getSupportActionBar()NullPointerException [英] getSupportActionBar() NullPointerException

问题描述

在onCreate()活动方法中，我有ToolBar的这段代码:

In onCreate() method of activity I have this code for ToolBar:

toolbar = (Toolbar) findViewById(R.id.tool_bar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);

我的IDE使我感到getSupportActionBar().setDisplayHomeAsUpEnabled(true);可能产生 NullPointerException .

My IDE warms me that getSupportActionBar().setDisplayHomeAsUpEnabled(true); may produce NullPointerException.

我的问题是我应该忽略它，如何解决它吗?

My question is should I ignore it and how can I fix it anyway?

推荐答案

IDE会警告您潜在的NullPointerException，因为在许多情况下，应用可能会抛出一个.例如，您可能为整个Application(或仅针对相关的activity)使用了 NoActionBar 主题，但是您仍然尝试使用getActionBar()(或getSupportActionBar()).

The IDE warns you about a potential NullPointerException because there are many cases where the app could throw one. For the example you could be using a NoActionBar theme for your whole Application (or just for the concerned activity), but still you're trying to retrieve a reference to the action bar using getActionBar() (or getSupportActionBar()).

只需忽略警告，但请记住上面的提示.

Just ignore the warning, but keep in mind the notes above.

更新:

您可以通过显式检查可空性来摆脱此警告:

You can get rid of the warning by explicitly checking for nullability:

toolbar = (Toolbar) findViewById(R.id.tool_bar);
if (toolbar != null) {
    // you can safely invoke methods on the Toolbar
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
} else {
    // Toolbar is null, handle it
}

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