我有以下代码：
String filter = getArguments().getString("filter", null);
if (type != null) {
mActivity.setTitle(title);
mActivity.getSupportActionBar().setDisplayShowHomeEnabled(true);
}else {
/*mActivity.getSupportActionBar().setDisplayHomeAsUpEnabled(false);
mActivity.getSupportActionBar().setDisplayShowHomeEnabled(true);
mActivity.getSupportActionBar().setHomeButtonEnabled(true);
mActivity.getSupportActionBar().setIcon(R.mipmap.ic_menu);*/
}
我一直得到Null Pointer Exception：
import java.io.File;
// Example of a BookStore main-class using CommandReader to read commands from input files.
public class BookStore {
//Declarations
String title;
String seller;
int price;
public static void main(String[] args) throws BookStoreException {
ListMultiIndex mi = new ListMultiIndex();
File file = new File ("Commands/commands_1_adds.txt");
CommandReader reader = new CommandReader(file);
String add = "add";
String remove = "remove";
while (reader.hasNext()){
String [] command = reader.next();
if((add).equals(command[0])){
mi.add(command[1], command[2],Integer.parseInt(command[3]));
System.out.println("Book Added:");
System.out.println("Title - " + command[1]);
System.out.println("Seller - " + command[2]);
System.out.println("Price - £" + command[3]);
System.out.println("");
}
else if(command[0].equals(remove)){
BookItem book = new BookItem(command[1], command[2], Integer.parseInt(command[3]));
mi.remove(book);
System.out.println("Book Removed:");
System.out.println("Title - " + command[1]);
System.out.println("Seller - " + command[2]);
System.out.println("Price - " + command[3]);
}
else System.out.println("Error:Retype the command, you've spelt 'add' or 'remove' wrong");
}
}
}
任何帮助感谢，谢谢
答案 0 :(得分：0)
你检查过命令是否为空？
if(command != null && add.equals(command[0])){ ... }