这个问题在这里已有答案：
我认为问题在于counter.getTag().toString();。我试着将它放在一个字符串中，然后将其传递给tappedCounter，但我的应用程序仍然崩溃了。
如果有人帮我解决如何使用Android Studio中的logcat来解决这样的问题，那将会非常有帮助。
这是logcat： -
12-22 02:09:59.790 14251-14251/com.example.msq.practice E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.msq.practice, PID: 14251
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:6256)
at android.view.View$PerformClick.run(View.java:24701)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:6256)
at android.view.View$PerformClick.run(View.java:24701)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at com.example.msq.practice.MainActivity.click(MainActivity.java:27)
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:6256)
at android.view.View$PerformClick.run(View.java:24701)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
小小的问题： -
package com.example.msq.practice;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;
import android.view.View;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
int activePlayer = 0;
int[] gameState = {2,2,2,2,2,2,2,2,2};
int[][] winningPositions = {{1,2,3}, {4,5,6}, {7,8,9}, {0,3,6},
{1,4,7,}, {2,5,8}, {0,4,8}, {2,4,6}};
boolean isGameActive = true;
String result;
String tag;
public void click(View view){
ImageView counter = (ImageView) view;
tag = counter.getTag().toString();
int tappedCounter = Integer.parseInt(tag);
if(gameState[tappedCounter] == 2 && isGameActive == true){
counter.setTranslationY(-5000f);
gameState[tappedCounter] = activePlayer;
if(activePlayer == 0){
counter.setImageResource(R.drawable.circle);
activePlayer = 1;
}
else{
counter.setImageResource(R.drawable.cross);
activePlayer = 0;
}
counter.animate().rotation(360f).translationYBy(5000f).setDuration(1000);
}
for(int[] winningPosition : winningPositions){
if(gameState[winningPosition[0]] == gameState[winningPosition[1]] &&
gameState[winningPosition[1]] == gameState[winningPosition[2]] &&
gameState[winningPosition[0]] != 2){
isGameActive = false;
if(gameState[winningPosition[0]]==0){
result = "PLayer 1 Won !";
}
else{
result = "PLayer 2 Won !";
}
}
else{
boolean isGameOver = true;
for(int counterState : gameState){
if(counterState == 2) isGameOver = false;
}
if(isGameOver)
result = "It's a Draw";
}
}
}
}
activity_main.xml文件： -
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.msq.practice.MainActivity">
<GridLayout
android:id="@+id/gLayout"
android:layout_width="300dp"
android:layout_height="300dp"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:layout_marginBottom="106dp"
android:layout_marginEnd="42dp"
android:layout_marginStart="42dp"
android:layout_marginTop="105dp"
android:background="@drawable/board"
android:columnCount="3"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:rowCount="3">
<ImageView
android:id="@+id/imageView0"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="0"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:layout_row="0"
android:contentDescription="@string/cross"
android:onClick="click" />
<ImageView
android:id="@+id/imageView1"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="1"
android:layout_marginStart="20dp"
android:layout_marginTop="10dp"
android:layout_row="0"
android:contentDescription="@string/cross"
android:onClick="click" />
<ImageView
android:id="@+id/imageView3"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="0"
android:layout_marginStart="10dp"
android:layout_marginTop="22dp"
android:layout_row="1"
android:contentDescription="@string/cross"
android:onClick="click" />
<ImageView
android:id="@+id/imageView4"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="1"
android:layout_marginStart="20dp"
android:layout_marginTop="22dp"
android:layout_row="1"
android:contentDescription="@string/cross"
android:onClick="click" />
<ImageView
android:id="@+id/imageView5"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="2"
android:layout_marginStart="20dp"
android:layout_marginTop="22dp"
android:layout_row="1"
android:contentDescription="@string/cross"
android:onClick="click"/>
<ImageView
android:id="@+id/imageView7"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="1"
android:layout_marginStart="20dp"
android:layout_marginTop="22dp"
android:layout_row="2"
android:contentDescription="@string/cross"
android:onClick="click" />
<ImageView
android:id="@+id/imageView8"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="2"
android:layout_marginStart="20dp"
android:layout_marginTop="22dp"
android:layout_row="2"
android:contentDescription="@string/cross"
android:onClick="click" />
<ImageView
android:id="@+id/imageView6"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="0"
android:layout_marginStart="10dp"
android:layout_marginTop="22dp"
android:layout_row="2"
android:contentDescription="@string/cross"
android:onClick="click" />
<ImageView
android:id="@+id/imageView2"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_column="2"
android:layout_marginStart="22dp"
android:layout_marginTop="10dp"
android:layout_row="0"
android:contentDescription="@string/cross"
android:onClick="click"/>
</GridLayout>
</android.support.constraint.ConstraintLayout>
您没有在应用程序或xml中的任何位置设置标记。所以getTag将返回null。如果您希望视图具有标记，则必须添加它。
“引发者：”部分的logcat标识了崩溃的原因。如果你仔细阅读logcat，崩溃的最后一个原因是NullPointerException。
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
现在，您尝试使用getTag()获取标记的值，但是您没有在XML布局中的任何ImageView上设置任何标记。因此，当null被调用时，标签是toString抛出异常。