当我尝试使用下面的代码连接Mysql DataBase时出现此错误。目标是将新产品添加到数据库中。
04-08 14:13:10.440: E/AndroidRuntime(1568): FATAL EXCEPTION: AsyncTask #2
04-08 14:13:10.440: E/AndroidRuntime(1568): Process: com.example.androidmanifest, PID: 1568
04-08 14:13:10.440: E/AndroidRuntime(1568): java.lang.RuntimeException: An error occured while executing doInBackground()
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.os.AsyncTask$3.done(AsyncTask.java:300)
04-08 14:13:10.440: E/AndroidRuntime(1568): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
04-08 14:13:10.440: E/AndroidRuntime(1568): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
04-08 14:13:10.440: E/AndroidRuntime(1568): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
04-08 14:13:10.440: E/AndroidRuntime(1568): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
04-08 14:13:10.440: E/AndroidRuntime(1568): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
04-08 14:13:10.440: E/AndroidRuntime(1568): at java.lang.Thread.run(Thread.java:841)
04-08 14:13:10.440: E/AndroidRuntime(1568): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.os.Handler.<init>(Handler.java:200)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.os.Handler.<init>(Handler.java:114)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.app.Dialog.<init>(Dialog.java:109)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.app.AlertDialog.<init>(AlertDialog.java:114)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.app.AlertDialog.<init>(AlertDialog.java:98)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.app.ProgressDialog.<init>(ProgressDialog.java:77)
04-08 14:13:10.440: E/AndroidRuntime(1568): at com.example.androidmanifest.load.NewProduct.onPreExecute(NewProduct.java:46)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.os.AsyncTask.execute(AsyncTask.java:535)
04-08 14:13:10.440: E/AndroidRuntime(1568): at com.example.androidmanifest.AddProductActivity$CreateNewProduct.doInBackground(AddProductActivity.java:89)
04-08 14:13:10.440: E/AndroidRuntime(1568): at com.example.androidmanifest.AddProductActivity$CreateNewProduct.doInBackground(AddProductActivity.java:1)
04-08 14:13:10.440: E/AndroidRuntime(1568): at android.os.AsyncTask$2.call(AsyncTask.java:288)
04-08 14:13:10.440: E/AndroidRuntime(1568): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
04-08 14:13:10.440: E/AndroidRuntime(1568): ... 4 more
04-08 14:13:13.440: I/Choreographer(1568): Skipped 41 frames! The application may be doing too much work on its main thread.
04-08 14:13:14.380: E/WindowManager(1568): android.view.WindowLeaked: Activity com.example.androidmanifest.AddProductActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{b4d56a20 V.E..... R.....ID 0,0-304,96} that was originally added here
04-08 14:13:14.380: E/WindowManager(1568): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:348)
04-08 14:13:14.380: E/WindowManager(1568): at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:248)
04-08 14:13:14.380: E/WindowManager(1568): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
04-08 14:13:14.380: E/WindowManager(1568): at android.app.Dialog.show(Dialog.java:286)
04-08 14:13:14.380: E/WindowManager(1568): at com.example.androidmanifest.AddProductActivity$CreateNewProduct.onPreExecute(AddProductActivity.java:76)
04-08 14:13:14.380: E/WindowManager(1568): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
04-08 14:13:14.380: E/WindowManager(1568): at android.os.AsyncTask.execute(AsyncTask.java:535)
04-08 14:13:14.380: E/WindowManager(1568): at com.example.androidmanifest.AddProductActivity$1.onClick(AddProductActivity.java:56)
04-08 14:13:14.380: E/WindowManager(1568): at android.view.View.performClick(View.java:4438)
04-08 14:13:14.380: E/WindowManager(1568): at android.view.View$PerformClick.run(View.java:18422)
04-08 14:13:14.380: E/WindowManager(1568): at android.os.Handler.handleCallback(Handler.java:733)
04-08 14:13:14.380: E/WindowManager(1568): at android.os.Handler.dispatchMessage(Handler.java:95)
04-08 14:13:14.380: E/WindowManager(1568): at android.os.Looper.loop(Looper.java:136)
04-08 14:13:14.380: E/WindowManager(1568): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-08 14:13:14.380: E/WindowManager(1568): at java.lang.reflect.Method.invokeNative(Native Method)
04-08 14:13:14.380: E/WindowManager(1568): at java.lang.reflect.Method.invoke(Method.java:515)
04-08 14:13:14.380: E/WindowManager(1568): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-08 14:13:14.380: E/WindowManager(1568): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-08 14:13:14.380: E/WindowManager(1568): at dalvik.system.NativeStart.main(Native Method)
这是我的活动课：
public class AddProductActivity extends Activity {
// Progress Dialog
private ProgressDialog pDialog;
JSONParser jsonParser = new JSONParser();
EditText inputName;
EditText inputPrice;
EditText inputDesc;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_product);
// Edit Text
inputName = (EditText) findViewById(R.id.inputName);
inputPrice = (EditText) findViewById(R.id.inputPrice);
inputDesc = (EditText) findViewById(R.id.inputDesc);
// Create button
Button btnCreateProduct = (Button) findViewById(R.id.btnCreateProduct);
// button click event
btnCreateProduct.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// creating new product in background thread
new CreateNewProduct().execute();
}
});
}
/**
* Background Async Task to Create new product
* */
class CreateNewProduct extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AddProductActivity.this);
pDialog.setMessage("Creating Product..");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* Creating product
* */
protected String doInBackground(String... args) {
String name = inputName.getText().toString();
String price = inputPrice.getText().toString();
String description = inputDesc.getText().toString();
// Building Parameters
NewProduct newProduct = new NewProduct(AddProductActivity.this, name, Integer.parseInt(price), description);
newProduct.execute();
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once done
pDialog.dismiss();
}
}
}
添加新产品类：
public class NewProduct extends AsyncTask<String, String, String> {
private String url_all_products = "http://127.0.0.1/Android/create_product.php";
private static final String TAG_SUCCESS = "success";
private ProgressDialog pDialog;
private Context context;
JSONParser jParser = new JSONParser();
private ArrayList<String> points = new ArrayList<String>();
private String name;
private int price;
private String desc;
public ArrayList<String> getPoints() {
return points;
}
/**
* Before starting background thread Show Progress Dialog
* */
public NewProduct(Context context, String name, int price, String desc){
this.context = context;
this.name=name;
this.price=price;
this.desc = desc;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(context);
pDialog.setMessage("Add New products. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("name", name));
params.add(new BasicNameValuePair("price", price+""));
params.add(new BasicNameValuePair("description", desc));
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);
// check log cat fro response
Log.d("Create Response", json.toString());
// check for success tag
try {
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// successfully created product
Intent i = new Intent(context.getApplicationContext(), MainScreenActivity.class);
context.startActivity(i);
// closing this screen
// context.finish();
} else {
// failed to create product
}
} catch (JSONException e) {
e.printStackTrace();
}
// Log.i("count: ", count+"");
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
}
}
JsonParser类：
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
// function get json from url
// by making HTTP POST or GET method
public JSONObject makeHttpRequest(String url, String method,
List<NameValuePair> params) {
// Making HTTP request
try {
// check for request method
if(method == "POST"){
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}else if(method == "GET"){
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
php文件：
<?php
$response = array();
if (isset($_REQUEST['name']) && isset($_REQUEST['price']) && isset($_REQUEST['description'])) {
$name = $_REQUEST['name'];
$price = $_REQUEST['price'];
$description = $_REQUEST['description'];
require_once __DIR__ . '/db_connect.php';
$db = new DB_CONNECT();
$result = mysql_query("INSERT INTO products(name, price, description) VALUES('$name', '$price', '$description')");
if ($result) {
$response["success"] = 1;
$response["message"] = "Product successfully created.";
echo json_encode($response);
} else {
$response["success"] = 0;
$response["message"] = "Oops! An error occurred.";
echo json_encode($response);
}
} else {
$response["success"] = 0;
$response["message"] = "Required field(s) is missing";
echo json_encode($response);
}
?>
答案 0 :(得分：1)
您获得的运行时异常是
无法在未调用的线程内创建处理程序 Looper.prepare（）
当您在background thread中执行需要在UI thread中执行的操作时，通常会得到此信息。 Reference
在您的情况下，您正在AsyncTask（CreateNewProduct）中执行AsyncTask（NewProduct）。您只能从UI线程执行AsyncTask。在NewProduct中，您尝试在后台线程中创建进度对话框，但需要UI线程。
请参阅AsyncTask文档中的线程规则部分。引用它：
- 必须在UI线程上加载AsyncTask类。这是从JELLY_BEAN开始自动完成的。
- 必须在UI线程上创建任务实例。
所以我建议只在一个AsyncTask中进行。您可以在onPostExecute或UI线程中执行第二个AsyncTask，但如果只能从一个线程执行，那么这将是多余的。