我正在制作一个简单的游戏，它首先要求在主要 Activity 中设置难度。它调用一个要求游戏模式的新 Activity 。这为实际游戏调用了一个新 Activity ，它只是告诉用户在颜色变化时点击屏幕，并测量他们的 react 时间。我一运行它，它就告诉我“不幸的是，应用程序已停止”并且有很多错误。我在其他问题中看到了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含糊不清，我很抱歉，我不知道该如何处理。以下是Android Manifest、三个Activity的代码和错误日志:

<?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>

Activity 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);
}
}

Activity 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);
}
}

Activity 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 

最佳答案

移动

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

在

setContentView(R.layout.type_layout);

当您尝试使用 findViewById() 查找按钮时，您的按钮不会被创建，因此您会得到一个 NullPointerException。

声明你的布局后，它们就被创建了。

关于java - Android 应用程序已停止，无法理解错误日志，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24519455/