问题描述
我的 switch-case 语句昨天运行良好.但是当我今天早上早些时候运行代码时,eclipse给了我一个错误,用红色强调了case语句并说:case表达式必须是常量表达式,它是常量我不知道发生了什么.下面是我的代码:
My switch-case statement works perfectly fine yesterday. But when I run the code earlier this morning eclipse gave me an error underlining the case statements in color red and says: case expressions must be constant expression, it is constant I don't know what happened. Here's my code below:
public void onClick(View src) { switch(src.getId()) { case R.id.playbtn: checkwificonnection(); break; case R.id.stopbtn: Log.d(TAG, "onClick: stopping srvice"); Playbutton.setImageResource(R.drawable.playbtn1); Playbutton.setVisibility(0); //visible Stopbutton.setVisibility(4); //invisible stopService(new Intent(RakistaRadio.this,myservice.class)); clearstatusbar(); timer.cancel(); Title.setText(" "); Artist.setText(" "); break; case R.id.btnmenu: openOptionsMenu(); break; } }
所有 R.id.int 都用红色下划线.
All R.id.int are all underlined in red.
推荐答案
在常规的Android项目中,资源R类中的常量声明如下:
In a regular Android project, constants in the resource R class are declared like this:
public static final int main=0x7f030004;
但是,从 ADT 14 开始,在库项目中,它们将被声明为:
However, as of ADT 14, in a library project, they will be declared like this:
public static int main=0x7f030004;
换句话说,常量在库项目中不是最终的.因此您的代码将不再编译.
In other words, the constants are not final in a library project. Therefore your code would no longer compile.
解决方案很简单:将 switch 语句转换为 if-else 语句.
The solution for this is simple: Convert the switch statement into an if-else statement.
public void onClick(View src) { int id = src.getId(); if (id == R.id.playbtn){ checkwificonnection(); } else if (id == R.id.stopbtn){ Log.d(TAG, "onClick: stopping srvice"); Playbutton.setImageResource(R.drawable.playbtn1); Playbutton.setVisibility(0); //visible Stopbutton.setVisibility(4); //invisible stopService(new Intent(RakistaRadio.this,myservice.class)); clearstatusbar(); timer.cancel(); Title.setText(" "); Artist.setText(" "); } else if (id == R.id.btnmenu){ openOptionsMenu(); } }
http://tools.android.com/tips/non-constant-fields
您可以使用以下命令将 switch 语句快速转换为 if-else 语句:
You can quickly convert a switch statement to an if-else statement using the following:
在 Eclipse 中
将光标移动到 switch 关键字并按 Ctrl + 1 然后选择
In Eclipse
Move your cursor to the switch keyword and press Ctrl + 1 then select
将switch"转换为if-else".
Convert 'switch' to 'if-else'.
在 Android Studio 中
将光标移动到 switch 关键字并按 Alt + Enter 然后选择
In Android Studio
Move your cursor to the switch keyword and press Alt + Enter then select
将开关"替换为如果".
Replace 'switch' with 'if'.