问题描述
我想创建一个项目列表，不同势每个i和j变量。我的code是：
I am trying to create an item list, diffrent for each i and j variable. My code is:
if (i == 0) {
if (j == 0) {
final CharSequence[] items = {"4:45", "5:00"}
} else if (j == 1) {
final CharSequence[] items = {"4:43", "4:58"}
} else if (j == 2) {
final CharSequence[] items = {"4:41", "4:56"}
} else {
final CharSequence[] items = {"4:38", "4:53"}
}
...
new AlertDialog.Builder(this)
.setTitle("Hours")
.setItems(items,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialoginterface, int i) {
// getStation(i);
}
})
.show();
}
我在该行得到一个错误 .setItems（项目，：
items cannot be resolved
我觉得编译器认为，的CharSequence []项目可能不被初始化或东西...我怎样才能让这个程序运行？
I think that the compiler thinks that the CharSequence[] items may not be initialised or something...How can I make this programme run?
推荐答案
现在的问题是变量范围。
The problem is variable scoping.
if (someCondition) {
final int i = 666;
} else {
final int i = 42;
}
int j = i + 1; // compile-time error
在这里，我们有两个局部变量我谁超出范围，他们正在申报和初始化之后。如果Ĵ需要的值我，然后我会必须在一个更大的范围内声明。
Here we have two local variables i who goes out of scope immediately after they're declared and initialized. If j needs the value of i, then i would have to be declared in a larger scope.
final int i;
if (someCondition) {
i = 666;
} else {
i = 42;
}
int j = i + 1; // compiles fine!
（应当指出，这正是那种场景下三元运算优异，即）
(It should be mentioned that this is exactly the kind of scenarios where the ternary operator excels, i.e.)
final int i = (someCondition) ? 666 : 42;
在您的具体情况，不幸的是，数组初始化的速记只能在声明初始化。那就是：
In your specific case, unfortunately the array initializer shorthand can only be used to initialize upon declaration. That is:
int[] arr1 = { 1, 2, 3 }; // compiles fine!
int[] arr2;
arr2 = { 4, 5, 6 }; // doesn't compile!
您可以拉出的项目申报之外如果并写出详细的code为每案例（见约阿希姆·绍尔的答案），但更简洁code是使用数组的数组，而不是。
You can pull out the declaration of items outside the if and write the verbose code for each case (see Joachim Sauer's answer), but a more concise code is to use array-of-arrays instead.
final CharSequence[][] allItems = {
{ "4:45", "5:00" },
{ "4:43", "4:58" },
{ "4:41", "4:56" },
{ "4:38", "4:53" }
};
final CharSequence[] items = allItems[j];
此方法效果很好在这种情况下，但在更一般的情况下，你需要使用地图或类似的东西。
This technique works well in this case, but in the more general case you want to use a Map or something similar.
请注意：这不是明确的在原来的code，但这个工作如果Ĵ可以是 0 ， 1 ， 2 或 3 。如果你想在最后的选项将在Ĵ比其他任何值 0 ， 1 ， 2 ，那么你必须检查是否存在并将其设置为 3 在此之前code。
Note: It's not explicit in the original code, but this works if j can either be 0, 1, 2, or 3. If you want the last option to apply when j is any value other than 0, 1, 2, then you have to check for that and set it to 3 before this code.
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