Android应用程序已停止，无法理解错误日志

Question

我正在制作一个简单的游戏，首先要求在主要活动中遇到困难。它调用一个新的活动，要求一个游戏模式。这就为实际游戏调用了一个新的活动，它只是告诉用户在颜色改变时点击屏幕，并测量他们的反应时间。只要我运行它，它告诉我“不幸的是，应用程序已经停止”，并且有很多错误。我在其他问题中看到几乎完全相同的一组错误，但没有一个答案适用于我。有什么建议么？如果这个问题看起来很模糊，我很抱歉，我不知道如何处理这个问题。以下是Android清单，对于三个活动的代码，错误日志：

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
package="com.dabaam.battlereaction" 
android:versionCode="1" 
android:versionName="1.0" > 

<uses-sdk 
    android:minSdkVersion="11" 
    android:targetSdkVersion="19" /> 

<application 
    android:allowBackup="true" 
    android:icon="@drawable/ic_launcher" 
    android:label="@string/app_name" 
    android:theme="@style/AppTheme" > 

    <activity 
     android:name="com.dabaam.battlereaction.MainActivity" 
     android:label="@string/app_name" > 
     <intent-filter> 
      <action android:name="android.intent.action.MAIN" /> 

      <category android:name="android.intent.category.LAUNCHER" /> 
     </intent-filter> 
    </activity> 

    <activity 
     android:name="com.dabaam.battlereaction.GameType"> 
    </activity> 

    <activity 
     android:name="com.dabaam.battlereaction.Game"> 
    </activity> 

</application> 

活动1：

package com.dabaam.battlereaction; 

import android.app.Activity; 
import android.content.Intent; 
import android.os.Bundle; 
import android.widget.Button; 
import android.view.View; 

public class MainActivity extends Activity { 

Button ezbtn = (Button) findViewById(R.id.ezbtn); 
Button medbtn = (Button) findViewById(R.id.medbtn); 
Button hardbtn = (Button) findViewById(R.id.hardbtn); 

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

    ezbtn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      askDifficulty("EASY"); 
     } 
    }); 

    medbtn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      askDifficulty("MEDIUM"); 
     } 
    }); 

    hardbtn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      askDifficulty("HARD"); 
     } 
    }); 
} 

private void askDifficulty(String whichDiff){ 
    Intent intent = new Intent(MainActivity.this, GameType.class); 
    intent.putExtra(GameType.difficulty, whichDiff); 
    startActivity(intent); 
} 
} 

活动2：

package com.dabaam.battlereaction; 

import android.app.Activity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.content.Intent; 

public class GameType extends Activity{ 
public static String difficulty = "difficulty"; 

public static final String EASY = "EASY"; 
public static final String MEDIUM = "MEDIUM"; 
public static final String HARD = "HARD"; 

Button visbtn = (Button) findViewById(R.id.vis_btn); 
Button tactbtn = (Button) findViewById(R.id.tact_btn); 
Button audbtn = (Button) findViewById(R.id.aud_btn); 

public void onCreate(Bundle b){ 
    super.onCreate(b); 
    setContentView(R.layout.type_layout); 

    Bundle extras = getIntent().getExtras(); 

    //if(extras.getString(difficulty).equals(EASY)){ 
     // Start EASY game 
    difficulty = extras.getString(difficulty); 

    visbtn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      launchGame(difficulty,"VISUAL"); 
     } 
    }); 

    tactbtn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      launchGame(difficulty,"TACTILE"); 
     } 
    }); 

    audbtn.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      launchGame(difficulty,"AUDITORY"); 
     } 
    }); 

} 

private void launchGame(String whichDiff, String whichMode){ 
    Intent intent = new Intent(GameType.this, Game.class); 
    intent.putExtra(Game.difficulty, whichDiff); 
    intent.putExtra(Game.mode, whichMode); 
    startActivity(intent); 
} 
} 

活动3：

package com.dabaam.battlereaction; 

import java.util.Random; 
import java.util.Timer; 
import java.util.TimerTask; 

import android.annotation.SuppressLint; 
import android.app.Activity; 
import android.os.Bundle; 
import android.view.MotionEvent; 
import android.view.View.OnTouchListener; 
import android.view.View; 
import android.widget.LinearLayout; 
import android.widget.TextView; 

public class Game extends Activity implements OnTouchListener{ 
LinearLayout glayout = (LinearLayout) findViewById(R.id.gameLayout); 
public static final String difficulty = "difficulty"; 
public static final String mode = "mode"; 
public Random r = new Random(); 
int after = r.nextInt(10000 - 2000) + 2000; 
public long time1 = 0; 
public long time2 = 0; 
public long elapsed = 1212121; //1212121 by default for debugging 
public String ms_score = "1212121"; //1212121 by default 

public void onCreate(Bundle b){ 
    super.onCreate(b); 
    setContentView(R.layout.game_layout); 
    new Timer().schedule(change(), after); 
} 
public boolean onTouch(View v, MotionEvent event) { 
    time2= System.nanoTime(); 
    elapsed = (time2-time1)/1000000; 

    TextView score = new TextView(getApplicationContext()); 
    ms_score = getString(R.string.score, elapsed); 
    score.setText(ms_score); 
    glayout.addView(score); 

    return false; 
} 

@SuppressLint("ResourceAsColor") public TimerTask change() { 
    glayout.setBackgroundColor(R.color.Blue); 
    time1= System.nanoTime(); 
    return null; 
}  
} 

错误日志：

07-01 17:01:43.490: E/AndroidRuntime(20563): FATAL EXCEPTION: main 
07-01 17:01:43.490: E/AndroidRuntime(20563): Process: com.dabaam.battlereaction, PID: 20563 
07-01 17:01:43.490: E/AndroidRuntime(20563): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.dabaam.battlereaction/com.dabaam.battlereaction.MainActivity}: java.lang.NullPointerException 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2514) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2653) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.app.ActivityThread.access$800(ActivityThread.java:156) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1355) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.os.Handler.dispatchMessage(Handler.java:102) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.os.Looper.loop(Looper.java:157) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.app.ActivityThread.main(ActivityThread.java:5872) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at java.lang.reflect.Method.invokeNative(Native Method) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at java.lang.reflect.Method.invoke(Method.java:515) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1069) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:885) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at dalvik.system.NativeStart.main(Native Method) 
07-01 17:01:43.490: E/AndroidRuntime(20563): Caused by: java.lang.NullPointerException 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.app.Activity.findViewById(Activity.java:1952) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at com.dabaam.battlereaction.MainActivity.<init>(MainActivity.java:11) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at java.lang.Class.newInstanceImpl(Native Method) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at java.lang.Class.newInstance(Class.java:1208) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.app.Instrumentation.newActivity(Instrumentation.java:1079) 
07-01 17:01:43.490: E/AndroidRuntime(20563): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2505) 
07-01 17:01:43.490: E/AndroidRuntime(20563): ... 11 more 
07-01 17:01:47.684: D/Process(20563): killProcess, pid=20563 
07-01 17:01:47.684: D/Process(20563): com.android.internal.os.RuntimeInit$UncaughtHandler.uncaughtException:131 java.lang.ThreadGroup.uncaughtException:693 java.lang.ThreadGroup.uncaughtException:690 

Answer 1

移动

Button ezbtn = (Button) findViewById(R.id.ezbtn); 
Button medbtn = (Button) findViewById(R.id.medbtn); 
Button hardbtn = (Button) findViewById(R.id.hardbtn); 

下

setContentView(R.layout.type_layout); 

当您尝试使用findViewById()找到他们不会创建你的按钮，所以你会得到一个NullPointerException。

声明您的布局后，它们被创建。因为该行的

Answer 2

您的应用程序崩溃：

LinearLayout glayout = (LinearLayout) findViewById(R.id.gameLayout); 

发生崩溃，因为你找不到一个View的内容查看已设置之前，这发生在你Activity的onCreate(...)方法。

在setContentView(...)调用下移动“glayout”的初始化。

除此之外，我会去yygyt's建议。