我尝试按照以下教程将 Android 与 PHP、MySQL 连接起来：
http://www.androidhive.info/2012/05/how-to-connect-android-with-php-mysql/
但是，我和大多数遵循本教程的用户在直接从下载的教程源运行应用程序并单击任一按钮时都会遇到强制关闭错误。
（看看评论部分 - 几乎每个人都对本教程有疑问）
日志猫：
03-17 14:40:10.064: D/dalvikvm(2936): GC_CONCURRENT freed 177K, 5% free 7488K/7812K, paused 2ms+11ms, total 33ms
03-17 14:40:16.294: D/dalvikvm(2936): GC_CONCURRENT freed 80K, 4% free 7856K/8140K, paused 3ms+2ms, total 26ms
03-17 14:40:16.784: E/JSON Parser(2936): Error parsing data org.json.JSONException: Value <br of type java.lang.String cannot be converted to JSONObject
03-17 14:40:16.794: W/dalvikvm(2936): threadid=15: thread exiting with uncaught exception (group=0x41d42930)
03-17 14:40:16.794: E/AndroidRuntime(2936): FATAL EXCEPTION: AsyncTask #5
03-17 14:40:16.794: E/AndroidRuntime(2936): java.lang.RuntimeException: An error occured while executing doInBackground()
03-17 14:40:16.794: E/AndroidRuntime(2936): at android.os.AsyncTask$3.done(AsyncTask.java:299)
03-17 14:40:16.794: E/AndroidRuntime(2936): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
03-17 14:40:16.794: E/AndroidRuntime(2936): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
03-17 14:40:16.794: E/AndroidRuntime(2936): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
03-17 14:40:16.794: E/AndroidRuntime(2936): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
03-17 14:40:16.794: E/AndroidRuntime(2936): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
03-17 14:40:16.794: E/AndroidRuntime(2936): at java.lang.Thread.run(Thread.java:856)
03-17 14:40:16.794: E/AndroidRuntime(2936): Caused by: java.lang.NullPointerException
03-17 14:40:16.794: E/AndroidRuntime(2936): at com.example.androidhive.NewProductActivity$CreateNewProduct.doInBackground(NewProductActivity.java:98)
03-17 14:40:16.794: E/AndroidRuntime(2936): at com.example.androidhive.NewProductActivity$CreateNewProduct.doInBackground(NewProductActivity.java:1)
03-17 14:40:16.794: E/AndroidRuntime(2936): at android.os.AsyncTask$2.call(AsyncTask.java:287)
03-17 14:40:16.794: E/AndroidRuntime(2936): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
03-17 14:40:16.794: E/AndroidRuntime(2936): ... 3 more
03-17 14:40:17.284: E/WindowManager(2936): Activity com.example.androidhive.NewProductActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{42488ea0 V.E..... R.....ID 0,0-296,153} that was originally added here
03-17 14:40:17.284: E/WindowManager(2936): android.view.WindowLeaked: Activity com.example.androidhive.NewProductActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{42488ea0 V.E..... R.....ID 0,0-296,153} that was originally added here
03-17 14:40:17.284: E/WindowManager(2936): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:354)
03-17 14:40:17.284: E/WindowManager(2936): at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:216)
03-17 14:40:17.284: E/WindowManager(2936): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
03-17 14:40:17.284: E/WindowManager(2936): at android.app.Dialog.show(Dialog.java:281)
03-17 14:40:17.284: E/WindowManager(2936): at com.example.androidhive.NewProductActivity$CreateNewProduct.onPreExecute(NewProductActivity.java:75)
03-17 14:40:17.284: E/WindowManager(2936): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
03-17 14:40:17.284: E/WindowManager(2936): at android.os.AsyncTask.execute(AsyncTask.java:534)
03-17 14:40:17.284: E/WindowManager(2936): at com.example.androidhive.NewProductActivity$1.onClick(NewProductActivity.java:55)
03-17 14:40:17.284: E/WindowManager(2936): at android.view.View.performClick(View.java:4204)
03-17 14:40:17.284: E/WindowManager(2936): at android.view.View$PerformClick.run(View.java:17355)
03-17 14:40:17.284: E/WindowManager(2936): at android.os.Handler.handleCallback(Handler.java:725)
03-17 14:40:17.284: E/WindowManager(2936): at android.os.Handler.dispatchMessage(Handler.java:92)
03-17 14:40:17.284: E/WindowManager(2936): at android.os.Looper.loop(Looper.java:137)
03-17 14:40:17.284: E/WindowManager(2936): at android.app.ActivityThread.main(ActivityThread.java:5041)
03-17 14:40:17.284: E/WindowManager(2936): at java.lang.reflect.Method.invokeNative(Native Method)
03-17 14:40:17.284: E/WindowManager(2936): at java.lang.reflect.Method.invoke(Method.java:511)
03-17 14:40:17.284: E/WindowManager(2936): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-17 14:40:17.284: E/WindowManager(2936): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-17 14:40:17.284: E/WindowManager(2936): at dalvik.system.NativeStart.main(Native Method)
JAVA: NewProductActivity.java
package com.example.androidhive;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class NewProductActivity extends Activity {
// Progress Dialog
private ProgressDialog pDialog;
JSONParser jsonParser = new JSONParser();
EditText inputName;
EditText inputPrice;
EditText inputDesc;
// url to create new product
private static String url_create_product = "http://linkingmanager.zxq.net/create_product.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
@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(NewProductActivity.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
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("name", name));
params.add(new BasicNameValuePair("price", price));
params.add(new BasicNameValuePair("description", description));
// getting JSON Object
// Note that create product url accepts POST method
JSONObject json = jsonParser.makeHttpRequest(url_create_product,
"POST", 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(getApplicationContext(), AllProductsActivity.class);
startActivity(i);
// closing this screen
finish();
} else {
// failed to create product
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once done
pDialog.dismiss();
}
}
}
XML: add_product.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<!-- Name Label -->
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Product Name"
android:paddingLeft="10dip"
android:paddingRight="10dip"
android:paddingTop="10dip"
android:textSize="17dip"/>
<!-- Input Name -->
<EditText android:id="@+id/inputName"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_margin="5dip"
android:layout_marginBottom="15dip"
android:singleLine="true"/>
<!-- Price Label -->
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Price"
android:paddingLeft="10dip"
android:paddingRight="10dip"
android:paddingTop="10dip"
android:textSize="17dip"/>
<!-- Input Price -->
<EditText android:id="@+id/inputPrice"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_margin="5dip"
android:layout_marginBottom="15dip"
android:singleLine="true"
android:inputType="numberDecimal"/>
<!-- Description Label -->
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Description"
android:paddingLeft="10dip"
android:paddingRight="10dip"
android:paddingTop="10dip"
android:textSize="17dip"/>
<!-- Input description -->
<EditText android:id="@+id/inputDesc"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_margin="5dip"
android:layout_marginBottom="15dip"
android:lines="4"
android:gravity="top"/>
<!-- Button Create Product -->
<Button android:id="@+id/btnCreateProduct"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Create Product"/>
</LinearLayout>
JAVA: AllProductsActivity.java
package com.example.androidhive;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class AllProductsActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList;
// url to get all products list
private static String url_all_products = "http://linkingmanager.zxq.net/get_all_products.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "products";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
// products JSONArray
JSONArray products = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_products);
// Hashmap for ListView
productsList = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadAllProducts().execute();
// Get listview
ListView lv = getListView();
// on seleting single product
// launching Edit Product Screen
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String pid = ((TextView) view.findViewById(R.id.pid)).getText()
.toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(),
EditProductActivity.class);
// sending pid to next activity
in.putExtra(TAG_PID, pid);
// starting new activity and expecting some response back
startActivityForResult(in, 100);
}
});
}
// Response from Edit Product Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user edited/deleted product
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all product by making HTTP Request
* */
class LoadAllProducts extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AllProductsActivity.this);
pDialog.setMessage("Loading products. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);
// Check your log cat for JSON reponse
Log.d("All Products: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_PID, id);
map.put(TAG_NAME, name);
// adding HashList to ArrayList
productsList.add(map);
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getApplicationContext(),
NewProductActivity.class);
// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} catch (JSONException e) {
e.printStackTrace();
}
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();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
AllProductsActivity.this, productsList,
R.layout.list_item, new String[] { TAG_PID,
TAG_NAME},
new int[] { R.id.pid, R.id.name });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
XML: all_products.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<!-- Main ListView
Always give id value as list(@android:id/list)
-->
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>