我目前正在做一个从php服务器检索数据的页面，现在尝试通过使用setImageResource从drawable中检索和图像，但是不能正常工作，我不知道它有什么问题，我是否有可能只保存图像名称数据库然后使用图像名称检索图像？ 除此之外，我尝试为数量做一个简单的加减按钮，但是一旦我点击按钮，应用程序强制停止..
public class FoodDetailActivity extends Activity
{
TextView FoodName;
TextView FoodDesc;
TextView FoodPrice;
ImageView FoodImg;
EditText Number;
Button plus;
Button minus;
Button Addcart;
String fid;
int number;
// Progress Dialog
private ProgressDialog pDialog;
// JSON parser class
JSONParser jsonParser = new JSONParser();
// single product url
private static final String url_food_details = "http://10.0.2.2/android_user/FoodDetail.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_FOOD = "food";
private static final String TAG_FID = "fid";
private static final String TAG_FOODNAME = "food_name";
private static final String TAG_FOODPRICE = "food_price";
private static final String TAG_FOODDESCRIPTION = "food_description";
private static final String TAG_FOODURL = "food_url";
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_food_detail);
// button
plus = (Button)findViewById(R.id.btn_plus);
plus.setOnClickListener(increase);
minus = (Button)findViewById(R.id.btn_minus);
minus.setOnClickListener(decrease);
Addcart = (Button)findViewById(R.id.btn_submit);
Number = (EditText)findViewById(R.id.text_number);
// getting food details from intent
Intent i = getIntent();
// getting food id (fid) from intent
fid = i.getStringExtra(TAG_FID);
// Getting complete product details in background thread
new GetFoodDetails().execute();
}
// Increase number of quantity
private OnClickListener increase = new OnClickListener()
{
public void onClick(View v)
{
String quantity = Number.getText().toString().trim();
number = Integer.parseInt(quantity);
if(number > 0 && number < 99)
{
number = number + 1;
Number.setText(Integer.toString(number));
}
else if(number == 99)
{
number = 1;
Number.setText(Integer.toString(number));
}
}
};
// Decrease number of quantity
private OnClickListener decrease = new OnClickListener()
{
public void onClick(View v)
{
String quantity = Number.getText().toString();
number = Integer.valueOf(quantity);
if(number > 1 && number <= 99)
{
number = number - 1;
Number.setText(Integer.toString(number));
}
else if(number == 1)
{
number = 99;
Number.setText(Integer.toString(number));
}
}
};
class GetFoodDetails extends AsyncTask<String, String, String>
{
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute()
{
super.onPreExecute();
pDialog = new ProgressDialog(FoodDetailActivity.this);
pDialog.setMessage("Loading food details. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* Getting product details in background thread
* */
protected String doInBackground(String... params)
{
// updating UI from Background Thread
runOnUiThread(new Runnable()
{
public void run()
{
// Check for success tag
int success;
try {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("fid", fid));
// getting product details by making HTTP request
// Note that product details url will use GET request
JSONObject json = JSONParser.makeHttpRequest(url_food_details, "GET", params);
// check your log for json response
Log.d("Single Food Details", json.toString());
// json success tag
success = json.getInt(TAG_SUCCESS);
if (success == 1)
{
// successfully received food details
JSONArray foodObj = json.getJSONArray(TAG_FOOD); // JSON Array
// get first product object from JSON Array
JSONObject food = foodObj.getJSONObject(0);
// Loader image - will be shown before loading image
int loader = R.drawable.loader;
String image_url = food.getString(TAG_FOODURL);
// product with this fid found
// Edit Text
FoodName = (TextView)findViewById(R.id.food_name);
FoodPrice = (TextView)findViewById(R.id.food_price);
FoodDesc = (TextView)findViewById(R.id.food_desc);
FoodImg = (ImageView)findViewById(R.id.img_food);
// display product data in EditText
FoodName.setText(food.getString(TAG_FOODNAME));
FoodPrice.setText("RM" + food.getString(TAG_FOODPRICE));
FoodDesc.setText(food.getString(TAG_FOODDESCRIPTION));
// ImageLoader class instance
ImageLoader imgLoader = new ImageLoader(getApplicationContext());
// display image
imgLoader.DisplayImage(image_url, loader, FoodImg);
}
else
{
// no food detail found
// Launch error message
AlertDialog.Builder ad = new AlertDialog.Builder(FoodDetailActivity.this);
ad.setTitle("Error");
ad.setMessage("Food Detail is empty!");
ad.setPositiveButton("OK", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialoginterface, int i)
{
}
});
ad.show();
}
} catch (JSONException e) {
e.printStackTrace();
}
}
});
return null;
}
protected void onPostExecute(String file_url)
{
// dismiss the dialog once got all details
pDialog.dismiss();
}
}
}
问题已解决，我使用ImageLoader在服务器端检索图像，并在数据库中使用url store。
答案 0 :(得分：2)
在这里：
Drawable d = getResources().getDrawable(R.drawable.mcchicken); //<<<<
您正在尝试在onCreate调用之前使用Activity的上下文。在Drawable d之后的onCreate方法中移动setContentView初始化为：
Drawable d; //<<< declare d here
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_food_detail);
d = getResources().getDrawable(R.drawable.mcchicken); //<< initialize d here
....
}
修改：：您正在尝试访问UI元素的doInBackground方法内部。而不是使用runOnUiThread从doInBackground更新UI。你需要移动onPostExecute中与doiBackground执行完成后调用Ui线程的所有UI相关代码。
答案 1 :(得分：1)
在你的代码中是非常混乱的材料。从一开始就很好。首先是唯一的问题。
为什么要放入doInBackground()方法runOnUiThread()？如果您想使用后台运行的任务中的某些信息更新UI，为此您可以使用 onProgressUpdate（）或onPostExecute()方法与UI Thread同步并允许其更新。 doInBackground（）方法直接指定用于后台处理，你不应该破坏它。
然后这一行：
if (food.getString(TAG_FOODNAME) == "McChicken")
将始终返回false，因为您要比较引用而不是值。总是在比较字符串，你必须使用equals()方法来制作技巧。
最后一件事是：
Drawable d = getResources().getDrawable(R.drawable.mcchicken);
在调用setContentView()之前，您无法调用它。原因是setContentView()的主要目的是创建UI元素和资源的所有实例，如果您需要在此方法之前调用资源，则始终会获得 NPE