我有一个 Activity ,我将对象添加到实现 Parcelable 接口(interface)的 ArrayList 中。然后我通过 bundle 将此列表传递给另一个 Activity 但是当我尝试在新 Activity 中打印列表大小时出现以下错误:
java.lang.RuntimeException: Unable to resume activity {com.example.test/com.example.test.SectionsActivity}: java.lang.NullPointerException
这是我添加到列表的第一个 Activity :
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
Toast.makeText(getApplicationContext(), l.getItemAtPosition(position).toString() + " added to order", Toast.LENGTH_SHORT).show();
// add clicked item to orderData....
MenuItem m = (MenuItem) l.getItemAtPosition(position);
// create new item
orderData.add(m);
subTotal += m.getPrice();
calc();
}
这是我通过 Intent 发送数据的第一个 Activity :
confirmBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
b.putParcelable("order", orderData);
Intent i = new Intent(v.getContext(), SectionsActivity.class);
i.putExtra("data",b);
startActivity(i);
}
});
这是我尝试检索包和显示大小的第二个 Activity :
@Override
protected void onResume() {
super.onResume();
getIntentData();
}
public void getIntentData(){
Intent i = getIntent();
if(i != null & i.hasExtra("data")){
Toast.makeText(this.getApplicationContext(), "recieved", Toast.LENGTH_LONG).show();
b = i.getExtras();
orderData = b.getParcelable("order");
int size = orderData.size();
Toast.makeText(this.getApplicationContext(), String.valueOf(size), Toast.LENGTH_LONG).show();
}
}
知道为什么我会得到空指针吗??这让我发疯!
orderData 是一个 MenuItemList 对象:
public class MenuItemList extends ArrayList <MenuItem> implements Parcelable{
/**
*
*/
private static final long serialVersionUID = 2998684930374219271L;
public MenuItemList(){
}
public static final Parcelable.Creator<MenuItemList> CREATOR = new Parcelable.Creator<MenuItemList>() {
@Override
public MenuItemList createFromParcel(Parcel source) {
return new MenuItemList(source);
}
@Override
public MenuItemList[] newArray(int size) {
return new MenuItemList[size];
}
};
public MenuItemList(Parcel source) {
readFromParcel(source);
}
private void readFromParcel(Parcel source) {
this.clear();
//read the size of the list
int size = source.readInt();
//Remember order of items written into the Parcel. Important here.
for(int i = 0; i < size; i ++){
MenuItem item = new MenuItem();
item.setName(source.readString());
item.setPrice(source.readDouble());
this.add(item);
}
}
@Override
public void writeToParcel(Parcel dest, int flags) {
int size = this.size();
dest.writeInt(size);
for(int i = 0; i < size; i ++){
MenuItem item = this.get(i);
dest.writeString(item.getName());
dest.writeDouble(item.getPrice());
}
}
@Override
public int describeContents() {
return 0;
}
解决问题的代码更改:
更改了 onClick( View v):
@Override
public void onClick(View v) {
Intent i = new Intent(v.getContext(), SectionsActivity.class);
i.putExtra("data", (ArrayList<MenuItem>)orderData);
startActivity(i);
}
已更改 getIntent():
public void getIntentData(){
Intent i = getIntent();
if(i != null && i.hasExtra("data")){
Toast.makeText(this.getApplicationContext(), "recieved", Toast.LENGTH_LONG).show();
orderData = i.getParcelableExtra("data");
int size = orderData.size();
Toast.makeText(this.getApplicationContext(), String.valueOf(size), Toast.LENGTH_LONG).show();
}
}
最佳答案
重写
问题是您有一个额外的 Bundle。当前在 getIntentData()
中你必须调用:
getIntent() // Fetch the Intent,
.getExtras() // Fetch the Bundle of extras,
.getBundle("data") // Fetch the Bundle "data",
.getParcelable("order"); // Then get your parcelable...
让我们删除不必要的 Bundle。
public void onClick(View v) {
Intent i = new Intent(v.getContext(), SectionsActivity.class);
i.putExtra("data", orderData);
startActivity(i);
}
现在更新getIntentData()
:
Intent i = getIntent();
if(i != null && i.hasExtra("data")){
orderData = i.getParcelableExtra("data");
...
}
关于android - 在 Activity 之间传递 ArrayList,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13830894/