看了一下volley框架的简单demo,发现使用后,如获取Json文件之类的,所写的代码非常的简单
如
public class JsonRequestAcitivity extends Activity implements OnClickListener,Listener<JSONObject>,ErrorListener{ private Button requestBtn; private TextView dispText; RequestQueue rq; Request request; private static final String URL = "http://httpbin.org/get?param1=hello"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_json_request); requestBtn = (Button) findViewById(R.id.requestBtn); dispText = (TextView) findViewById(R.id.dispText); requestBtn.setOnClickListener(this); } @Override public void onClick(View v) { dispText.setText("请求中..."); doJsonRequest(); } private void doJsonRequest() { //第三个参数 //A JSONObject to post with the request. Null is allowed and indicates no parameters will be posted along with request. JsonObjectRequest jsonObjectRequest = new JsonObjectRequest( Request.Method.GET,URL,null, JsonRequestAcitivity.this,JsonRequestAcitivity.this); jsonObjectRequest.setTag(JsonRequestAcitivity.class.getSimpleName());//设置tag callAll的时候使用 VolleyTool.getInstance(this).getmRequestQueue().add(jsonObjectRequest); } @Override public void onResponse(JSONObject response) { //success dispText.setText("Success::"+response.toString()); } @Override public void onErrorResponse(VolleyError error) { dispText.setText("Fail::"+error.toString()); } @Override protected void onDestroy() { super.onDestroy(); VolleyTool.getInstance(this).getmRequestQueue().cancelAll(JsonRequestAcitivity.class.getSimpleName()); } }显而易见,TextView中的setText方法并无直接的调用,而数据之间传递和交互只在那句简单的
VolleyTool.getInstance(this).getmRequestQueue().add(jsonObjectRequest);
首先是实例化一个VolleyTool,然后获取一个请求队列,然后将jsonObjectRequest放入队列之中执行;
而VolleyTool文件中,最关键的一句便是
mRequestQueue = Volley.newRequestQueue(context);
public class VolleyTool { private static VolleyTool mInstance = null; private RequestQueue mRequestQueue; private ImageLoader mImageLoader; private VolleyTool(Context context) { mRequestQueue = Volley.newRequestQueue(context); mImageLoader = new ImageLoader(mRequestQueue, new BitmapCache()); } public static VolleyTool getInstance(Context context){ if(mInstance == null){ mInstance = new VolleyTool(context); } return mInstance; } public RequestQueue getmRequestQueue() { return mRequestQueue; } public ImageLoader getmImageLoader() { return mImageLoader; } public void release() { this.mImageLoader = null; this.mRequestQueue = null; mInstance = null; } }因为这一句话,直接从Volley.jar包中调用了volley的这个类,从而获取里面的方法。
public class Volley { /** Default on-disk cache directory. */ private static final String DEFAULT_CACHE_DIR = "volley"; /** * Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it. * * @param context A {@link Context} to use for creating the cache dir. * @param stack An {@link HttpStack} to use for the network, or null for default. * @return A started {@link RequestQueue} instance. */ public static RequestQueue newRequestQueue(Context context, HttpStack stack) { File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR); String userAgent = "volley/0"; try { String packageName = context.getPackageName(); PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0); userAgent = packageName + "/" + info.versionCode; } catch (NameNotFoundException e) { } if (stack == null) { if (Build.VERSION.SDK_INT >= 9) { stack = new HurlStack(); } else { // Prior to Gingerbread, HttpUrlConnection was unreliable. // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html stack = new HttpClientStack(AndroidHttpClient.newInstance(userAgent)); } } Network network = new BasicNetwork(stack); RequestQueue queue = new RequestQueue(new DiskBasedCache(cacheDir), network); queue.start(); return queue; } /** * Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it. * * @param context A {@link Context} to use for creating the cache dir. * @return A started {@link RequestQueue} instance. */ public static RequestQueue newRequestQueue(Context context) { return newRequestQueue(context, null); } }而后,从代码中显而易见的是queue.start()方法的执行,就可以从RequestQueue中的networkparseResponse()方法,获取真正的response并实例化。
若是自己也下载了这个volley.jar,便可以知道,实例化时所用的构造方法中,调用了success()方法,从而间接的实现了文本的获取。
-总结:
- 要活用eclipse中的search功能,一步一步的解析问题,把问题简单话。
-不懂解压包里面的文件就解压出来,一步步看,还可以改写。