public class MainActivity extends AppCompatActivity {
    protected static final int CHANGE_UI = 1;
    protected static final int ERROR = 2;
    private EditText et_path;
    private ImageView ivPic;
    private Handler handler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            if (msg.what == CHANGE_UI) {
                Bitmap bitmap = (Bitmap) msg.obj;
                ivPic.setImageBitmap(bitmap);
            } else if (msg.what == ERROR) {
                Toast.makeText(MainActivity.this, "显示图片错误",
                        Toast.LENGTH_SHORT).show();
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_path = (EditText) findViewById(R.id.et_path);
        ivPic = (ImageView) findViewById(R.id.iv_pic);
    }
    public void click(View view) {
        final String path = et_path.getText().toString().trim();
        if (TextUtils.isEmpty(path)) {
            Toast.makeText(this, "图片路径不能为空", Toast.LENGTH_SHORT).show();
        } else {
             new Thread() {
                private HttpURLConnection conn;
                private Bitmap bitmap;
                public void run() {
                     try {
                       URL url = new URL(path);
                       conn = (HttpURLConnection) url.openConnection();
                       conn.setRequestMethod("GET");
                       conn.setConnectTimeout(5000);
                       int code = conn.getResponseCode();
                       if (code == 200) {
                          InputStream is = conn.getInputStream();
                          bitmap = BitmapFactory.decodeStream(is);
                          Message msg = new Message();
                            msg.what = CHANGE_UI;
                            msg.obj = bitmap;
                            handler.sendMessage(msg);
                        } else {
                           Message msg = new Message();
                            msg.what = ERROR;
                            handler.sendMessage(msg);
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                        Message msg = new Message();
                        msg.what = ERROR;
                        handler.sendMessage(msg);
                    }
                    conn.disconnect();
                }
            }.start();
        }
    }
}