Question

同一个.java文件中为什么不能定义两个activity？

一个Activity不是以一个类的形式写在一个.java文件中嘛，而且类名要和.java文件名相同,例如，我的一个activity定义：public class FirstAppActivity extends Activity {}
然后它保存在FirstAppActivity.java文件中，在这个FirstAppActivity.java文件中为什么我定义另外一个activity类，例如SecondAppActivity extends Activity{}后（已取消掉SecondAppActivity的public标识）可以通过编译，只不过在first中调用second时程序就崩溃了
我查到了，由于activity必须是public的，而Java不允许在一个.java文件中存在两个public类，所以一个.java文件中只能包含一个activity
Q：I am new to android development and am currently working my way through the "Hello..." Tutorials on the developer website.
I got stuck on the Tab Layout walkthrough and the only way I could resolve it was to put each Activity Class in a separate .java file.
I was wondering if all Activities need to be in separate .java files, or am I missing something.

A:There can only be one public class in a Java file and it must have the same name as the file.
Why are you trying to get them into one file to begin with?

Q:Right, I am with you now. I just wanted one file which would have all the classes in it, I didn't realise that Activity Classes have to be public. Thanks

Answer 1

SecondAppActivity是内部类

Answer 2

重复可以的，可以参考android SDK里的sample例子， 建议你check一下manifest.xml里是否添加了你的MyActivity

追问

已经添加了

追答

还是那个错误吗

追问

嗯，只要把activity放到另外一个java文件中一切ok

Answer 3

重复的当然不可以啦

Answer 4

麻烦楼主把代码贴上来，你的定义方式是正确的，应该是代码有问题！

追问

很简单的，我在FirstAppActivity中定义了一个basic_button响应函数，启动同一个.java文件下定义的MyActivity，结果一点这个button就崩溃
basic_button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
startActivity(new Intent(FirstAppActivity.this,MyActivity.class));
}
});

追答

是不是贴不下啊？不贴代码怎么解决问题啊？程序崩溃时出现什么异常还是出现error？描述的太笼统了！
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请问楼主，程序崩溃时什么意思？能不能把异常消息贴出来看看！

追问

06-18 09:16:30.384: E/AndroidRuntime(610): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.baidu.FirstApp/com.baidu.FirstApp.MyActivity2}: java.lang.IllegalAccessException: access to class not allowed

追答

对不起，我还真看不出来！