在内部类中访问的变量

Question

我有以下代码用于执行root命令:

public static String sudo(final String cmd, Context ctx) {
    String output = null;  //init string output
    if (RootTools.isRootAvailable()) {
        if (RootTools.isAccessGiven()) {
            try {
                CommandCapture command = new CommandCapture(0, cmd) {
                    @Override
                    public void output(int id, String line) {
                        Log.d("com.vwade79.aokpdelta.Functions.sudo", "cmd:"+cmd+"\noutput:"+line);
                        if (line.equals("")) {
                            return;
                        }
                        else {
                            output = line;  //ERROR
                        }
                    }
                };
                RootTools.getShell(true).add(command).waitForFinish();
            } catch (Exception e) {
                Toast.makeText(ctx, "There was an error executing root command : "+cmd, Toast.LENGTH_LONG).show();
                e.printStackTrace();
            }
        }
        else {
            Toast.makeText(ctx, "Root permission isn't given!", Toast.LENGTH_LONG).show();
            Intent intent = new Intent(ctx, MainActivity.class);
            ctx.startActivity(intent);
        }
    }
    else {
        Toast.makeText(ctx, "You're not rooted! Come back when you are!", Toast.LENGTH_LONG).show();
        Intent intent = new Intent(ctx, MainActivity.class);
        ctx.startActivity(intent);
    }
    return output;
}

我收到一个错误:

variable "output" is accessed from within inner class. Needs to be declared final.

我不知道如何分配"内部类"的输出.

Answer 1

错误消息说明了一切:您只能final从内部类中访问变量.

一个快速的解决方案是定义:

final String output[] = new String[1];  //init string output

在内部阶级:

                        output[0] = line;  // No ERROR :-)

然后:

return output[0];

这是因为数组本身是最终的,但是数组的内容仍然可以改变(final如果你问我,在Java中有点奇怪的定义;最终并不意味着不可变).