android - Android Studio Kotlin二维Button数组得到java.lang.ArrayIndexOutOfBoundsException:length = 0;索引= 0

Question

我想和Kotlin做井字游戏。

按钮二维3x3，但收到此错误消息。我不知道 Kotlin 如何准确地声明二维数组并初始化，以及如何解决这个问题……

2020-03-28 16:27:45.705 30315-30315/com.leaf76.tictactoe E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.leaf76.tictactoe, PID: 30315
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.leaf76.tictactoe/com.leaf76.tictactoe.MainActivity}: java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3448)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2147)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:237)
        at android.app.ActivityThread.main(ActivityThread.java:7811)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1076)
     Caused by: java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
        at com.leaf76.tictactoe.MainActivity.onCreate(MainActivity.kt:46)
        at android.app.Activity.performCreate(Activity.java:7955)
        at android.app.Activity.performCreate(Activity.java:7944)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3423)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2147) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:237) 
        at android.app.ActivityThread.main(ActivityThread.java:7811) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1076) 

我宣布这个

.....
private var buttons = arrayOf<Array<Button>>()
private var player1Turn: Boolean = true
.....

我使用循环将 View 按钮ID添加到按钮数组，并使按钮单击更改文本“X”和“O”

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    textViewPlayer1 = text_view_p1
    textViewPlayer2 = text_view_p2

    for (i in 0 until 3) {
        for (j in 0 until 3) {
            val buttonId = "button_$i$j"
            val resId = resources.getIdentifier(buttonId, "id", packageName)

            buttons[i][j] = findViewById(resId)  // **here got error**

            buttons[i][j].setOnClickListener { v ->
                if (player1Turn) {
                    (v as Button).text = "X"
                } else {
                    (v as Button).text = "O"
                }
              ....
            }
        }
    }
}

Answer 1

您实际上已经用这一行代码声明了一个空数组。

arrayOf<Array<Button>>()

您需要向该数组添加一些项目。因此，您需要执行以下操作:

private var buttons = arrayOf<Array<Button>>(arrayOfNulls<Button>(3), arrayOfNulls<Button>(3), arrayOfNulls<Button>(3))

因此，在本部分中，我们将创建一个数组数组，其中包含3种可为空的Button类型。由于数组内部具有可为空的类型，因此无论访问数组项的位置如何，都需要使用 ?。例如，当您在单个Button上调用clickListener时，您需要这样做:

buttons[i][j]?.setOnClickListener

但以您为例，我不会使用数组来存储Button，而是会使用ArrayList，它可以动态接受项目。使用ArrayList，您的代码将如下所示:

数组声明:

private var buttons =  arrayOf<ArrayList<Button>>(arrayListOf(), arrayListOf(), arrayListOf())

用于循环:

for (i in 0 until 3) {
        for (j in 0 until 3) {
            val buttonId = "button_$i$j"
            val resId = resources.getIdentifier(buttonId, "id", packageName)

            buttons[i].add(findViewById(resId))

            buttons[i][j].setOnClickListener { v ->
                if (player1Turn) {
                    (v as Button).text = "X"
                } else {
                    (v as Button).text = "O"
                }
                ....
            }
        }