的newInstance失败：无＆LT; INIT＆GT;

问题描述

我不能实例化一个子活动。在logcat的我看到这行：

I cannot instantiate a sub activity. In the logcat I see this line:

01-22 15:14:38.906: DEBUG/dalvikvm(411): newInstance failed: no <init>()

这是该行的Dalvik的，其产生的logcat。

This is the line in dalvik that generates that logcat.

/*
 * public T newInstance() throws InstantiationException, IllegalAccessException
 *
 * Create a new instance of this class.
 */
static void Dalvik_java_lang_Class_newInstance(const u4* args, JValue* pResult)
...
    /* find the "nullary" constructor */
    init = dvmFindDirectMethodByDescriptor(clazz, "<init>", "()V");
    if (init == NULL) {
        /* common cause: secret "this" arg on non-static inner class ctor */
        LOGD("newInstance failed: no <init>()\n");
        dvmThrowExceptionWithClassMessage("Ljava/lang/InstantiationException;",
            clazz->descriptor);
        RETURN_VOID();
    }

下面是我的行动采取激活一个计时器处理程序中的活动。

Here is the action I take to activate the activity in a timer handler.

// move on to Activation
// ePNSplash is this activity a splash screen

Intent i = new Intent (ePNSplash.this, Activation.class);
startActivity (i);

这是我尝试启动活动是2扩展上述活动

The activity that I am trying to start is 2 extensions above Activity

这是第一个扩展

public abstract class AndroidScreen extends Activity {
    ....

public AndroidScreen (String title, AndroidScreen parent, AndroidScreen main)
{
    super ();

    myGlobals = Globals.getGlobals ();

    myGlobals.myLogger.logString("AndroidScreen: 001");

    myParent = parent;
    myMainScreen = main;
    myTitle = title;
}

这是唯一的构造，这似乎是有问题的部分。这里是第二个扩展和类我试图实例。

This is only the constructor, which seems to be the part that has the problem. Here is the 2nd extension and the class i am trying to instantiate.

public class Activation extends AndroidScreen {

public Activation (String title, AndroidScreen parent, AndroidScreen main)
{
    super (title, parent, main);
}

我绝对困惑，我有一个构造函数，我要确保我打电话给我的超级构造函数，什么可能是错误的？

I am absolutely confused, I have a constructor, I make sure I call my super constructors, what could possibly be wrong?

感谢您

朱利安

推荐答案

dalvikvm的寻找一个零参数的构造函数（这就是他们所说的无元，如二进制的2个参数，一元1说法，它是无元0参数）。

dalvikvm's looking for a zero-argument constructor (that's what they mean by "nullary", as in "binary" for 2 arguments, "unary" for 1 argument, it's "nullary" for 0 arguments).

中的代码片段，你已经证明，你只有三个参数的构造函数。这是没有好。你不带参数进行实例化，所以你需要一个零参数的构造函数

in the snippet you've shown, you only have a three-argument constructor. that's no good: you'll be instantiated with no arguments, so you need a zero-argument constructor.

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