Question

我正在创建一个2玩家反应应用程序，试图学习一些关于Java / Android的新东西（比如线程），并意识到每当我试图打开应用程序时，它就会变成黑色屏幕，并立即说“你的应用程序混淆哈哈它不响应”（或类似的东西），即使我几乎没有编码任何东西。

我的主要活动类：

public class MainActivity extends Activity implements View.OnClickListener {

Button player1, player2;
Random random;
Double color;
Thread timer;
long x, elapsed;

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

private void game() {
    color = random.nextDouble();
    x = System.currentTimeMillis();
}

private void initializeVar() {
    Button player1 = (Button) findViewById(R.id.bPlayer1);
    Button player2 = (Button) findViewById(R.id.bPlayer2);
    player1.setOnClickListener(this);
    player2.setOnClickListener(this);
    player1.getBackground().setColorFilter(0xFFFF0000,
            PorterDuff.Mode.MULTIPLY);
    player2.getBackground().setColorFilter(0xFFFF0000,
            PorterDuff.Mode.MULTIPLY);
}

@Override
public void onClick(View v) {
    switch (v.getId()) {

    case R.id.bPlayer1:
        elapsed = System.currentTimeMillis();
        elapsed = elapsed - x;
        if (elapsed < 10) {
        } else {
        }
        break;

    case R.id.bPlayer2:
        elapsed = System.currentTimeMillis();
        elapsed = elapsed - x;
        if (elapsed < 10) {

        } else {

        }
        break;
    }
}

}

活动XML：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >

<Button
    android:id="@+id/bPlayer1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="100dp"
    android:src="@drawable/ic_launcher" />

<Button
    android:id="@+id/bPlayer2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="100dp"
    android:src="@drawable/ic_launcher" />

</RelativeLayout>

我的宣言：

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

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="17" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
    <activity
        android:name="com.meteorfiber.reaction.MainActivity"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

</manifest>

我的LOGCAT：

02-20 20:27:54.803: E/AndroidRuntime(1747): FATAL EXCEPTION: main
02-20 20:27:54.803: E/AndroidRuntime(1747): java.lang.RuntimeException: Unable to start       activity ComponentInfo{com.meteorfiber.reaction/com.meteorfiber.reaction.MainActivity}: java.lang.NullPointerException
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.os.Looper.loop(Looper.java:137)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.app.ActivityThread.main(ActivityThread.java:4424)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at java.lang.reflect.Method.invokeNative(Native Method)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at java.lang.reflect.Method.invoke(Method.java:511)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at dalvik.system.NativeStart.main(Native Method)
02-20 20:27:54.803: E/AndroidRuntime(1747): Caused by: java.lang.NullPointerException
02-20 20:27:54.803: E/AndroidRuntime(1747):     at com.meteorfiber.reaction.MainActivity.game(MainActivity.java:28)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at com.meteorfiber.reaction.MainActivity.onCreate(MainActivity.java:24)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.app.Activity.performCreate(Activity.java:4465)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
02-20 20:27:54.803: E/AndroidRuntime(1747):     at   android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)

Answer 1

random对象为null。初始化它！

private void initializeVar() 
{

    random = new Random(); // HERE!
    Button player1 = (Button) findViewById(R.id.bPlayer1);
    Button player2 = (Button) findViewById(R.id.bPlayer2);
    player1.setOnClickListener(this);
    player2.setOnClickListener(this);
    player1.getBackground().setColorFilter(0xFFFF0000,
            PorterDuff.Mode.MULTIPLY);
    player2.getBackground().setColorFilter(0xFFFF0000,
            PorterDuff.Mode.MULTIPLY);
}

Answer 2

在使用变量之前，您似乎没有初始化变量'random'。

Random random = new Random();

Answer 3

你应该初始化随机对象

Random random = new Random;

为什么我的应用程序在打开后立即崩溃？

3 个答案: