[使用findViewWithTag和getTag的应用程序崩溃

Question

我是新手android开发人员。我在活动布局中声明了3x3 gridLayout，在其中放置了9个imageViews，它们的标签从0到8。下面是布局代码的片段：

<GridLayout
        android:id="@+id/gridLayout"
        android:background="@drawable/board"
        android:columnCount="3"
        android:rowCount="3">

        <ImageView
            android:id="@+id/counter_topLeft"
            android:onClick="drop_in"
            android:tag="0"
            android:layout_column="0"
            android:layout_row="0" />

在我的主要方法中，在方法drop_in()中，我试图检查用户是否已调用它，并且如果系统已调用它，我正在尝试使用标签来通过标签检索ImageView。随机数作为标签。这是drop_in()方法：

public void drop_in(View view) // method invoked on tapping any grid cell
    {
        int i;
        ImageView counter = (ImageView) view;
        i = Integer.parseInt(counter.getTag().toString()); // getting the associated tags or basically cell number
        if(isHuman)
        { // do some stuff and then 
            isHuman=false;
        }
        //  now app will perform actions and wait for user input to do stuff again
        if(!isHuman)
        {
            Random random=new Random();
            i=random.nextInt(9);

            Object o=i;
            ViewGroup group = (ViewGroup) findViewById(R.id.gridLayout)
            myview=(View) group.findViewWithTag(o);
            Log.i("Info","View tag is "+myview.getTag().toString());
            isHuman=true;
         }
    }

在logcat中，它显示以下错误：

2020-05-15 12:26:40.605 10000-10000/com.s090.tttsingleplayer E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.s090.tttsingleplayer, PID: 10000
    java.lang.IllegalStateException: Could not execute method for android:onClick
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.view.View.getTag()' on a null object reference
        at com.s090.tttsingleplayer.MainActivity.drop_in(MainActivity.java:133)

如何使用标签检索视图？

Answer 1

使用此行

ImageView计数器=（ImageView）view.findViewById（R.id.counter_topLeft）;