嗨，我根据本教程从 http 服务器创建了解析 JSON 。但我想从 sdcard 解析这个 JSON 文件。我可以使用 Environment.getExternalStorageDirectory().getAbsolutePath() 打印 json 文件位置，但我不知道如何更改 AsyncTask 读取文件。有人可以帮我做这件事吗？（我是 android 开发新手）代码如下所示：
public class ClientActivity extends Activity {
TextView capitalTextView;
ProgressDialog progressDialog;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main1);
capitalTextView = (TextView) findViewById(R.id.capital_textview);
this.retrieveCapitals();
}
void retrieveCapitals() {
progressDialog = ProgressDialog.show(this,
"Please wait...", "Retrieving data...", true, true);
CapitalsRetrieverAsyncTask task = new CapitalsRetrieverAsyncTask();
task.execute();
progressDialog.setOnCancelListener(new CancelListener(task));
}
private class CapitalsRetrieverAsyncTask extends AsyncTask<Void, Void, Void> {
Response response;
@Override
protected Void doInBackground(Void... params) {
String url = "http://sample.com/sample_data.json";
HttpGet getRequest = new HttpGet(url);
File file = new File( Environment.getExternalStorageDirectory().getAbsolutePath() + "/example.json");
System.out.println(file);
try {
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpResponse getResponse = httpClient.execute(getRequest);
final int statusCode = getResponse.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK) {
Log.w(getClass().getSimpleName(), "Error " + statusCode + " for URL " + url);
return null;
}
HttpEntity getResponseEntity = getResponse.getEntity();
InputStream httpResponseStream = getResponseEntity.getContent();
Reader inputStreamReader = new InputStreamReader(httpResponseStream);
Gson gson = new Gson();
this.response = gson.fromJson(inputStreamReader, Response.class);
System.out.println(this.response);
}
catch (IOException e) {
getRequest.abort();
Log.w(getClass().getSimpleName(), "Error for URL " + url, e);
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
StringBuilder builder = new StringBuilder();
for (Shop shop : this.response.shops) {
builder.append(String.format("<br>ID: <b>%s</b><br>Shop: <b>%s</b><br>Description: <b>%s</b><br><br>", shop.getId(), shop.getName(), shop.getDescription()));
}
capitalTextView.setText(Html.fromHtml(builder.toString()));
progressDialog.cancel();
}
}
private class CancelListener implements OnCancelListener {
AsyncTask<?, ?, ?> cancellableTask;
public CancelListener(AsyncTask<?, ?, ?> task) {
cancellableTask = task;
}
@Override
public void onCancel(DialogInterface dialog) {
cancellableTask.cancel(true);
}
}
}