我正在使用一个可打包的对象来传递一个意图。传递方使用此代码：
Parcelable product = new Product(res.getData(), alcohol.toLowerCase(Locale.ENGLISH).trim(), selectedSize, location);
Intent intent = new Intent(Search.this, ProductPage.class);
intent.putExtra("Product", product);
startActivity(intent);
要取出我正在使用的对象：
Intent parentIntent = getIntent();
Product newProduct = (Product)parentIntent.getParcelableExtra("Product");
我遇到的问题是 newProduct 的数据成员都是空的。通过签入调试器，我知道该产品在其字段中具有真实数据。这是我的产品类：
public class Product implements Parcelable {
private int mData;
private Location location;
/** Product name of this alcohol. */
private String productName;
/** Size of this alcohol. */
private String size;
/** The list of ProductInfo's for the given product. */
private ArrayList<ProductInfo> productInfos;
// Test string
String jsonStr = "{\"result\":{\"status\":200,\"message\":\"OK\"},\"data\":[{\"storeID\":2,\"store_name\":\"safeway\",\"store_gps\":\"still dont know\",\"price\":3.99},{\"storeID\":1,\"store_name\":\"Hammy\",\"store_gps\":\"don't know\",\"price\":4.99}]}";
/**
* Takes a JSON string and parses its data field turning it into an array
* of ProducInfo's. Note any exception thrown here is caught and not
* thrown again. It's assumed that the JSON string is correctly formated.
*
* @param jsonStr
* The JSON string being parsed for it's data field.
*/
public Product(JSONArray productInfo, String productName, String size, Location location) {
this.location = location;
productInfos = new ArrayList<ProductInfo>();
this.productName = productName;
this.size = size;
try {
parseData(productInfo);
} catch (JSONException e) {
// Response now handles the parse error
// TODO: if data is in incorrect format it can throw an error...
}
}
/**
* Parses the data field of a JSONObject. If this field is not found or any
* of the fields assumed to be contained in this field, {storeID, store_name,
* price, store_gps} a JSONException is thrown.
*
* @param dataObj
* The JSONObject containing a data field.
* @throws JSONException
* If it can't find the data field, or any of data's fields.
*/
private void parseData(JSONArray dataObj) throws JSONException {
for (int i = 0; i < dataObj.length(); i++) {
JSONObject dataField = dataObj.getJSONObject(i);
int storeID = Integer.parseInt(dataField.getString("storeID"));
String storeName = dataField.getString("store_name");
double price = Double.parseDouble(dataField.getString("price"));
double dist = calculateGPSDistance(dataField.getString("store_gps"));
productInfos.add(new ProductInfo(storeID, storeName, price, dist));
}
}
/**
* Calculates the distance between GPSCoord and the users current GPS
* coordinates.
*
* @param GPSCoord
* GPS coordinates. Assumes that GPSCoord follows the following
* format "latitude, longitude"
* @return the distance between GPSCoord and the users current GPS coordinates.
*/
private double calculateGPSDistance(String GPSCoord) {
double lat1 = location.getLatitude();
double long1 = location.getLongitude();
String[] coordinates = GPSCoord.split(",");
double lat2 = Double.parseDouble(coordinates[0]);
double long2 = Double.parseDouble(coordinates[1]);
// Check http://www.smokycogs.com/blog/finding-the-distance-between-two-gps-coordinates/
// for details.
lat1 = degToRad(lat1);
long1 = degToRad(long1);
lat2 = degToRad(lat2);
long2 = degToRad(long2);
double earthRadius = 6371; // km
double deltaLat = lat2 - lat1;
double deltaLong = long2 - long1;
double a = Math.sin(deltaLat / 2.0) * Math.sin(deltaLat / 2.0) +
Math.cos(lat1) * Math.cos(lat2) *
Math.sin(deltaLong / 2.0) * Math.sin(deltaLong / 2.0);
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
double distance = earthRadius * c;
return distance;
}
private double radToDeg(double radians) {
return radians * (180 / Math.PI);
}
private double degToRad(double degrees) {
return degrees * (Math.PI / 180);
}
/*
* GETTER METHODS
*/
public String getProductName() {
return productName;
}
public String getSize() {
return size;
}
/*
* Check http://developer.android.com/reference/android/os/Parcelable.html
* for details. These are all methods for Parcelable.
*/
public int describeContents() {
return 0;
}
public void writeToParcel(Parcel out, int flags) {
out.writeInt(mData);
}
public static final Parcelable.Creator<Product> CREATOR = new Parcelable.Creator<Product>() {
public Product createFromParcel(Parcel in) {
return new Product(in);
}
public Product[] newArray(int size) {
return new Product[size];
}
};
private Product(Parcel in) {
mData = in.readInt();
}
/**
* productInfos getter
*/
public ArrayList<ProductInfo> getProductInfos() {
return productInfos;
}
}
Parcelables 已经让我感到困惑了，所以我不太确定这里发生了什么......谢谢
另请注意，因此，我的代码中出现空指针异常。