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我有以下代码:无法访问的LinkedHashMap在内部类
final LinkedHashMap<String, Line> trainLinesMap = MetraRail.myDbHelper.getTrainLinesHashMap();
// Create an array of proper line names for the listview adapter.
String[] train_lines_long_names = new String[trainLinesMap.size()];
Iterator<Entry<String, Line>> it = trainLinesMap.entrySet().iterator();
for (int i = 0; it.hasNext(); i++) {
Map.Entry<String, Line> pairs = (Map.Entry<String, Line>) it.next();
train_lines_long_names[i] = (String) pairs.getKey();
}
// Override the default list adapter so we can do 2 things: 1) set custom background colors
// on each item, and 2) so we can more easily add onclick handlers to each item.
listview.setAdapter(
new ArrayAdapter<String>(this, R.layout.select_line_row_layout,
R.id.select_line_line_label, train_lines_long_names) {
@Override
public View getView(int position, View convertView, ViewGroup parent) {
TextView textView = (TextView) super.getView(position, convertView, parent);
// Change the background color of each item in the list.
final String line_label_long = textView.getText().toString();
final int line_color = trainLinesMap.get(line_label_long).getColorInt();
textView.setBackgroundColor(line_color);
// Add onclick handlers to each item.
textView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent();
i.setClassName("garrettp.metrarail",
"garrettp.metrarail.screens.SelectStations");
i.putExtra("garrettp.metrarail.line.short",
trainLinesMap.get(line_label_long).getShortName());
i.putExtra("garrettp.metrarail.line.long", line_label_long);
i.putExtra("garrettp.metrarail.line.color", line_color);
startActivity(i);
}
});
return textView;
}
});
在生产线:
final int line_color = trainLinesMap.get(line_label_long).getColorInt();
我得到一个NullPointerException:
10-26 16:10:35.922: E/AndroidRuntime(1785): java.lang.NullPointerException
10-26 16:10:35.922: E/AndroidRuntime(1785): at garrettp.metrarail.screens.SelectLine$1.getView(SelectLine.java:74)
这是为什么?在调试器中,我已验证trainLinesMap已正确初始化并填充了值。它在第一个for循环中被成功迭代,所以我知道那里有值。但是,当从我的匿名内部类访问LinkedHashMap时,它始终为空。
我能够从这个内部类访问一个字符串数组,为什么我不能访问一个LinkedHashMap?
你可以,NPE很可能来自你的地图,在该行之前添加 “System.err.println(line_label_long +”:“+ trainLinesMap.get(line_label_long));” 它可能是空的 –
看到我的答案在下面,我解决了这个问题,将trainLinesMap.get(line_label_long)的结果赋给一个临时变量,并从临时变量中调用.getColorInt()。 – pwnsauce