我是Android開發人員的新手，我一直在努力研究如何在向Mysql數據庫發出HTTP請求之後繪製一些圖形。我已經研究過SyncTask，自定義視圖和onDraw方法，但我必須缺少一些東西，因爲我無法讓它工作。基本上，http請求從db中選擇一些記錄（我得到了這個工作），我需要用數據創建一個圖。 http請求是一個異步進程，所以到http請求完成時，onDraw方法在沒有數據的情況下執行，這就是爲什麼我開始研究SyncTask但我無法設法傳遞存儲要繪製數據的數組來自onPostExecute方法。任何幫助將不勝感激，如果你可以指出一些很好的示例代碼。謝謝如何在httprequest之後實現對數據庫的提取
下面是我在網上找到的一些代碼，我一直在努力使它工作，到目前爲止我可以獲取數據，以簡化它我只使用字段位置，並且我想繪製文本位置：
public class TestFragment extends Fragment {
private static final String TAG = "AsyncTestFragment";
// get some fake data
private static final String TEST_URL = "http://jsonplaceholder.typicode.com/comments";
//private static final String TEST_URL = "http://localhost/~juan/A_get_tanks.php";
private static final String ACTION_FOR_INTENT_CALLBACK = "THIS_IS_A_UNIQUE_KEY_WE_USE_TO_COMMUNICATE";
ProgressDialog progress;
@Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_test, container, false);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
getContent();
}
private void getContent() {
// the request
try {
HttpGet httpGet = new HttpGet(new URI(TEST_URL));
RestTask task = new RestTask(getActivity(), ACTION_FOR_INTENT_CALLBACK);
task.execute(httpGet);
progress = ProgressDialog.show(getActivity(), "Getting Data ...", "Waiting For Results...", true);
}
catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}
@Override
public void onResume() {
super.onResume();
getActivity().registerReceiver(receiver, new IntentFilter(ACTION_FOR_INTENT_CALLBACK));
}
@Override
public void onPause() {
super.onPause();
getActivity().unregisterReceiver(receiver);
}
/**
* Our Broadcast Receiver. We get notified that the data is ready, and then we
* put the content we receive (a string) into the TextView.
*/
public BroadcastReceiver receiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String location;
// clear the progress indicator
if (progress != null) {
progress.dismiss();
}
String response = intent.getStringExtra(RestTask.HTTP_RESPONSE);
try {
JSONObject mainObject = new JSONObject(response);
JSONArray tank_data = mainObject.getJSONArray("tank_data");
JSONObject tankObj = tank_data.getJSONObject(0);
location = (String) tankObj.getString("Location");
} catch (JSONException e) {
location = null;
e.printStackTrace();
}
new TankView(context, location);
Log.i(TAG, "RESPONSE = " + location);
}
};
}
public class RestTask extends AsyncTask<HttpUriRequest, Void, String>
{
private static final String TAG = "AsyncRestTask";
public static final String HTTP_RESPONSE = "httpResponse";
private Context mContext;
private HttpClient mClient;
private String mAction;
public RestTask(Context context, String action) {
mContext = context;
mAction = action;
mClient = new DefaultHttpClient();
}
public RestTask(Context context, String action, HttpClient client) {
mContext = context;
mAction = action;
mClient = client;
}
@Override
protected String doInBackground(HttpUriRequest... params) {
try {
HttpUriRequest request = params[0];
HttpResponse serverResponse = mClient.execute(request);
BasicResponseHandler handler = new BasicResponseHandler();
return handler.handleResponse(serverResponse);
}
catch (Exception e) {
// TODO handle this properly
e.printStackTrace();
return "";
}
}
@Override
protected void onPostExecute(String result) {
Log.i(TAG, "RESULT = " + result);
Intent intent = new Intent(mAction);
intent.putExtra(HTTP_RESPONSE, result);
// broadcast the completion
mContext.sendBroadcast(intent);
}
}
package com.alvinalexander.asynctest;
import android.app.Activity;
import android.content.res.Configuration;
import android.os.Bundle;
public class TestActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
TestFragment testFragment = new TestFragment();
getFragmentManager().beginTransaction().add(android.R.id.content, testFragment).commit();
setContentView(new TankView(this, ""));
}
}
}
public class TankView extends View {
private String location;
private Paint _paintTank = new Paint();
public TankView(Context context, String location) {
super(context);
// TODO Auto-generated constructor stub
init(null, 0);
this.location = location;
}
public TankView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
init(attrs, 0);
}
public TankView(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
init(attrs, 0);
}
public TankView(TestActivity testActivity, String location) {
super(testActivity);
this.location = location;
}
public TankView(TestActivity testActivity, Object o) {
super(testActivity, (AttributeSet) o);
}
private void init(AttributeSet attrs, int defStyle) {
_paintTank.setColor(Color.RED);
_paintTank.setAntiAlias(true);
_paintTank.setStyle(Paint.Style.STROKE);
}
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (this.location != null) {
canvas.drawText(this.location, 10, 10, _paintTank);
}
}
}
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:background="#AEECFF">
<!-- fill the screen with a textview. the app will write text into it. -->
<com.alvinalexander.asynctest.TankView
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
向我們顯示您的代碼。 –