在Android的API级别21空指针例外？ [英] Null pointer exceptio in android api level 21

问题描述

大家在我的应用我使用以下code：

Hi all In my application I am using following code:

 final String cachePath = Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) ||
            !Environment.isExternalStorageRemovable() ? getExternalCacheDir(context).getPath()
            : context.getCacheDir().getPath();

在上面Android版本pre棒棒糖code运行正常，但在API级别21我正在dollowing误差：

Above code run fine on android version pre lolipop, But on API level 21 I am getting dollowing error as:

 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.io.File.getPath()' on a null object reference

任何建议将AP preciated。谢谢advace

Any suggestion will be appreciated. Thanks in advace

推荐答案

看code你贴，你自己做你的权利是：

Look at the code you posted, did you right this yourself?:

final String cachePath = Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) ||
            !Environment.isExternalStorageRemovable() ? getExternalCacheDir(context).getPath()
            : context.getCacheDir().getPath();

您在Android中，得到了最常见的错误 NullPointerException异常：

You got the most common error in Android, a NullPointerException:

 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.io.File.getPath()' on a null object reference

您在呼唤的getPath（）不检查空两次。

试试这个：

String cachePath; // you still need a default value if not mounted

if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) || !Environment.isExternalStorageRemovable()) {
    if (getExternalCacheDir(context) != null) {
        cachePath = getExternalCacheDir(context).getPath(); // most likely your null value
    }
} else {
    if (context.getCacheDir() != null) {
        cachePath = context.getCacheDir().getPath();
    }
}

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