Android Studio //尝试打开第二个布局后，应用程序崩溃

Question

我做了一个简单的点击游戏应用程序。我知道它的可编程性差，但我真的不明白，为什么我的应用程序在尝试打开其他布局后不断崩溃。我刚刚从今天开始使用Android Studio，因此希望我不会看到问题，但它可能很明显。

MainActivity

import android.os.Bundle; 
 
import android.support.v7.app.AppCompatActivity; 
 
import android.view.View; 
 
import android.widget.Button; 
 
import android.widget.TextView; 
 
import android.content.Intent; 
 

 
public class MainActivity extends AppCompatActivity { 
 
    public static final int REQUEST_CODE_CURRENTCLICKS = 10; 
 
    public int amountClicks = 0; 
 
    public int incrementAmount = 1; 
 
    @Override 
 
    protected void onCreate(Bundle savedInstanceState) { 
 
     super.onCreate(savedInstanceState); 
 
     setContentView(R.layout.activity_main); 
 

 
     Button btnClick = (Button) findViewById(R.id.btnClick); 
 
     final TextView tvAmountClicks = (TextView) findViewById(R.id.tvAmoutClicks); 
 
     Button btnShop = (Button) findViewById(R.id.btnShop); 
 

 
     amountClicks = getIntent().getIntExtra("currentClicks", 0); 
 
     incrementAmount = getIntent().getIntExtra("upgradedClicks", 1); 
 

 

 
     btnClick.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View v) { 
 
       amountClicks +=incrementAmount; 
 
       tvAmountClicks.setText(""+amountClicks); 
 

 
      } 
 
     }); 
 
     btnShop.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View v) { 
 
       Intent intent = new Intent(getApplicationContext(),ShopActivity.class); 
 
       intent.putExtra("currentClicks",amountClicks); 
 
       startActivityForResult(intent, REQUEST_CODE_CURRENTCLICKS); 
 
      } 
 
     }); 
 
    } 
 
}

ShopActivity

import android.content.Context; 
 
import android.content.Intent; 
 
import android.os.Bundle; 
 
import android.support.v7.app.AppCompatActivity; 
 
import android.view.View; 
 
import android.widget.Button; 
 
import android.widget.TextView; 
 
import android.widget.Toast; 
 

 
public class ShopActivity extends AppCompatActivity { 
 
    public int currentClicks; 
 
    public int incrementAmount = 1; 
 
    public int upgradedClicks = 1; 
 
    public int upgradeCost = 100; 
 

 
    @Override 
 
    protected void onCreate(Bundle savedInstanceState) { 
 
     super.onCreate(savedInstanceState); 
 
     setContentView(R.layout.activity_shop); 
 

 
     currentClicks = getIntent().getIntExtra("currentClicks",0); 
 

 
     TextView tvCurrentClicks = (TextView) findViewById(R.id.tvAmoutClicks); 
 
     tvCurrentClicks.setText(""+currentClicks); 
 

 
     Button btnUpgrade = (Button) findViewById(R.id.btnUpgrade); 
 
     btnUpgrade.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View v) { 
 

 
       if(upgradeCost > currentClicks) 
 
       { 
 
        Context context = getApplicationContext(); 
 
        CharSequence text = "You don't have enough Clicks"; 
 
        int duration = Toast.LENGTH_SHORT; 
 
        Toast cantUpgrade = Toast.makeText(context, text,duration); 
 
        cantUpgrade.show(); 
 
       } 
 
       else 
 
       { 
 
        currentClicks =- upgradeCost; 
 
        upgradedClicks =+ incrementAmount; 
 
       } 
 

 
       Intent intent = new Intent(); 
 
       intent.putExtra("currentClicks",currentClicks); 
 
       intent.putExtra("upgradedClicks",upgradedClicks); 
 

 
       setResult(RESULT_OK, intent); 
 
      } 
 
     }); 
 

 
    } 
 
}

感谢您的帮助！

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03-08 21:24:08.263 14893-14893/de.iwanow.zilly.zillysclicker E/AndroidRuntime: FATAL EXCEPTION: main 
                      Process: de.iwanow.zilly.zillysclicker, PID: 14893 
                      java.lang.RuntimeException: Unable to start activity ComponentInfo{de.iwanow.zilly.zillysclicker/de.iwanow.zilly.zillysclicker.ShopActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference 
                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379) 
                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2442) 
                       at android.app.ActivityThread.access$800(ActivityThread.java:156) 
                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1351) 
                       at android.os.Handler.dispatchMessage(Handler.java:102) 
                       at android.os.Looper.loop(Looper.java:211) 
                       at android.app.ActivityThread.main(ActivityThread.java:5389) 
                       at java.lang.reflect.Method.invoke(Native Method) 
                       at java.lang.reflect.Method.invoke(Method.java:372) 
                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020) 
                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815) 
                      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference 
                       at de.iwanow.zilly.zillysclicker.ShopActivity.onCreate(ShopActivity.java:26) 
                       at android.app.Activity.performCreate(Activity.java:5990) 
                       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) 
                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2332) 
                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2442)  
                       at android.app.ActivityThread.access$800(ActivityThread.java:156)  
                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1351)  
                       at android.os.Handler.dispatchMessage(Handler.java:102)  
                       at android.os.Looper.loop(Looper.java:211)  
                       at android.app.ActivityThread.main(ActivityThread.java:5389)  
                       at java.lang.reflect.Method.invoke(Native Method)  
                       at java.lang.reflect.Method.invoke(Method.java:372)  
                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020)  
                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815)  

Answer 1

就从我了解的日志的问题是在这些线路：

TextView tvCurrentClicks = (TextView) findViewById(R.id.tvAmoutClicks); 
tvCurrentClicks.setText(""+currentClicks); 

似乎tvCurrentClicks为空。 您确定tvAmoutClicks ID存在于ShopActivity的布局中吗？