LENGTH_LONG).show();

Toast 属于UI操作，放在了子线程导致崩溃。

总结下来就是，刷新UI必须在主线程，网络请求必须在子线程。安卓的包是坑。。。。