我正在学习C而且我很难理解两个指针之间的区别
double **X;
和
double** X;
两者都一样吗？
还有一个问题。
我们什么时候实际上使用指针来指向上面**X
答案 0 :(得分：0)
这两个例子都是一样的。它将//Downloading data asynchronously
public class AsyncHttpTask extends AsyncTask<String, Void, Integer> {
@Override
protected Integer doInBackground(String... params) {
Integer result = 0;
try {
// Create Apache HttpClient
HttpClient httpclient = new DefaultHttpClient();
HttpResponse httpResponse = httpclient.execute(new HttpGet(params[0]));
int statusCode = httpResponse.getStatusLine().getStatusCode();
// 200 represents HTTP OK
if (statusCode == 200) {
String response = streamToString(httpResponse.getEntity().getContent());
parseResult(response);
result = 1; // Successful
} else {
result = 0; //"Failed
}
} catch (Exception e) {
Log.d(TAG, e.getLocalizedMessage());
}
return result;
}
@Override
protected void onPostExecute(Integer result) {
// Download complete. Let us update UI
if (result == 1) {
mGridAdapter.setGridData(mGridImages);
mGridAdapter.notifyDataSetChanged();
} else {
Toast.makeText(MainActivity.this, "No Connection found,Check your Connection!", Toast.LENGTH_SHORT).show();
}
mProgressBar.setVisibility(View.GONE);
}
}
String streamToString(InputStream stream) throws IOException {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stream));
String line;
String result = "";
while ((line = bufferedReader.readLine()) != null) {
result += line;
}
// Close stream
if (null != stream) {
stream.close();
}
return result;
}
/**
* Parsing the feed results and get the list
* @param result
*/
private void parseResult(String result) {
try {
JSONObject response = new JSONObject(result);
JSONArray posts = response.optJSONArray("result");
GridImages item;
for (int i = 0; i < posts.length(); i++) {
JSONObject post = posts.optJSONObject(i);
String title = post.optString("name");
String image=post.optString("path");
item = new GridImages();
item.Settitle(title);
item.Setimage(image);
// JSONArray attachments = post.getJSONArray("attachments");
// if (null != attachments && attachments.length() > 0) {
// JSONObject attachment = attachments.getJSONObject(0);
// if (attachment != null)
// item.Setimage(attachment.getString("url"));
//}
mGridImages.add(item);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
的类型定义为指向double的指针。
数组是一个连续的内存片段，您可以通过指向它的第一个元素来访问它。如果你有一个数组数组，那么它的类型是X。
例如，字符串是字符数组，以'\ 0'字节结尾。所以字符串数组的类型为'whatever element type is'**
示例用法非常常见，char**函数，可以声明如下
main()所以int main(int argc, char** argv)
是一个字符串数组，它们是参数或程序，argv是它的长度。