Question

我在这段代码的第40行得到一个NullPointerException。以下是Google广告移动广告服务的实施示例，该服务将于今年8月生效。这段代码实际上是从他们的文档中剪切和粘贴的，但是我得到了例外并且无法解决它。

这是班级：

package com.example.com.stringtheory.newadmobtest;

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdSize;
import com.google.android.gms.ads.AdView;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.LinearLayout;

/**
 * A simple {@link Activity} that embeds an AdView.
 */
public class MainActivity extends Activity {
/** The view to show the ad. */
private AdView adView;

/* Your ad unit id. Replace with your actual ad unit id. */
private static final String AD_UNIT_ID = "ca-app-pub-6817177749834558/8445203226";

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

// Create an ad.
adView = new AdView(this);
adView.setAdSize(AdSize.BANNER);
adView.setAdUnitId(AD_UNIT_ID);

    // Add the AdView to the view hierarchy. The view will have no size
    // until the ad is loaded.
    LinearLayout layout = (LinearLayout) findViewById(R.id.linear);
    if (layout == null) 
        { Log.w("", "LinearLayout is null");

        }
    layout.addView(adView);

    // Create an ad request. Check logcat output for the hashed device ID to
    // get test ads on a physical device.
    AdRequest adRequest = new AdRequest.Builder()

        .build();

    // Start loading the ad in the background.
    adView.loadAd(adRequest);
  }

  @Override
  public void onResume() {
    super.onResume();
    if (adView != null) {
      adView.resume();
    }
  }

  @Override
  public void onPause() {
    if (adView != null) {
      adView.pause();
    }
    super.onPause();
  }

  /** Called before the activity is destroyed. */
  @Override
  public void onDestroy() {
    // Destroy the AdView.
    if (adView != null) {
      adView.destroy();
    }
    super.onDestroy();
  }
}

这是相关的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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.com.stringtheory.newadmobtest.MainActivity$PlaceholderFragment" >
    <LinearLayout
    android:id="@+id/linear"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="18dp"
    android:layout_marginTop="112dp"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
</LinearLayout>

有什么想法导致这个？

PS - 导致问题的特定行读取：

    layout.addView(adView);

Answer 1

我修好了。这是问题所在：

为了启动测试应用程序，我在eclipse中创建了一个新项目。这带有2个布局（activity_main和fragment_main）。

我在fragment_main布局中看到了hello world文本，由于某种原因，我错误地将我的linearLayout添加到该xml中。

虽然我认为我指的是正确的布局，但系统看到布局确实不存在于我认为的位置。简单地忽略了它。在这个小错误上煮了大约2个小时。

Eclipse中的LinearLayout NullPointerException

1 个答案: