获取资源错误

每次我在主要活动中调用 getResources 时，都会导致错误并且应用程序被迫退出。如果我调用 getApplicationContext().getResources() 甚至在 Eclips 中的全新项目中也会发生这种情况。在通话之前我需要做任何事情吗？ Android 2.1 的 AVD 和 OpenEtna (2.1) 的 LG GW620 上出现错误

MainActivity.java：

package com.robin.blatest;

import android.app.Activity;
import android.content.res.Resources;
import android.os.Bundle;

public class MainActivity extends Activity {

    Resources res = this.getResources();

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
}

清单.xml：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.robin.blatest"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="7" />

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".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>

    </application>
</manifest>

LogCat:

W/dalvikvm(  229): threadid=3: thread exiting with uncaught exception (group=0x4001b188)
E/AndroidRuntime(  229): Uncaught handler: thread main exiting due to uncaught exception
E/AndroidRuntime(  229): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.robin.blatest/com.robin.blatest.MainActivity}: java.lang.NullPointerException
E/AndroidRuntime(  229):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2417)
E/AndroidRuntime(  229):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
E/AndroidRuntime(  229):    at android.app.ActivityThread.access$2200(ActivityThread.java:119)
E/AndroidRuntime(  229):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
E/AndroidRuntime(  229):    at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(  229):    at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime(  229):    at android.app.ActivityThread.main(ActivityThread.java:4363)
E/AndroidRuntime(  229):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(  229):    at java.lang.reflect.Method.invoke(Method.java:521)
E/AndroidRuntime(  229):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
E/AndroidRuntime(  229):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
E/AndroidRuntime(  229):    at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(  229): Caused by: java.lang.NullPointerException
E/AndroidRuntime(  229):    at android.content.ContextWrapper.getResources(ContextWrapper.java:80)
E/AndroidRuntime(  229):    at com.robin.blatest.MainActivity.<init>(MainActivity.java:9)
E/AndroidRuntime(  229):    at java.lang.Class.newInstanceImpl(Native Method)
E/AndroidRuntime(  229):    at java.lang.Class.newInstance(Class.java:1479)
E/AndroidRuntime(  229):    at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
E/AndroidRuntime(  229):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2409)
E/AndroidRuntime(  229):    ... 11 more

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Edit：添加代码

你不能这样做

Resources res = this.getResources();

在字段声明中。那时它是空的！

把它放进去onCreate反而。

你会做类似的事情：

private Resources res = null;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    res = this.getResources();
}

如果您想要一个包含该数据的字段。

但这同样容易做到this.getResources()每当您需要它时。