Java 运算符 != 未定义参数类型 long, null
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The operator != is undefined for the argument type(s) long, null
提问by WardaLyn
I am beginner android developer, and this is my first project. I should have to display selected data from ListView on ViewData.java to ListView on EntryTO.java. First, I get an error nullPointerException. I try to detect where is the problem with if function. and that error appears. "The operator != is undefined for the argument type(s) long, null"
我是初学者 android 开发人员，这是我的第一个项目。我应该必须将 ViewData.java 上的 ListView 中的选定数据显示到 EntryTO.java 上的 ListView。首先，我收到一个错误 nullPointerException。我尝试检测 if 函数的问题出在哪里。并出现该错误。“运算符 != 未定义参数类型 long, null”
This is the code when I try to get data from listview ViewData.java
这是我尝试从 listview ViewData.java 获取数据时的代码
ListView lv = (ListView) findViewById(android.R.id.list);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener(){
@Override
public void onItemClick(final AdapterView<?> adapter, View v, int pos, final long id) {
final Dialog dialog = new Dialog(ViewData.this);
dialog.setContentView(R.layout.dialog_view);
dialog.setTitle("Masukkan Qty");
dialog.show();
final product b = (product) getListAdapter().getItem(pos);
edtqty = (EditText) dialog.findViewById(R.id.edtqty);
buttonok = (Button) dialog.findViewById(R.id.buttonok);
buttonok.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
switchToEdit(b.getId());
Toast.makeText(ViewData.this, "Ambil product\n"+ b.getId() +"\n"+ b.getname() +"\n"+ b.getbrand()
+ edtqty.getText().toString(), Toast.LENGTH_LONG).show();
dialog.dismiss();
};
});
}
});
public void switchToEdit(long id){
product b = dataSource.getproduct(id);
Intent i = new Intent(this, EntryTO.class);
Bundle bun = new Bundle();
bun.putLong("id", b.getId());
bun.putString("brand", b.getbrand());
bun.putString("qty",edtqty.getText().toString());
i.putExtras(bun);
finale();
startActivity(i);
}
And this the code when I try to display selected data from ListView ViewData.java to another listview on EntryTO.java
这是我尝试将 ListView ViewData.java 中的选定数据显示到 EntryTO.java 上的另一个列表视图时的代码
Bundle bun = null;
if(bun.getLong("id")!=null && bun.getString("brand")!=null && bun.getString("qty")!=null)
{ bun = EntryTO.this.getIntent().getExtras();
id = bun.getLong("id");
brand = bun.getString("brand");
qty = bun.getString("qty");
String[]array ={brand,qty};
adapter = new ArrayAdapter<String>(EntryTO.this,
R.layout.item_list,R.id.edtnama, array);
setListAdapter(adapter);
}
Please help me.
请帮我。
采纳答案by niushuai
You can use the Long parameter. Like this:
您可以使用 Long 参数。像这样：
if( bun.getLong("id") != 0L)
if( bun.getLong("id") != 0L)
回答by John3136
bun.getLong("id")!=nullmakes no sense. You can't have a "null long".
bun.getLong("id")!=null没有意义。你不能有一个“空长”。
Something like bun.getLong("id")!=0Lmight make more sense (assuming 0 is the "default" value...) You are also repeating all the getLong()and getString()calls. More efficient to call them once and store the returned values for later use.
类似的东西bun.getLong("id")!=0L可能更有意义（假设 0 是“默认”值......）你也在重复所有的getLong()andgetString()调用。调用一次并存储返回值以供以后使用更有效。
