Question

我制作了一个简单的点击游戏应用。我知道它糟糕的编程，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..我刚刚开始使用Android Studio，所以期待我不会看到问题，尽管它可能很明显。< / p>

MainActivity

＆＃13;

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);
            }
        });
    }
}

＆＃13;

＆＃13; ShopActivity

＆＃13;

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);
            }
        });

    }
}

＆＃13;

感谢您的帮助！

编辑：登录

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

据我从日志中了解，问题出在以下几行：

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

似乎tvCurrentClicks为null。您确定ShopActivity的布局中是否存在tvAmoutClicks ID？

Android Studio // App尝试打开第二个布局后崩溃

1 个答案: