Android实现获取meta-data和build.gradle的值

<meta-data
      android:name="UMENG_CHANNEL"
      android:value="0"/>

 /**
   * 不同的类型要区别获取，以下是String类型的
   * @param context 上下午
   * @param metaName meta-data定义的名字
   * @param defaultValue 默认值
   * @return
   */
  public static String getAppMetaDataString(Context context, String metaName, String defaultValue) {
    try {
      //application标签下用getApplicationinfo，如果是activity下的用getActivityInfo
      //Sting类型的用getString，Boolean类型的getBoolean，其他具体看api
      String value = context.getPackageManager()
            .getApplicationInfo(context.getPackageName(), PackageManager.GET_META_DATA)
          .metaData.getString(metaName, defaultValue);
      return value;
    } catch (PackageManager.NameNotFoundException e) {
      e.printStackTrace();
      return defaultValue;
    }
  }

 manifestPlaceholders = [
        JPUSH_PKGNAME : applicationId,
        JPUSH_APPKEY : "xxxxxxxxxxxxxxxxx", //JPush上注册的包名对应的appkey.
        JPUSH_CHANNEL : "developer-default", //暂时填写默认值即可.
    ]

<meta-data android:name="JPUSH_CHANNEL"
          android:value="${JPUSH_CHANNEL}"/>

 /**
   * 获取MetaData信息
   *
   * @param name
   * @param def
   * @return
   */
  public static String getMetaDataValue(Context context, String name,
                     String def) {
    String value = getMetaDataValue(context, name);
    return (value == null) ? def : value;
  }

  public static String getMetaDataValue(Context context, String name) {
    Object value = null;
    PackageManager packageManager = context.getPackageManager();
    ApplicationInfo applicationInfo;
    try {
      applicationInfo = packageManager.getApplicationInfo(
          context.getPackageName(), PackageManager.GET_META_DATA);
      if (applicationInfo != null && applicationInfo.metaData != null) {
        value = applicationInfo.metaData.get(name);
      }
    } catch (PackageManager.NameNotFoundException e) {
      throw new RuntimeException(
          "Could not read the name in the manifest file.", e);
    }
    if (value == null) {
      throw new RuntimeException("The name '" + name
          + "' is not defined in the manifest file's meta data.");
    }
    return value.toString();
  }

<meta-data
  android:name="appkey"
  android:value="\ 1234567890" />

<meta-data
  android:name="appkey"
  android:resource="@string/AppKey" />

public static String getStringMetaData(String name) {
  int valueId = 0;
  try {
    ApplicationInfo appInfo = getApplicationContext().getPackageManager()
        .getApplicationInfo(getApplicationContext().getPackageName(),
            PackageManager.GET_META_DATA);
    valueId = appInfo.metaData.getInt(name);
    if (valueId != 0) {
      return getApplicationContext().getResources().getString(valueId);
    }
  } catch (PackageManager.NameNotFoundException e) {
    e.printStackTrace();
  }
  return "";
}